Device having a micro fluid actuator

Abstract

The invention relates to a device having an opening defining a fluid connection between a fluid channel in the device and ambient air, a sensor coupled to the fluid channel, configured to sense at least one component of the ambient air, and a micro fluid actuator connected downstream of the sensor, configured, in the suction stroke, to suck in fluid through the fluid channel and to transport the same towards the sensor, and, in the pressure stroke, to transport the sucked-in fluid through said fluid channel back towards the opening. According to the invention, the sensor is arranged spaced apart from the opening, and the volume of the fluid channel between the sensor and the opening is equal to or smaller than the stroke volume which the micro fluid actuator may convey with a single suction stroke.

Claims

1. Device comprising: a housing with a housing opening defining a fluid connection between a fluid channel in the device and ambient air, a sensor coupled to the fluid channel and disposed in the housing, configured to sense at least one component of the ambient air, a micro fluid actuator arranged downstream of the sensor and disposed in the housing, configured, in the suction stroke, to suck in fluid through the fluid channel and to transport the same towards the sensor, and, in the pressure stroke, to transport the sucked-in fluid through said fluid channel back towards the housing opening, the sensor being arranged spaced apart from the housing opening, and the volume of the fluid channel between the sensor and the housing opening being equal to or smaller than the stroke volume which the micro fluid actuator may convey with a single suction stroke, wherein the stroke volume of the micro fluid actuator is at least 2.5 times larger than the volume of a fluid channel portion between the sensor and the housing opening, and wherein the micro fluid actuator is a membrane actuator having a carrier and a deflectable membrane arranged at the same, and the membrane is mechanically biased so that the membrane is spaced apart from the carrier in an unoperated idle position and, upon operation, moves towards the carrier.

2. Device according to claim 1, wherein the fluid channel extends between the housing opening and the micro fluid actuator, and the fluid channel, the sensor coupled to the fluid channel, and the micro fluid actuator together form a fluid-tight arrangement which is sealed against the interior of the device.

3. Device according to claim 1, wherein the stroke volume of the micro fluid actuator is at least 10 times larger than the volume of the fluid channel portion between the sensor and the housing opening.

4. Device according to claim 1, wherein the sensor is configured to sense at least one ambient air component from the group of carbon monoxide (CO), carbon dioxide (CO.sub.2), nitrogen (N.sub.2), nitrous oxide (N.sub.2O), volatile organic compounds (VOC), humidity and fine dust.

5. Device according to claim 1, wherein the micro fluid actuator is a membrane actuator having a deflectable membrane, and the membrane is operable in a piezoelectric or electromagnetic or electrostatic manner or by means of electroactive polymer actuators or by means of an element comprising a shape memory alloy.

6. Device according to claim 1, wherein the micro fluid actuator is a membrane actuator having a deflectable double membrane.

7. Device according to claim 1, wherein the micro fluid actuator is a membrane actuator having a carrier and a deflectable membrane arranged at the same, and the membrane including the carrier comprises a height of 0.50 mm or less.

8. Device according to claim 1, wherein the device comprises two or more sensors arranged successively in series in the flow direction.

9. Device according to claim 1, wherein the device comprises two or more sensors arranged in parallel in the flow direction.

10. Device according to claim 8, wherein the device comprises two or more micro fluid actuators, each micro fluid actuator being in fluid connection with a respective sensor.

11. Device according to claim 1, wherein an air-permeable filter element is arranged between the housing opening and the sensor, configured to collect liquid condensed in the sucked-in fluid.

12. Device according to claim 1, wherein an air-permeable filter element is arranged between the sensor and the micro fluid actuator, configured to collect liquid condensed in the sucked-in fluid.

13. Device according to claim 1, wherein the device is a mobile device.

14. Device according to claim 13, wherein the mobile device is a mobile telephone, and the housing opening provided in the mobile telephone is a microphone opening.

15. Device according to claim 13, wherein the mobile device is a mobile telephone having a vibrating alert motor, and the micro fluid actuator is a membrane actuator having a deflectable membrane, the membrane being operable by means of the vibrating alert motor.

16. Device according to claim 15, wherein the mobile device is a mobile telephone or a smartphone or a wearable or a mobile computer.

