WO2022191830A1 - Vannes microfluidiques destructibles - Google Patents

Vannes microfluidiques destructibles Download PDF

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Publication number
WO2022191830A1
WO2022191830A1 PCT/US2021/021664 US2021021664W WO2022191830A1 WO 2022191830 A1 WO2022191830 A1 WO 2022191830A1 US 2021021664 W US2021021664 W US 2021021664W WO 2022191830 A1 WO2022191830 A1 WO 2022191830A1
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WO
WIPO (PCT)
Prior art keywords
generating material
gas
microfluidic
solid gas
microfluidic channel
Prior art date
Application number
PCT/US2021/021664
Other languages
English (en)
Inventor
Viktor Shkolnikov
Alexander Govyadinov
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.)
Filing date
Publication date
Application filed by Hewlett-Packard Development Company, L.P. filed Critical Hewlett-Packard Development Company, L.P.
Priority to PCT/US2021/021664 priority Critical patent/WO2022191830A1/fr
Publication of WO2022191830A1 publication Critical patent/WO2022191830A1/fr

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Classifications

    • 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
    • F16K99/0032—Constructional types of microvalves; Details of the cutting-off member using phase transition or influencing viscosity
    • 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

Definitions

  • Microfluidics relates to the behavior, precise control and manipulation of fluids that are geometrically constrained to a small, typically sub- millimeter, scale. Numerous applications employ passive fluid control techniques such as capillary forces. In some applications, external actuation techniques are employed for a directed transport of fluid. A variety of applications for microfluidics exist, with various applications involving differing controls over fluid flow, mixing, temperature, evaporation, and so on.
  • FIGs.1A-1B are schematic cross-sectional side views of an example destructible microfluidic valve in accordance with the present disclosure
  • FIG.2 is a schematic cross-sectional side view of another example destructible microfluidic valve in accordance with the present disclosure
  • FIGG.3 is a schematic cross-sectional side view of another example destructible microfluidic valve in accordance with the present disclosure
  • FIGG.4 is a schematic cross-sectional side view of yet another example destructible microfluidic valve in accordance with the present disclosure
  • FIG.5 is a schematic cross-sectional side view of still another example destructible microfluidic valve in accordance with the present disclosure
  • a destructible microfluidic valve includes a microfluidic channel, a solid gas-generating material positioned to block fluid flow through the microfluidic channel, and an electric initiator adjacent to the solid gas-generating material.
  • the solid gas-generating material is convertible to a gas through chemical reaction or sublimation.
  • the electric initiator is configured to initiate a chemical reaction or sublimation of the solid gas-generating material to convert the solid gas-generating material to a gas and allow fluid to flow through the microfluidic channel.
  • the electric initiator can include a thermal resistor or a spark gap.
  • the solid gas-generating material can be chemically reactive to form a gas by a thermal decomposition reaction or by a combustion reaction.
  • the solid gas-generating material can include an Azobis compound, a peroxide, a carbonate, a nitrate, a nitrite, an azide, nitrocellulose, polyvinyl nitrate, nitrated poly(aryl ether ketone), a mixture of a polymer with an oxidizer, naphthalene, anthracene, anthraquinone, a sublimation dye, ferrocene, oxyquinoline, para-terphenyl, poly(3,4- ethylenedioxythiophene), or a combination thereof.
  • the microfluidic channel can include a gas vent positioned to vent gas generated by the solid gas-generating material.
  • the solid gas-generating material can be positioned at a fluid reservoir that is connected to the microfluidic channel, and the solid gas-generating material can block fluid in the reservoir from flowing into the microfluidic channel, and gas generated by the solid gas-generating material can fill a volume in the reservoir to push the fluid out of the reservoir into the microfluidic channel when the solid gas-generating material is converted to gas.
  • the reservoir can be formed as a blister having a flexible cover.
  • the solid gas-generating material can be positioned in a first location within the microfluidic channel
  • the destructible microfluidic valve can also include a second solid gas-generating material positioned in a second location in the microfluidic channel, and a second electric initiator adjacent to the second solid gas-generating material.
  • the microfluidic channel can include an interior channel wall dividing the microfluidic channel into a first sub-channel and a second sub- channel, and the first location of the solid gas-generating material can be in the first sub-channel, and the second location of the second solid gas-generating material can be in the second sub-channel.
  • a microfluidic device in one example, includes a fluid reservoir, a microfluidic channel connected to the fluid reservoir, a solid gas-generating material positioned to block fluid flow from the reservoir through the microfluidic channel, and an electric initiator adjacent to the solid gas-generating material.
  • the solid gas-generating material is convertible to a gas.
  • the electric initiator is configured to convert the solid gas-generating material to a gas and allow fluid to flow through the microfluidic channel.
  • the reservoir can be formed as a blister having a flexible cover, and the microfluidic device can also include an additional layer of solid gas-generating material to generate sufficient gas to propel the fluid out of the reservoir through the microfluidic channel when the solid gas- generating material is converted to gas.
  • the flexible cover can be a foil cover
  • the additional layer of solid gas-generating material can be on an interior surface of the foil cover
  • the foil cover can act as a thermal resistor to heat the additional layer of solid gas-generating material.
  • the present disclosure also describes methods of making microfluidic valves.
  • a method of making a microfluidic valve includes forming a microfluidic channel, forming an electric initiator including an electrically conductive layer proximate to the microfluidic channel, and positioning a solid gas-generating material over the electrically conductive layer such that the solid gas-generating material blocks fluid flow through the microfluidic channel.
  • the solid gas-generating material is convertible to a gas through chemical reaction or sublimation.
