WO2022159098A1 - In place fluid mixing within microfluidic device chamber - Google Patents

In place fluid mixing within microfluidic device chamber Download PDF

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Publication number
WO2022159098A1
WO2022159098A1 PCT/US2021/014598 US2021014598W WO2022159098A1 WO 2022159098 A1 WO2022159098 A1 WO 2022159098A1 US 2021014598 W US2021014598 W US 2021014598W WO 2022159098 A1 WO2022159098 A1 WO 2022159098A1
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WO
WIPO (PCT)
Prior art keywords
chamber
microfluidic device
fluidic
thermal firing
sidewalls
Prior art date
Application number
PCT/US2021/014598
Other languages
French (fr)
Inventor
Erik D. Torniainen
Richard W. Seaver
Carson DENISON
Alexander Govyadinov
Pavel Kornilovich
Anand Samuel JEBAKUMAR
Original Assignee
Hewlett-Packard Development Company, L.P.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Publication date
Application filed by Hewlett-Packard Development Company, L.P. filed Critical Hewlett-Packard Development Company, L.P.
Priority to PCT/US2021/014598 priority Critical patent/WO2022159098A1/en
Publication of WO2022159098A1 publication Critical patent/WO2022159098A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D1/00—Evaporating
    • B01D1/0011—Heating features
    • B01D1/0017—Use of electrical or wave energy
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01L—CHEMICAL OR PHYSICAL LABORATORY APPARATUS FOR GENERAL USE
    • B01L3/00—Containers or dishes for laboratory use, e.g. laboratory glassware; Droppers
    • B01L3/50—Containers for the purpose of retaining a material to be analysed, e.g. test tubes
    • B01L3/502—Containers for the purpose of retaining a material to be analysed, e.g. test tubes with fluid transport, e.g. in multi-compartment structures
    • B01L3/5027—Containers for the purpose of retaining a material to be analysed, e.g. test tubes with fluid transport, e.g. in multi-compartment structures by integrated microfluidic structures, i.e. dimensions of channels and chambers are such that surface tension forces are important, e.g. lab-on-a-chip
    • B01L3/50273—Containers for the purpose of retaining a material to be analysed, e.g. test tubes with fluid transport, e.g. in multi-compartment structures by integrated microfluidic structures, i.e. dimensions of channels and chambers are such that surface tension forces are important, e.g. lab-on-a-chip characterised by the means or forces applied to move the fluids
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01L—CHEMICAL OR PHYSICAL LABORATORY APPARATUS FOR GENERAL USE
    • B01L2400/00—Moving or stopping fluids
    • B01L2400/04—Moving fluids with specific forces or mechanical means
    • B01L2400/0403—Moving fluids with specific forces or mechanical means specific forces
    • B01L2400/0442—Moving fluids with specific forces or mechanical means specific forces thermal energy, e.g. vaporisation, bubble jet

Definitions

  • Microfluidic devices leverage the physical and chemical properties of liquids and gases at a small scale, such as at a sub-millimeter scale.
  • Microfluidic devices geometrically constrain fluids to precisely control and manipulate the fluids for a wide variety of different applications.
  • Such applications can include digital microfluidic (DMF) and DNA applications, singlecell technologies, as well as applications as varied as lab-on-a-chip, inkjet, electrophoresis, microreactors, capacitance sensing, fluidic heat sink, and fluidic sensor probe applications, among other applications.
  • DMF digital microfluidic
  • DNA applications singlecell technologies
  • applications as varied as lab-on-a-chip, inkjet, electrophoresis, microreactors, capacitance sensing, fluidic heat sink, and fluidic sensor probe applications, among other applications.
  • FIG. 1 A is a cross-sectional top view diagram of an example microfluidic device providing in place fluid mixing within a chamber of the device.
  • FIGs. 1 B and 1C are cross-sectional front and back view diagrams, respectively, of the example microfluidic device of FIG. 1A.
  • FIGs. 1 D and 1 E are cross-sectional right and left side view diagrams, respectively of the example microfluidic device of FIG. 1A.
  • FIGs. 2A, 2B, and 2C are cross-sectional top view and left and right side view diagrams, respectively, of another example microfluidic device providing in place fluid mixing within a chamber of the device.
  • FIG. 3 is a flowchart of an example method for in place fluid mixing within a microfluidic device chamber.
  • FIG. 4 is a diagram of an example graph of in place fluid mixing within a microfluidic device chamber over time.
  • FIG. 5 is a block diagram of an example microfluidic device providing in place fluid mixing within a chamber of the chamber.
  • a fluidic sample may be mixed with a fluidic reagent to determine the presence or absence of a type of DNA to which the reagent is sensitive.
  • the resulting fluidic mixture may change in color in the presence of the type of DNA in question.
  • the sample and reagent fluids should be mixed thoroughly. Further the fluidic mixture may not change in color until a length of time after the fluids have been mixed.
  • a microfluidic device is described herein that provides for in place mixing of different fluids.
  • the microfluidic device includes a chamber and multiple thermal firing elements.
  • the chamber includes fluidic inlets that respectively receive different fluids. Firing the thermal firing elements mixes the different fluids in place within the chamber in which the fluids have been introduced. For instance, the thermal firing elements may be alternately or simultaneously periodically fired at a specified frequency over a specified length of time.
