US20050220644A1 - Pneumatic actuator for bolus generation in a fluid handling circuit - Google Patents
Pneumatic actuator for bolus generation in a fluid handling circuit Download PDFInfo
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- US20050220644A1 US20050220644A1 US11/095,635 US9563505A US2005220644A1 US 20050220644 A1 US20050220644 A1 US 20050220644A1 US 9563505 A US9563505 A US 9563505A US 2005220644 A1 US2005220644 A1 US 2005220644A1
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- channel
- pneumatic
- bolus
- pneumatic actuator
- gas pocket
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16K—VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
- F16K99/00—Subject matter not provided for in other groups of this subclass
- F16K99/0001—Microvalves
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B19/00—Machines or pumps having pertinent characteristics not provided for in, or of interest apart from, groups F04B1/00 - F04B17/00
- F04B19/20—Other positive-displacement pumps
- F04B19/24—Pumping by heat expansion of pumped fluid
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16K—VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
- F16K99/00—Subject matter not provided for in other groups of this subclass
- F16K99/0001—Microvalves
- F16K99/0003—Constructional types of microvalves; Details of the cutting-off member
- F16K99/0017—Capillary or surface tension valves, e.g. using electro-wetting or electro-capillarity effects
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16K—VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
- F16K99/00—Subject matter not provided for in other groups of this subclass
- F16K99/0001—Microvalves
- F16K99/0003—Constructional types of microvalves; Details of the cutting-off member
- F16K99/0019—Valves using a microdroplet or microbubble as the valve member
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16K—VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
- F16K99/00—Subject matter not provided for in other groups of this subclass
- F16K99/0001—Microvalves
- F16K99/0034—Operating means specially adapted for microvalves
- F16K99/0042—Electric operating means therefor
- F16K99/0044—Electric operating means therefor using thermo-electric means
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16K—VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
- F16K99/00—Subject matter not provided for in other groups of this subclass
- F16K2099/0073—Fabrication methods specifically adapted for microvalves
- F16K2099/0074—Fabrication methods specifically adapted for microvalves using photolithography, e.g. etching
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16K—VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
- F16K99/00—Subject matter not provided for in other groups of this subclass
- F16K2099/0073—Fabrication methods specifically adapted for microvalves
- F16K2099/0078—Fabrication methods specifically adapted for microvalves using moulding or stamping
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16K—VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
- F16K99/00—Subject matter not provided for in other groups of this subclass
- F16K2099/0082—Microvalves adapted for a particular use
- F16K2099/0084—Chemistry or biology, e.g. "lab-on-a-chip" technology
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16K—VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
- F16K99/00—Subject matter not provided for in other groups of this subclass
- F16K2099/0082—Microvalves adapted for a particular use
- F16K2099/0086—Medical applications
Definitions
- the present invention relates, in general, to a pneumatic actuator for bolus generation in a fluid handling circuit and, more particularly, to a pneumatic actuator for bolus generation in a fluid handling circuit wherein the pneumatic actuator is used to insert an air pocket into the fluid stream to create the bolus. Further, The present invention relates, in general, to a pneumatic fluid handling circuit including a pneumatic actuator for bolus generation and, more particularly, to a pneumatic fluid handling circuit including a pneumatic actuator for bolus generation wherein the pneumatic actuator is used to insert an air pocket into the fluid stream to create the bolus.
- the present invention is directed to a pneumatic actuator for bolus generation in a fluid handling circuit.
- the pneumatic actuator includes a channel including the fluid, a controller, a pressure generator connected to the controller and an isolator for isolating the pressure generator from the channel.
- the pressure generator includes a gas pocket connected to the channel through the isolator and a heater controlled by the controller and adapted to heat gas in the gas pocket.
- the pressure generator includes a vent adapted to vent gas from the gas pocket.
- the present invention is directed to a pneumatic actuator for bolus generation in a fluid handling circuit
- the pneumatic actuator includes a channel including the fluid, a controller, a pressure generator connected to the controller and an isolator for isolating the pressure generator from the channel.
- the pressure generator includes a gas pocket connected to the channel by the isolator, a flexible bladder connected to the gas pocket, a plunger connected to the flexible bladder, the plunger being controlled by the controller.
- the pressure generator includes a vent adapted to vent gas from the gas pocket.
- the isolator includes a hydrophobic patch.
- the present invention is also directed to a pneumatic fluid handling circuit including a pneumatic actuator for bolus generation.
- the pneumatic fluid handling circuit includes a channel including the fluid, a fill detector positioned in the channel, a pneumatic actuator connected to the channel upstream from the fill detector, a controller connected between the fill detector and the pneumatic actuator, a vent connected to the channel at a predetermined distance downstream from the fill detector and an analyte sensor positioned in the channel downstream from the vent.
- the pneumatic actuator includes a channel including the fluid, a controller, a pressure generator connected to the controller and an isolator for isolating the pressure generator from the channel.
- the pressure generator includes a gas pocket connected to the channel through the isolator, a heater controlled by the controller and adapted to heat gas in the gas pocket.
- the pressure generator includes a vent adapted to vent gas from the gas pocket.
- the present invention is directed to a pneumatic fluid handling circuit including a pneumatic actuator for bolus generation.
- the pneumatic fluid handling circuit includes a channel including the fluid, a fill detector positioned in the channel, a pneumatic actuator connected to the channel upstream from the fill detector, a controller connected between the fill detector and the pneumatic actuator, a vent connected to the channel at a predetermined distance downstream from the fill detector and an analyte sensor positioned in the channel downstream from the vent.
- the pneumatic actuator includes a channel including the fluid, a controller, a pressure generator connected to the controller and an isolator for isolating the pressure generator from the channel.
- the pressure generator includes a gas pocket connected to the channel by the isolator, a flexible bladder connected to the gas pocket and a plunger connected to the flexible bladder, the plunger being controlled by the controller.
- FIG. 1 is a schematic illustration of sample liquid entering a pneumatic liquid handling circuit, according to one embodiment of the present invention.
- FIG. 2 is a schematic illustration of sample liquid reaching a fill detector in the pneumatic liquid handling circuit of FIG. 1 .
- FIG. 3 is a schematic illustration of first sample bolus formation in the pneumatic liquid handling circuit of FIG. 1 .
- FIG. 4 is a schematic illustration of first sample bolus positioning in the pneumatic liquid handling circuit of FIG. 1 .
- FIG. 5 is a schematic illustration of sample liquid flow in the pneumatic liquid handling circuit of FIG. 1 .
