CARTRIDGE, DIGITAL MICROFLUIDICS SYSTEM AND METHOD OF CONTROL AND MANIPULATION OF LIQUIDS

Abstract

A cartridge configured to control and manipulate liquids and to be positioned at a cartridge accommodation site of a digital microfluidics system is disclosed. The digital microfluidics system has a number or array of individual electrodes attached to a first substrate or PCB, a central control unit in operative contact with individual electrodes for controlling selection and for providing a number of individual electrodes that define a path of individual electrodes with voltage for manipulating liquid portions or liquid droplets by electrowetting, and a cartridge accommodation site that is configured for taking up the cartridge.

Claims

1. A method for control and manipulation of liquids in a small volume, the method comprising the steps of: a) providing a cartridge with a flexible working film (19) that comprises a semi-permeable constitution or a semi-permeable property; b) providing an underpressure for avoiding bubbles inside the working gap (4) of the cartridge (17).

2. A method for controlling and manipulating liquids in a small volume, in particular in the micro- or nanoscale format, the method comprising the steps of: a) providing a digital microfluidics system (1) comprising: a number or array of individual electrodes (2) attached to a first substrate or PCB (3); a central control unit (7) in operative contact with said individual electrodes (2) for controlling selection and for providing a number of said individual electrodes (2) that define a path of individual electrodes (2′) with voltage for manipulating liquid portions (8-2) or liquid droplets (8-1) by electrowetting; and a cartridge accommodation site (18) that is configured for taking up a cartridge (17); b) providing a cartridge (17), in particular a disposable cartridge, which comprises a first hydrophobic surface (5) that belongs to a flexible working film (19), a second hydrophobic surface (6) that belongs to a cover plate (20) of the cartridge (17), and a working gap (4) that is located in-between the two hydrophobic surfaces (5,6), wherein the flexible working film (19) comprises a semipermeable constitution or a semi-permeable property; c) positioning said cartridge (17) at a cartridge accommodation site (18) of said digital microfluidics system (1); the flexible working film (19) comprising a backside (21); d) providing on the hydrophobic surface (5) and above a path of selected electrodes (2′) at least one liquid portion (8-2) or liquid droplet (8-1); e) using a vacuum source (23) of the digital microfluidics system (1) for providing an underpressure established in an evacuation space (24) between the uppermost surface (22) of the cartridge accommodation site (18) and the backside (21) of the flexible working film (19) of the cartridge (17).

3. The method according to claim 1, wherein the underpressure is in a range of −2 psi to −6 psi or about −6 psi.

4. The method according to claim 1, wherein the flexible working film (19) configured for being attract as entire flexible working film.

5. The method according to claim 1, wherein the cover plate (20) of the cartridge (17) is configured as a rigid cover plate, evenly defining a top of said working gap (4).

6. The method according to claim 1, wherein the cartridge accommodation site (18) of the digital microfluidics system (1) or the cartridge (17) comprise a gasket (27), with which said evacuation space (24) is sealingly enclosed and a height (28) of the working gap (4) between said hydrophobic surfaces (5,6) is defined.

7. The method according to claim 1, wherein the positioning of said cartridge (17) at a cartridge accommodation site (18) comprises touching an uppermost surface (22) of the cartridge accommodation site (18) with the backside (21) of the flexible working film (19), when the cartridge (17) is accommodated on said cartridge accommodation site (18), in particular spreading the flexible working film (19) on the uppermost surface (22) of the cartridge accommodation site (18) upon providing the underpressure in the evacuation space (24).

8. The method according to claim 1, comprising the controlling and manipulating of the liquids in at least one of: in a small volume, in a microscale format, and in a nanoscale format.

9. The method according to claim 1 comprising the step of: providing a cartridge with a flexible working film that comprises a semi-permeable constitution or a semi-permeable property, wherein the cartridge is configured to control and manipulate liquids and to be positioned at a cartridge accommodation site of a digital microfluidics system, wherein the cartridge comprises a rigid cover plate, a first hydrophobic surface that belongs to a flexible working film, a second hydrophobic surface that belongs to a rigid cover plate and a working gap that is located in-between the two hydro-phobic surfaces, the flexible working film comprising a backside that, when the cartridge is accommodated on a cartridge accommodation site, provides an evacuation space between the upper-most surface of the cartridge accommodation site and the backside for establishing an underpressure produced in the evacuation space produced by a vacuum source (23) of the digital microfluidics system (1).

10. The method according to claim 1 comprising the step of: providing a vacuum source for establishing an underpressure in an evacuation space between the uppermost surface of a cartridge accommodation site and the backside of the flexible working film.

11. The method according to claim 1, comprising control and manipulation of liquids in a small volume in the micro- or nanoscale format.

12. The method according to claim 1, wherein the underpressure is a high underpressure.

Description

BRIEF INTRODUCTION OF THE DRAWINGS

[0039] Integration of barrier elements that narrow the working gap of a disposable cartridge as well as integration of magnetic conduits into the PCB or first substrate and/or second substrate according to the present invention is described with the help of the attached schematic drawings that show selected and exemplary embodiments of the present invention without narrowing the scope and gist of this invention. It is shown in:

[0040] FIG. 1 a biplanar setup known from the prior art in a cross section view with a disposable cartridge located at a cartridge accommodation site of a PCB of a digital microfluidics system with an activated magnet located below an individual operation electrode and a droplet with concentrated beads in the magnetic field on top;

[0041] FIG. 2 the biplanar setup known from the prior art of the cross section view of FIG. 1, the droplet with beads clumped by the magnet field moved away from the magnetic field;

[0042] FIG. 3 an inventive biplanar setup in a cross section view with a disposable cartridge located at a cartridge accommodation site of a PCB of a digital microfluidics system with two barrier elements located on two individual operation electrodes adjacent to a single operation electrode and a droplet with beads clumped by a magnetic field on top another electrode;

[0043] FIG. 4 the inventive biplanar setup of the cross section view of FIG. 3 with the droplet moved (preferably repeated) over at least one of the barrier elements, the droplet comprising re-dispersed magnetically responsive beads;

[0044] FIG. 5 an alternative biplanar setup in a cross section view with a disposable cartridge located at a cartridge accommodation site of a PCB of a digital microfluidics system with one conical, pyramidal magnetic conduit located in a PCB or first substrate and backed with an activated, individual backing magnet; the magnetic conduit being located in a blind hole below a space between two narrowed operation electrodes;

[0045] FIG. 6 the alternative biplanar setup of the cross section view of FIG. 5 with the droplet moved away from the magnetic conduit, the droplet comprising a considerably reduced number of beads leaving a small liquid portion with beads behind;

[0046] FIG. 7 an inventive biplanar setup in a cross section view with a disposable cartridge located at a cartridge accommodation site of a PCB of a digital microfluidics system with one frustoconical magnetic conduit located in a PCB or first substrate and backed with an activated, individual backing magnet in combination with two barrier elements at least partially located on two individual operation electrodes adjacent to the magnetic conduit, which is located in a blind hole below a space between two narrowed operation electrodes and which has a droplet with concentrated beads on top;

[0047] FIG. 8 the inventive biplanar setup of the cross section view of FIG. 7 with the droplet moved away from the magnetic conduit, the droplet substantially comprising no beads leaving a small liquid portion with practically all beads behind;

[0048] FIG. 9 the inventive biplanar setup of the cross section view of FIGS. 7 and 8 with the droplet moved back to the magnetic conduit with the now deactivated backing magnet, all beads being present again and dispersed in the droplet;

[0049] FIG. 10 an inventive biplanar setup in a cross section view with a disposable cartridge located at a cartridge accommodation site of a PCB of a digital microfluidics system with one cylindrical magnetic conduit located below the center of an electrowetting electrode, the magnetic conduit being located in the PCB or first substrate and backed with an activated, individual backing magnet in combination with a single barrier element located on an individual operation electrode adjacent to the magnetic conduit; the droplet moved over the barrier element comprises practically no beads leaving a small liquid portion with substantially all beads behind on top of the magnetic conduit;

[0050] FIG. 11 an inventive biplanar setup in a cross section view with a disposable cartridge located at a cartridge accommodation site of a PCB of a digital microfluidics system with two check valves located between electrowetting electrodes, the check valves each being located in the PCB or first substrate and in projection under a pipetting guide of the disposable cartridge: [0051] on the left, the check valve is closed by pushing the valve ball up by the valve spring, this enables establishing an overpressure in the filler fluid inside of the gap; [0052] on the right, the check valve is open by pressing a liquid (here a sample portion) via the sealing pipetting guide into the gap of the disposable cartridge, such liquid injection moves the valve ball against the force of the valve spring and opens the check valve;

[0053] FIG. 12 a plane view of a linear array of operation electrodes on a PCB of a digital microfluidics system; a single magnetic conduit positioned on an activated backing magnet is located below the center of an electrowetting electrode in the path of a droplet; two barrier elements according to a first embodiment are at least partially located on two individual operation electrodes adjacent to the electrode with the magnetic conduit; the droplet being moved away from the electrode with the magnetic conduit and over a barrier element, the droplet substantially comprises no beads leaving a small liquid portion with practically all beads behind on top of the magnetic conduit;