17. Device according to claim 1, wherein the device is a stationary device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the present invention will be detailed subsequently referring to the appended drawings, in which:

(2) FIG. 1 shows a top view of an embodiment of the mobile device according to the invention,

(3) FIG. 2 shows a sectional view of an embodiment of a mobile device according to the invention along the section line II-II shown in FIG. 1,

(4) FIG. 3 shows a sectional view of an embodiment of a mobile device according to the invention,

(5) FIG. 4 shows a sectional view of an embodiment of a mobile device according to the invention having a series connection of several sensors,

(6) FIG. 5 shows a top view of an embodiment of a mobile device according to the invention having a parallel connection of several sensors, and

(7) FIG. 6 shows a top view of a further embodiment of a mobile device according to the invention having a parallel connection of several sensors.

DETAILED DESCRIPTION OF THE INVENTION

(8) With reference to the figures, embodiments are described in the following based on mobile devices. In embodiments, the device may be a stationary device such as a sensor node or the like so that the respective discussions also apply for stationary devices. For example, a stationary sensor node may function with a battery in an independent manner and may record sensor data and communicate the same.

(9) FIG. 1 shows an embodiment of a mobile device 1 according to the invention having an opening 2. The opening 2 is a housing opening defining a fluid connection between a fluid channel in the mobile device and ambient air.

(10) FIG. 2 is a sectional view through the mobile device 1 along the sectional line II-II shown in FIG. 1. In FIG. 2, the housing 20 of the mobile device 1 can be recognized. The housing 20 comprises the opening 2.

(11) The above-mentioned fluid connection 3 is arranged in the mobile device 1. A sensor 4 is coupled to the fluid channel 3. The sensor 4 is configured to sense at least one component of the ambient air.

(12) Furthermore, a micro fluid actuator 5 is arranged in the mobile device 1. The micro fluid actuator 5 is also coupled to the fluid channel 3. The micro fluid actuator 5 is arranged downstream of the sensor 4 in the fluid channel 3. In other words, the sensor 4 is fluidically coupled to the fluid channel 3 and is arranged between the opening 2 and the micro fluid actuator 5.

(13) Thus, the fluid channel 3 comprises a first portion 3a extending between the opening 2 and the sensor 4, and a second portion 3b extending between the sensor 4 and the micro fluid actuator 5.

(14) The micro fluid actuator 5 is configured to suck in, in the suction stroke, a fluid through the fluid channel 3 and to transport the same towards the sensor 4. Furthermore, the micro fluid actuator 5 is configured to transport, in the pressure stroke, the sucked-in fluid located in the fluid channel 3 through the fluid channel 3 back towards the opening 2.

(15) The sensor 4 is arranged spaced apart from the opening 2. Compared to known solution in which the sensor 4 is placed as close as possible to the opening 2 in order to keep the paths of the fluid flow as short as possible, a spaced-apart arrangement of the sensor 4 according to the invention provides the possibility to arrange the sensor 4 at almost all locations in the mobile device 1. In particular, this is desirable with respect to ever flatter mobile devices 1 as these do not provide unlimited space for installing sensor systems.

(16) According to the invention, the volume of the first portion 3a of the fluid channel 3 between the sensor 4 and the opening 2 is as large as or smaller than the stroke volume which the micro fluid actuator 5 may convey with a single suction stroke.

(17) The fluid channel 3 extends between the opening 2 and the micro fluid actuator 5. Together, the fluid channel 3, the sensor 4 coupled to the fluid channel 3, and the micro fluid actuator 5 form an arrangement which is sealed against the interior of the mobile device (1). That is, the fluid channel 3 as well as the sensor 4 and the micro fluid actuator 5 are embodied in a sealed manner, in particular air-tight.

(18) In the embodiments illustrated in FIGS. 2 and 3, the micro fluid actuator 5 is configured as a membrane actuator. The micro fluid actuator 5 comprises a deflectable membrane 6. The membrane 6 may be operated in a piezoelectric, electromagnetic, electrostatic manner by means of electroactive polymer actuators or by means of an element comprising a shape memory alloy.

(19) An operating means 7 configured accordingly is arranged at the membrane 6 for the purpose of deflecting the same. As can be recognized in the figures, the membrane 6 is arranged with one side 22 at a carrier 8. For example, the carrier 8 may be configured as a silicon chip or as a metal body or a polymer body.

(20) In particular, the membrane 6 is arranged at the carrier 8 at the laterally outer portions 23 of the same. In the top view, the membrane 6 may comprise a round or a rectangular shape, in particular a hexagonal shape. The membrane 6 may be attached, or fixed, on the carrier 8 by means of an attaching means, e.g., by means of an appropriate adhesive.