- FIG. 6 is a schematic illustration of second sample bolus formation in the pneumatic liquid handling circuit of FIG. 1 .
- FIG. 7 is a schematic illustration of combined sample bolus formation in the pneumatic liquid handling circuit of FIG. 1 .
- FIG. 8 is a schematic illustration of combined sample bolus positioning in the pneumatic liquid handling circuit of FIG. 1 .
- FIG. 9 is an illustration of an alternative embodiment of the pneumatic liquid handling circuit of FIG. 1 .
- FIG. 10 is a schematic illustration of a bladder-containing pneumatic liquid handling circuit.
- FIG. 1 is a schematic illustration of a pneumatic liquid handling circuit, according to an embodiment of the present invention.
- FIGS. 2 through 8 illustrate flow of sample liquid through the pneumatic liquid handling circuit of FIG. 1 .
- FIG. 9 is an illustration of an alternative embodiment of the pneumatic liquid handling circuit of FIG. 1 .
- FIG. 10 is a schematic illustration of a bladder-containing pneumatic liquid handling circuit
- the pneumatic liquid handling circuits illustrated in FIGS. 1 through 10 can be used to measure analyte in sample liquid.
- Sample liquid can be interstitial fluid, whole blood, or plasma.
- Flow into pneumatic liquid handling circuits can be driven by capillary, gravitational, and centrifugal forces.
- Flow into pneumatic liquid handling circuits can also be driven by pressurized gas, pumps, or by pressure at the source of sample liquid.
- Flow channels in pneumatic liquid handling circuits can be rectangular, square, or semicircular in cross section, although most preferably flow channels are rectangular in cross section, making them easier to manufacture.
- Pneumatic liquid handling circuits can be constructed using laminated layers of plastic, bonded with adhesive, or can be injection molded plastic. Suitable plastics include polyester, polycarbonate, acrylic, polystyrene, polyolefins, polyimides, and any other thermoplastic polymers. Pneumatic liquid handling circuits may also be constructed using etched silicon or glass.
- FIG. 1 is a schematic illustration of sample liquid 20 entering pneumatic liquid handling circuit 2 in the direction of arrow 200 , according to an embodiment of the present invention.
- Pneumatic liquid handling circuit 2 includes main channel 10 , in which sample liquid 20 flows from left to right.
- Fill detector 30 located within main channel 10 , is used to detect the presence of sample liquid 20 .
- Pneumatic actuator 95 includes gas pocket 70 , heater 80 , and controller 90 .
- Gas pocket 70 is connected to main channel 10 by way of first branching channel 65 .
- First branching channel 65 includes first hydrophobic area 62 .
- First hydrophobic area 62 prevents sample liquid 20 from flowing into gas pocket 70 , for reasons explained below.
- Pneumatic liquid handling circuit 2 When multiplied by the cross sectional area of main channel 10 , measured distance 35 defines a fixed volume within main channel 10 , between branching channel 65 and fill detector 30 .
- Pneumatic liquid handling circuit 2 includes vent 50 . Gas flows through vent 50 , but sample liquid 20 does not. Vent 50 branches from main channel 10 , and includes second hydrophobic area 60 .
- Pneumatic liquid handling circuit 2 includes analyte sensor 40 , located down stream of vent 50 . Analyte sensor 40 is used to determine analyte concentration in sample liquid 20 .
- analyte sensor 40 measures glucose, and sample liquid 20 is interstitial fluid.
- analyte sensor 40 can contain a redox reagent system that includes an enzyme and redox active compounds or mediators.
- mediators are known in the art, such as ferricyanide, phenazine ethosulphate, phenazine methosulfate, pheylenediamine, 1-methoxy-phenazine methosulfate, 2,6-dimethyl-1,4-benzoquinone, 2,5-dichloro-1,4-benzoquinone, ferrocene derivatives, osmium bipyridyl complexes, and ruthenium complexes.
- Suitable enzymes include glucose oxidase and dehydrogenase (both NAD and PQQ based).
- Other substances that may be present in a redox reagent system include buffering agents (e.g., citraconate, citrate, malic, maleic, and phosphate buffers); divalent cations (e.g., calcium chloride, and magnesium chloride); surfactants (e.g., Triton, Macol, Tetronic, Silwet, Zonyl, and Pluronic); and stabilizing agents (e.g., albumin, sucrose, trehalose, mannitol and lactose).
- buffering agents e.g., citraconate, citrate, malic, maleic, and phosphate buffers
- divalent cations e.g., calcium chloride, and magnesium chloride
- surfactants e.g., Triton, Macol, Tetronic, Silwet, Zonyl, and Pluronic
- Hydrophobic areas 60 and 62 allow air to pass, but not liquid. This is because hydrophobic areas 60 and 62 repel aqueous samples, such as interstitial fluid, blood, and plasma. For flow of aqueous sample to occur beyond hydrophobic areas 60 and 62 , the pressure of sample liquid 20 must exceed the burst pressures of the hydrophobic areas 60 and 62 . Burst pressure is determined by channel geometry, physical properties of the channels surface, and physical properties of sample liquid 20 . In designing pneumatic liquid handling circuit 2 , burst pressures can be selected that prevent flow of sample liquid 20 beyond hydrophobic areas 60 and 62 .
- Hydrophobic areas 60 and 62 may also be referred to as an insulator since hydrophobic area 62 insulates gas pocket 70 from the fluid in main channel 10 and channel 50 from the fluid in main channel 10 but allows air to pass out of gas pocket 70 and into channel 50 .
- a structural passive valve useable as an insulator or in place of hydrophobic areas 60 or 62 may also be formed by a sudden widening in the channel (e.g. a widening in channel 65 if used to replace hydrophobic area 62 or a widening in channel 50 if used to replace hydrophobic area 60 ) such that when a liquid front reaches the sudden widening, a meniscus is formed at the point of the widening (angle preferable more acute than 90 degrees.
- burst pressure a minimum pressure which is referred to as burst pressure.
- hydrophobic areas 60 and 62 At least one side of the flow channel is rendered hydrophobic. This can be accomplished using commercially available hydrophobic inks, and various printing techniques including screen printing, gravure, slot coating, flexo, offset, and spray coating.
- the ink FluoroPel PFC MH can be used to form hydrophobic areas 60 and 62 .
- FluoroPel PFC MH can be purchased from Cytonix Inc., of Beltsville, Md.