  • the different fluids are mixed in place, or in situ, in that the fluids are not flowing through the chamber at the time of mixing. Rather, the fluids are received at the chamber, and then remain stationary within the chamber at the time of mixing via firing of the thermal firing elements. This ensures that the fluids can be mixed thoroughly, which may not be possible if the fluids were passing through the chamber or a channel while the thermal firing elements are fired.
  • a reagent fluid may become locally exhausted within the chamber. Therefore, mixing the fluids in place ensures that inter-fluidic reactions occur throughout the chamber without the potential of local reagent fluid exhaustion.
  • thermal firing elements In place fluid mixing via agitation of the fluid resulting from firing thermal firing elements is also much faster than in place fluid mixing that relies on just fluidic diffusion. Particularly for micron-sized fluidic particles, diffusion may occur much too slowly for adequate fluid mixing to occur within a reasonable amount of time. By comparison, the firing of thermal firing elements introduces disturbances and movements into the fluids, permitting them to mix more efficiently in a convection-like manner.
  • FIGs. 1A, 1 B, 1C, 1D, and 1E show an example microfluidic device 100 that provides in place fluid mixing.
  • FIG. 1A is a cross-sectional top view of the device 100 at the cross-sectional arrows 101A of FIGs. 1B, 1C, 1 D, and 1 E.
  • FIGs. 1 B and 1C are cross-sectional front and back views of the device 100 at the cross-sectional arrows 101 B and 101C, respectively, of FIGs. 1A, 1D, and 1 E.
  • FIGs. 1 D and 1 E are cross-sectional right and left views of the device 100 at the cross-sectional arrows 101 D and 101 E, respectively of FIGs. 1A, 1 B, and 1C.
  • the microfluidic device 100 includes a chamber 102.
  • the chamber 102 has fluidic inlets 104A and 104B, which are collectively referred to as the fluidic inlets 104, and which are respectively fluidically connected to fluidic channels 106A and 106B that are collectively referred to as the fluidic channels 106. Whereas two fluidic inlets 104 and two corresponding fluidic channels 106 are depicted in the example, there can be more or fewer than two inlets 104 and two channels 106. Whereas the fluidic inlets 104 and thus the fluidic channels 106 are depicted as circular in cross-sectional shape, they can have a different shape.
  • the microfluidic device 100 can also include other channels, other chambers, and/or other fluidic components in addition to those depicted. For instance, the chamber 102 can include a fluidic outlet.
  • the chamber 102 receives different fluids at the fluidic inlets 104. That is, the chamber 102 receives a first fluid at the fluidic inlet 104A and a different, second fluid at the fluidic inlet 104B.
  • the fluids may be introduced into and flow through the fluidic channels 106 and then enter the chamber 102 at the fluidic inlets 104 that fluidically connect to the channels 106 to the chamber 102.
  • the fluids remain stationary and in place, or in situ, within the chamber 102. The fluids remain stationary within the chamber 102 in that the fluids are not subject to fluidic flow through or out of the chamber, at least until the fluids have been mixed.
  • the microfluidic device 100 includes thermal firing elements 108A and 108B, collectively referred to as the firing elements 108, within the chamber 102.
  • the thermal firing elements 108 may be thermal firing resistors of the type ordinarily found within fluid-ejection devices, such as inkjet-printing devices, to eject fluid like ink from a fluidic printhead die. Firing of the thermal firing element 108 causes mixing of the fluids introduced into the chamber 102 at the inlets 104.
  • a thermal firing element 108 is fired by passing an electrical current through the thermal firing element 108 sufficient to nucleate a vapor bubble within the fluid in the chamber 102 near the thermal firing element 108, which in turn imparts a force to the fluid that results in fluidic displacement and thus fluid mixing within the chamber 102.
  • the thermal firing elements 108 may be of the same size or different sizes, and may be of the same aspect or different aspect ratios. In general, the greater the size of a thermal firing element 108, the greater the mixing of the fluids that firing of the thermal firing element 108 causes.
  • the chamber 102 of the microfluidic device 100 has sidewalls 110A, 110B, 110C, and 110D, which are collectively referred to as the sidewalls 110.
  • the front sidewall 110A is opposite the back sidewall 110B, and the sidewalls 110A and 110B define a centerline 112A halfway between them.
  • the left sidewall 110C is opposite the right sidewall 110D, and the sidewalls 110C and 110D define a centerline 112B halfway between them.
  • the centerlines 112A and 112B are collectively referred to as the centerlines 112, and are perpendicular to one another.
  • the fluidic inlet 104A is disposed between the sidewall 110C and the centerline 112B between the sidewalls 110C and 110D, and is closer to the sidewall 110C than to the centerline 112B.
  • the fluidic inlet 104B is disposed between the sidewall 110D and the centerline 112B and is closer to the sidewall 110D than to the centerline 112B.
  • the fluidic inlets 104 are centered between the sidewalls 110A and 110B, such that the centerline 112A symmetrically bisects each fluidic inlet 104.
  • the thermal firing element 108A is disposed between the fluidic inlet 104A and the centerline 112B between the sidewalls 110C and 110D, and is closer to the fluidic inlet 104A than to the centerline 112B.