(21) In the embodiments illustrated in the figures, the membrane 6 is arranged on the carrier 8 under a mechanical bias. That is, due to the bias, the membrane 6 comprises a concave arch (directed away from the carrier 8). As a result, a cavity 24 is formed between the carrier 8 and the membrane 6 in the area of this arch. The volume of this cavity 24 essentially determines the stroke volume of the micro fluid actuator 5.

(22) As is indicated by the double arrow 21 in FIGS. 2 and 3, the micro fluid actuator 5 may essentially move in two directions. In an unoperated idle position, the micro fluid actuator 5 is located in the illustrated position in which the membrane 6 is biased and the above-mentioned cavity 24 is configured. Thus, in this idle position, the membrane 6 is spaced apart from the carrier 8.

(23) Now, the operating means 7 may operate the membrane 6. For example, the operating means 7 may be a piezo element which, upon applying a voltage, deflects the membrane 6 downwardly, i.e., towards the carrier 8. Thus, upon operating the membrane 6, the same moves towards the carrier 8 until the membrane 6 contacts the carrier 8 with its bottom side 22.

(24) In doing so, the micro fluid actuator 5 displaces the volume of the fluid located in the cavity 24 at this point in time. Then, this fluid volume is transported through the fluid channel 3 and exits from the opening 2 into the surroundings. Thus, in this case, the micro fluid actuator 5 executed a pressure stroke and the ejected fluid volume substantially corresponds to the stroke volume of the micro fluid actuator 5.

(25) Now, the operating means 7 may move the membrane 6 back in the opposite direction, i.e., in the direction away from the carrier 8. In the case of a biased membrane 6, it is already sufficient if the operating means 7 does no longer apply an operating force to the membrane 6. Then, the membrane 6 returns back to its original initial position due to the mechanical bias.

(26) Hence, in this case, the membrane 6 moves away from the carrier 8 and, thus, again increases the cavity 24 formed between the membrane bottom side 22 and the carrier 8. A negative pressure is formed in the fluid-tight arrangement (micro fluid actuator 5, sensor 4, fluid channel 3) and a fluid is sucked in from the surroundings through the opening 2. Hence, in this case, the micro fluid actuator 5 executes a suction stroke.

(27) The fluid channel 3, i.e., the front portion 3a, the rear portion 3b and the portion 3c circumflowing the sensor 4 of the fluid channel 3 comprise a certain volume. This volume is also referred to as total dead volume.

(28) According to the invention, the stroke volume of the micro fluid actuator 5 is at least as large as the total dead volume. However, it may already be sufficient if the stroke volume of the micro fluid actuator 5 is at least as large as the volume of the front fluid channel portion 3a. Thus, a suction stroke of the micro fluid actuator 5 just conveys a sufficient amount of volume through the front fluid channel portion 3a so that a fluid sucked in at the opening 2 just reaches the sensor 4.

(29) In order to ensure circumflowing the sensor 4 with a sucked-in fluid, embodiments of the invention provide that the stroke volume of the micro fluid actuator 5 is at least 2.5 times larger than the volume of the fluid channel 3 between the sensor 4 and the opening 2, i.e., than the front fluid channel portion 3a.

(30) In the embodiment illustrated in FIG. 2, the sensor 4 is fluidically coupled to the fluid channel 3 by arranging the sensor 4 at the fluid channel 3. In the embodiment illustrated in FIG. 3, the sensor 4 is fluidically coupled to the fluid channel 3 by arranging the sensor 4 not at the fluid channel 3, but in the same.

(31) As can be recognized in FIG. 3, the micro fluid actuator 5 comprises a height H extending between the bottom side of the carrier 8 and the top side of the membrane 6, or of the operating means 7 arranged at the membrane 6. According to advantageous embodiments, the micro fluid actuator 5 comprises a height H of 0.50 mm or less.

(32) FIG. 4 shows a further embodiment of a mobile device 1 according to the invention. Here, the mobile device 1 comprises three sensors 4a, 4b, 4c arranged successively in series in the flow direction (both in the suction direction and in the ejection direction).

(33) FIG. 5 shows a further embodiment, wherein the mobile device 1 comprises four sensors 4a, 4b, 4c, 4d, arranged in parallel in the flow direction. In this embodiment, the mobile device 1 comprises a micro fluid actuator 5 configured to supply the parallel connection of several sensors 4a to 4d together with sucked-in ambient air.

(34) FIG. 6 shows a further embodiment, wherein the mobile device 1 comprises four micro fluid actuators 5a, 5b, 5c, 5d as well as four sensors 4a, 4b, 4c, 4d. Here, each micro fluid actuator 5a, 5b, 5c, 5d is in fluid connection with a respective sensor 4a, 4b, 4c, 4d. For example, each of the four sensors 4a to 4d may analyze a certain ambient air parameter. Thus, the sensors 4a to 4d may work in a needs-based manner by separately driving the respectively associated micro fluid actuator 5a to 5d.