  • the electric initiator is configured to initiate a chemical reaction or sublimation of the solid gas-generating material to convert the solid gas-generating material to a gas and allow fluid to flow through the microfluidic channel.
  • the solid gas-generating material can be positioned at an opening of the microfluidic channel to block fluid flow into the microfluidic channel, and the method can also include forming a fluid reservoir in contact with the solid gas-generating material.
  • the fluid reservoir can contain a fluid that contacts the solid gas-generating material.
  • the method can also include forming an additional layer of solid gas-generating material within the reservoir to generate sufficient gas to propel the fluid out of the reservoir through the microfluidic channel when the solid gas-generating material is converted to gas.
  • microfluidic valves described herein can provide reliable valves for microfluidic channels, without complex mechanical components. Providing valves for small microfluidic channels can be difficult. Microfluidic channels can have a width on the order of 1 mm or less. Many microfluidic channels can be considerably smaller, such as having widths of 500 ⁇ m or less, or 100 ⁇ m or less, 50 ⁇ m or less, or even 35 ⁇ m or less. Making miniature mechanical valves for such small channels can be difficult and expensive, if possible at all. Some types of valves that have been used in microfluidic devices include pneumatic valves, which often have complicated designs and bulky external drivers.
  • microfluidic valves are also subject to failure caused by random mechanical, interfacial, and electrostatic forces. This makes miniaturized mechanical valves less reliable. Certain types of dynamic valves have been used, but these valves can be leaky and may not work against a significant pressure head. Many valves used in microfluidic devices have slow response times. Many valves also occupy a large space in the microfluidic device, which results in a large dead volume where fluid filling the dead volume is not able to otherwise participate in the intended function of the microfluidic device. This can be particularly detrimental because microfluidic devices often operate with very small volumes of fluids. [0028] In contrast, the microfluidic valves described herein have no moving parts other than the fluid in the microfluidic channel.
  • valves are small, possibly having approximately the same width as the microfluidic channel itself. No external components are used to actuate the valves, other than a source of electric current to be supplied to the electric initiator of the valve.
  • a solid gas-generating material can be positioned in a microfluidic channel to block fluid flow through the microfluidic channel.
  • the solid gas- generating material can be a destructible material that is convertible to a gas through a chemical reaction or through sublimation.
  • An electric initiator can be formed adjacent to the solid gas-generating material. The electric initiator can initiate chemical reaction or sublimation of the solid gas-generating material to convert the solid gas-generating material to a gas.
  • the destructible microfluidic valves described herein can be in a “closed” state until the electric initiator is used to convert the solid gas-generating material to a gas. After this, the valve can be in an “open” state to allow fluid to flow through the microfluidic channel. As such, the valves described herein can be used as release valves in some examples.
  • the electric initiator can be a thermal resistor or a spark gap that is located just next to or under the solid gas-generating material.
  • the electric initiator can provide heat or a spark that can, depending on the specific type of gas-generating material, initiate a chemical reaction the converts the gas-generating material to a gas.
  • the microfluidic channel can include a vent to allow the gas to escape from the channel.
  • the microfluidic channel can include a dedicated vent opening at or near the location where the solid gas-generating material is positioned.
  • the vent can simply be an outlet of the microfluidic channel.
  • the microfluidic valves described herein can include features to allow variable flowrate valves, valves for on-demand introduction of reactants, valves that can apply gas pressure to drive flow of fluids, and others. These examples are described in more detail below.
  • FIG.1A is a cross-sectional side view of one example destructible microfluidic valve 100 in accordance with the present disclosure.
  • the destructible microfluidic valve includes a microfluidic channel 110 enclosed by channel walls 112, and a solid gas-generating material 120 blocking the microfluidic channel. Fluid 102 is present in one portion of the microfluidic channel, but the fluid is blocked by the solid gas-generating material.
  • An electric initiator 130 is positioned under the solid gas-generating material.
  • a gas vent 140 is formed in one of the channel walls adjacent to the solid gas-generating material.
  • FIG.1A shows the microfluidic valve in an initial closed state. The solid gas-generating material blocks the microfluidic channel and prevents the fluid from flowing through the microfluidic channel.
  • FIG.1B shows the destructible microfluidic valve 100 in an open state. This figure shows the valve after the electric initiator 130 has been used to cause a chemical reaction or sublimation of the solid gas-generating material.
  • the solid gas-generating material has reacted or sublimated to form a gas, and the gas escapes through the gas vent 140.
  • the gas vent can include an opening or another feature that allows gas to pass out of the microfluidic channel, but which retains liquid inside the microfluidic channel.
  • the gas vent can include a small opening and a hydrophobic surface.
  • the opening can be sufficiently small and sufficiently hydrophobic that water or aqueous liquids will not flow out through the opening.
  • a hydrophobic coating can be applied to the surfaces of the channel wall near and within the opening.
  • gases can freely flow through the opening.
  • the gas vent can include a gas-permeable membrane that can retain the liquid inside the microfluidic channel.
  • the vent can have a width or diameter from 500 nm to 50 ⁇ m, 1 ⁇ m to 30 ⁇ m, or 1 ⁇ m to 20 ⁇ m in some cases.
  • the vent can have a width that is from 1% to 99% the width of the microfluidic channel, 5% to 50% the width of the microfluidic channel, or 5% to 25% the width of the microfluidic channel.
  • the shape of the vent is not particularly limited. In some examples, the vent can be circular, square, rectangular, or another shape.
  • the electric initiator can be configured to initiate a chemical reaction or sublimation of the solid gas-generating material to cause the solid gas-generating material to form a gas when an electric current is applied to the electric initiator.