  • the thermal firing element 108A is also disposed between the sidewall 110A and the centerline 112A between the sidewalls 110A and 110B, and is closer to the sidewall 110A than to the centerline 112A.
  • the thermal firing element 108B is similarly disposed between the fluidic inlet 104B and the centerline 112B and is closer to the fluidic inlet 104B than to the centerline 112B.
  • the thermal firing element 108B is similarly also disposed between the sidewall 110B and the centerline 112A and is closer to the sidewall 110B than to the centerline 112B.
  • each thermal firing element 108 is asymmetrically located between the sidewalls 110A and 110B as well as between the sidewalls 110C and 110D.
  • Each thermal firing element 108 is asymmetrically located between a corresponding sidewall 110A or 110B and the centerline 112A as well as between a corresponding fluidic inlet 104 and the centerline 112B.
  • thermal firing elements 108 relative to one another, relative to the sidewalls 110, and relative to the fluidic inlets 104 can also provide for better in place fluid mixing as compared to certain other configurations.
  • In place fluid mixing may be improved by locating each thermal firing elements 108 closer to a sidewall 110A or 110B than to the centerline 112A between the sidewalls 110.
  • In place fluid mixing may be improved by locating the thermal firing elements 108 halfway between the fluidic inlets 104, such as symmetrically bisecting the centerline 112B between the sidewalls 110C and 110D.
  • In place fluid mixing may be improved by locating the thermal firing elements 108 closer to one another, either touching or not touching each another, and simultaneously firing them.
  • the chamber 102 also has a floor 114A and a ceiling 114B opposite the floor 114A.
  • the fluid inlets 104 and the thermal firing elements 108 are disposed at the floor 114A.
  • either or both of the fluid inlets 104 may be disposed at the ceiling 114B, at any sidewall 110, and so on.
  • one fluid inlet 104 may be disposed at the floor 114A, the ceiling 114B, or one of sidewalls 110, and the other fluid inlet 104 may be disposed at a different one of the floor 114A, the ceiling 114B, and the sidewalls 110.
  • the microfluidic device 100 can also include a pillar 116 extending from the floor 114A to the ceiling 114B of the chamber 102.
  • a pillar 116 extending from the floor 114A to the ceiling 114B of the chamber 102.
  • Each such pillar 116 may have the same or different shape, including square, diamond, rectangular, round, and so on.
  • the presence of the pillar 116 extending from the floor 114A to the ceiling 114B and centrally located within the chamber 102 has been shown to provide for better in place fluid mixing as compared to if the pillar 116 were absent.
  • the pillar 116 presents a fluidic barrier that creates fluidic vortices within the chamber 102 during firing of the thermal firing elements 108. These fluidic vortices in turn increase the degree to which fluid mixing occurs at a given time.
  • the pillar 116 may be also be present to ensure that the ceiling
  • the microfluidic device 100 may include the pillar 116 even if collapse or bowing of the ceiling 114B is not a concern.
  • the pillar 116 is thus configured to improve in place fluid mixing.
  • FIGs. 1A, 1 B, 1C, 1D, and 1E includes a chamber 102 that has two inlets 104 located at the floor 114A of the chamber 102. However, as has also been noted, there may be more or fewer than two inlets 104. Each inlet 104 may be located at any sidewall 114, the floor 114A, or the ceiling 114B of the chamber.
  • FIGs. 2A, 2B, and 2C show the example microfluidic device 100 in which the chamber 102 includes just one fluidic inlet 104B located at the sidewall 110A.
  • FIG. 2A is a cross-sectional top view of the microfluidic device 100 at the cross-sectional arrows 101 A of FIGs. 2B and 2C.
  • FIG. 2B is a cross-sectional left view of the microfluidic device 100 at the cross-sectional arrow 101E of FIG. 2A.
  • FIG. 2C is a cross-sectional right view of the microfluidic device 100 at the cross-sectional arrow 101D of FIG. 2A.
  • the singular fluidic inlet 104B in the example of FIGs. 2A, 2B, and 2C is located closer to the sidewall 110D than to the opposing sidewall 110C.
  • the fluidic inlet 104B is further located closer to the floor 114A than to the ceiling 114B.
  • the microfluidic device 100 in the example of FIGs. 2A, 2B, and 2C again includes two thermal firing elements 108A and 108B, but does not include any pillars like the device 100 of FIGs. 1A, 1 B, 1C, 1 D, and 1 E does.
  • the microfluidic device 100 can include one or multiple pillars in the example of FIGs. 2A, 2B, and 2C.
  • the microfluidic device 100 of FIGs. 2A, 2B, and 2C further includes a fluidic outlet 202 that is fluidically coupled to a channel 204 and that is located at the sidewall 110B opposite the sidewall 110A at which the fluidic inlet 104B is located.
  • a fluidic outlet 202 that is fluidically coupled to a channel 204 and that is located at the sidewall 110B opposite the sidewall 110A at which the fluidic inlet 104B is located.
  • the fluidic outlet 202 is located closer to the sidewall 110C than to the opposing sidewall 110D.
  • the fluidic outlet 202 is further located closer to the floor 114A than to the ceiling 114B.