[0054] FIG. 13 a plane view of a linear array of operation electrodes on a PCB of a digital microfluidics system; a single magnetic conduit is located in neighboring notches in-between two of the electrowetting electrodes that in each case define the path, the magnetic conduit being positioned on an activated backing magnet; two barrier elements according to a second embodiment are at least partially located on two individual operation electrodes adjacent to the magnetic conduit; the droplet being moved away from the magnetic conduit and over a barrier element, the droplet substantially comprises no beads leaving a small droplet with practically all beads behind on top of the magnetic conduit;

[0055] FIG. 14 a plane view of a linear array of operation electrodes on a PCB of a digital microfluidics system; a single magnetic conduit is located in a notch at one side of one of the electrowetting electrodes that define the electrowetting path, the magnetic conduit being positioned on an inactive backing magnet; two barrier elements according to a third and fourth embodiment are at least partially located on two individual operation electrodes adjacent to the electrode with the magnetic conduit on which is the droplet that comprises all dispersed beads;

[0056] FIG. 15 a plane view of a linear array of operation electrodes on a PCB of a digital microfluidics system; a single magnetic conduit is located in a notch at one side of one of the electrowetting electrodes that define the electrowetting path, the magnetic conduit being positioned on an activated backing magnet; two barrier elements according to a fifth and sixth embodiment are at least partially located on two individual operation electrodes adjacent to the electrode with the magnetic conduit; the droplet being moved away from the magnetic conduit and over a barrier element, the droplet substantially comprises no beads leaving a small liquid portion with practically all beads behind on top of the magnetic conduit;

[0057] FIG. 16 a plane view of a linear array of operation electrodes on a PCB of a digital microfluidics system; two types of electrodes are shown, square and elongated ones; between two of the elongated electrodes, a barrier element is located to reach about the midst of the electrodes and a large droplet is moved back and through for re-suspension of magnetic beads, the droplet is deformed when passing the barrier element;

[0058] FIG. 17 a plane view of a linear array of elongated operation electrodes on a PCB of a digital microfluidics system; two sets of barrier elements are located between two of the elongated electrodes in each case, the two sets of barrier elements are located such that a large droplet is deformed on one side more than on the other when passing the first set of barrier elements and more deformed on the opposite side when passing the second set of barrier elements; moving the large droplet back and through and/or around both sets of barrier elements provides accelerated re-suspension of magnetic beads.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0059] The inventive barrier elements, their combination with magnetic conduits with backing magnets and their use is now described in detail.

[0060] In the context of the present invention, an electrode array is a regular arrangement of electrodes, e.g. in an orthogonal lattice or in any other regular arrangement such as a linear or hexagonal array.

[0061] In the context of the present invention, a liquid droplet 8-1,8-1′ has a size that covers on the hydrophobic surface 5 an area that is larger than a single individual electrode 2. Thus, a liquid droplet 8-1,8-1′ is the smallest liquid volume that may be manipulated (i.e. transported) by electrowetting. In the context of the present invention, a liquid portion 8-2,8-2′ has a size that covers on the hydrophobic surface 5 an area that is larger than two adjacent individual electrodes 2. Thus, a liquid portion 8-2,8-2′ is larger than the smallest liquid volume that may be manipulated (i.e. transported) by electrowetting.

[0062] According to the present invention, in the first substrate 3 of the microfluidics system 1 and below said individual electrodes 2 there may be located at least one magnetic conduit 9 that is configured to be backed by a backing magnet 10. The term “below” is to be understood in the context of the present invention as “on the backside of the PCB to which's front-side the electrodes 2 are attached, no matter what spatial orientation the PCB may have. Further according to the present invention, said at least one magnetic conduit 9 is located in close proximity to individual electrodes 2 (see FIGS. 5-10 as described below).

[0063] FIG. 1 shows a biplanar setup basically known from the prior art (see e.g. WO 2010/069977). In the cross section view, a disposable cartridge 17 that comprises a first hydrophobic surface 5 and a second hydrophobic surface 6 with a working gap 4 in-between. The working gap 4 has gap height 28. The flat working film 19′ of the disposable cartridge 17 is laying with its backside 21 on the uppermost surface 22 of the cartridge accommodation site 18 of a PCB 3 of a digital microfluidics system 1. An activated magnet 10 (preferably supported by a support 35) is located below at least one individual operation electrode 2 and a droplet 8-1 with magnetically responsive beads 11 is located in the magnetic field on top of the activated magnet 10. By the action of the magnetic field, the magnetically responsive beads 11 are concentrated within the droplet 8-1. A number or array of individual electrodes 2 are attached to a first substrate or PCB 3; these individual operating electrodes 2 are connected with and in operative contact to a central control unit 7. The control unit 7 is designed for controlling selection and for providing a number of said individual electrodes 2 that define a path of individual electrodes 2′ with voltage for manipulating liquid portions 8-2 or liquid droplets 8-1 by electrowetting.

[0064] FIG. 2 shows the biplanar setup known from the prior art of the cross section view of FIG. 1. The droplet 8-1 with the magnetically responsive beads that previously have been clumped within the droplet 8-1 by the magnet field is moved away from the magnetic field by electrowetting action of the individual operation electrodes 2 of the PCB 3. Such moving away is controlled by the central control unit 7, but often has no or little influence on a re-suspension of the magnetically responsive beads in that droplet 8-1 whether or not the magnet 10 is activated. As can be seen, some magnetically responsive beads 1 may be retained in a small liquid portion 8″ by the activated magnet 10.

[0065] FIG. 3 shows an inventive biplanar setup in a cross section view with a disposable cartridge 17 located at a cartridge accommodation 18 site of a PCB 3 of a digital microfluidics system 1. According to the present invention, two (or at least one) barrier elements 40 are located on two individual operation electrodes 2 adjacent to a single operation electrode 2. A droplet 8-1 with magnetically responsive beads 11 (e.g. previously clumped by a magnetic field) is situated on top another electrode on its path 2′ (see FIGS. 12-15) to the at least one barrier element 40. Preferably, the microfluidics system 1 comprises a cartridge accommodation site 18 that is configured for taking up a disposable cartridge 17 (see for example US 2013/0134040).

[0066] A preferred and inventive method of keeping suspended or re-suspending magnetically responsive beads in liquid portions or droplets in digital microfluidics takes advantage of this setup and comprises the steps of [0067] a) providing a digital microfluidics system 1 comprising: [0068] a number or array of individual electrodes 2 attached to a first substrate or PCB 3, [0069] a central control unit 7 in operative contact with said individual electrodes 2 for controlling selection and for providing a number of said individual electrodes 2 that define a path of individual electrodes 2′ with voltage for manipulating liquid portions 8-2 or liquid droplets 8-1 by electrowetting; and [0070] a cartridge accommodation site 18 that is configured for taking up a disposable cartridge 17 which comprises a first hydrophobic surface 5 that belongs to a flexible working film 19, a second hydrophobic surface 6 that belongs to a cover plate 20 of the disposable cartridge 17, and a working gap 4 that is located in-between the two hydrophobic surfaces 5,6; [0071] b) providing at least one barrier element 40 and positioning said barrier element 40 at least partially on an individual operating electrode 2 located at the cartridge accommodation site 18 of the PCB 3, the barrier element 40 narrowing the working gap 4 of a disposable cartridge 17 situated on a surface of said cartridge accommodation site 18; [0072] c) providing a disposable cartridge 17 and positioning said disposable cartridge 17 at a cartridge accommodation site 18 of said digital microfluidics system 1; the flexible working film 19 comprising a backside 21 that, when the disposable cartridge 17 is accommodated on said cartridge accommodation site 18, touches an uppermost surface 22 of the cartridge accommodation site 18 of the digital microfluidics system 1 and of said at least one barrier element 40; [0073] d) providing on the hydrophobic surface 5 and above a path of selected electrodes 2′ at least one liquid portion 8-2 or liquid droplet 8-1 containing magnetically responsive beads 11; and [0074] e) moving by electrowetting said at least one liquid portion 8-2 or liquid droplet 8-1 containing magnetically responsive beads 11 on said path of selected electrodes 2′ at least once over and/or around said at least one barrier element 40 and thereby keeping suspended or re-suspending the magnetically responsive beads 11 in said liquid portion 8-2 or liquid droplet 8-1.

[0075] Carrying out the step b) produces a narrowed gap height 46 that is reduced with respect to the normal gap height 28, which is defined by a gasket 27 that preferably belongs to the disposable cartridge 17 or to the cartridge accommodation site 18 of the microfluidics system 1.

[0076] FIG. 4 shows the inventive biplanar setup of the cross section view of FIG. 3. There is shown a result of the above preferred method of keeping suspended or re-suspending magnetically responsive beads in liquid portions or droplets in digital microfluidics. The droplet 8-1 has been moved at least once (preferably repeatedly, see double arrow) over and/or around at least one of the barrier elements 40, and now, the droplet 8-1 comprises re-dispersed magnetically responsive beads 11.

