Sample applicator for point of care device

Abstract

The invention relates to a microfluidic system for processing biological samples comprising a transfer pipette; a platform adapted to provide at least one receiving chamber and configured to receive said transfer pipette, and a distal output chamber wherein a biological sample from the transfer pipette is dispensed into the output chamber when a centrifugal force is applied.

Claims

1. A microfluidic system for processing a sample, the system comprising: a transfer capillary pipette comprising a sample transfer body adapted to contain the sample, said sample transfer body having a first end and a second end; and a cartridge defining a linear receiving chamber having a first end and a second end, and an output chamber connected to the first end of the linear receiving chamber, said linear receiving chamber configured to receive said sample transfer body, wherein said first end of said sample transfer body is positioned in said output chamber when the sample transfer body is positioned within said linear receiving chamber, wherein said cartridge is configured to rotate about a center of rotation, wherein said linear receiving chamber is positioned non-radially with respect to said center of rotation of said cartridge, and wherein said output chamber is positioned closer to said center of rotation of said cartridge than said second end of said linear receiving chamber is positioned to the center of rotation of said cartridge.

2. The microfluidic system as claimed in claim 1 wherein the transfer capillary pipette comprises a fluidic barrier such that when in use the distance from the fluid barrier to a leading meniscus of said sample is greater than the distance from the fluid barrier to the trailing meniscus of said sample within the said transfer capillary pipette.

3. The microfluidic system as claimed in claim 2 wherein the fluidic barrier within the transfer capillary pipette is adapted to prevent the escape of the sample through the air vent of the transfer capillary pipette.

4. A method of processing samples in a microfluidic system as claimed in claim 1 said method comprising the steps of: providing a cartridge comprising a linear receiving chamber, the linear receiving chamber having a first end and a second end, wherein an output chamber is connected to the first end of the linear receiving chamber; coupling a transfer capillary pipette to the cartridge by inserting a sample transfer body of said transfer pipette to the linear receiving chamber of said cartridge, and wherein the sample transfer body comprises a first end and a second end, the first end of the sample transfer body positioned in said output chamber when the sample transfer body is inserted into the linear receiving chamber; and rotating the cartridge about a center of rotation such that the sample from the transfer capillary pipette is dispensed into an output chamber of the cartridge.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be more clearly understood from the following description of an embodiment thereof, given by way of example only, with reference to the accompanying drawings, in which:

(2) FIG. 1 illustrates a transfer pipette inserted into a receiving chamber of a centrifugal cartridge according to one embodiment of the invention;

(3) FIG. 2 illustrates a whole blood sample from a lanced finger being applied to the removed transfer pipette according to one embodiment of the invention; and

(4) FIG. 3 illustrates schematically the transfer pipette and disc structures which provide the mechanism to dispense the applied sample into an integrated output chamber.

DETAILED DESCRIPTION OF THE INVENTION

(5) Herein is described a sample application method comprising a transfer pipette wherein a sample is applied to same through capillary action, said pipette is inserted into a receiving chamber on a centrifugal cartridge, with the pipette designed to ensure the sample is dispensed into an integrated output chamber.

(6) FIG. 1 illustrates a high-level sample applicator and cartridge construction comprising a centrifugal microfluidic cartridge 101 with centre 102, which is coupled to a rotary motor (not shown), and circumference 103 drawn with two segments removed, according to one embodiment of the invention. The sample applicator comprises a transfer pipette with handle 104 attached to its sample transfer body 105. FIG. 1 illustrates the transfer pipette inserted within the cartridge, without a sample applied. Later illustrations describe geometrical relationships and the function of the integrated output chamber 106 with an outlet channel 107. An air vent 108 in the transfer pipette's handle, enables air displacement within the transfer pipette to allow sample application and dispensing, through capillary and centrifugal forces, respectively. A fluidic barrier 109 minimises the leakage of applied sample to the outside environment