  • multiple different fluids can be introduced into the chamber 102 at the fluidic inlet 104B via the channel 106B.
  • the different fluids may be added to the chamber 102 at the same time, but in an unmixed state.
  • the different fluids may be added to the chamber 102 sequentially, such that one type of fluid is added, another type of fluid is then added, and so on.
  • the thermal firing elements 108 are fired to mix the fluids, as has been described in relation to FIGs. 1A, 1 B, 1C, 1 D and 1 E.
  • the resulting mixed fluids may then be caused to exit the chamber 102 at the fluidic outlet 202 via the channel 204.
  • FIG. 3 shows an example method 300 for in place fluid mixing within a microfluidic device chamber.
  • the method 300 is described in relation to the microfluidic device 100 of FIGs. 1A, 1B, 1C, 1 D, and 1 E.
  • the method 300 includes adding different fluids to the chamber 102 of the microfluidic device 100 at respective fluidic inlets 104 of the chamber 102 (302). For instance, a first fluid may be introduced to the chamber 102 at the fluidic inlet 104A, and a second, different fluid may be introduced to the chamber 102 at the fluidic inlet 104B.
  • fluids may also be introduced to the chamber 102 in an unmixed state at the same time or sequentially at the same fluidic inlet 104, such as in the example of FIGs. 2A and 2B in which there is just one inlet 104B.)
  • the fluids Once the fluids have been added to the chamber 102, the fluids remain stationary within the chamber 102 in that the fluids are not subject to net fluidic flow through or out of the chamber, at least until the fluids have been mixed.
  • the method 300 includes firing the thermal firing elements 108 of the microfluidic device 100 to mix the different fluids in place within the chamber 102 (304).
  • the thermal firing elements 108 may be alternately or simultaneously periodically fired a specified number of times at a specified frequency for a specified duration. Whether the thermal firing elements 108 are alternately or simultaneously fired, the number of times the thermal firing elements 108 are fired, the frequency at which the thermal firing elements 108 are fired, and the duration during which the thermal firing elements 108 are fired may be specified to ensure a desired degree of mixing of the fluids.
  • FIG. 4 shows an example graph 400 of in place fluid mixing within a microfluidic device chamber, specifically the chamber 102 of the microfluidic device 100 of FIGs. 1A, 1 B, 1C, 1 D, and 1 E, over time.
  • the graph 400 includes a line 406 corresponding to in place fluid mixing that can be achieved by performing the method 300 of FIG. 3.
  • the x-axis 402 denotes time
  • the y- axis 404 denotes the mixed state of the different fluids increasing downwards along the y-axis 404 from completely unmixed (i.e., 0% mixed) to 60% mixed where the y-axis 404 meets the x-axis 402.
  • the thermal firing element 108A is fired at the indicated short hash marks 408, whereas the thermal firing element 108B is fired at the indicated tall hash marks 410.
  • the example of FIG. 4 results in in place, or in situ, mixing of the fluids within the chamber 102 about 100,000 faster than if the fluids were instead mixed via natural diffusion alone.
  • FIG. 5 shows a block diagram of the example microfluidic device 100 that has been described.
  • the microfluidic device 100 includes a chamber 102 having one or multiple fluidic inlets 104 to respectively receive different fluids.
  • the microfluidic device 100 includes one or multiple thermal firing elements 108 to mix the different fluids in place within the chamber 102.
  • Techniques have been described for in place, or in situ, fluid mixing within a microfluidic device chamber. Thermal firing elements within the chamber are fired to mix the fluid within the chamber while the fluid is stationary within the chamber without any net fluidic motion into or out of the chamber.
  • the chamber may include one or multiple pillars to improve fluid mixing resulting from firing of the thermal firing elements.

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Abstract

A microfluidic device includes a chamber and one or multiple thermal firing elements. The chamber of the microfluidic device includes one or multiple fluidic inlets. The fluidic inlets of the chamber receive different fluids. The thermal firing elements of the microfluidic device mix the different fluids in place within the chamber.

Description

IN PLACE FLUID MIXING WITHIN MICROFLUIDIC DEVICE CHAMBER
BACKGROUND
[0001] Microfluidic devices leverage the physical and chemical properties of liquids and gases at a small scale, such as at a sub-millimeter scale.
Microfluidic devices geometrically constrain fluids to precisely control and manipulate the fluids for a wide variety of different applications. Such applications can include digital microfluidic (DMF) and DNA applications, singlecell technologies, as well as applications as varied as lab-on-a-chip, inkjet, electrophoresis, microreactors, capacitance sensing, fluidic heat sink, and fluidic sensor probe applications, among other applications.
BRIEF DESCRIPTION OF THE DRAWINGS
[0002] FIG. 1 A is a cross-sectional top view diagram of an example microfluidic device providing in place fluid mixing within a chamber of the device.
[0003] FIGs. 1 B and 1C are cross-sectional front and back view diagrams, respectively, of the example microfluidic device of FIG. 1A.
[0004] FIGs. 1 D and 1 E are cross-sectional right and left side view diagrams, respectively of the example microfluidic device of FIG. 1A.