  • the chemical reaction or sublimation can be initiated by heat.
  • the electric initiator can include a thermal resistor to generate heat when electric current is applied to the thermal resistor.
  • the thermal resistor can include a heating element made of a resistive material such as metal, metal alloys, metal nitrides, metal oxides, or others.
  • thermal resistors can include metals such as aluminum, tantalum, nickel, copper, chromium, tin, and alloys thereof.
  • the thermal resistor can be formed by thin film deposition processes, in some examples.
  • the thermal resistor can be similar to a thermal inkjet resistor, and may be formed using similar techniques.
  • the size of the thermal resistor can be suitable for initiating the chemical reaction of the solid gas-generating material.
  • the thermal resistor can have a width that is about equal to or less than a width of the microfluidic channel.
  • the thermal resistor can have a width or a length that is from 1 ⁇ m to 500 ⁇ m, or from 1 ⁇ m to 100 ⁇ m, or from 1 ⁇ m to 50 ⁇ m, or from 1 ⁇ m to 35 ⁇ m.
  • a thin film thermal resistor can have a relatively small thickness, such as from 1 nm to 5 ⁇ m, or from 1 nm to 1 ⁇ m, or from 1 nm to 500 nm.
  • Thermal resistors can also be formed using other techniques, such as thick film resistors. In such examples, the thickness can be larger, such as from 1 ⁇ m to 100 ⁇ m, or from 1 ⁇ m to 50 ⁇ m, or from 1 ⁇ m to 20 ⁇ m.
  • Some types of solid gas-generating material can be combustible, and a combustion reaction can be initiated to generate gas from the solid gas- generating material.
  • Combustion can be initiated using an electric initiator that includes a thermal resistor, as described above, or a spark gap.
  • a spark gap, or spark plug can include two electrodes separated by a gap. When a sufficient voltage difference is applied between the two electrodes, a spark or arc can form between the electrodes. This spark can ignite the solid gas-generating material.
  • the electrodes of the spark gap can also be formed by thin film deposition processes.
  • the electrodes can be made of a metal such as aluminum, tantalum, nickel, copper, chromium, tin, gold, silver, or alloys thereof.
  • the electrodes of the spark gap can be separated by a distance from 1 ⁇ m to 100 ⁇ m, or from 1 ⁇ m to 50 ⁇ m, or from 1 ⁇ m to 35 ⁇ m, or from 1 ⁇ m to 20 ⁇ m, or from 1 ⁇ m to 10 ⁇ m.
  • the solid gas-generating material, or a portion thereof can be located at or near the area between the two electrodes so that the solid gas-generating material can be ignited by the spark between the electrodes.
  • the electrodes can be formed using similar processes to the thermal resistors described above.
  • the electrodes can also have a similar width, length, and thickness to the thermal resistors described above. Therefore, the dimensions of the thermal resistors described above also apply to the electrodes of spark gaps.
  • the electric initiator can be located adjacent to the solid gas- generating material.
  • adjacent as used herein regarding the electric initiators can mean that the electric initiator is either in direct physical contact with the solid gas-generating material or sufficiently proximate to the solid gas- generating material that applying an electric current to the electric initiator can cause the solid gas-generating material to react and form a gas.
  • a thermal resistor can be placed in direct contact with the solid gas-generating material or there may be other materials between the thermal resistor and the solid gas-generating material, provided that sufficient heat from the thermal resistor can be conducted to the gas-generating material to initiate a chemical reaction or sublimation.
  • the thermal resistor can be separated from the solid gas-generating material by a wall of the microfluidic channel. In other examples, the thermal resistor can be formed as a thin layer on an interior wall of the microfluidic channel and the solid gas-generating material can be placed directly over the thermal resistor. [0037] In examples that utilize a spark gap as the electric initiator, the spark gap electrodes can be in direct contact with the solid gas-generating material or proximate to the solid gas-generating material so that a spark between the electrodes will ignite the gas-generating material. In some examples, the solid gas-generating material, or a portion of the solid gas-generating material, can be located directly between the electrodes.
  • the electrodes can both be formed on an interior wall surface of the microfluidic channel and the solid gas-generating material can be placed over the electrodes, or over an area between the electrodes.
  • the solid gas-generating material can include a variety of chemical compounds that are capable of producing a gas through a chemical reaction or sublimation.
  • the solid gas-generating material can form a gas through a thermal decomposition reaction or a combustion reaction.
  • Thermal decomposition reactions can refer to a reaction in which a compound breaks down into two or more simpler compounds. This reaction can be initiated by heat supplied by a thermal resistor as described above.
  • Combustion reactions can involve a fuel and oxidizer mixture that is ignited.
  • the microfluidic channel will often be filled with a liquid such as water or an aqueous solution. Therefore, oxygen gas will often not be available as an oxidizer. Therefore, in some examples the solid gas-generating material itself can include an oxidizer. In certain examples, the solid gas-generating material can include a mixture of a solid fuel compound and a solid oxidizing compound. In other examples, the solid gas-generating material can include a compound that can act as fuel and oxidizer together. These various examples are described in more detail below. [0039]Some examples of compounds that undergo a thermal decomposition reaction can include Azobis compounds.
  • Specific examples can include: Azobisisobutyronitrile, which decomposes to produce nitrogen gas at a decomposition temperature of 90 °C to 107 °C; 2-2’-Azobis(2,4- dimethylvaleronitrile), which decomposes to produce nitrogen gas at a temperature of 50 °C to 60 °C; 1,1’-Azobis(cyanocyclohexane), which decomposes to produce nitrogen gas at a temperature of 114 °C to 118 °C; 2,2’- Azobis(2-methylbutyronitrile); and other Azobis compounds.