- Cytonix offers hydrophobic ink formulations that have been optimized for use with other types of printing, such as flexo and offset, as well as spray coating. Hydrophobic inks such as those used in printing microscope slides are also suitable for use in printing hydrophobic areas. Alternatively, commercially available screen printing inks can be modified for use in printing hydrophobic areas. For example, Zonyl fluoroadditives, sold by DuPont Corporation of Delaware, can be used as an additive to traditional screen printing inks.
- FIG. 2 is a schematic illustration of sample liquid 20 flowing in the direction of arrow 202 and reaching fill detector 30 .
- Fill detector 30 detects the presence of sample liquid 20 using various methods.
- fill detector 30 can include electrodes for measuring conductivity and/or capacitance of sample liquid 20 .
- fill detector 30 can be optical, and detect sample by measuring a change in optical properties when sample liquid 20 reaches fill detector 30 . Further details in regard to fill detectors suitable for use in devices according to the present invention are included in U.S. patent application Ser. No. 10/811,446 filed on Mar. 26, 2004, which is hereby incorporated by reference.
- Feedback loop 31 provides electronic connection between fill detector 30 and controller 90 .
- sample liquid 20 flows in the direction of arrow 202 , and reaches fill detector 30 , it is detected and pneumatic actuator 95 is activated by a signal from feedback loop 31 .
- pneumatic actuator 95 When pneumatic actuator 95 is activated, heater 80 turns on, heating the air in gas pocket 70 .
- air in gas pocket 70 expands as it is heated, expanding into branching channel 65 and main channel 10 .
- Expanded air pocket 300 forms first sample bolus 20 a , which may also be referred to as a sample plug, and forces first sample bolus 20 a towards vent 50 , in the direction of arrow 206 .
- the volume of first sample bolus 20 a is determined by multiplying measured distance 35 times the cross sectional area of main channel 10 , as discussed in reference to FIG. 1 .
- heater 80 continues to heat the air in gas pocket 70 , causing the air to expand in the direction of arrow 208 , and increasing the size of expanded air pocket 302 .
- expanded air pocket 302 is vented to atmosphere by way of vent 50 in the direction of arrow 210 .
- Movement of first sample bolus 20 a in the direction of arrow 230 stops.
- Heater 80 is then turned off, and the air contained in gas pocket 70 and expanded air pocket 302 returns to ambient temperature and pressure.
- the change in pressure to atmospheric is almost instantaneous, resulting in substantially immediate stabilization of first sample bolus 20 a.
- Various means can be used for determining when to turn off heater 80 . This includes using a fixed time after first sample bolus 20 a has been detected at analyte sensor 40 , or by using a fixed time after first sample bolus 20 a leaves contact with fill detector 30 . In either case, heater 80 is turned off seconds after trailing edge 21 makes contact with vent 50 .
- first sample bolus 20 a While first sample bolus 20 a is in contact with analyte sensor 40 , various measurements can be made. This includes, for example, electrochemical determination of glucose concentration in bolus 20 a . Measurements can be made while first sample bolus 20 a is stationary, or while first sample bolus 20 a is flowing over analyte sensor 40 .
- FIG. 5 The next step in the sequence is illustrated in FIG. 5 . While measurements are made on first sample bolus 20 a using analyte sensor 40 , air pocket 304 remains at atmospheric pressure because it is in direct contact with the atmosphere by way of vent 50 in the direction of arrow 214 . Sample liquid 20 flows in the direction of arrow 212 , towards fill detector 30 . As sample liquid 20 flows in the direction of arrow 212 , air pocket 304 is vented by way of vent 50 , leaving first sample bolus 20 a stationary. Sample bolus 20 a is stationary because the pressure on either side of sample bolus 20 a is the same.
- first hydrophobic area 62 can be designed to have a burst pressure in excess of the pressure differential caused by cooling the gas in gas pocket 70 .
- FIG. 9 A second technique for preventing the flow of sample liquid 20 into gas pocket 70 is illustrated in FIG. 9 .
- gas pocket 70 is provided with gas pocket vent 76 that is always open to atmosphere.
- gas pocket 70 maintains direct contact with atmosphere by way of gas pocket vent 76 .
- heater 80 is turned off, and gas in gas pocket 70 cools, air is drawn into gas pocket 70 through gas pocket vent 76 in the direction of arrow 232 , maintaining atmospheric pressure in gas pocket 70 .
- gas pocket vent 76 This decreases the difference in pressure between sample liquid 20 and the gas in gas pocket 70 , minimizing the driving force for flow of sample liquid 20 into gas pocket 70 .
- heater 80 can be driven with sufficient power to compensate for escape of gas by way of gas pocket vent 76 , allowing the pressure of gas in gas pocket 70 to increase, as needed.
- the resistance to flow in gas pocket vent 76 can be controlled. Two variables that effect the resistance to flow in gas pocket vent 76 are its cross sectional area and its length. Gas pocket vent 76 can be fabricated using laminates or injection molding, or with any of the techniques outlined earlier.
- a signal is sent to controller 90 by way of feedback loop 31 .
- Heater 80 is activated, increasing the temperature and pressure of the air in gas pocket 70 .
- a second sample bolus 20 b forms, as illustrated in FIG. 6 .
- expanded air pocket 306 increases in size, forcing second sample bolus 20 b to move in the direction of arrow 218 , towards vent 50 and first sample bolus 20 a .
- the air in air pocket 308 escapes through vent 50 in the direction of arrow 220 .
- first sample bolus 20 a remains stationary because the pressure on either side of it is the same.
- leading edge 22 of second sample bolus 20 b reaches trailing edge 21 of first sample bolus 20 a , and the bolus combine, forming combined sample bolus 20 c , as illustrated in FIG. 7 .
- the point at which first sample bolus 20 a and second sample bolus 20 b combine is indicated by label 100 .
- Heater 80 continues to heat the air in gas pocket 70 , increasing the size of expanded air pocket 310 and causing combined sample 20 c to flow in the direction of arrow 224 .
- second trailing edge 23 reaches vent 50 , as illustrated in FIG. 8 .
- a measurement can be made using analyte sensor 40 .
- the portion of sample in contact with analyte sensor 40 originates from second sample bolus 20 b .
- measurement on a portion of combined sample bolus 20 c originating from second sample bolus 20 b is possible.
- Factors effecting laminar flow include the cross sectional area of main channel 10 , the flow rate of combined sample bolus 20 c , and the physical properties of combined sample bolus 20 c .