[0005] FIGs. 2A, 2B, and 2C are cross-sectional top view and left and right side view diagrams, respectively, of another example microfluidic device providing in place fluid mixing within a chamber of the device.
[0006] FIG. 3 is a flowchart of an example method for in place fluid mixing within a microfluidic device chamber. [0007] FIG. 4 is a diagram of an example graph of in place fluid mixing within a microfluidic device chamber over time.
[0008] FIG. 5 is a block diagram of an example microfluidic device providing in place fluid mixing within a chamber of the chamber.
DETAILED DESCRIPTION
[0009] In some types of microfluidic device applications, different fluids may be mixed. For example, in polymerase chain reaction (PCR) microfluidic devices, a fluidic sample may be mixed with a fluidic reagent to determine the presence or absence of a type of DNA to which the reagent is sensitive. The resulting fluidic mixture may change in color in the presence of the type of DNA in question. For accurate diagnosis, the sample and reagent fluids should be mixed thoroughly. Further the fluidic mixture may not change in color until a length of time after the fluids have been mixed.
[0010] A microfluidic device is described herein that provides for in place mixing of different fluids. The microfluidic device includes a chamber and multiple thermal firing elements. The chamber includes fluidic inlets that respectively receive different fluids. Firing the thermal firing elements mixes the different fluids in place within the chamber in which the fluids have been introduced. For instance, the thermal firing elements may be alternately or simultaneously periodically fired at a specified frequency over a specified length of time.
[0011] The different fluids are mixed in place, or in situ, in that the fluids are not flowing through the chamber at the time of mixing. Rather, the fluids are received at the chamber, and then remain stationary within the chamber at the time of mixing via firing of the thermal firing elements. This ensures that the fluids can be mixed thoroughly, which may not be possible if the fluids were passing through the chamber or a channel while the thermal firing elements are fired.
[0012] In place fluid mixing also ensures that the mixture can remain within the chamber for a specified length of time, such as the minimum length of time for the mixture to change in color or otherwise complete a given reaction.
Furthermore, without in place fluid mixing, a reagent fluid may become locally exhausted within the chamber. Therefore, mixing the fluids in place ensures that inter-fluidic reactions occur throughout the chamber without the potential of local reagent fluid exhaustion.
[0013] In place fluid mixing via agitation of the fluid resulting from firing thermal firing elements is also much faster than in place fluid mixing that relies on just fluidic diffusion. Particularly for micron-sized fluidic particles, diffusion may occur much too slowly for adequate fluid mixing to occur within a reasonable amount of time. By comparison, the firing of thermal firing elements introduces disturbances and movements into the fluids, permitting them to mix more efficiently in a convection-like manner.
[0014] FIGs. 1A, 1 B, 1C, 1D, and 1E show an example microfluidic device 100 that provides in place fluid mixing. FIG. 1A is a cross-sectional top view of the device 100 at the cross-sectional arrows 101A of FIGs. 1B, 1C, 1 D, and 1 E.
FIGs. 1 B and 1C are cross-sectional front and back views of the device 100 at the cross-sectional arrows 101 B and 101C, respectively, of FIGs. 1A, 1D, and 1 E.
FIGs. 1 D and 1 E are cross-sectional right and left views of the device 100 at the cross-sectional arrows 101 D and 101 E, respectively of FIGs. 1A, 1 B, and 1C.
[0015] The microfluidic device 100 includes a chamber 102. The chamber 102 has fluidic inlets 104A and 104B, which are collectively referred to as the fluidic inlets 104, and which are respectively fluidically connected to fluidic channels 106A and 106B that are collectively referred to as the fluidic channels 106. Whereas two fluidic inlets 104 and two corresponding fluidic channels 106 are depicted in the example, there can be more or fewer than two inlets 104 and two channels 106. Whereas the fluidic inlets 104 and thus the fluidic channels 106 are depicted as circular in cross-sectional shape, they can have a different shape. The microfluidic device 100 can also include other channels, other chambers, and/or other fluidic components in addition to those depicted. For instance, the chamber 102 can include a fluidic outlet.