  • Additional compounds that can decompose to form a gas can include organic peroxides.
  • Organic peroxides can decompose to produce oxygen gas. If combusted, organic peroxides can also produce carbon dioxide gas. Types of organic peroxides that can be included in the gas-generating material include: dialkyl peroxides, diacyl peroxides, hydroperoxides, peroxyacids, peroxyesters, peroxyketals, peroxycarbonates, peroxydicarbonates, and ketone peroxides.
  • Some specific organic peroxides that can be included in the gas- generating material can include: benzoyl peroxide, which can decompose at a temperature of 105 °C to 140 °C; tert-butyl peroxy-3,5,5-trimethylhexanoate, which can decompose at a temperature of 114 °C; dicumyl peroxide, which can decompose at a temperature of 143 °C; tert-butyl peroxy-2-ethylhexanoate, which can decompose at a temperature of 96 °C; tert-butyl peroxy-2- ethylhexylcarbonate, which can decompose at a temperature of 125 °C; 2,5- dimethyl-2,5-di(tert-butylperoxy)hexane, which can decompose at a temperature of 148 °C; tert-butyl peroxypivalate, which can decompos
  • the solid gas-generating material can include a material that can sublimate to form a gas, in some examples. Materials that can be solid at room temperature and sublimate at an elevated temperature can be used.
  • Some specific sublimation materials that can be used include naphthalene, which can sublimate at about 80 °C; anthracene; anthraquinone; sublimation dyes; ferrocene; oxyquinoline; para-terphenyl; poly(3,4-ethylenedioxythiophene); and others.
  • Some example sublimation dyes include Disperse Red 60, Disperse Blue 3, and Disperse Yellow 54.
  • Additional compounds that can be included in the solid gas- generating material can include: nitrocellulose, which can combust to form carbon dioxide and nitrogen gas; ammonium nitrite, which can decompose to form water and nitrogen gas; ammonium nitrate mixed with cellulose, which can combust to form carbon dioxide, nitrogen gas, and water; sodium nitrate, which can decompose to form sodium nitrite and oxygen gas; azides such as sodium azide, barium azide, or others, which can decompose to produce nitrogen gas.
  • gases that can be formed by the gas- generating material can include acetylene, ammonia, bromine, carbon dioxide, carbon monoxide, chlorine, ethane, ethylene, hydrogen, hydrogen sulfide, methane, nitrogen, oxygen, sulfur dioxide, water vapor, and others.
  • gases that can decompose or combust to generate gas may be unstable at normal conditions, such as room temperature and pressure.
  • microfluidic devices incorporating these materials can be stored at low temperatures, such as under refrigeration, in order to preserve the gas-generating material.
  • a reactive gas- generating compound can be mixed with an inert material to stabilize the material.
  • the compounds described above can be mixed with an inert material such as a polymer.
  • the gas- generating compound can be mixed with an epoxy paste such as SU-8.
  • the solid gas-generating material can be a mixture of a reactive gas-generating compound and an inert material in some examples.
  • the solid gas-generating material can be deposited in a microfluidic channel using methods such as lyophilization, drop deposition, and so on.
  • the gas-generating material can be dissolved in a solvent such as hexane, acetone, ethanol, water, or others. A drop of this solution can then be deposited in the desired location for the solid gas-generating material.
  • the solvent can evaporate as the solution dried, leaving behind the dry solid gas- generating material.
  • the solid gas-generating material can be powder.
  • the powder can be mixed with a binder such as nitrocellulose, epoxy nitrate, or others.
  • the mixture can be allowed to dry to form the solid gas- generating material in the microfluidic channel.
  • the amount of solid gas- generating material that is deposit can be sufficient to block the microfluidic channel.
  • the solid gas-generating material can form a plug having the same width and height as the microfluidic channel in order to fully block the microfluidic channel.
  • the length (i.e., thickness) of the plug can be any suitable length that can stably maintain the solid gas-generating material in place.
  • the solid gas-generating material can have a length from 1 ⁇ m to 5 mm, or from 1 ⁇ m to 1 mm, or from 1 ⁇ m to 500 ⁇ m, or from 1 ⁇ m to 100 ⁇ m, or from 1 ⁇ m to 50 ⁇ m, or from 1 ⁇ m to 35 ⁇ m.
  • the solid gas-generating material can have a width or a length that is from 1 ⁇ m to 5mm, or from 1 ⁇ m to 1 mm, or from 1 ⁇ m to 500 ⁇ m, or from 1 ⁇ m to 100 ⁇ m, or from 1 ⁇ m to 50 ⁇ m, or from 1 ⁇ m to 35 ⁇ m.
  • the types of solid gas-generating materials and electric initiators described herein can be used in any of the example microfluidic valves and microfluidic devices described herein.
  • FIG.2 shows another example destructible microfluidic valve 100.
  • the destructible microfluidic valves includes a microfluidic channel 110 enclosed by channel walls 112, with a solid gas-generating material 120 blocking the microfluidic channel.
  • a fluid 102 is in one portion of the channel, but the fluid is blocked by the solid gas-generating material so that the fluid cannot flow through the microfluidic channel.
  • An electric initiator is positioned under the solid gas-generating material.
  • a gas vent 140 is formed as an opening in the channel wall directly above the plug of solid gas- generating material.
  • FIG.3 shows an additional example destructible microfluidic valve 100.
  • the gas vent 140 is the outlet of the microfluidic channel 110.