- Measurements using analyte sensor 40 should be made within seconds after second trailing edge 23 reaches vent 50 . This minimizes diffusion of analyte between portions from the first and second sample bolus.
- a mechanical approach can be used to move sample liquid in a pneumatic liquid handling circuit.
- a flexible bladder is used.
- An actuator compresses the bladder, generating pressure and causing flow.
- a bladder-containing pneumatic liquid handling circuit 400 is illustrated in FIG. 10 .
- the procedure for using bladder-containing pneumatic liquid handling circuit 400 is identical to that used for the circuits illustrated in FIGS. 1 through 9 with the exception that an actuator and bladder is used instead of a heater.
- a variety of bladder designs can be used.
- a pocket is created, and at least one flexible cover is placed over the pocket.
- the pocket is directly connected to the flow channels, and, when squeezed, generates pressure that moves liquid.
- Covers can be fabricated using many materials, such as metals and plastics.
- a particularly suitable material includes thin polymer films, such as 0.004′′ thick polyester, polycarbonate, polyolefins, or acrylic. Elastomeric films can also be used.
- Pockets can be created using injection molded plastics, such as ABS, polycarbonate, or acrylics, or can be formed using die cut laminates.
- Actuators for compressing a bladder can take many shapes.
- a particularly useful actuator includes the use of a solenoid coupled to a plunger. When energized, the solenoid moves a plunger that compresses the bladder. When the solenoid is de-energized, the bladder returns to its original shape. Solenoids and plungers are typically housed in an external device.
- FIG. 10 is an illustration of a bladder-containing pneumatic liquid handling circuit 400 .
- Bladder-containing pneumatic liquid handling circuit 400 includes main channel 408 , in which sample liquid 420 flows.
- Fill detector 414 located within main channel 420 , is used to detect sample liquid 420 .
- Pneumatic actuator 402 includes plunger 418 , solenoid 406 .
- Bladder 404 is connected to main channel 408 by way of first branching channel 410 .
- First branching channel 410 includes first hydrophobic area 412 .
- First hydrophobic area 412 prevents sample liquid 420 from entering bladder 404 .
- Feedback loop 416 provides electronic connection between fill detector 414 and solenoid 406 .
- solenoid 406 When sample liquid 420 reaches fill detector 414 , it is detected, and solenoid 406 is activated by way of feedback loop 416 . When solenoid 406 is activated, it causes plunger 418 to compress bladder 404 and displaces air within bladder 404 , in the same way heater 80 causes displacement in the designs illustrated in FIGS. 1 through 9 .
- FIGS. 1-10 Methods of using the pneumatic liquid handling circuits illustrated in FIGS. 1-10 are envisioned. The method described below is in reference to the embodiment illustrated in FIGS. 1-9 . However, it can be easily adapted for use with the design illustrated in FIG. 10 .
- a method begins with application of sample liquid 20 to main channel 10 .
- the driving force for flow of sample liquid 20 through main channel 10 can be capillary, gravitational, centrifugal, or can be provided by pressurized gas or a pump. It can also be provided by the source of sample liquid 20 .
- the driving force should be sufficient to cause flow through main channel 10 , but not so great as to cause flow beyond hydrophobic areas 60 and 62 .
- a next step in the method includes the detection of sample at fill detector 30 , followed by a signal from fill detector 30 to controller 90 by way of feedback loop 31 . In response to the signal, heater 80 is turned on, leading to the formation of first sample bolus 20 a .
- first sample bolus 20 a Once the trailing edge 21 of first sample bolus 20 a has reached vent 50 , heater 80 is turned off, and the concentration of analyte in the sample liquid 20 is monitored using analyte sensor 40 .
- a signal is sent from fill detector 30 to controller 90 by way of feedback loop 31 , and heater 80 is once again turned on.
- a second sample bolus 20 b is formed, and moves toward the first sample bolus 20 a and vent 50 .
- heater 80 is turned off, and the concentration of analyte in the second sample bolus 20 b is determined using analyte sensor 40 . This method can be repeated as necessary, and can be part of a broader monitoring method.
Abstract
The invention described herein includes a pneumatic actuator for bolus generation in a fluid handling circuit and a pneumatic actuator for bolus generation in a fluid handling circuit wherein the pneumatic actuator is used to insert an air pocket into the fluid stream to create the bolus. Further, The invention described herein includes a pneumatic fluid handling circuit including a pneumatic actuator for bolus generation including a pneumatic fluid handling circuit including a pneumatic actuator for bolus generation wherein the pneumatic actuator is used to insert an air pocket into the fluid stream to create the bolus.
Description
- This application claims the benefit of U.S. Provisional Application No. 60/558,390, filed Mar. 31, 2004, which application is incorporated herein by reference. This application claims the benefit of U.S. Provisional Application No. 60/558,375, filed Mar. 31, 2004, which application is incorporated herein by reference.
- This application is related to the following copending patent applications: application Ser. No. ______ [Attorney Docket No. DDI-5080]; and application Ser. No. ______ [Attorney Docket No. DDI-5081]; and application Ser. No. ______ [Attorney Docket No. DDI-5082]; and application Ser. No. ______ [Attorney Docket No. DDI-5083]; and application Ser. No. ______ [Attorney Docket No. DDI-5085]; which are hereby incorporated herein by reference.
- The present invention relates, in general, to a pneumatic actuator for bolus generation in a fluid handling circuit and, more particularly, to a pneumatic actuator for bolus generation in a fluid handling circuit wherein the pneumatic actuator is used to insert an air pocket into the fluid stream to create the bolus. Further, The present invention relates, in general, to a pneumatic fluid handling circuit including a pneumatic actuator for bolus generation and, more particularly, to a pneumatic fluid handling circuit including a pneumatic actuator for bolus generation wherein the pneumatic actuator is used to insert an air pocket into the fluid stream to create the bolus.
- The present invention is directed to a pneumatic actuator for bolus generation in a fluid handling circuit. In one embodiment of the present invention, the pneumatic actuator includes a channel including the fluid, a controller, a pressure generator connected to the controller and an isolator for isolating the pressure generator from the channel. In a further embodiment of the present invention, the pressure generator includes a gas pocket connected to the channel through the isolator and a heater controlled by the controller and adapted to heat gas in the gas pocket. In a further embodiment of the present invention, the pressure generator includes a vent adapted to vent gas from the gas pocket.