[0016] The chamber 102 receives different fluids at the fluidic inlets 104. That is, the chamber 102 receives a first fluid at the fluidic inlet 104A and a different, second fluid at the fluidic inlet 104B. For example, the fluids may be introduced into and flow through the fluidic channels 106 and then enter the chamber 102 at the fluidic inlets 104 that fluidically connect to the channels 106 to the chamber 102. Once the fluids enter the chamber 102, the fluids remain stationary and in place, or in situ, within the chamber 102. The fluids remain stationary within the chamber 102 in that the fluids are not subject to fluidic flow through or out of the chamber, at least until the fluids have been mixed. [0017] The microfluidic device 100 includes thermal firing elements 108A and 108B, collectively referred to as the firing elements 108, within the chamber 102. The thermal firing elements 108 may be thermal firing resistors of the type ordinarily found within fluid-ejection devices, such as inkjet-printing devices, to eject fluid like ink from a fluidic printhead die. Firing of the thermal firing element 108 causes mixing of the fluids introduced into the chamber 102 at the inlets 104. [0018] A thermal firing element 108 is fired by passing an electrical current through the thermal firing element 108 sufficient to nucleate a vapor bubble within the fluid in the chamber 102 near the thermal firing element 108, which in turn imparts a force to the fluid that results in fluidic displacement and thus fluid mixing within the chamber 102. The thermal firing elements 108 may be of the same size or different sizes, and may be of the same aspect or different aspect ratios. In general, the greater the size of a thermal firing element 108, the greater the mixing of the fluids that firing of the thermal firing element 108 causes. [0019] The chamber 102 of the microfluidic device 100 has sidewalls 110A, 110B, 110C, and 110D, which are collectively referred to as the sidewalls 110. The front sidewall 110A is opposite the back sidewall 110B, and the sidewalls 110A and 110B define a centerline 112A halfway between them. The left sidewall 110C is opposite the right sidewall 110D, and the sidewalls 110C and 110D define a centerline 112B halfway between them. The centerlines 112A and 112B are collectively referred to as the centerlines 112, and are perpendicular to one another. [0020] The fluidic inlet 104A is disposed between the sidewall 110C and the centerline 112B between the sidewalls 110C and 110D, and is closer to the sidewall 110C than to the centerline 112B. Similarly, the fluidic inlet 104B is disposed between the sidewall 110D and the centerline 112B and is closer to the sidewall 110D than to the centerline 112B. The fluidic inlets 104 are centered between the sidewalls 110A and 110B, such that the centerline 112A symmetrically bisects each fluidic inlet 104.
[0021] The thermal firing element 108A is disposed between the fluidic inlet 104A and the centerline 112B between the sidewalls 110C and 110D, and is closer to the fluidic inlet 104A than to the centerline 112B. The thermal firing element 108A is also disposed between the sidewall 110A and the centerline 112A between the sidewalls 110A and 110B, and is closer to the sidewall 110A than to the centerline 112A. The thermal firing element 108B is similarly disposed between the fluidic inlet 104B and the centerline 112B and is closer to the fluidic inlet 104B than to the centerline 112B. The thermal firing element 108B is similarly also disposed between the sidewall 110B and the centerline 112A and is closer to the sidewall 110B than to the centerline 112B.
[0022] The described and shown configuration of the thermal firing elements 108 relative to one another, relative to the sidewalls 110, and relative to the fluidic inlets 104 has been shown to provide for better in place fluid mixing as compared to certain other configurations. That is, the thermal firing elements 108 are configured to improve in place fluid mixing. In the example, each thermal firing element 108 is asymmetrically located between the sidewalls 110A and 110B as well as between the sidewalls 110C and 110D. Each thermal firing element 108 is asymmetrically located between a corresponding sidewall 110A or 110B and the centerline 112A as well as between a corresponding fluidic inlet 104 and the centerline 112B.
[0023] Other configuration of the thermal firing elements 108 relative to one another, relative to the sidewalls 110, and relative to the fluidic inlets 104 can also provide for better in place fluid mixing as compared to certain other configurations. In place fluid mixing may be improved by locating each thermal firing elements 108 closer to a sidewall 110A or 110B than to the centerline 112A between the sidewalls 110. In place fluid mixing may be improved by locating the thermal firing elements 108 halfway between the fluidic inlets 104, such as symmetrically bisecting the centerline 112B between the sidewalls 110C and 110D. In place fluid mixing may be improved by locating the thermal firing elements 108 closer to one another, either touching or not touching each another, and simultaneously firing them.
[0024] The chamber 102 also has a floor 114A and a ceiling 114B opposite the floor 114A. In the example, the fluid inlets 104 and the thermal firing elements 108 are disposed at the floor 114A. However, in another implementation, either or both of the fluid inlets 104 may be disposed at the ceiling 114B, at any sidewall 110, and so on. For example, one fluid inlet 104 may be disposed at the floor 114A, the ceiling 114B, or one of sidewalls 110, and the other fluid inlet 104 may be disposed at a different one of the floor 114A, the ceiling 114B, and the sidewalls 110. Either or both of the thermal firing elements 108 may similarly be disposed at the ceiling 114B, at any sidewall 110, and so on. [0025] The microfluidic device 100 can also include a pillar 116 extending from the floor 114A to the ceiling 114B of the chamber 102. In the example, there is one pillar 116 that is square in shape and that is centrally located within the chamber 102, at the intersection of the centerlines 112. However, there may be more than one pillar 116. Each such pillar 116 may have the same or different shape, including square, diamond, rectangular, round, and so on.
[0026] The presence of the pillar 116 extending from the floor 114A to the ceiling 114B and centrally located within the chamber 102 has been shown to provide for better in place fluid mixing as compared to if the pillar 116 were absent. Specifically, the pillar 116 presents a fluidic barrier that creates fluidic vortices within the chamber 102 during firing of the thermal firing elements 108. These fluidic vortices in turn increase the degree to which fluid mixing occurs at a given time.
[0027] The pillar 116 may be also be present to ensure that the ceiling
114B of the chamber 102 does not collapse or bow due to the size of the area of the chamber 102 defined by the perimeter of the sidewalls 110. However, since the pillar 116 does provide for better fluid mixing, the microfluidic device 100 may include the pillar 116 even if collapse or bowing of the ceiling 114B is not a concern. The pillar 116 is thus configured to improve in place fluid mixing.