(35) After the embodiment of the mobile device 1 according to the invention has been described structurally, the mode of operation is to be explained in the following.

(36) For example, the sensor 4 may be a sensor for measuring carbon monoxide (CO), carbon dioxide (CO.sub.2), nitrogen (N), nitrous oxide (N.sub.2O) volatile organic compounds (VOC), humidity or fine dust. For this purpose, the sensor 4 has to be circumflowed with ambient air.

(37) For example, the mobile device 1 may be a smartphone having an already existing microphone opening 2. The ambient air may be sucked in through this microphone opening 2. For this purpose, a fluid line 3 is arranged at the microphone opening 2. This fluid line 3 leads to the sensor 4.

(38) Diffusion of the ambient air from the opening 2 to the sensor 4 takes a relatively long time. Therefore, the invention provides the micro fluid actuator 5 which sucks in the ambient air through the opening 2. Thus, the sucked in ambient air flows substantially faster to the sensor 4 which, on the other hand, may generate signals more quickly. Hence, known solutions functioning with the diffusion principle are replaced by convection.

(39) Thus, the micro fluid actuator 5 executes a suction stroke in which the same sucks in the ambient air through the opening 2. According to the invention, the volume of the fluid channel 3 is smaller than the stroke volume of the micro fluid actuator 5. Thus, the ambient air sucked in through the opening 2 flows through the front fluid channel portion 3a, through the portion 3c adjacent to the sensor 4 and through the rear fluid channel portion 3b into the cavity 24 of the micro fluid actuator 5. Thus, the sucked-in ambient air circumflows the sensor 4.

(40) Subsequently, the sucked-in ambient air is ejected back out by the micro fluid actuator 5 through the opening 2. For this purpose, the micro fluid actuator 5 executes a pressure stroke in which the sucked-in air flows through the fluid channel 3 in the reverse direction and is released to the surroundings through the opening 2.

(41) Thus, the invention solves the problem of the prior art in which a micro pump sucks in air and subsequently ejects the sucked-in air into the mobile device. Whereas, in the mobile device 1 according to the invention, the micro fluid actuator 5 sucks in a fluid volume through the fluid channel 3 and ejects the sucked-in fluid volume via this fluid channel 3. In other words, the micro fluid actuator 5 pushes a fluid volume back and forth in the fluid channel 3.

(42) In the following, embodiments of the invention are summarized in other words.

(43) One component of this disclosure is a flat membrane actuator which may shift an air volume (back and forth) in a cyclic manner, and to which one (or several) sensor(s) and a fluid line are connected.

(44) The dead volume in the hose and in the fluid adapter up to the sensor is to be smaller than the (air) volume which the actuator may shift.

(45) For example, the actuator may be driven in the following manners: piezo-electrically monomorphic bending converter adhered PZT ceramic thin layer (AIN, zinc oxide . . . ) thick layer PZT electromagnetically electrostatically by electroactive polymer actuators thermically, e.g., by a shape memory alloy with the motor for the vibrating alert as a drive for the membrane, etc.

(46) A conceivable embodiment is a piezo membrane converter 5. The same may be built in a very flat manner (precondition for mobile radio devicesdesign height with a carrier of less than 0.5 mm), and may still shift a large stroke volume of several mm.sup.3. See FIG. 2 with a piezo membrane actuator 5, for supplying a sensor 4 with fresh air.

(47) Instead of a hose, a rigid tube may be used as the fluid channel 3.

(48) All fluid connectors should be sealed so that the air from the opening 2 is sucked in. Also, several sensors 4 may be arranged (preferably in series).

(49) A parallel arrangement makes sense when the flow resistances of all sensors 4 are approximately the same.

(50) Also, several actuators 5 may be used, e.g., one for each sensor 4.

(51) As appropriate, a double membrane may also be used in order to keep the voltage low.

(52) The fluidic paths should be designed such that there are as few corners and dead rooms present as possible. In this case, it is ensured that little dispersion and carry-over occurs. In the best case, the stroke volume of the micro fluid actuator 5 just has to be as large as the dead volume (from the suction opening 2 up to the sensor 4). In reality, the stroke volume will be made larger than the dead volume by a certain factor.