  • the microfluidic channel does not include an additional opening that is specially made to be the gas vent.
  • fluid 102 is present in one portion of the microfluidic channel, but the fluid is blocked by the solid gas- generating material 120.
  • An electric initiator 130 is positioned under the solid gas- generating material.
  • FIG.4 shows yet another example destructible microfluidic valve 100.
  • a gas vent 140 is present as an opening in a channel wall 112 downstream from the plug of solid gas-generating material 120.
  • a fluid 102 is present upstream of the plug of solid gas-generating material.
  • An electric initiator 130 is positioned under the solid gas-generating material.
  • the gas can escape through the gas vent and the microfluidic channel can be open for the fluid to flow.
  • downstream refers to the direction starting on the side of the valve where fluid is present and flowing through the valve into the portion of the microfluidic channel where no fluid is initially present. It is noted that the fluid may not actually flow in this direction when the valve is opened, depending on the design of the particular microfluidic device in which the valve is used. For example, opening the valve can cause the fluid to flow downstream by capillary force in some examples. In other examples, a pressure head can be applied to the fluid to drive the fluid in the downstream direction.
  • the air pressure may push the fluid in the upstream direction when the valve is opened.
  • the actual direction of fluid flow can depend on the design of a particular microfluidic device.
  • the examples shown in FIGs.2-4 include a fluid occupying the microfluidic channel on one side of the plug of solid gas-generating material, while the microfluidic channel on the opposite side of the plug is empty.
  • the microfluidic channel can be empty on both sides of the plug of solid gas-generating material.
  • the microfluidic channel can be filled with air on both sides of the plug.
  • a priming fluid can be introduced into the microfluidic channel.
  • priming fluid can flow through the microfluidic channel capillary force so that the microfluidic channel is self-priming.
  • air pressure in the microfluidic channel can prevent the priming fluid from flowing into the microfluidic channel under capillary force.
  • the destructible valve can be opened to release this air pressure, allowing the priming fluid to prime the microfluidic channel.
  • the destructible microfluidic valves described herein ca be used to initiate priming of microfluidic channels on demand.
  • a destructible microfluidic valve can be present in a microfluidic channel where fluid is present on both sides of the closed valve.
  • FIG.5 shows an example microfluidic valve 100 in which fluid 102 is present on both sides of a plug of solid gas-generating material 120. This type of valve can be used, for example, to keep two different fluids from mixing together until after the valve opens, or to prevent both fluids from flowing before the valve is opened.
  • an electric initiator 130 is positioned under the solid gas-generating material.
  • This example also includes two gas vents 140. The gas vents are positioned on either side of the plug of solid gas-generating material.
  • FIG.6 shows an example destructible microfluidic valve 100 that is designed to hold a reactant 104 and cause the reactant to be mixed with fluid 102 in the microfluidic channel 110 when the valve is opened.
  • This example includes two plugs of solid gas-generating material 120.
  • the reactant is contained in a volume enclosed between the two plugs of solid gas-generating material.
  • the reactant can be a liquid reactant or a solid reactant.
  • This example also includes two gas vents 140.
  • the two gas vents can allow gas from the solid gas-generating material to escape no matter which direction the fluid flows.
  • Two electric initiators 130 are positioned under the two plugs of solid gas-generating material.
  • the gas can escape through one or both of the gas vents and the reactant can mix with the fluid in the microfluidic channel.
  • one of the plugs of solid gas-generating material can be converted to gas while the other plug can remain solid. This can allow the fluid on one side of the valve to mix with the reactant.
  • this valve can also be used to selectively mix the reactant with fluid on one side of the valve.
  • the destructible microfluidic valves described herein can also be designed to allow for variable flow rates through a microfluidic channel.
  • a microfluidic channel can be blocked by a solid gas-generating material as described above.
  • the microfluidic channel can then be partially unblocked by converting a portion of the solid gas-generating material to a gas. A remaining portion of the material can remain in the solid state so that the material partially blocks the microfluidic channel, allowing fluid to flow past as a slower flow rate. If it is desired to increase the flow rate, then the remaining portion of the solid gas-generating material can be converted to a gas to fully open the microfluidic channel.
  • the valve can be designed to allow multiple different portions of the solid gas-generating material to be converted to gas by using multiple different electric initiators.
  • a single body of solid gas-generating material can be used with multiple electric initiators positioned adjacent to different sections of the solid gas-generating material. Individual sections of the solid gas-generating material can then be converted to gas by activating individual electric initiators.
  • the solid gas- generating material can be divided into multiple bodies, where the individual bodies of solid gas-generating material can have individual electric initiators associated therewith.
  • the microfluidic channel can be divided into multiple sub-channels. For example, interior channel walls can be positioned within the microfluidic channel to divide the channel into multiple sub-channels.
  • FIG.7 shows a top-down cross-sectional view of one such example destructible microfluidic valve 100.
  • This example includes a microfluidic channel 110 that is enclosed by channel walls 112.
  • the microfluidic channel also includes interior walls 114 spaced apart within the channel. The interior walls divide the microfluidic channel into three sub-channels. Three plugs of solid gas- generating material 120 are positioned to block these sub-channels.
  • FIG.8 shows a top-down cross-sectional view of another example destructible microfluidic valve 100 that allows for control over fluid flow rate.
  • This example includes a microfluidic channel 110 that is divided into three sub- channels by interior channel walls 114.
  • the interior channel walls have differing lengths, which can affect the flow resistance of the sub-channels.