[0028] As noted, the described example microfluidic device 100 of
FIGs. 1A, 1 B, 1C, 1D, and 1E includes a chamber 102 that has two inlets 104 located at the floor 114A of the chamber 102. However, as has also been noted, there may be more or fewer than two inlets 104. Each inlet 104 may be located at any sidewall 114, the floor 114A, or the ceiling 114B of the chamber.
[0029] FIGs. 2A, 2B, and 2C, for instance, show the example microfluidic device 100 in which the chamber 102 includes just one fluidic inlet 104B located at the sidewall 110A. FIG. 2A is a cross-sectional top view of the microfluidic device 100 at the cross-sectional arrows 101 A of FIGs. 2B and 2C. FIG. 2B is a cross-sectional left view of the microfluidic device 100 at the cross-sectional arrow 101E of FIG. 2A. FIG. 2C is a cross-sectional right view of the microfluidic device 100 at the cross-sectional arrow 101D of FIG. 2A.
[0030] The singular fluidic inlet 104B in the example of FIGs. 2A, 2B, and 2C is located closer to the sidewall 110D than to the opposing sidewall 110C. The fluidic inlet 104B is further located closer to the floor 114A than to the ceiling 114B. The microfluidic device 100 in the example of FIGs. 2A, 2B, and 2C again includes two thermal firing elements 108A and 108B, but does not include any pillars like the device 100 of FIGs. 1A, 1 B, 1C, 1 D, and 1 E does. However, in another implementation, the microfluidic device 100 can include one or multiple pillars in the example of FIGs. 2A, 2B, and 2C.
[0031] The microfluidic device 100 of FIGs. 2A, 2B, and 2C further includes a fluidic outlet 202 that is fluidically coupled to a channel 204 and that is located at the sidewall 110B opposite the sidewall 110A at which the fluidic inlet 104B is located. There may be more than one fluidic outlet 202, and each such outlet 202 may be located on the same or different sidewall 110, the floor 114A or the ceiling 114B. The fluidic outlet 202 is located closer to the sidewall 110C than to the opposing sidewall 110D. The fluidic outlet 202 is further located closer to the floor 114A than to the ceiling 114B.
[0032] Therefore, in the example of FIGs. 2A and 2B, multiple different fluids can be introduced into the chamber 102 at the fluidic inlet 104B via the channel 106B. The different fluids may be added to the chamber 102 at the same time, but in an unmixed state. The different fluids may be added to the chamber 102 sequentially, such that one type of fluid is added, another type of fluid is then added, and so on. Once the different fluids have been introduced into the chamber 102, the thermal firing elements 108 are fired to mix the fluids, as has been described in relation to FIGs. 1A, 1 B, 1C, 1 D and 1 E. The resulting mixed fluids may then be caused to exit the chamber 102 at the fluidic outlet 202 via the channel 204.
[0033] FIG. 3 shows an example method 300 for in place fluid mixing within a microfluidic device chamber. The method 300 is described in relation to the microfluidic device 100 of FIGs. 1A, 1B, 1C, 1 D, and 1 E. The method 300 includes adding different fluids to the chamber 102 of the microfluidic device 100 at respective fluidic inlets 104 of the chamber 102 (302). For instance, a first fluid may be introduced to the chamber 102 at the fluidic inlet 104A, and a second, different fluid may be introduced to the chamber 102 at the fluidic inlet 104B. (Different fluids may also be introduced to the chamber 102 in an unmixed state at the same time or sequentially at the same fluidic inlet 104, such as in the example of FIGs. 2A and 2B in which there is just one inlet 104B.) Once the fluids have been added to the chamber 102, the fluids remain stationary within the chamber 102 in that the fluids are not subject to net fluidic flow through or out of the chamber, at least until the fluids have been mixed.
[0034] The method 300 includes firing the thermal firing elements 108 of the microfluidic device 100 to mix the different fluids in place within the chamber 102 (304). The thermal firing elements 108 may be alternately or simultaneously periodically fired a specified number of times at a specified frequency for a specified duration. Whether the thermal firing elements 108 are alternately or simultaneously fired, the number of times the thermal firing elements 108 are fired, the frequency at which the thermal firing elements 108 are fired, and the duration during which the thermal firing elements 108 are fired may be specified to ensure a desired degree of mixing of the fluids.
[0035] In general, the greater the number of times the thermal firing elements 108 are fired, such as by increasing the frequency at which the thermal firing elements 108 are fired and/or the length of time during which the thermal firing elements 108 are fired, the greater the degree to which the fluids are mixed in place within the chamber 102. That the fluids are mixed in place or in situ does not mean that the fluids do not move within the chamber 102, but rather that there is no net motion of the fluids into or out of the chamber 102. The fluids are thus not flowing or passing through the chamber 102 during firing of the thermal firing elements 108. The fluids therefore remain stationary within the chamber 102 in this respect during fluid mixing. [0036] FIG. 4 shows an example graph 400 of in place fluid mixing within a microfluidic device chamber, specifically the chamber 102 of the microfluidic device 100 of FIGs. 1A, 1 B, 1C, 1 D, and 1 E, over time. The graph 400 includes a line 406 corresponding to in place fluid mixing that can be achieved by performing the method 300 of FIG. 3. The x-axis 402 denotes time, and the y- axis 404 denotes the mixed state of the different fluids increasing downwards along the y-axis 404 from completely unmixed (i.e., 0% mixed) to 60% mixed where the y-axis 404 meets the x-axis 402.