[0077] When carrying out the above preferred method of keeping suspended or re-suspending magnetically responsive beads in liquid portions or droplets in digital microfluidics, it is preferred that for spreading of the flexible working film 19 of the disposable cartridge 17 on the uppermost surface 22 of the cartridge accommodation site 18 of the digital microfluidics system 1 and over said at least one barrier element 40: [0078] an underpressure is established between the uppermost surface 22 of the cartridge accommodation site 18 and the backside 21 of the flexible working film 19 of the disposable cartridge 17, using a vacuum source 23 of the digital microfluidics system 1; or [0079] an overpressure is established within the working gap 4 of the disposable cartridge 17, using a filler-fluid or other fluid.

[0080] For applying such underpressure, there are vacuum lines 23′ preferably arranged in the microfluidics device 1, the vacuum lines 23′ connecting an evacuation space 24 with the vacuum source 23 of the digital microfluidics system 1. According to the present invention, such evacuation space 24 is defined by the flexible working film 19 of the cartridge 17, a gasket 27, and the uppermost surface 22 of the cartridge accommodation site 18. This vacuum source 23 of the digital microfluidics system 1 is configured for establishing an underpressure in an evacuation space 24 between the uppermost surface 22 of the cartridge accommodation site 18 and the backside 21 of the working film 19 of a disposable cartridge 17 that is accommodated at the cartridge accommodation site 18 (see e.g. US 2013/0134040 A1).

[0081] When working with underpressure or overpressure as described, it is further preferred that the cover plate 20 of the disposable cartridge 17 is configured as a rigid cover plate, evenly defining a top of said working gap 4. For applying such overpressure inside the working gap 4, a filler fluid (e.g. silicone oil) or another fluid that preferably is not miscible with the droplets or liquid portions that are to be manipulated within the working gap 4 is pressed into the working gap 4.

[0082] FIG. 5 shows an alternative biplanar setup in a cross section view with a disposable cartridge 17 located at a cartridge accommodation 18 site of a PCB 3 of a digital microfluidics system 1. One conical or pyramidal magnetic conduit 9″ is located in a PCB or first substrate 3 and backed with an activated, individual backing magnet 10. Preferably, such a backing magnet is a movable permanent magnet 10′ (see FIG. 10), a switchable permanent magnet 10″ (see FIGS. 7-9), or an electromagnet 10′″ (see FIGS. 5-6). Here, the magnetic conduit 9″ is located in a blind hole below a space 14 between two narrowed operation electrodes 2″. As shown, in the first substrate 3 of the microfluidics system 1 and located in a blind hole below a space 14 between two narrowed operation electrodes 2″, there is located a magnetic conduit 9″ that is configured to be backed by a backing magnet 10, said at least one magnetic conduit 9 being located in close proximity to individual electrodes 2″.

[0083] On this first hydrophobic surface 5, magnetically responsive beads 11 in the liquid droplet 8-1 are attracted by the magnetic field produced by the activated electromagnet 10′″ and directed by the magnetic conduit 9″.

[0084] FIG. 6 shows the alternative biplanar setup of the cross section view of FIG. 5 with the droplet 8-1′ moved away from the magnetic conduit 9″. Because the magnetic field delivered by the magnetic conduit 9″ attracts most of the magnetically responsive beads 11, the liquid droplet 8-1′ comprises a considerably reduced number of beads 11 leaving a small liquid portion 8″ with beads 11 behind.

[0085] FIG. 7 shows an inventive biplanar setup in a cross section view with a disposable cartridge 17 located at a cartridge accommodation site 18 of a PCB 3 of a digital microfluidics system 1. The PCB 3 is equipped with one frustoconical magnetic conduit 9″ located, which is backed with an activated, individual backing magnet 10″ in combination with two barrier elements 40 at least partially located on two individual operation electrodes 2″ adjacent to the magnetic conduit 9″. The magnetic conduit 9″ is located in a blind hole below neighboring notches 12 between two narrowed operation electrodes 2″ and has a liquid droplet 8-1 with concentrated magnetically responsive beads 11 on top.

[0086] On this first hydrophobic surface 5, magnetically responsive beads 11 in the liquid droplet 8-1 are attracted by the magnetic field produced by the switchable permanent magnet 10″ and directed by the magnetic conduit 9″. Because the magnetic field of the permanent magnet of the PE-magnet is not compensated by the electromagnet of the PE-magnet. Such PE-magnets 32 (e.g. ITS-PE 1212-24 VDC-TEC of M RED MAGNETICS® (Intertec Components GmbH, 85356 Freising, Germany) may have a diameter of 12 mm, a height of 12 mm, and work with 24 V DC. A great advantage of using such PE-magnets 32 is the fact that absolutely no moving parts are involved or necessary for switching on and off the switchable permanent magnets 10″. Preferably, the microfluidics system 1 comprises a cartridge accommodation site 18 that is configured for taking up a disposable cartridge 17 (see for example US 2013/0134040, herein incorporated by reference in its entirety).

[0087] A preferred and inventive method of substantially removing magnetically responsive beads from liquid portions or droplets in digital microfluidics takes advantage of this setup and comprises the steps of: [0088] a) providing a digital microfluidics system 1 comprising: [0089] a number or array of individual electrodes 2 attached to a first substrate or PCB 3; [0090] a central control unit 7 in operative contact with said individual electrodes 2 for controlling selection and for providing a number of said individual electrodes 2 that define a path of individual electrodes 2′ with voltage for manipulating liquid portions 8-2 or liquid droplets 8-1 by electrowetting; [0091] a cartridge accommodation site 18 that is configured for taking up a disposable cartridge 17 which comprises a first hydrophobic surface 5 that belongs to a flexible working film 19, a second hydrophobic surface 6 that belongs to a cover plate 20 of the disposable cartridge 17, and a working gap 4 that is located in-between the two hydrophobic surfaces 5,6; and [0092] at least one magnetic conduit 9 located in the first substrate or PCB 3 of the microfluidics system 1 and below said individual electrodes 2, said at least one magnetic conduit 9 being backed by a backing magnet 10 with a magnetic field, being configured for directing said magnetic field through the magnetic conduit 9 to the first hydrophobic surface 5 on said individual electrodes 2, and being located in close proximity to individual electrodes 2; [0093] b) providing at least one barrier element 40 and positioning said barrier element 40 at least partially on an individual operating electrode 2 located at the cartridge accommodation site 18 of the PCB 3, the barrier element 40 narrowing the working gap 4 of a disposable cartridge 17 situated on a surface of said cartridge accommodation site 18; [0094] c) providing a disposable cartridge 17 and positioning said disposable cartridge 17 at a cartridge accommodation site 18 of said digital microfluidics system 1; the flexible working film 19 comprising a backside 21 that, when the disposable cartridge 17 is accommodated on said cartridge accommodation site 18, touches an uppermost surface 22 of the cartridge accommodation site 18 of the digital microfluidics system 1 and of said at least one barrier element 40; [0095] d) providing on the hydrophobic surface 5 and above a path of selected electrodes 2′ at least one liquid portion 8-2 or liquid droplet 8-1 that comprises magnetically responsive beads 11; [0096] e) moving by electrowetting said at least one liquid portion 8-2 or liquid droplet 8-1 with the magnetically responsive beads 11 on said path of selected electrodes 2′ until said magnetic field of the at least one magnetic conduit 9 backed by a backing magnet 10 is reached; and [0097] f) activating said backing magnet 10 before and during moving by electrowetting said at least one liquid portion 8-2 or liquid droplet 8-1 with the magnetically responsive beads 11 on said path of selected electrodes 2′ and over and/or around said at least one barrier element 40, thereby attracting and substantially removing magnetically responsive beads 11 from said liquid portion 8-2 or liquid droplet 8-1.

[0098] FIG. 8 shows the inventive biplanar setup of the cross section view of FIG. 7 with the droplet 8-1′ moved away from the magnetic conduit. There is shown a result of the above preferred method of substantially removing magnetically responsive beads from liquid portions or droplets in digital microfluidics. The droplet 8-1′ substantially comprises no beads 11 leaving a small liquid portion 8″ with practically all magnetically responsive beads behind.

[0099] When carrying out the above removing method, on the one hand it is preferred for spreading the flexible working film 19 of the disposable cartridge 17 on the uppermost surface 22 of the cartridge accommodation site 18 of the digital microfluidics system 1 and over said at least one barrier element 40 to using a vacuum source 23 of the digital microfluidics system 1 for establishing an underpressure in an evacuation space 24 between the uppermost surface 22 of the cartridge accommodation site 18 and the backside 21 of the flexible working film 19 of the disposable cartridge 17.

[0100] When carrying out the above removing method, on the other hand it is preferred for spreading the flexible working film 19 of the disposable cartridge 17 on the uppermost surface 22 of the cartridge accommodation site 18 of the digital microfluidics system 1 and over said at least one barrier element 40 to using a filler-fluid or other fluid for establishing an overpressure within the working gap 4 of the disposable cartridge 17.