- In an alternate embodiment of the present invention, the present invention is directed to a pneumatic actuator for bolus generation in a fluid handling circuit the pneumatic actuator includes a channel including the fluid, a controller, a pressure generator connected to the controller and an isolator for isolating the pressure generator from the channel. In this embodiment, the pressure generator includes a gas pocket connected to the channel by the isolator, a flexible bladder connected to the gas pocket, a plunger connected to the flexible bladder, the plunger being controlled by the controller. In a further embodiment of the present invention the pressure generator includes a vent adapted to vent gas from the gas pocket. In a further embodiment of this invention, the isolator includes a hydrophobic patch.
- The present invention is also directed to a pneumatic fluid handling circuit including a pneumatic actuator for bolus generation. In one embodiment of the present invention the pneumatic fluid handling circuit includes a channel including the fluid, a fill detector positioned in the channel, a pneumatic actuator connected to the channel upstream from the fill detector, a controller connected between the fill detector and the pneumatic actuator, a vent connected to the channel at a predetermined distance downstream from the fill detector and an analyte sensor positioned in the channel downstream from the vent. In a further embodiment of a pneumatic fluid handling circuit according to the present invention, the pneumatic actuator includes a channel including the fluid, a controller, a pressure generator connected to the controller and an isolator for isolating the pressure generator from the channel. In a further embodiment of a pneumatic fluid handling circuit according to the present invention, the pressure generator includes a gas pocket connected to the channel through the isolator, a heater controlled by the controller and adapted to heat gas in the gas pocket. In a further embodiment of a pneumatic fluid handling circuit according to the present invention, the pressure generator includes a vent adapted to vent gas from the gas pocket.
- In an alternate embodiment of the present invention, the present invention is directed to a pneumatic fluid handling circuit including a pneumatic actuator for bolus generation. In one embodiment of the present invention the pneumatic fluid handling circuit includes a channel including the fluid, a fill detector positioned in the channel, a pneumatic actuator connected to the channel upstream from the fill detector, a controller connected between the fill detector and the pneumatic actuator, a vent connected to the channel at a predetermined distance downstream from the fill detector and an analyte sensor positioned in the channel downstream from the vent. In a further embodiment of a pneumatic fluid handling circuit according to the present invention, the pneumatic actuator includes a channel including the fluid, a controller, a pressure generator connected to the controller and an isolator for isolating the pressure generator from the channel. In a further embodiment of a pneumatic fluid handling circuit according to the present invention, the pressure generator includes a gas pocket connected to the channel by the isolator, a flexible bladder connected to the gas pocket and a plunger connected to the flexible bladder, the plunger being controlled by the controller.
- The novel features of the invention are set forth with particularity in the appended claims. A better understanding of the features and advantages of the present invention will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the invention are utilized, and the accompanying drawings of which:
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FIG. 1 is a schematic illustration of sample liquid entering a pneumatic liquid handling circuit, according to one embodiment of the present invention. -
FIG. 2 is a schematic illustration of sample liquid reaching a fill detector in the pneumatic liquid handling circuit ofFIG. 1 . -
FIG. 3 is a schematic illustration of first sample bolus formation in the pneumatic liquid handling circuit ofFIG. 1 . -
FIG. 4 is a schematic illustration of first sample bolus positioning in the pneumatic liquid handling circuit ofFIG. 1 . -
FIG. 5 is a schematic illustration of sample liquid flow in the pneumatic liquid handling circuit ofFIG. 1 . -
FIG. 6 is a schematic illustration of second sample bolus formation in the pneumatic liquid handling circuit ofFIG. 1 . -
FIG. 7 is a schematic illustration of combined sample bolus formation in the pneumatic liquid handling circuit ofFIG. 1 . -
FIG. 8 is a schematic illustration of combined sample bolus positioning in the pneumatic liquid handling circuit ofFIG. 1 . -
FIG. 9 is an illustration of an alternative embodiment of the pneumatic liquid handling circuit ofFIG. 1 . -
FIG. 10 is a schematic illustration of a bladder-containing pneumatic liquid handling circuit. -
FIG. 1 is a schematic illustration of a pneumatic liquid handling circuit, according to an embodiment of the present invention.FIGS. 2 through 8 illustrate flow of sample liquid through the pneumatic liquid handling circuit ofFIG. 1 .FIG. 9 is an illustration of an alternative embodiment of the pneumatic liquid handling circuit ofFIG. 1 .FIG. 10 is a schematic illustration of a bladder-containing pneumatic liquid handling circuit - The pneumatic liquid handling circuits illustrated in
FIGS. 1 through 10 (which may also be referred to as fluid handling circuits including a pneumatic actuator) can be used to measure analyte in sample liquid. Sample liquid can be interstitial fluid, whole blood, or plasma. Flow into pneumatic liquid handling circuits can be driven by capillary, gravitational, and centrifugal forces. Flow into pneumatic liquid handling circuits can also be driven by pressurized gas, pumps, or by pressure at the source of sample liquid. Flow channels in pneumatic liquid handling circuits can be rectangular, square, or semicircular in cross section, although most preferably flow channels are rectangular in cross section, making them easier to manufacture. The length, width, and depth of flow channels vary, but are generally on the order of 25 to 2500 microns, and are often 500 microns or less. Pneumatic liquid handling circuits can be constructed using laminated layers of plastic, bonded with adhesive, or can be injection molded plastic. Suitable plastics include polyester, polycarbonate, acrylic, polystyrene, polyolefins, polyimides, and any other thermoplastic polymers. Pneumatic liquid handling circuits may also be constructed using etched silicon or glass. -