(53) An air-permeable membrane may be arranged between the suction opening 2 and the sensor 4, or between the sensor 4 and the micro fluid actuator 5 (e.g., micro pump), which does not let pass condensed liquids, e.g., a hydrophobic (e.g., teflon-coated) filter membrane having a small pore size and a large bubble point in order to protect the sensor 4 from liquid. According to the design, this membrane has to overcome a flow resistance. Furthermore, there may be pressure drops in the supply.

(54) Thus, the micro fluid actuator 5 should also be able: to generate a certain blocking pressure, and also to satisfy a certain compression ratio between the stroke volume and the total dead volume (that volume of the fluid line 3, the sensor 4, the fluid adapter 5 and the actuator chamber 24).

(55) In order to ensure this, the micro fluid actuator 5 is preferably applied by the bias method (patented by Fraunhofer EMFT) in order to minimize the dead volume of the actuator chamber 24.

(56) Before sucking in the air sample, the membrane actuator 5 is operated (e.g., by applying a positive voltage) and moves to its lower position. Now, the dead volume is at a minimum.

(57) Then, the actuator 5 is moved to its upper position (e.g., by switching off the voltage, or by applying an appropriate negative voltage). In doing so, a negative pressure is generated in the actuator chamber 24, ambient air is rapidly sucked in and is supplied to the sensor 4 so that measuring the air parameters may take place.

NUMERICAL EXAMPLE

(58) Actuator 1 (diameter: 9.6 mm) Size: 10100.5 mm.sup.3, Membrane diameter: 9.6 mm Membrane thickness: 30 m Piezo thickness: 60 m d31: 250 m/V Drive voltage: +90/24 V

(59) Resulting Stroke Data: Stroke volume: 2.35 mm.sup.3 Blocking pressure: 14 kPa

(60) Actuator 2 (diameter: 14.6 mm) Size: 15150.5 mm.sup.3, Membrane diameter: 14.6 mm Membrane thickness: 40 m Piezo thickness: 80 m d31: 250 m/V Drive voltage: +120/32 V

(61) Resulting Stroke Data: Stroke volume: 9.4 mm.sup.3 Blocking pressure: 11 kPa

(62) Dead Volume from the Opening to the Sensor:

(63) Hose or Tube Length: 10 mm Inner diameter 0.2 mm Dead volume=I r.sup.2 =10 mm(0.1 mm).sup.23.14=0.32 mm.sup.3

(64) Fluid Adapter Length: 2 mm Inner diameter 0.2 mm Dead volume=I r.sup.2 =2 mm(0.1 mm).sup.23.14=0.06 mm.sup.3

(65) Sensor Housing Length: 1.51.5 mm.sup.2 Height: 0.2 mm Dead volume=0.45 mm.sup.3

(66) Total Dead Volume 0.83 mm.sup.3

(67) I.e., in the actuator 1, the stroke volume is larger than the dead volume by a factor of 2.8, in the actuator 2 by a factor of 11.3; fresh air reaches the sensor safely with each stroke.

(68) If applicable, it may make sense to use thicker piezo ceramics, since, when using thin ceramics having such large lateral dimensions, the mechanical stresses in the piezo ceramics may become large, and breakage in the piezo ceramics may arise due to high tensile stresses.

(69) Here, an embodiment would be:

(70) Actuator 3 (diameter: 9.6 mm) Size: 10100.5 mm.sup.3, Membrane diameter: 9.6 mm Membrane thickness: 30 m Piezo thickness: 150 m d31: 250 m/V Drive voltage: +225/60 V

(71) Resulting Stroke Data: Stroke volume: 1.3 mm.sup.3 Blocking pressure: 29 kPa

(72) Actuator 4 (diameter: 14.6 mm) Size: 15150.5 mm.sup.3, Membrane diameter: 14.6 mm Membrane thickness: 50 m Piezo thickness: 150 m d31: 250 m/V Drive voltage: +225/60 volts

(73) Resulting Stroke Data: Stroke volume: 6.3 mm.sup.3 Blocking pressure: 23 kPa

(74) The last two actuators comprise less stroke volume (however, with an appropriate design of the supply line, still enough), but the same are designed more conservatively with respect to mechanical stress.

(75) With a double stroke actuator, the respective stroke volume may be doubled.

(76) While this invention has been described in terms of several advantageous embodiments, there are alterations, permutations, and equivalents which fall within the scope of this invention. It should also be noted that there are many alternative ways of implementing the methods and compositions of the present invention. It is therefore intended that the following appended claims be interpreted as including all such alterations, permutations, and equivalents as fall within the true spirit and scope of the present invention.