[0101] Preferably for carrying out the above removing method in one way or the other, the cover plate 20 of the disposable cartridge 17 is configured as a rigid cover plate, evenly defining a top of said working gap 4.

[0102] It is preferred that said at least one magnetic conduit 9 consists of a single solid ferromagnetic element, or of a multitude of randomly orientated ferromagnetic elements, or of an amorphous paste filled with ferromagnetic material. It is further preferred that said at least one magnetic conduit 9 is located under and is covered by an individual electrode 2 or that said at least one magnetic conduit 9 is located beside of and is not covered by at least one individual electrode 2.

[0103] The backing magnet 10 that is used to operatively back at least one magnetic conduit 9, preferably is configured as a movable permanent magnet 10′ (see FIG. 10), or as a switchable permanent magnet 10″ (see FIGS. 7-9), or as an electromagnet 10′″ (see FIGS. 5-6).

[0104] In consequence, actuating said backing magnet (10) is achieved by: [0105] a) moving a permanent magnet 10′ to a backside of the at least one magnetic conduit 9; or [0106] b) switching-on a switchable permanent magnet 10″ that is located at the backside of the at least one magnetic conduit 9; switching-on a switchable permanent magnet 10″ is carried out by switching-off an electromagnet that is compensating the magnetic field of a PE-magnet; or [0107] c) energizing an electromagnet 10′″ that is located at the backside of the at least one magnetic conduit 9.

[0108] Preferably, said at least one magnetic conduit 9 is a cylindrical, cuboid, pyramidal, frustoconical, conical, or magnetic conduit 9′,9″ located in a blind hole 15 or in a through hole 16 in the first substrate 3 of the digital microfluidics system 1.

[0109] Independent from the method of working, it is preferred that the cartridge accommodation site 18 of the digital microfluidics system 1 or the disposable cartridge 17 comprise a gasket 27, using which said evacuation space 24 (if present) is sealingly enclosed and always, a height 28 of the working gap 4 between said hydrophobic surfaces 5,6 of the disposable cartridge 17 is defined.

[0110] When working with overpressure in the gap 4, it is preferred that the cartridge accommodation site 18 of the digital microfluidics system 1 comprises at least one check valve 42, using which said working gap 4 is sealingly closed and an overpressure produced by a filler fluid or other fluid inside said working gap 4 is enabled (see FIG. 11).

[0111] FIG. 9 shows the inventive biplanar setup of the cross section view of FIGS. 7 and 8 with the droplet 8-1 moved back to the magnetic conduit 9″ with the now deactivated backing magnet 10. All magnetically responsive beads 11 are present again and dispersed in the droplet 8-1. Such re-suspension was achieved by moving by electrowetting said liquid droplet 8-1 containing magnetically responsive beads 11 on said path of selected electrodes 2′ at least once over and/or around said at least one barrier element 40 and thereby re-suspending the magnetically responsive beads 11 in said liquid droplet 8-1.

[0112] FIG. 10 shows an inventive biplanar setup in a cross section view with a disposable cartridge 17 located at a cartridge accommodation site 18 of a PCB 3 of a digital microfluidics system 1. One cylindrical magnetic conduit 9′ is located below the center of an electrowetting electrode 2, the magnetic conduit 9′ being located in the PCB 3 or first substrate 3 and backed with an activated, individual backing magnet 10 in combination with a single barrier element 40 located on an individual operation electrode 2 adjacent to the magnetic conduit 9″. Here and in contrast to the barrier elements 40 shown so far, the barrier element 40 shows a trapezoid cross section instead of a square or rectangular cross section.

[0113] Using barrier elements 40 with rectangular cross section is preferred when working with “low” underpressure in the range of about—2 psi (which is equal to 875 mbar). The low underpressure does not attract the entire flexible working film 19, which thus forms ramp-like transitions between the normal gap height 28 and the narrowed gap height 46.

[0114] Using barrier elements 40 with trapezoid cross section is preferred when working with “high” underpressure in the range of about—6 psi (which is equal to 600 mbar). The high underpressure does attract the entire flexible working film 19. The preferred ramp-like transitions between the normal gap height 28 and the narrowed gap height 46 are defined by the trapezoid flanks of the barrier elements 40.

[0115] When using such high underpressure, avoidance of bubbles inside the gap 4 has been observed. This effect is most likely supported or due by a semi-permeable constitution or property of the flexible working film 19.

[0116] The liquid droplet 8-1′ has been moved over and/or around the barrier element 40 and comprises practically no magnetically responsive beads 11. A small liquid portion 8″ with substantially all beads is left behind on top of the magnetic conduit 9″.

[0117] It is to be noted that here, a movable permanent magnet 10′ is depicted. The permanent magnet 10′ is supported by a movable support 35. In this case, the support 35 is turnable around an axis (see dashed double arrow and chain dotted line). In order to move the permanent magnet away from and again to the magnetic conduit 9, also other sorts of movement, such as sliding or lifting are possible too.

[0118] FIG. 11 shows an inventive biplanar setup in a cross section view with a disposable cartridge 17 located at a cartridge accommodation site 18 of a PCB 3 of a digital microfluidics system 1. The microfluidics system 1 comprising two check valves 42 located between electrowetting electrodes 2. The location of one check valve close to one electrowetting electrode 2 would be sufficient for delivery of liquids, such as filler fluid, sample portions, reagents as well. The check valves 42 each are located in the PCB or first substrate 3 and in projection under (or opposite to) a pipetting guide 41 of the disposable cartridge 17.

[0119] The check valve 42 on the left is closed by pushing the valve ball 43 up by the valve spring 44. This pushing up lifts the flexible working film 19 and presses it against an opening of the pipetting guide 41 of the disposable cartridge 17 that is inserted in or attached to the ridge accommodation site 18 of a PCB 3 of a digital microfluidics system 1. In consequence, establishing an overpressure in the filler fluid inside of the working gap 4 is enabled.

[0120] The check valve 42 on the right is open by pressing a liquid (here a sample portion) via the sealing pipetting guide 41 into the working gap 4 of the disposable cartridge 17. The pipette tip 47 used (preferably a disposable polypropylene pipette tip) is pushed into the pipetting guide 41 such that its circumference is sealingly pressed against the pipetting guide 41. When doing this, the pipette tip 47 pushes about halfway down the working gap height 28 the valve ball 43 against the force of the valve spring 44. Liquid injection additionally moves the valve ball 43 against the force of the valve spring 44 and opens the check valve more. Such injecting of liquid portions gradually enhances the internal pressure inside of the working gap 4, whereupon the flexible working film 19 of the disposable cartridge 17 more evenly spreads on the uppermost surface 22 of the cartridge accommodation site 18 of the digital microfluidics system 1 and over said at least one barrier element 40.

[0121] The pipetting guides 41 may be sealed and blocked by pushing-in cones 48 of appropriate size and shape. However, these cones 48 shall not reach to the inside of the working gap 4. Alternatively, the pipetting guides 41 may be sealed with portions of liquid wax poured-in, which portions then solidify. For removing and disposing a disposable cartridge 17 equipped with pipetting guides 41 and with an overpressure inside the working gap 4, such blocking of all pipetting guides 41 is advisable for safety reasons. It is feasible that, when removing such a sealed disposable cartridge 17 from the cartridge accommodation site 18 of a digital microfluidics system 1, the overpressure previously applied to the working gap is balanced by the flexibility of the working film 19. This is even more so, if a number of barrier elements 40 have been placed on the uppermost surface 22 of that cartridge accommodation site 18.

[0122] It may be required to add underpressure to the working film 19 from the outside. For this purpose, it is preferred to additionally equip the digital microfluidics system 1 with a vacuum source 23 that is linked to the uppermost surface 22 of the that cartridge accommodation site 18 by vacuum lines 23′.

[0123] FIG. 12 shows a plane view of a linear array of operation electrodes 2 on a PCB 3 of a digital microfluidics system 1. A single magnetic conduit 9 is positioned on an activated backing magnet 10 (not shown) that is located below a central void 13 in the center of an electrowetting electrode 2 that belongs to a path 2′ of a liquid droplet 8-1′. Two barrier elements 40 according to a first embodiment of the current invention are at least partially located on two individual operation electrodes 2 adjacent to the electrode 2 with the magnetic conduit 9. The liquid droplet 8-1′ has been moved on the first hydrophobic surface 5 of the flexible working film 19 away from the electrode 2 with the magnetic conduit 9 and over a barrier element 40. Thus, the liquid droplet 8-1′ substantially comprises no magnetically responsive beads 11 leaving a small liquid portion 8″ with practically all beads 11 behind on top of the magnetic conduit 9. In this case, two rectangular barrier elements 40 with rectangular cross sections have been deposited to the uppermost surface 22 of the cartridge accommodation site 18.