  • the sub-channel having the longest walls can have the highest resistance, while the sub-channel having the shortest walls can have the lowest resistance. Therefore, the flow rate of fluid 102 through the sub-channels can further be controlled by selecting a particular sub-channel to open.
  • this valve includes three plugs of solid gas-generating material 120 with three electric initiators 130.
  • gas vents 140 are formed as openings in the ceiling of the microfluidic channel. The gas vents are illustrated as dashed circles.
  • FIG.9 shows one such example destructible microfluidic valve 100.
  • This example includes a microfluidic channel 110 with two sub-channels that are formed by an interior channel wall 114.
  • One sub-channel has a relatively greater width than the other sub-channel.
  • the sub-channels are blocked by two plugs of solid gas- generating material 120.
  • Two electric initiators 130 are positioned under the two plugs of solid gas-generating material, and gas vents 140 are positioned in the ceiling of the microfluidic channel over the plugs of solid gas-generating material.
  • FIG.10 shows a top-down cross-sectional view of a particular example destructible microfluidic valve 100.
  • This example includes an interior wall 114 dividing the microfluidic channel 110 into two sub-channels.
  • One sub- channel has a relatively smaller width.
  • the smaller sub-channel also includes a capillary break at a downstream end of the sub-channel.
  • the capillary break can be a narrowed portion of the sub-channel, which can prevent fluid from flowing across because capillary forces prevent the liquid/gas interface from proceeding across the capillary break.
  • a dry reactant 104 can be stored inside the smaller sub-channel. Both of the sub-channels can initially be blocked by plugs of solid gas-generating material 120. Two electric initiators 130 are positioned under the plugs of solid gas-generating material, and gas vents 140 are positioned in the ceiling of the microfluidic channel over the plugs of solid gas-generating material. In one example, the larger sub-channel can be opened to allow fluid 102 to flow through the microfluidic channel.
  • the fluid can flow through the microfluidic channel without wetting the dry reactant because the plug of solid gas-generating material and the capillary break prevent the fluid from entering the smaller sub- channel.
  • the smaller plug of solid gas-generating material can be converted to gas to allow fluid to flow into the smaller sub-channel.
  • the capillary break ceases to function when liquid flows from both sides and the liquid merges from both sides, eliminating the liquid/gas interface.
  • the dry reactant can mix with the fluid and the fluid can flow past the capillary break into the main microfluidic channel. This design can allow for a reactant to be introduced into a flowing stream of fluid on demand.
  • the destructible microfluidic valves described herein can be used with a fluid reservoir to open the fluid reservoir on demand.
  • Many example microfluidic devices can include fluid reservoirs incorporated in the device. Depending on the particular application, fluid reservoirs can contain solvents, buffers, reagents, and so on.
  • a destructible microfluidic valve as described herein can be positioned at a fluid reservoir to provide a reliable and fast way to open the reservoir and allow the reservoir contents to flow into a microfluidic channel.
  • FIG.11 shows an example destructible microfluidic valve 100 that is positioned at a fluid reservoir 150 filled with a fluid 102.
  • This example includes a plug of solid gas-generating material 120 blocking a microfluidic channel 110 that leads out of the reservoir.
  • An electric initiator 130 is positioned under the plug of solid gas-generating material. The electric initiator can be activated to generate heat or a spark that can cause a reaction or sublimation of the solid gas- generating material, thereby converting the solid gas-generating material to a gas. The fluid in the fluid reservoir can then flow out of the reservoir into the microfluidic channel.
  • the reservoir in the example of FIG.11 is formed as a fluid-filled blister.
  • Some other microfluidic devices include blister packs having one or multiple fluid-filled blisters. The blisters can contain solvents, reagents, buffers, or other fluids used in the particular microfluidic device.
  • such blisters are designed to be pressed manually to rupture a sealing layer and release the contents of the blisters.
  • Some microfluidic systems employ a mechanical element for pressing the blisters, such as a piston or a robotic finger.
  • a mechanical element for pressing the blisters such as a piston or a robotic finger.
  • using the destructible microfluidic valves described herein can be more reliable, simpler, and faster.
  • the integrated destructible valves can be cheaper and simpler than complex external devices such as pistons or robotic fingers for pressing blisters.
  • the destructible microfluidic valves can be more reliable and faster than manually pressing the blisters.
  • the blister reservoirs described herein can be made from similar materials to blister packs in other devices.
  • the blister cover can be made from a flexible material such as aluminum foil.
  • the blister cover can be made from a rigid material.
  • gas from the solid gas-generating material can also be utilized to create pressure in the fluid reservoir and push liquid out of the fluid reservoir. If sufficient gas-generating material is used, then the fluid reservoir can be completely self-emptying, meaning that all the liquid in the reservoir can be pushed out of the reservoir by the generated gas without any pressing of blister.
  • a sufficient amount of gas-generating material can be used so that the gas provides extra pressure to push the fluid through microfluidic channels in a microfluidic device, and/or to increase the speed of flow of the fluid through the microfluidic channels.
  • the gas-generating material can be included as a single body of gas-generating material that both blocks the exit of the fluid reservoir and provides pressure to push fluid out of the fluid reservoir.
  • the gas-generating material can be included as multiple bodies, such as a small plug of gas-generating material to block the exit of the fluid reservoir and a second body of gas-generating material to generate gas pressure to push the fluid out of the resistor.
  • these bodies of gas-generating material can be activated in sequence. The smaller plug can be activated first to open the reservoir, and then the other body of gas- generating material can be activated to generate gas to pressurize the fluid reservoir and push out the fluid.
  • microfluidic devices described herein can include a fluid reservoir connected to a destructible microfluidic valve, where opening the destructible microfluidic valve allows fluid to flow out of the fluid reservoir.