FIG. 1 is a schematic illustration ofsample liquid 20 entering pneumaticliquid handling circuit 2 in the direction ofarrow 200, according to an embodiment of the present invention. Pneumaticliquid handling circuit 2 includesmain channel 10, in whichsample liquid 20 flows from left to right.Fill detector 30, located withinmain channel 10, is used to detect the presence ofsample liquid 20.Pneumatic actuator 95 includesgas pocket 70,heater 80, andcontroller 90.Gas pocket 70 is connected tomain channel 10 by way of first branchingchannel 65. First branchingchannel 65 includes firsthydrophobic area 62. Firsthydrophobic area 62 prevents sample liquid 20 from flowing intogas pocket 70, for reasons explained below. When multiplied by the cross sectional area ofmain channel 10, measureddistance 35 defines a fixed volume withinmain channel 10, between branchingchannel 65 and filldetector 30. Pneumaticliquid handling circuit 2 includesvent 50. Gas flows throughvent 50, butsample liquid 20 does not. Vent 50 branches frommain channel 10, and includes secondhydrophobic area 60. Pneumaticliquid handling circuit 2 includesanalyte sensor 40, located down stream ofvent 50.Analyte sensor 40 is used to determine analyte concentration insample liquid 20. - In a preferred embodiment,
analyte sensor 40 measures glucose, and sample liquid 20 is interstitial fluid. When measuring glucose,analyte sensor 40 can contain a redox reagent system that includes an enzyme and redox active compounds or mediators. A variety of mediators are known in the art, such as ferricyanide, phenazine ethosulphate, phenazine methosulfate, pheylenediamine, 1-methoxy-phenazine methosulfate, 2,6-dimethyl-1,4-benzoquinone, 2,5-dichloro-1,4-benzoquinone, ferrocene derivatives, osmium bipyridyl complexes, and ruthenium complexes. Suitable enzymes include glucose oxidase and dehydrogenase (both NAD and PQQ based). Other substances that may be present in a redox reagent system include buffering agents (e.g., citraconate, citrate, malic, maleic, and phosphate buffers); divalent cations (e.g., calcium chloride, and magnesium chloride); surfactants (e.g., Triton, Macol, Tetronic, Silwet, Zonyl, and Pluronic); and stabilizing agents (e.g., albumin, sucrose, trehalose, mannitol and lactose). Other analytes and indicators which can be measured in the system of the present invention include urea, hemoglobin, lactate, alcohol, cholesterol, amino acids, choline, and coagulation factors. -
Hydrophobic areas hydrophobic areas hydrophobic areas sample liquid 20 must exceed the burst pressures of thehydrophobic areas sample liquid 20. In designing pneumaticliquid handling circuit 2, burst pressures can be selected that prevent flow ofsample liquid 20 beyondhydrophobic areas Hydrophobic areas hydrophobic area 62 insulatesgas pocket 70 from the fluid inmain channel 10 andchannel 50 from the fluid inmain channel 10 but allows air to pass out ofgas pocket 70 and intochannel 50. A structural passive valve useable as an insulator or in place ofhydrophobic areas channel 65 if used to replacehydrophobic area 62 or a widening inchannel 50 if used to replace hydrophobic area 60) such that when a liquid front reaches the sudden widening, a meniscus is formed at the point of the widening (angle preferable more acute than 90 degrees. In order for the liquid to move into the wider section of the channel, the liquid needs to be pressurized so that the menicus is pushed ‘around the edge’ thereby wetting the wider area. This requires, as with the hydrophobic based passive valve, a minimum pressure which is referred to as burst pressure. - In fabricating
hydrophobic areas hydrophobic areas - When characterizing the wettability of a surface, its contact angle with water is often measured. To do this, a drop of water is placed onto the surface, and the angle is measured between the surface and a line drawn tangent to the liquid drop. As a point of reference, completely hydrophobic material has a contact angle with water of 180 degrees, while untreated polyester typically has a contact angle of approximately 70 degrees. Hydrophilic surfaces can have a contact angle as low as 0 degrees. In this invention, hydrophobic areas typically have a contact angle of between 70 and 180 degrees, while hydrophilic areas typically have a contact angle of between 0 and 70 degrees. When screen printed onto polyester, FluoroPel PFC MH forms a hydrophobic area having a contact angle with water of approximately 150 degrees.
- Cytonix offers hydrophobic ink formulations that have been optimized for use with other types of printing, such as flexo and offset, as well as spray coating. Hydrophobic inks such as those used in printing microscope slides are also suitable for use in printing hydrophobic areas. Alternatively, commercially available screen printing inks can be modified for use in printing hydrophobic areas. For example, Zonyl fluoroadditives, sold by DuPont Corporation of Delaware, can be used as an additive to traditional screen printing inks.
-
FIG. 2 is a schematic illustration ofsample liquid 20 flowing in the direction ofarrow 202 and reachingfill detector 30.Fill detector 30 detects the presence ofsample liquid 20 using various methods. For example, filldetector 30 can include electrodes for measuring conductivity and/or capacitance ofsample liquid 20. Alternatively, filldetector 30 can be optical, and detect sample by measuring a change in optical properties whensample liquid 20 reaches filldetector 30. Further details in regard to fill detectors suitable for use in devices according to the present invention are included in U.S. patent application Ser. No. 10/811,446 filed on Mar. 26, 2004, which is hereby incorporated by reference. -
Feedback loop 31 provides electronic connection betweenfill detector 30 andcontroller 90. Assample liquid 20 flows in the direction ofarrow 202, and reachesfill detector 30, it is detected andpneumatic actuator 95 is activated by a signal fromfeedback loop 31. Whenpneumatic actuator 95 is activated,heater 80 turns on, heating the air ingas pocket 70. As illustrated inFIG. 3 , air ingas pocket 70 expands as it is heated, expanding into branchingchannel 65 andmain channel 10. Expandedair pocket 300 formsfirst sample bolus 20 a, which may also be referred to as a sample plug, and forcesfirst sample bolus 20 a towardsvent 50, in the direction ofarrow 206. The volume offirst sample bolus 20 a is determined by multiplying measureddistance 35 times the cross sectional area ofmain channel 10, as discussed in reference toFIG. 1 . - As illustrated in
FIG. 4 ,heater 80 continues to heat the air ingas pocket 70, causing the air to expand in the direction ofarrow 208, and increasing the size of expandedair pocket 302. This causesfirst sample bolus 20 a to move downmain channel 10 in the direction ofarrow 230. As the trailingedge 21 offirst sample bolus 20 a reaches vent 50, expandedair pocket 302 is vented to atmosphere by way ofvent 50 in the direction ofarrow 210. Movement offirst sample bolus 20 a in the direction ofarrow 230 stops.Heater 80 is then turned off, and the air contained ingas pocket 70 and expandedair pocket 302 returns to ambient temperature and pressure.First sample bolus 20 a stops because the pressure inmain channel 10 is atmospheric on both sides ofsample bolus 20 a. The change in pressure to atmospheric is almost instantaneous, resulting in substantially immediate stabilization offirst sample bolus 20 a. - Various means can be used for determining when to turn off