(7) FIG. 2 illustrates a typical protocol by which the sample is first applied to the transfer pipette and further details the high-level cartridge structures. Herein is shown a cartridge 201 comprising a centre 202, which is coupled to a rotary motor (not shown), and output chamber 203 with associated outlet channel 204, as already shown in FIG. 1. The transfer pipette 205 is removed from the cartridge, thereby showing the receiving chamber 206 on the cartridge, connected to the output chamber which is distal from the receiving chamber. The air vent 207 within the transfer pipette and associated fluidic barrier 208 are as previously described. The figure illustrates the use case for a finger-prick of whole blood, whereby a finger 209 upon being lanced, using a procedure known to those skilled in the art, produces a whole blood sample 210 on the surface of the finger. It will be appreciated that the transfer pipette can receive a sample by any contact with the sample and not necessarily from the surface of the finger. Upon contact with the transfer pipette, the blood sample begins to fill by capillary action towards the pipette head up to a point which shall be defined as the trailing sample meniscus 211.

(8) FIG. 3 illustrates the detailed workings of this invention. As before, the cartridge 301 comprises centre 302, which is coupled to a rotary motor (not shown). The transfer pipette 303 is re-inserted into the cartridge via the receiving chamber previously illustrated in FIG. 2. A first notional centreline 1 is shown intersecting the cartridge centre and scribed perpendicular to the receiving chamber. A second notional centreline 2 is shown perpendicular to 1 and projects along the centre axis of the transfer pipette. The transfer pipette is shown with applied sample 304 filled between the trailing sample meniscus 305 and leading sample meniscus 306 at the pipette's tip. The radial distance from the cartridge centre to the trailing sample meniscus is noted as r1; the radial distance from the cartridge centre to the leading sample meniscus is noted as r2; and the distance between the leading and trailing menisci is noted as y, which may be described as the approximate height of the applied sample within the transfer pipette. In other words the radial distance of the sample meniscus 305 proximate to the pipette tip should be larger than the radial distance of the sample meniscus 306 distal from the tip.

(9) The output chamber 307 is arranged to be distal from the leading sample meniscus. Subsequent sample processing elsewhere in the cartridge may occur through methods and structures connected to the outlet channel 308.

(10) In operation the transfer pipette is designed such that capillary forces retain the sample, unless a pressure is applied to overcome them. When a rotational velocity is applied by the rotary motor to generate a centrifugal force, the net flow of sample in a centrifugal microfluidic cartridge structure will always be radially outwards, i.e. from a proximal radius towards a distal radius. Therefore, once a rotational velocity is applied to generate a centrifugal force greater than the capillary forces at the pipette's tip, the sample will dispense into the distal output chamber, enabled by air displacement through the air vent 309, once the condition r.sub.2>r.sub.1 is maintained. To maintain the relationship, r.sub.2>r.sub.1, the height of the applied sample within the transfer pipette, y, should not exceed two times x (2), where 2 is defined by mirroring x around 1, always noting that 1 is perpendicular to the receiving chamber. A fluidic barrier 310 can be used to minimise the risk of applied sample dispensing into the outside environment prior to application of centrifugal force through the rotary motor's rotation, or otherwise, and can also be positioned to ensure y<2, by design.

(11) In practice, the aforementioned parameters are dimensioned such that once sufficient centrifugal force is applied to overcome the capillary forces at the tip of the transfer pipette, the sample is dispensed into the more distal output chamber. To avoid inadvertent movement, or removal, of the transfer pipette upon generation of centrifugal force by the rotation of the rotary motor, a single-use locking mechanism 311 may be used, or design variants of same.

(12) The embodiments in the invention described with reference to the drawings may comprise a computer apparatus and/or processes performed in a computer apparatus.

(13) However, the invention also extends to computer programs, particularly computer programs stored on or in a carrier adapted to bring the invention into practice. The program may be in the form of source code, object code, or a code intermediate source and object code, such as in partially compiled form or in any other form suitable for use in the implementation of the method according to the invention. The carrier may comprise a storage medium such as ROM, e.g. CD ROM, or magnetic recording medium, e.g. a floppy disk or hard disk. The carrier may be an electrical or optical signal which may be transmitted via an electrical or an optical cable or by radio or other means.

(14) In the specification the terms comprise, comprises, comprised and comprising or any variation thereof and the terms include, includes, included and including or any variation thereof are considered to be totally interchangeable and they should all be afforded the widest possible interpretation and vice versa.

(15) The invention is not limited to the embodiments hereinbefore described but may be varied in both construction and detail.