[0124] FIG. 13 shows a plane view of a linear array of operation electrodes 2 on a PCB 3 of a digital microfluidics system 1. A single magnetic conduit 9 is located in neighboring notches 12 in-between two of narrowed electrowetting electrodes 2″. The electrodes 2,2″ define the path of electrodes 2′ selected for electrowetting. The magnetic conduit 9 is positioned on an activated backing magnet 10 (not shown). Two barrier elements 40 according to a second embodiment are at least partially located on two individual operation electrodes 2″ adjacent to the magnetic conduit 9. The liquid droplet 8-1′ is being moved on the first hydrophobic surface 5 of the flexible working film 19 away from the magnetic conduit 9 and over a barrier element 40. Thus, the liquid droplet 8-1′ substantially comprises no magnetically responsive beads and a small liquid portion 8″ with practically all beads is left behind on top of the magnetic conduit 9. In this case, two rectangular barrier elements 40 with trapezoid cross sections have been deposited to the uppermost surface 22 of the cartridge accommodation site 18.

[0125] FIG. 14 shows a plane view of a linear array of operation electrodes 2 on a PCB 3 of a digital microfluidics system 1. A single magnetic conduit 9 is located in a notch 12 at one side of one of the electrowetting electrodes 2 that define the electrowetting path 2′. The magnetic conduit 9 is positioned on an inactive backing magnet 10 (not shown). Two barrier elements 40 according to a third and fourth embodiment are at least partially located on two individual operation electrodes 2 adjacent to the narrowed electrode 2″ with the magnetic conduit 9 on which is the liquid droplet 8-1 that comprises all dispersed magnetically responsive beads 11. Moving on the first hydrophobic surface 5 of the flexible working film 19 back and fro over and/or around one or the other (or both) barrier elements 40 keeps the magnetically responsive beads 11 in suspension.

[0126] In this case on the left side, an angled barrier element 40 has been deposited to the uppermost surface 22 of the cartridge accommodation site 18; the broader, angled central part having a rectangular cross section and the smaller, angled extension parts having a square cross section.

[0127] In this case on the right side, two broad, angled barrier elements 40 have been deposited to the uppermost surface 22 of the cartridge accommodation site 18. Both broad, angled barrier elements 40 have a rectangular cross section and are not touching each other; thus, an open passage is left between them.

[0128] While the droplet 8-1 may be moved over the barrier element 40 on the left, it may be moved around (i.e. through the open passage between) the barrier elements 40 on the right.

[0129] FIG. 15 shows a plane view of a linear array of operation electrodes 2 on a PCB 3 of a digital microfluidics system 1. A single magnetic conduit 9 is located in a notch 12 at one side of one of a narrowed electrowetting electrode 2″ that defines the electrowetting path 2′. The magnetic conduit 9 is positioned on an activated backing magnet 10. Two barrier elements 40 according to a fifth and sixth embodiment are at least partially located on two individual operation electrodes 2 adjacent to the electrode 2″ with the magnetic conduit 9. The liquid droplet 8-1′ is being moved on the first hydrophobic surface 5 of the flexible working film 19 away from the magnetic conduit 9 and over a barrier element 40. In consequence, the liquid droplet 8-1′ substantially comprises no beads and a small liquid portion 8″ with practically all magnetically responsive beads 11 is left behind on top of the magnetic conduit 9.

[0130] In this case on the left side, an broad, angled barrier element 40 has been deposited to the uppermost surface 22 of the cartridge accommodation site 18; the broad, angled barrier element 40 having a trapezoid cross section over its entire length.

[0131] In this case on the right side, an angled barrier element 40 has been deposited to the uppermost surface 22 of the cartridge accommodation site 18. Two broad, angled parts of the barrier element 40 have a rectangular cross section and are connected to each other by a small, straight part of the barrier element 40 with a square cross section.

[0132] While the droplet 8-1 may be moved over the barrier element 40 on the left, it may partly be moved around and partly moved over the barrier element 40 on the right.

[0133] FIG. 16 shows a plane view of a linear array of operation electrodes 2 on a PCB 3 of a digital microfluidics system 1. Two types of electrodes 2 are shown, square and elongated ones. Between two of the elongated electrodes 2, a barrier element 40 is located to reach about the midst of the electrodes 2 and a large liquid portion 8-2 is moved on the first hydrophobic surface 5 of the flexible working film 19 back and through for re-suspension of magnetic beads 11 therein. The liquid portion 8-2 is deformed when passing the barrier element 40 (the dashed line is showing the normal shape and the full line is showing the deformed shape of the liquid portion 8-2). Such deformation introduces internal movement within the liquid portion 8-2 and increases effectiveness of suspending the beads 11. The large straight barrier element 40 preferably has a trapezoid cross section over its entire length. The liquid portion 8-2 is moved partly around and partly over the barrier element 40.

[0134] FIG. 17 shows a plane view of a linear array of elongated operation electrodes 2 on a PCB 3 of a digital microfluidics system 1. Two sets of barrier elements 40 are located between two of the elongated electrodes 2 in each case. The two sets of barrier elements 40 are located such that a large liquid portion 8-2 is deformed on one side more than on the other when passing the first set of barrier elements 40. The large liquid portion 8-2 is more deformed on the opposite side when passing the second set of barrier elements 40. Moving the large liquid portion 8-2 back and through both sets of barrier elements 40 provides accelerated re-suspension of magnetic beads 11. The large straight barrier elements 40 preferably have a trapezoid cross section over their entire length. The liquid portion 8-2 is moved partly around and partly over the barrier elements 40.

[0135] Preferably, an inventive digital microfluidics system 1 configured for substantially removing or suspending magnetically responsive beads from or in liquid portions or droplets comprises, [0136] (a) a number or array of individual electrodes 2 attached to a first substrate or PCB; [0137] (b) a central control unit 7 in operative contact with said individual electrodes 2 for controlling selection and for providing a number of said individual electrodes 2 that define a path of individual electrodes 2′ with voltage for manipulating liquid portions 8-2 or liquid droplets 8-1 by electrowetting; and [0138] (c) a cartridge accommodation site 18 that is configured for taking up a disposable cartridge 17 which comprises a first hydrophobic surface 5 that belongs to a flexible working film 19, a second hydrophobic surface 6 that belongs to a cover plate 20 of the disposable cartridge 17, and a working gap 4 that is located in-between the two hydrophobic surfaces 5,6; the flexible working film 19 comprising a backside 21 that, when the disposable cartridge 17 is accommodated on a cartridge accommodation site 18 of the digital microfluidics system 1, touches an uppermost surface 22 of the cartridge accommodation site 18 of the digital microfluidics system 1;
wherein the digital microfluidics system 1 further comprises at least one barrier element 40 positioned at least partially on an individual operating electrode 2 located at the cartridge accommodation site 18 of the PCB 3, the barrier element 40 narrowing the working gap 4 of a disposable cartridge 17 situated on a surface of said cartridge accommodation site 18.

[0139] Preferably, said least one barrier element 40 comprises a material chosen of a group of materials, said group comprising Kapton® tape, Teflon® sheets, solder mask and silk screen printing, and paper strips.

[0140] Preferably, said least one barrier element 40 has a thickness of 0.02 to 0.25 mm, a width of 0.4 to 1.0 mm, and a length of 3 to 5 mm.

[0141] Preferably, said least one barrier element 40 has a cross section in a trapezoid, rectangular, or square shape. Combinations of these shapes are possible and preferred too.

[0142] Preferably, in combination with a mixing zone of the electrode path 2′, one, two, or four barrier elements 40 are provided.

[0143] Preferably, in the first substrate or PCB 3 of the microfluidics system 1 and below said individual electrodes 2 there is located at least one magnetic conduit 9 that is backed by a backing magnet 10, said at least one magnetic conduit 9 being located in close proximity to individual electrodes 2.

[0144] Preferably, said at least one magnetic conduit 9 is located under and is covered by an individual electrode 2.

[0145] Preferably, said at least one magnetic conduit 9 is located beside of and is not covered by at least one individual electrode 2.

[0146] Preferably, said backing magnet 10 is configured as a moving permanent magnet 10′, a switchable permanent magnet 10″, or as an electromagnet 10′″.

[0147] Preferably, in combination with a magnetic conduit 9 and a backing magnet 10, one or two barrier elements 40 are provided.

[0148] Preferably, the digital microfluidics system 1 comprises a vacuum source 23 for establishing an underpressure in an evacuation space 24 between the uppermost surface 22 of the cartridge accommodation site 18 and the backside 21 of the flexible working film 19 of the disposable cartridge 17.

[0149] Preferably, the cartridge accommodation site 18 of the digital microfluidics system 1 comprises at least one check valve 42 configured to sealingly close the working gap 4 and to enable an overpressure in a filler fluid or other fluid inside said working gap 4.

[0150] Preferably, the cartridge accommodation site 18 of the digital microfluidics system 1 comprises a pressure sensor for measuring the actual underpressure between the uppermost surface 22 of the cartridge accommodation site 18 and the flexible working film 19 of the disposable cartridge 17. If an underpressure is to be established, a pressure of −2 psi to −6 psi i.e. 875 to 600 mbar is preferred.