heater 80. This includes using a fixed time afterfirst sample bolus 20 a has been detected atanalyte sensor 40, or by using a fixed time afterfirst sample bolus 20 a leaves contact withfill detector 30. In either case,heater 80 is turned off seconds after trailingedge 21 makes contact withvent 50. - While
first sample bolus 20 a is in contact withanalyte sensor 40, various measurements can be made. This includes, for example, electrochemical determination of glucose concentration inbolus 20 a. Measurements can be made whilefirst sample bolus 20 a is stationary, or whilefirst sample bolus 20 a is flowing overanalyte sensor 40. - The next step in the sequence is illustrated in
FIG. 5 . While measurements are made onfirst sample bolus 20 a usinganalyte sensor 40,air pocket 304 remains at atmospheric pressure because it is in direct contact with the atmosphere by way ofvent 50 in the direction ofarrow 214. Sample liquid 20 flows in the direction ofarrow 212, towardsfill detector 30. Assample liquid 20 flows in the direction ofarrow 212,air pocket 304 is vented by way ofvent 50, leavingfirst sample bolus 20 a stationary.Sample bolus 20 a is stationary because the pressure on either side ofsample bolus 20 a is the same. - While
sample liquid 20 flows in the direction ofarrow 212,heater 80 is off, and the gas ingas pocket 70 cools. While the gas ingas pocket 70 cools, its pressure decreases, causing a pressure differential across firsthydrophobic area 62. This can be undesirable, in that it provides a driving force for flow ofsample liquid 20 intogas pocket 70. Flow ofsample liquid 20 intogas pocket 70 could interfere withheater 80 in subsequent steps. Flow ofsample liquid 20 intogas pocket 70 can be avoided using a variety of techniques. In one technique, firsthydrophobic area 62 can be designed to have a burst pressure in excess of the pressure differential caused by cooling the gas ingas pocket 70. In this case, the decrease in pressure while the gas ingas pocket 70 cools is insufficient to causesample liquid 20 to flow beyond firsthydrophobic area 62. A second technique for preventing the flow ofsample liquid 20 intogas pocket 70 is illustrated inFIG. 9 . In this technique,gas pocket 70 is provided withgas pocket vent 76 that is always open to atmosphere. Whensample liquid 20 flows in the direction ofarrow 212,gas pocket 70 maintains direct contact with atmosphere by way ofgas pocket vent 76. Whenheater 80 is turned off, and gas ingas pocket 70 cools, air is drawn intogas pocket 70 throughgas pocket vent 76 in the direction ofarrow 232, maintaining atmospheric pressure ingas pocket 70. This decreases the difference in pressure between sample liquid 20 and the gas ingas pocket 70, minimizing the driving force for flow ofsample liquid 20 intogas pocket 70. When heating the gas ingas pocket 70,heater 80 can be driven with sufficient power to compensate for escape of gas by way ofgas pocket vent 76, allowing the pressure of gas ingas pocket 70 to increase, as needed. In designinggas pocket vent 76, the resistance to flow ingas pocket vent 76 can be controlled. Two variables that effect the resistance to flow ingas pocket vent 76 are its cross sectional area and its length.Gas pocket vent 76 can be fabricated using laminates or injection molding, or with any of the techniques outlined earlier. - Returning to
FIG. 5 , as the leadingedge 22 ofsample liquid 20 reaches filldetector 30, a signal is sent tocontroller 90 by way offeedback loop 31.Heater 80 is activated, increasing the temperature and pressure of the air ingas pocket 70. As the air ingas pocket 70 expands, asecond sample bolus 20 b forms, as illustrated inFIG. 6 . As the air ingas pocket 70 continues to expand, expandedair pocket 306 increases in size, forcingsecond sample bolus 20 b to move in the direction ofarrow 218, towardsvent 50 andfirst sample bolus 20 a. The air inair pocket 308 escapes throughvent 50 in the direction ofarrow 220. During this time,first sample bolus 20 a remains stationary because the pressure on either side of it is the same. - In time, leading
edge 22 ofsecond sample bolus 20 b reaches trailingedge 21 offirst sample bolus 20 a, and the bolus combine, forming combinedsample bolus 20 c, as illustrated inFIG. 7 . The point at whichfirst sample bolus 20 a andsecond sample bolus 20 b combine is indicated bylabel 100.Heater 80 continues to heat the air ingas pocket 70, increasing the size of expandedair pocket 310 and causing combinedsample 20 c to flow in the direction ofarrow 224. Eventually, second trailingedge 23 reaches vent 50, as illustrated inFIG. 8 . - As trailing
edge 23 reaches vent 50, expandedair pocket 312 is vented to atmosphere by way ofvent 50 in the direction ofarrow 228. Since the pressure on both sides of combinedsample bolus 20 c are at atmospheric pressure, combinedsample bolus 20 c remains stationary. At this point,heater 80 is turned off, and sample liquid 20 flows intomain channel 10, repeating the sequence outlined above. - While combined
sample bolus 20 c is stationary, a measurement can be made usinganalyte sensor 40. As indicated bylabel 100, the portion of sample in contact withanalyte sensor 40 originates fromsecond sample bolus 20 b. As long as flow inmain channel 10 remains laminar, measurement on a portion of combinedsample bolus 20 c originating fromsecond sample bolus 20 b is possible. Factors effecting laminar flow include the cross sectional area ofmain channel 10, the flow rate of combinedsample bolus 20 c, and the physical properties of combinedsample bolus 20 c. Measurements usinganalyte sensor 40 should be made within seconds after second trailingedge 23 reaches vent 50. This minimizes diffusion of analyte between portions from the first and second sample bolus. - In an alternative embodiment, a mechanical approach can be used to move sample liquid in a pneumatic liquid handling circuit. Instead of using a heater to generate pressure, a flexible bladder is used. An actuator compresses the bladder, generating pressure and causing flow. A bladder-containing pneumatic
liquid handling circuit 400 is illustrated inFIG. 10 . The procedure for using bladder-containing pneumaticliquid handling circuit 400 is identical to that used for the circuits illustrated inFIGS. 1 through 9 with the exception that an actuator and bladder is used instead of a heater. - A variety of bladder designs can be used. In some designs, a pocket is created, and at least one flexible cover is placed over the pocket. The pocket is directly connected to the flow channels, and, when squeezed, generates pressure that moves liquid. Covers can be fabricated using many materials, such as metals and plastics. A particularly suitable material includes thin polymer films, such as 0.004″ thick polyester, polycarbonate, polyolefins, or acrylic. Elastomeric films can also be used. Pockets can be created using injection molded plastics, such as ABS, polycarbonate, or acrylics, or can be formed using die cut laminates.