  • the structure shown in FIG.11 can also be referred to as a microfluidic device.
  • a microfluidic device can include a fluid reservoir, a microfluidic channel connected to the fluid reservoir, a solid gas-generating material positioned to block fluid flow from the reservoir through the microfluidic channel, and an electric initiator adjacent to the solid gas- generating material.
  • the solid gas-generating material can be convertible to a gas through chemical reaction or sublimation.
  • the electric initiator can be configured to initiate a chemical reaction or sublimation of the solid gas-generating material to convert the solid gas-generating material to a gas and allow fluid to flow through the microfluidic channel.
  • FIG.12 shows an example microfluidic device 200 that includes a fluid reservoir 150 with a single body of solid gas-generating material 120.
  • the solid gas-generating material is positioned over the bottom of the fluid reservoir, and the material blocks a microfluidic channel 110 leading out of the fluid reservoir.
  • the body of solid gas-generating material is also large enough to generate gas to pressurize the fluid reservoir and push the fluid 102 out of the fluid reservoir.
  • FIG.13 shows a different example in which two bodies of solid gas- generating material 120 are present at a fluid reservoir 150.
  • a plug of solid gas- generating material blocks a microfluidic channel 110 leading out of the fluid reservoir.
  • a second body of solid gas-generating material is positioned on the floor of the fluid reservoir.
  • Two electric initiators 130 are positioned under the two bodies of solid gas-generating material respectively.
  • the smaller plug of solid gas-generating material can be activated first to unblock the microfluidic channel.
  • the second body of solid gas-generating material can then be activated to generate gas pressure to push the fluid 102 out of the fluid reservoir.
  • FIG.14 shows another example microfluidic device 200 that includes two bodies of solid gas-generating material 120 positioned at a fluid reservoir 150.
  • a small plug of solid gas-generating material blocks a microfluidic channel 110 as in the previous example.
  • a second body of solid gas-generating material is formed as a layer in contact with an interior surface of the fluid reservoir cover.
  • the fluid reservoir cover can be made of an electrically conductive material, such as aluminum foil.
  • This fluid reservoir cover can be used as an electric initiator for the layer of solid gas-generating material. Electric current can be passed through the fluid reservoir cover to generate heat, and the heat can cause the layer of solid gas-generating material to be converted to gas.
  • Another electric initiator 130 is also included under the plug of solid gas- generating material.
  • FIG.15 shows an example microfluidic device 200 that includes a single body of solid gas-generating material 120 that is formed as a capsule enclosing a fluid 102 in a fluid reservoir 150.
  • the solid gas-generating material blocks the microfluidic channel 110 and also fully encloses the fluid.
  • An electric initiator 130 is positioned under the solid gas-generating material.
  • the solid gas-generating material used in this example can be a type of material that can be ignited and combusted.
  • the electric initiator can be a thermal resistor or a spark gap.
  • the electric initiator can ignite the solid gas-generating material at one location, and then entire capsule of solid gas-generating material can be combusted in some examples. This can unblock the microfluidic channel and also generate gas to push the fluid out of the fluid reservoir.
  • FIG.16 shows yet another example microfluidic device 200. This example includes a vertical microfluidic channel 110. The microfluidic channel is blocked by a solid gas-generating material 120 that is formed as a layer on the floor of a fluid reservoir 150. An electric initiator is positioned under the solid gas- generating material.
  • FIG.17 shows a different example microfluidic device 200.
  • This example includes a layer of solid gas-generating material 120 on a floor of a fluid reservoir 150, similar to the previous example.
  • a layer of fluid-permeable mesh 132 is positioned under the solid gas-generating material.
  • the fluid permeable mesh can act as a support for the solid gas-generating material.
  • the fluid permeable mesh can be made of an electrically conductive material so that the mesh can be used as an electric initiator.
  • an electric initiator can be embedded in the fluid permeable mesh, such as a resistive wire or wires that can generate heat to activate the solid gas-generating material.
  • the fluid permeable mesh or an electric initiator embedded therein can be used to convert the solid gas-generating material to a gas.
  • the gas can push fluid 102 out of the fluid reservoir through the vertical microfluidic channel 110.
  • FIG.18 is a flowchart illustrating an example method 300 of making a microfluidic valve.
  • This method includes: forming a microfluidic channel 310; forming an electric initiator including an electrically conductive layer proximate to the microfluidic channel 320; and positioning a solid gas-generating material over the electrically conductive layer such that the solid gas-generating material blocks fluid flow through the microfluidic channel, wherein the solid gas- generating material is convertible to a gas through chemical reaction or sublimation, and wherein the electric initiator is configured to initiate a chemical reaction or sublimation of the solid gas-generating material to convert the solid gas-generating material to a gas and allow fluid to flow through the microfluidic channel 330.
  • methods of making microfluidic valves can include forming any of the features described above, such as fluid reservoirs, reservoir covers, thermal resistors, spark gaps, gas vents, microfluidic channel walls and interior walls, dried reactants, and so on. Additionally, the features of the microfluidic valves can be formed using any techniques described herein. [0072]Regarding the electric initiators, in some examples the electric initiators can be formed as layers of conductive material as described above. Thermal resistors can be formed as a single layer of conductive material connected to a source of electric current. Spark gaps can be formed as two separate layers of conductive material that are separated by a gap. When a sufficient voltage is applied between the electrodes, a spark can arc between the electrodes.
  • FIGs. 19A-19D show top-down views of destructible microfluidic valves 100 that include several different designs of spark gaps.
  • the spark gaps are made up of electrodes 134 separated by a gap.