[0151] Preferably, the cartridge accommodation site 18 of the digital microfluidics system 1 comprises a pressure sensor for measuring the actual overpressure between the uppermost surface 22 of the cartridge accommodation site 18 and the flexible working film 19 of the disposable cartridge 17.

[0152] It is evident from this description that the liquid droplets 8-1,8-1′ or liquid portions 8-2,8-2′ with or without magnetically responsive beads 11 in each case may also be moved from the right to the left of the shown electrode paths 2′. It is further evident from this description that such movements can also be directed in any other direction of an electrode array. Moreover, inverse movements and inverse actions on the removal of magnetically responsive beads 11 from liquid droplets 8-1 or liquid portions 8-2 as well as on the suspension of magnetically responsive beads 11 within liquid droplets 8-1′ or liquid portions 8-2′ are disclosed and evident from the present description and drawings.

[0153] In general, the magnetic conduits 9,9′,9″ according to the present invention preferably consist of or comprises material with the potential for a high degree of magnetization. The type of material that can be a ferromagnetic element (iron, nickel, cobalt) or an alloy (permalloy, Kovar, mu-metal, stainless-steel 410). The magnetic conduits 9 according to the present invention may comprise a single solid ferromagnetic element, or of a multitude of randomly orientated ferromagnetic elements (e.g. metallic shavings, preferably iron shavings), or of an amorphous paste filled with ferromagnetic material (e.g. magnetic epoxy). Preferably, the ferromagnetic material is kept inside a magnetic conduit 9 with epoxy or with a tape at the bottom of the magnetic conduit 9 or of the PCB 3.

[0154] In general, the magnetic conduits 9 according to the present invention can be located in a through hole or in a blind hole. Blind holes provide less magnetic coupling than the through holes. Both allow the use of vertical electrical vias in the PCB 3.

[0155] The blind holes allow better electrical insulation and pressure difference between the uppermost surface 22 of the cartridge accommodation site 18 or PCB 3 and the bottom surface of the PCB or first substrate 3. Typically but not exclusively, the voltage in a digital microfluidics system 1 is applied in pulses to one or more selected electrodes 2′ that define one or more paths for one or more liquid portions 8-2 or liquid droplets 8-1 (see for example US 2013/0134040 A1 and US 2013/0175169 A1, herein incorporated by reference in their entirety).

[0156] Preferably and in general, the backing magnet 10 is configured as a permanent magnet 10′, or as a switchable permanent magnet 10″, or as an electromagnet 10′″. Most preferred are permanent magnets 10′ or switchable permanent magnets 10″. Such backing magnets 10 may be activated by a selection of the following alternatives: [0157] a) Moving a permanent magnet 10′ to the backside of the at least one specific magnetic conduit 9. Such moving a permanent magnet 10′ may be carried out e.g. by lifting, or by swinging, or by rotating the permanent magnet 10′ until its magnetic field is aligned with the at least one specific magnetic conduit 9. Means for enabling such moving a permanent magnet 10′ to the backside of the at least one specific magnetic conduit 9 may be conceived by a person of average skill in the art. Such means preferably comprise a support 35 for holding at least one backing magnet 10. [0158] b) Switching on a switchable permanent magnet 10″ that is located at the backside of the at least one specific magnetic conduit 9. Such switching on a switchable permanent magnet 10″ may be carried out e.g. by turning a permanent magnet into an “ON” position of a magnetic base 29 or by switching off an electromagnet 33 that is compensating the magnetic field of a PE-mag-net 32. A particularly preferred PE-magnet is the ITS-PE 1212—24 VDC-TEC of M RED MAGNETICS® (Intertec Components GmbH, 85356 Freising, Germany). [0159] c) Energizing an electromagnet 10′″ that is located at the backside of the at least one specific magnetic conduit 9.

[0160] It is noted expressly that all features in the shown and described embodiments that appear reasonable to a person of skill may be combined with each and every one of these features. Especially preferred materials and dimensions are disclosed in Table 1 below: Cytop is an amorphous fluoropolymer with high optical transparency (AGC Chemicals Europe). Mylar®, Neoprene®, Teflon®, and Viton® are Trademarks of DuPont, Wilmington, USA.

[0161] Preferably, the magnetic conduits 9 are in physical contact or in close proximity to the backing magnet 10 when the magnetic force is enabled. Preferred distances (if there are some) range from 1 μm to 1 mm, more preferably from 1 μm to 100 μm.

[0162] In some embodiments, the permanent magnet height is 5 mm-20 mm, preferably 10 mm-15 mm with a diameter of preferably 3 mm-7 mm. If a single, large permanent magnet is used, the magnet length can be 30-100 mm, preferably 50 mm-70 mm. The magnetic force generated on a single 1-μm-diameter magnetic bead is 100 fN-10 pN, preferably 500 fN-2 pN.

[0163] Even if not particularly described in each case, the reference numbers refer to similar elements of the digital microfluidics system 1 and in particular of the disposable cartridge 17 of the present invention. All drawings are schematic and not to scale.

TABLE-US-00001 TABLE 1 Part No Material Dimension and Shape Liquid portion or droplet 8 Aqueous, alcohol Volume: 0.1-25 μl First Substrate 3 PCB; synth. Polymer; Cu Thickness about 1.6 mm Electrodes 2 Al; Cu; Au; Pt Plating, preferably: 1.375 mm × 1.375 mm Working film 19 Fluorinated ethylene Foil: 8-50 μm propylene (FEP), Cyclo olefin polymer (COP), Polypropylene (PP) 1.sup.st hydrophobic surface 5 COP, FEP, PP Foil: 8-50 μm Second substrate or 36 Mylar ®; acrylic; Plate: 0.5-10.0 mm; Cover plate 20 Polypropylene (PP) preferably 1.5 mm 2.sup.nd hydrophobic surface 6 Teflon ® (PTFE), amor- Spin coating: 5-500 nm; phous fluoropolymer preferably 20 nm Gap height 28 — 0.3-2.0 mm; preferably 0.5 mm Pipetting orifice — — Diameter: 0.3-3.0 mm Body — Mylar ®; acrylic; 127 x 85 mm; Polypropylene (PP) 6-25 mm Magnetic conduit 9 Cylindrical preferred Diameter up to 3 mm Gasket 27 Synthetic or natural rubber Frame: 0.2-2.0 mm; preferably 0.5 mm Seal — Viton ®; Neoprene ® O-ring ∅ 3.0 mm Insertion guide — Al; Al/Mg; steel; Frame: 5-30 mm Teflon ® (PTFE) Dielectric layer — Fluorinated ethylene Foil or casting: propylene (FEP) 20-100 μm Hydrophobic layer — FEP; PTFE; Teflon ® AF; 2-200 nm Cytop; Cytonix Filler fluid; Oil — Silicone Volume: 1-5 ml Underpressure (−2psi to −6psi) 875 to 600 mbar Electrically conductive — Au, Pt, ITO, PP, PA Layer: 20-100 μm; material preferably 50 μm Barrier element 40 Kapton ® tape, Thickness: Teflon® sheets, 0.02-0.25 mm solder mask and silk Size: screen printing, (0.4-1.0 mm)(3-5 mm) paper strips Cross section: square, rectangular, trapezoid

REFERENCE NUMBERS

[0164]

TABLE-US-00002 1 digital microfluidics system 10′′′ electromagnet 2 individual (operating, 11 magnetically responsive beads electrowetting) electrode 12 neighboring notches, notch 2′ path of selected (operating, 13 central void electrowetting) electrodes, 14 space droplet path, electrode path 17 disposable cartridge 2″ narrowed individual (operating, 18 cartridge accommodation site electrowetting) electrode 19 flexible working film 3 first substrate or PCB 19′ working film 4 working gap 20 cover plate 5 first hydrophobic surface 21 backside of 19, 19′ 6 second hydrophobic surface 22 uppermost surface of 18 7 central control unit 23 vacuum source 8-1 liquid droplet 23′ vacuum line with magnetic beads 24 evacuation space 8-1′ liquid droplet 25 cooperating magnetic conduit without magnetic beads 26 cooperating magnet 8-2 liquid portion 27 gasket with magnetic beads 28 height of 4 8-2′ liquid portion without magnetic beads 35 support for 10 8″ small liquid portion with magnetic beads 40 barrier (obstacle) element 9 magnetic conduit 41 sealing pipetting guide 9′ cuboid, cylindrical 42 check valve magnetic conduit 43 valve ball 9″ pyramidal, frustoconical 44 valve spring magnetic conduit 46 narrowed gap height 10 backing magnet; magnet 47 pipette tip 10′ movable permanent magnet 48 cone 10″ switchable permanent magnet