- Actuators for compressing a bladder can take many shapes. A particularly useful actuator includes the use of a solenoid coupled to a plunger. When energized, the solenoid moves a plunger that compresses the bladder. When the solenoid is de-energized, the bladder returns to its original shape. Solenoids and plungers are typically housed in an external device.
- Further details in regard to bladders and actuators suitable for use in devices according to the present invention are included in U.S. patent application Ser. No. 10/666,846 filed on Sep. 18, 2004, and U.S. patent application Ser. No. 09/637,504 filed on Aug. 11, 2000, which are hereby incorporated by reference.
-
FIG. 10 is an illustration of a bladder-containing pneumaticliquid handling circuit 400. Bladder-containing pneumaticliquid handling circuit 400 includesmain channel 408, in which sample liquid 420 flows. Fill detector 414, located within main channel 420, is used to detect sample liquid 420.Pneumatic actuator 402 includesplunger 418,solenoid 406.Bladder 404 is connected tomain channel 408 by way of first branchingchannel 410. First branchingchannel 410 includes firsthydrophobic area 412. Firsthydrophobic area 412 prevents sample liquid 420 from enteringbladder 404.Feedback loop 416 provides electronic connection between fill detector 414 andsolenoid 406. When sample liquid 420 reaches fill detector 414, it is detected, andsolenoid 406 is activated by way offeedback loop 416. When solenoid 406 is activated, it causesplunger 418 to compressbladder 404 and displaces air withinbladder 404, in thesame way heater 80 causes displacement in the designs illustrated inFIGS. 1 through 9 . - Methods of using the pneumatic liquid handling circuits illustrated in
FIGS. 1-10 are envisioned. The method described below is in reference to the embodiment illustrated inFIGS. 1-9 . However, it can be easily adapted for use with the design illustrated inFIG. 10 . - A method begins with application of
sample liquid 20 tomain channel 10. The driving force for flow ofsample liquid 20 throughmain channel 10 can be capillary, gravitational, centrifugal, or can be provided by pressurized gas or a pump. It can also be provided by the source ofsample liquid 20. The driving force should be sufficient to cause flow throughmain channel 10, but not so great as to cause flow beyondhydrophobic areas fill detector 30, followed by a signal fromfill detector 30 tocontroller 90 by way offeedback loop 31. In response to the signal,heater 80 is turned on, leading to the formation offirst sample bolus 20 a. Once the trailingedge 21 offirst sample bolus 20 a has reachedvent 50,heater 80 is turned off, and the concentration of analyte in thesample liquid 20 is monitored usinganalyte sensor 40. Assample liquid 20 reaches filldetector 30 again, a signal is sent fromfill detector 30 tocontroller 90 by way offeedback loop 31, andheater 80 is once again turned on. As the air ingas pocket 70 expands, asecond sample bolus 20 b is formed, and moves toward thefirst sample bolus 20 a andvent 50. As thesecond trailing edge 23 reaches vent 50,heater 80 is turned off, and the concentration of analyte in thesecond sample bolus 20 b is determined usinganalyte sensor 40. This method can be repeated as necessary, and can be part of a broader monitoring method. - It will be recognized that equivalent structures may be substituted for the structures illustrated and described herein and that the described embodiment of the invention is not the only structure which may be employed to implement the claimed invention. In addition, it should be understood that every structure described above has a function and such structure can be referred to as a means for performing that function. While preferred embodiments of the present invention have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions will now occur to hose skilled in the art without departing from the invention. It should be understood that various alternatives to the embodiments of the invention described herein may be employed in practicing the invention. It is intended that the following claims define the scope of the invention and that methods and structures within the scope of these claims and their equivalents be covered thereby.
Claims (11)
1. A pneumatic actuator for bolus generation in a fluid handling circuit, said pneumatic actuator comprising:
a channel including said fluid;
a controller;
a pressure generator connected to said controller; and
an isolator for isolating said pressure generator from said channel.
2. A pneumatic actuator for bolus generation according to claim 1 wherein said pressure generator further comprises:
a gas pocket connected to said channel through said isolator; and
a heater controlled by said controller and adapted to heat gas in said gas pocket.
3. A pneumatic actuator for bolus generation according to claim 3 wherein said pressure generator comprises a vent adapted to vent gas from said gas pocket.
4. A pneumatic actuator for bolus generation according to claim 2 wherein said pressure generator comprises:
a gas pocket connected to said channel by said isolator;
a flexible bladder connected to said gas pocket; and
a plunger connected to said flexible bladder, said plunger being controlled by said controller.
5. A pneumatic actuator for bolus generation according to claim 4 wherein said pressure generator comprises a vent adapted to vent gas from said gas pocket.
6. A pneumatic actuator for bolus generation according to claim 5 wherein said isolator comprises a hydrophobic patch.
7. A pneumatic fluid handling circuit including a pneumatic actuator for bolus generation, said pneumatic fluid handling circuit comprising:
a channel including said fluid;
a fill detector positioned in said channel;
a pneumatic actuator connected to said channel upstream from said fill detector;
a controller connected between said fill detector and said pneumatic actuator;
a vent connected to said channel at a predetermined distance downstream from said fill detector; and
an analyte sensor positioned in said channel downstream from said vent.
8. A pneumatic fluid handling circuit according to claim 7 wherein said pneumatic actuator comprises:
a channel including said fluid;
a controller;
a pressure generator connected to said controller; and
an isolator for isolating said pressure generator from said channel.
9. A pneumatic fluid handling circuit according to claim 8 wherein said pressure generator comprises:
a gas pocket connected to said channel through said isolator; and
a heater controlled by said controller and adapted to heat gas in said gas pocket.
10. A pneumatic fluid handling circuit according to claim 9 wherein said pressure generator further comprises a vent adapted to vent gas from said gas pocket.
11. A pneumatic fluid handling circuit according to claim 8 wherein said pressure generator comprises:
a gas pocket connected to said channel by said isolator;
a flexible bladder connected to said gas pocket; and
a plunger connected to said flexible bladder, said plunger being controlled by said controller.
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US11/095,635 US20050220644A1 (en) | 2004-03-31 | 2005-03-30 | Pneumatic actuator for bolus generation in a fluid handling circuit |
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US55839004P | 2004-03-31 | 2004-03-31 | |
US55837504P | 2004-03-31 | 2004-03-31 | |
US11/095,635 US20050220644A1 (en) | 2004-03-31 | 2005-03-30 | Pneumatic actuator for bolus generation in a fluid handling circuit |
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