[0037] Once the different fluids have been introduced into the chamber 102 via the fluidic inlets 104, the thermal firing elements 108 are fired starting at denoted time t=0 over a duration of 1 .53 milliseconds, at which time the fluids are about 50% mixed. Specifically, the thermal firing elements 108 are alternately fired every 85 microseconds, for a total of 19 times. The thermal firing element 108A is fired at the indicated short hash marks 408, whereas the thermal firing element 108B is fired at the indicated tall hash marks 410. The example of FIG. 4 results in in place, or in situ, mixing of the fluids within the chamber 102 about 100,000 faster than if the fluids were instead mixed via natural diffusion alone.
[0038] FIG. 5 shows a block diagram of the example microfluidic device 100 that has been described. The microfluidic device 100 includes a chamber 102 having one or multiple fluidic inlets 104 to respectively receive different fluids. The microfluidic device 100 includes one or multiple thermal firing elements 108 to mix the different fluids in place within the chamber 102. [0039] Techniques have been described for in place, or in situ, fluid mixing within a microfluidic device chamber. Thermal firing elements within the chamber are fired to mix the fluid within the chamber while the fluid is stationary within the chamber without any net fluidic motion into or out of the chamber. The chamber may include one or multiple pillars to improve fluid mixing resulting from firing of the thermal firing elements.

Claims

We claim:
1 . A microfluidic device comprising: a chamber having one or multiple fluidic inlets to receive different fluids; and one or multiple thermal firing elements to mix the different fluids in place within the chamber.
2. The microfluidic device of claim 1 , wherein the thermal firing elements are thermal firing resistors.
3. The microfluidic device of claim 2, wherein the thermal firing resistors are of a same size.
4. The microfluidic device of claim 2, wherein the thermal firing resistors are of different sizes.
5. The microfluidic device of claim 1 , wherein the chamber has a plurality of sidewalls, a floor, and a ceiling opposite the floor, and wherein the thermal firing elements are disposed at the floor of the chamber.
6. The microfluidic device of claim 5, wherein the fluidic inlets are disposed at the floor or at the ceiling of the chamber.
7. The microfluidic device of claim 6, wherein the sidewalls of the chamber comprise first and second sidewalls opposite one another, the chamber having a first centerline halfway between the first and second sidewalls, wherein the thermal firing elements comprise first and second thermal firing elements that are respectively disposed closer to the first and second sidewalls than to the first centerline.
8. The microfluidic device of claim 7, wherein the sidewalls of the chamber comprise third and fourth sidewalls opposite one another, the chamber having a second centerline halfway between the third and fourth sidewalls, wherein the fluidic inlets comprise first and second fluidic inlets that are respectively disposed closer to the third and fourth sidewalls than to the second centerline.
9. The microfluidic device of claim 8, wherein the first thermal firing element is disposed between the first fluidic inlet and the second centerline and closer to the first fluidic inlet than to the second centerline, and wherein the second thermal firing element is disposed between the second fluidic inlet and the second centerline and closer to the second fluidic inlet than to the second centerline.
10. The microfluidic device of claim 6, further comprising a pillar extending from the floor to the ceiling of the chamber and configured to improve in place mixing of the different fluids.
11 . The microfluidic device of claim 10, wherein the pillar is centered within the chamber.
12. A method comprising: adding different fluids to a chamber at one or multiple fluidic inlets of the chamber; and firing a plurality of thermal firing elements to mix the different fluids in place within the chamber.
13. The method of claim 12, wherein the thermal firing elements are alternately fired.
14. The method of claim 12, wherein the thermal firing elements are simultaneously fired.
15. The method of claim 12, wherein the thermal firing elements are periodically fired over a length of time.
16
PCT/US2021/014598 2021-01-22 2021-01-22 In place fluid mixing within microfluidic device chamber WO2022159098A1 (en)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2014046687A1 (en) * 2012-09-24 2014-03-27 Hewlett-Packard Development Company, L.P. Microfluidic mixing device
US9174182B2 (en) * 2009-04-23 2015-11-03 Koninklijke Philips N.V. Mixer with zero dead volume and method for mixing
US20160136642A1 (en) * 2013-06-28 2016-05-19 Danmarks Tekniske Universitet A Microfluidic Device with Pillars
US20190060898A1 (en) * 2016-04-14 2019-02-28 Hewlett-Packard Development Company, L.P. Microfluidic device with capillary chamber

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9174182B2 (en) * 2009-04-23 2015-11-03 Koninklijke Philips N.V. Mixer with zero dead volume and method for mixing
WO2014046687A1 (en) * 2012-09-24 2014-03-27 Hewlett-Packard Development Company, L.P. Microfluidic mixing device
US20160136642A1 (en) * 2013-06-28 2016-05-19 Danmarks Tekniske Universitet A Microfluidic Device with Pillars
US20190060898A1 (en) * 2016-04-14 2019-02-28 Hewlett-Packard Development Company, L.P. Microfluidic device with capillary chamber

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