[0165] For completeness, the following contains the subject matter of the claims as originally filed as numbered examples. [0166] 1. A method of substantially removing magnetically responsive beads from liquid portions or droplets in digital microfluidics, wherein the method comprises the steps of: [0167] a) providing a digital microfluidics system (1) comprising: [0168] a number or array of individual electrodes (2) attached to a first substrate or PCB (3); [0169] a central control unit (7) in operative contact with said individual electrodes (2) for controlling selection and for providing a number of said individual electrodes (2) that define a path of individual electrodes (2′) with voltage for manipulating liquid portions (8-2) or liquid droplets (8-1) by electrowetting; [0170] a cartridge accommodation site (18) that is configured for taking up a disposable cartridge (17) which comprises a first hydrophobic surface (5) that belongs to a flexible working film (19), a second hydrophobic surface (6) that belongs to a cover plate (20) of the disposable cartridge (17), and a working gap (4) that is located in-between the two hydrophobic surfaces (5,6); and [0171] at least one magnetic conduit (9) located in the first substrate or PCB (3) of the microfluidics system (1) and below said individual electrodes (2), said at least one magnetic conduit (9) being backed by a backing magnet (10) with a magnetic field, being configured for directing said magnetic field through the magnetic conduit (9) to the first hydrophobic surface (5) on said individual electrodes (2), and being located in close proximity to individual electrodes (2); [0172] b) providing at least one barrier element (40) and positioning said barrier element (40) at least partially on an individual operating electrode (2) located at the cartridge accommodation site (18) of the PCB (3), the barrier element (40) narrowing the working gap (4) of a disposable cartridge (17) situated on a surface of said cartridge accommodation site (18); [0173] c) providing a disposable cartridge (17) and positioning said disposable cartridge (17) at a cartridge accommodation site (18) of said digital microfluidics system (1); the flexible working film (19) comprising a backside (21) that, when the disposable cartridge (17) is accommodated on said cartridge accommodation site (18), touches an uppermost surface (22) of the cartridge accommodation site (18) of the digital microfluidics system (1) and of said at least one barrier element (40); [0174] d) providing on the hydrophobic surface (5) and above a path of selected electrodes (2′) at least one liquid portion (8-2) or liquid droplet (8-1) that comprises magnetically responsive beads (11); [0175] e) moving by electrowetting said at least one liquid portion (8-2) or liquid droplet (8-1) with the magnetically responsive beads (11) on said path of selected electrodes (2′) until said magnetic field of the at least one magnetic conduit (9) backed by a backing magnet (10) is reached; and [0176] f) activating said backing magnet (10) before and during moving by electrowetting said at least one liquid portion (8-2) or liquid droplet (8-1) with the magnetically responsive beads (11) on said path of selected electrodes (2′) and over and/or around said at least one barrier element (40), thereby attracting and substantially removing magnetically responsive beads (11) from said liquid portion (8-2) or liquid droplet (8-1). [0177] 2. The removing method of example 1, [0178] wherein using a vacuum source (23) of the digital microfluidics system (1), an underpressure is established in an evacuation space (24) between the uppermost surface (22) of the cartridge accommodation site (18) and the backside (21) of the flexible working film (19) of the disposable cartridge (17), whereupon the flexible working film (19) of the disposable cartridge (17) spreads on the uppermost surface (22) of the cartridge accommodation site (18) of the digital microfluidics system (1) and over said at least one barrier element (40). [0179] 3. The removing method of example 1, [0180] wherein using a filler-fluid or other fluid, an overpressure is established within the working gap (4) of the disposable cartridge (17), whereupon the flexible working film (19) of the disposable cartridge (17) spreads on the uppermost surface (22) of the cartridge accommodation site (18) of the digital microfluidics system (1) and over said at least one barrier element (40). [0181] 4. The removing method of example 2 or 3, [0182] wherein the cover plate (20) of the disposable cartridge (17) is configured as a rigid cover plate, evenly defining a top of said working gap (4). [0183] 5. The removing method of example 1, [0184] wherein said at least one magnetic conduit (9) consists of a single solid ferromagnetic element, or of a multitude of randomly orientated ferromagnetic elements, or of an amorphous paste filled with ferromagnetic material. [0185] 6. The removing method of example 5, [0186] wherein said at least one magnetic conduit (9) is located under and is covered by an individual electrode (2). [0187] 7. The removing method of example 5, [0188] wherein said at least one magnetic conduit (9) is located beside of and is not covered by at least one individual electrode (2). [0189] 8. The removing method of one of the examples 5 to 7, [0190] wherein said backing magnet (10) is used to operatively back at least one magnetic conduit (9) and is configured as a permanent magnet (10′), or as a switchable permanent magnet (10″), or as an electromagnet (10′″). [0191] 9. The removing method of example 8, [0192] wherein actuating said backing magnet (10) is achieved by: [0193] a) moving a permanent magnet (10′) to a backside of the at least one magnetic conduit (9); or [0194] b) switching-on a switchable permanent magnet (10″) that is located at the backside of the at least one magnetic conduit (9); or [0195] c) energizing an electromagnet (10′) that is located at the backside of the at least one magnetic conduit (9). [0196] 10. The removing method of example 9, [0197] wherein switching-on a switchable permanent magnet (10″) is carried out by switching-off an electromagnet (33) that is compensating the magnetic field of a PE-magnet (32). [0198] 11. The removing method of one of the examples 1 to 10, [0199] wherein said at least one magnetic conduit (9) is a cylindrical, cuboid, pyramidal, frustoconical, conical, or magnetic conduit (9′,9″) located in a blind hole (15) or in a through hole (16) in the first substrate (3) of the digital microfluidics system (1). [0200] 12. The removing method of examples 1 or 2, [0201] wherein the cartridge accommodation site (18) of the digital microfluidics system (1) or the disposable cartridge (17) comprise a gasket (27), using which said evacuation space (24) is sealingly enclosed and a height (28) of the working gap (4) between said hydrophobic surfaces (5,6) of the disposable cartridge (17) is defined. [0202] 13. The removing method of examples 1 or 3, [0203] wherein the cartridge accommodation site (18) of the digital microfluidics system (1) comprises at least one check valve (42), using which said working gap is sealingly closed and an overpressure produced by a filler fluid or other fluid inside said working gap is enabled. [0204] 14. A method of substantially suspending magnetically responsive beads in liquid portions or droplets in digital microfluidics, [0205] wherein the method comprises the steps of: [0206] a) providing a digital microfluidics system (1) comprising: [0207] a number or array of individual electrodes (2) attached to a first substrate or PCB (3), [0208] a central control unit (7) in operative contact with said individual electrodes (2) for controlling selection and for providing a number of said individual electrodes (2) that define a path of individual electrodes (2′) with voltage for manipulating liquid portions (8-2) or liquid droplets (8-1) by electrowetting; and [0209] a cartridge accommodation site (18) that is configured for taking up a disposable cartridge (17) which comprises a first hydrophobic surface (5) that belongs to a flexible working film (19), a second hydrophobic surface (6) that belongs to a cover plate (20) of the disposable cartridge (17), and a working gap (4) that is located in-between the two hydrophobic surfaces (5,6); [0210] b) providing at least one barrier element (40) and positioning said barrier element (40) at least partially on an individual operating electrode (2) located at the cartridge accommodation site (18) of the PCB (3), the barrier element (40) narrowing the working gap (4) of a disposable cartridge (17) situated on a surface of said cartridge accommodation site (18); [0211] c) providing a disposable cartridge (17) and positioning said disposable cartridge (17) at a cartridge accommodation site (18) of said digital microfluidics system (1); the flexible working film (19) comprising a backside (21) that, when the disposable cartridge (17) is accommodated on said cartridge accommodation site (18), touches an uppermost surface (22) of the cartridge accommodation site (18) of the digital microfluidics system (1) and of said at least one barrier element (40); [0212] d) providing on the hydrophobic surface (5) and above a path of selected electrodes (2′) at least one liquid portion (8-2′) or liquid droplet (8-1′) that lacks magnetically responsive beads (11); [0213] e) moving by electrowetting said at least one liquid portion (8-2′) or liquid droplet (8-1′) without magnetically responsive beads (11) on said path of selected electrodes (2′) until said liquid portion (8-2′) or liquid droplet (8-1′) is merged with a small droplet that contains concentrated magnetically responsive beads, thus a merged droplet is created; and [0214] f) moving at least once by electrowetting the merged droplet with magnetically responsive beads over and/or around said at least one barrier element (40) and thereby re-suspending the magnetically responsive beads in the merged droplet. [0215] 15. A method of keeping suspended or re-suspending magnetically responsive beads in liquid portions or droplets in digital microfluidics, [0216] wherein the method comprises the steps of: [0217] a) providing a digital microfluidics system (1) comprising: [0218] a number or array of individual electrodes (2) attached to a first substrate or PCB (3), [0219] a central control unit (7) in operative contact with said individual electrodes (2) for controlling selection and for providing a number of said individual electrodes (2) that define a path of individual electrodes (2′) with voltage for manipulating liquid portions (8-2) or liquid droplets (8-1) by electrowetting; and [0220] a cartridge accommodation site (18) that is configured for taking up a disposable cartridge (17) which comprises a first hydrophobic surface (5) that belongs to a flexible working film (19), a second hydrophobic surface (6) that belongs to a cover plate (20) of the disposable cartridge (17), and a working gap (4) that is located in-between the two hydrophobic surfaces (5,6); [0221] b) providing at least one barrier element (40) and positioning said barrier element (40) at least partially on an individual operating electrode (2) located at the cartridge accommodation site (18) of the PCB (3), the barrier element (40) narrowing the working gap (4) of a disposable cartridge (17) situated on a surface of said cartridge accommodation site (18); [0222] c) providing a disposable cartridge (17) and positioning said disposable cartridge (17) at a cartridge accommodation site (18) of said digital microfluidics system (1); the flexible working film (19) comprising a backside (21) that, when the disposable cartridge (17) is accommodated on said cartridge accommodation site (18), touches an uppermost surface (22) of the cartridge accommodation site (18) of the digital microfluidics system (1) and of said at least one barrier element (40); [0223] d) providing on the hydrophobic surface (5) and above a path of selected electrodes (2′) at least one liquid portion (8-2) or liquid droplet (8-1) containing magnetically responsive beads (11); [0224] e) moving by electrowetting said at least one liquid portion (8-2) or liquid droplet (8-1) containing magnetically responsive beads (11) on said path of selected electrodes (2′) at least once over and/or around said at least one barrier element (40) and thereby keeping suspended or re-suspending the magnetically responsive beads (11) in said liquid portion (8-2) or liquid droplet (8-1). [0225] 16. The method of example 14 or 15, [0226] wherein for spreading of the flexible working film (19) of the disposable cartridge (17) on the uppermost surface (22) of the cartridge accommodation site (18) of the digital microfluidics system (1) and over said at least one barrier element (40): [0227] an underpressure is established between the uppermost surface (22) of the cartridge accommodation site (18) and the backside (21) of the flexible working film (19) of the disposable cartridge (17), using a vacuum source (23) of the digital microfluidics system (1); or [0228] an overpressure is established within the working gap (4) of the disposable cartridge (17), using a filler-fluid or other fluid. [0229] 17. The method of example 16, [0230] wherein the cover plate (20) of the disposable cartridge (17) is configured as a rigid cover plate, evenly defining a top of said working gap (4). [0231] 18. The suspending method of example 14, [0232] wherein in the first substrate or PCB (3) of the microfluidics system (1) and below said individual electrodes (2) there is provided at least one magnetic conduit (9) being backed by a backing magnet (10) with a magnetic field, and being configured for directing said magnetic field through the magnetic conduit (9) to the first hydrophobic surface (5) on said individual electrodes (2), said at least one magnetic conduit (9) being located in close proximity to individual electrodes (2), [0233] and wherein said backing magnet is de-activated before and during moving by electrowetting said at least one liquid portion (8-2′) or liquid droplet (8-1′) without magnetically responsive beads (11) on said path of selected electrodes (2′) until said liquid portion (8-2′) or liquid droplet (8-1′) is merged with a small droplet that contains concentrated magnetically responsive beads and a merged droplet is created. [0234] 19. The suspending method of example 18, [0235] wherein de-actuating said backing magnet (10) is achieved by: [0236] a) moving a permanent magnet (10′) away from a backside of the at least one magnetic conduit (9); or [0237] b) switching-off a switchable permanent magnet (10″) that is located at the backside of the at least one magnetic conduit (9); or [0238] c) de-energizing an electromagnet that is located at the backside of the at least one magnetic conduit (9). [0239] 20. The suspending method of example 19, [0240] wherein switching-off a switchable permanent magnet (10″) is carried out by switching-on an electromagnet (33) to compensate the magnetic field of a PE-magnet (32). [0241] 21. A digital microfluidics system configured for substantially removing or suspending magnetically responsive beads from or in liquid portions or droplets, [0242] wherein the digital microfluidics system (1) comprises: [0243] (a) a number or array of individual electrodes (2) attached to a first substrate or PCB (3); [0244] (b) a central control unit (7) in operative contact with said individual electrodes (2) for controlling selection and for providing a number of said individual electrodes (2) that define a path of individual electrodes (2′) with voltage for manipulating liquid portions (8-2) or liquid droplets (8-1) by electrowetting; and [0245] (c) a cartridge accommodation site (18) that is configured for taking up a disposable cartridge (17) which comprises a first hydrophobic surface (5) that belongs to a flexible working film (19), a second hydrophobic surface (6) that belongs to a cover plate (20) of the disposable cartridge (17), and a working gap (4) that is located in-between the two hydrophobic surfaces (5,6); the flexible working film (19) comprising a backside (21) that, when the disposable cartridge (17) is accommodated on a cartridge accommodation site (18) of the digital microfluidics system (1), touches an uppermost surface (22) of the cartridge accommodation site (18) of the digital microfluidics system (1); [0246] wherein the digital microfluidics system (1) further comprises at least one barrier element (40) positioned at least partially on an individual operating electrode (2) located at the cartridge accommodation site (18) of the PCB (3), the barrier element (40) narrowing the working gap (4) of a disposable cartridge (17) situated on a surface of said cartridge accommodation site (18). [0247] 22. The digital microfluidics system (1) of example 21, [0248] wherein said least one barrier element (40) comprises a material chosen of a group of materials, said group comprising Kapton tape, Teflon sheets, solder mask and silk screen printing, and paper strips. [0249] 23. The digital microfluidics system (1) of example 21, [0250] wherein said least one barrier element (40) has a thickness of 0.02 to 0.25 mm, a width of 0.4 to 1.0 mm, and a length of 3 to 5 mm. [0251] 24. The digital microfluidics system (1) of example 21, [0252] wherein said least one barrier element (40) has a cross section in a trapezoid, rectangular, or square shape. [0253] 25. The digital microfluidics system (1) of example 21, [0254] wherein in combination with a mixing zone of the electrode path (2′), one, two, or four barrier elements (40) are provided. [0255] 26. The digital microfluidics system (1) of one of the examples 21 to 25, [0256] wherein in the first substrate or PCB (3) of the microfluidics system (1) and below said individual electrodes (2) there is located at least one magnetic conduit (9) that is backed by a backing magnet (10), said at least one magnetic conduit (9) being located in close proximity to individual electrodes (2). [0257] 27. The digital microfluidics system (1) of example 26, [0258] wherein said at least one magnetic conduit (9) is located under and is covered by an individual electrode (2). [0259] 28. The digital microfluidics system (1) of example 27, [0260] wherein said at least one magnetic conduit (9) is located beside of and is not covered by at least one individual electrode (2). [0261] 29. The digital microfluidics system (1) of one of the examples 26 to 28, [0262] wherein said backing magnet (10) is configured as a moving permanent magnet (10′), a switchable permanent magnet (10″), or as an electromagnet (10′″). [0263] 30. The digital microfluidics system (1) of one of the examples 26 to 29, [0264] wherein in combination with a magnetic conduit (9) and a backing magnet (10), one or two barrier elements (40) are provided. [0265] 31. The digital microfluidics system (1) of one of the examples 21 to 30, [0266] wherein the digital microfluidics system (1) comprises a vacuum source (23) for establishing an underpressure in an evacuation space (24) between the uppermost surface (22) of the cartridge accommodation site (18) and the backside (21) of the flexible working film (19) of the disposable cartridge (17). [0267] 32. The digital microfluidics system (1) of one of the examples 21 to 30, [0268] wherein the cartridge accommodation site (18) of the digital microfluidics system (1) comprises at least one check valve (42) configured to sealingly close the working gap (4) and to enable an overpressure in a filler fluid or other fluid inside said working gap (4). [0269] 33. The digital microfluidics system (1) of one of the examples 31 or 32, [0270] wherein the cartridge accommodation site (18) of the digital microfluidics system (1) comprises at least one pressure sensor for measuring the actual underpressure and/or overpressure between the uppermost surface (22) of the cartridge accommodation site (18) and the flexible working film (19) of the disposable cartridge (17). [0271] 34. A disposable cartridge (17) configured to be positioned at a cartridge accommodation site (18) of a digital microfluidics system (1) according to example 31, [0272] wherein the disposable cartridge (17) comprises a rigid cover plate (20), [0273] and wherein the flexible working film (19) of the disposable cartridge (17) is configured to spread on the uppermost surface (22) of the cartridge accommodation site (18) of the digital microfluidics system (1) by an underpressure produced in the evacuation space (24) that is produced by a vacuum source (23) of the digital microfluidics system (1). [0274] 35. A disposable cartridge (17) configured to be positioned at a cartridge accommodation site (18) of a digital microfluidics system (1) according to example 32, [0275] wherein the disposable cartridge (17) comprises a rigid cover plate (20) and at least one sealing pipetting guide (41), [0276] and wherein the flexible working film (19) of the disposable cartridge (17) is configured to spread on the uppermost surface (22) of the cartridge accommodation site (18) of the digital microfluidics system (1) by an overpressure produced in the working gap (4) of the disposable cartridge (17). [0277] 36. The disposable cartridge (17) of example 31 or 32, [0278] wherein the disposable cartridge (17) or the cartridge accommodation site (18) of the digital microfluidics system (1) comprise a gasket (27) that defines a height (28) of the working gap (4) between said hydrophobic surfaces (5,6) of the disposable cartridge (17).