  • the electrodes can be formed by depositing metal or another conductive material on the floor of the microfluidic channel 110.
  • a solid gas-generating material 120 is deposited over the electrodes so that a spark between the electrodes can ignite the solid gas- generating material.
  • the solid gas-generating material is outlined with a dashed line so that the shape of the underlying electrodes can be seen.
  • any of the microfluidic devices described herein can be formed from multiple layers of material.
  • the one or multiple of the layers can be formed photolithographically using a photoresist.
  • the layers can be formed from an epoxy-based photoresist, such as SU-8 or SU-82000 photoresist, which are epoxy-based negative photoresists.
  • SU-8 and SU-82000 are Bisphenol A Novolac epoxy-based photoresists that are available from various sources, including MicroChem Corp.
  • microfluidic devices can be formed on a substrate formed of a silicon material.
  • the substrate can be formed of single crystalline silicon, polycrystalline silicon, gallium arsenide, glass, silica, ceramics or a semiconducting material.
  • the substrate can have a thickness from about 500 ⁇ m to about 1200 ⁇ m.
  • channels or holes can be formed in the silicon substrate by laser machining and/or chemical etching.
  • a layer of photoresist can be formed or placed on the substrate and patterns to form the microfluidic channel and other microfluidic features such as the fluid reservoir described above.
  • a layer of photoresist can be exposed to a pattern of UV light that defines the microfluidic channel walls and walls of the fluid reservoir. If the microfluidic channel includes interior channel walls, capillary breaks, fluid reservoirs, or other such features then these features can be a part of the pattern. After exposure, any unexposed photoresist can be washed away.
  • this layer of photoresist can have a thickness from about 2 ⁇ m to 100 ⁇ m.
  • the microfluidic channels can be formed having a width from about 2 ⁇ m to about 100 ⁇ m, from about 10 ⁇ m to about 50 ⁇ m, or from about 20 ⁇ m to about 35 ⁇ m in some examples.
  • a top layer can be formed over the layer defining the microfluidic channels. This top layer can form the ceiling of the microfluidic channels.
  • the top layer can be formed by laminating a dry film photoresist over the microfluidic channel layer and exposing the dry film photoresist with a UV pattern defining any features of the top layer.
  • gas vents can be formed by using a pattern that leaves a small opening for the gas vents uncured.
  • the top layer can be a substantially solid layer without any openings.
  • the top layer can have a thickness from about 2 ⁇ m to about 200 ⁇ m.
  • some other methods of forming the top layer can utilize additional ports in the top layer.
  • the microfluidic channels can be filled with a wax before applying the top layer. The wax can then be removed from the microfluidic channels.
  • fluid reservoirs can be closed by adhering a fluid reservoir cover material such as aluminum foil or another layer of material over a fluid reservoir.
  • the fluid reservoir can have the form of a fluid-filled blister in some examples.
  • FIGs.20A-20D illustrate on example method of forming a microfluidic device 200 that includes such a fluid reservoir 150.
  • a microfluidic layer is patterned that includes a microfluidic channel 110, a fluid reservoir 150, a reservoir fill channel 116 and a gas outlet channel 118.
  • an electric initiator 130 is formed by depositing a layer of electrically conductive material on the floor of the fluid reservoir.
  • two bodies of solid gas-generating material 120 are formed. One body is formed as a plug blocking the microfluidic channel. The second body is formed as a layer of solid gas-generating material over the floor of the fluid reservoir.
  • a fluid reservoir cover 152 made of foil is adhered over the cavity of the fluid reservoir in the microfluidic layer. Additionally, although not shown in these figures, a top layer can be deposited over the microfluidic channel to provide a ceiling for the microfluidic channel.
  • the fluid reservoir can then be filled with fluid using the reservoir fill channel and the gas outlet channel. Fluid can be injected into the reservoir through the reservoir fill channel. As the fluid is injected into the reservoir, gas inside the reservoir can be displaced and exit through the gas outlet channel. After the reservoir is full, the reservoir fill channel and the gas outlet channel can both be sealed using a solid material such as epoxy paste.
  • the layer of metal has a length and width of 30 ⁇ m and a thickness of 5 ⁇ m.
  • Electric connections are formed to the thermal resistor, and the electric connections are connected to a power source that can supply electric current to the thermal resistor.
  • a primer layer of SU-8 photoresist is then spin coated onto the substrate, with a thickness of about 4 ⁇ m.
  • a microfluidic layer is formed on the primer layer.
  • a 17 ⁇ m thick layer of SU-8 is spin coated onto the primer layer.
  • a 14 ⁇ m thick dry photoresist layer is laminated onto the previous layer. The dry layer is exposed to a UV pattern that includes a microfluidic channel with a width of 50 ⁇ m.
  • the microfluidic channel is oriented so that the thermal resistors are on a floor of the microfluidic channel.
  • the photoresist is then developed by dissolving unexposed portions of the photoresist.
  • a plug of solid gas-generating material is then deposited over the thermal resistor.
  • the solid gas-generating material is benzoyl peroxide mixed with epoxy paste.
  • the thermal resistor can act as an electric initiator to cause a decomposition reaction of the benzoyl peroxide, forming oxygen gas.
  • a top layer is then formed by laminating a 14 ⁇ m thick dry photoresist layer over the microfluidic layer. The top layer is exposed to a UV- light pattern defining a gas vent opening directly over the plug of solid gas- generating material.

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Dispersion Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Micromachines (AREA)

Abstract

La présente divulgation concerne des vannes microfluidiques destructibles et des dispositifs microfluidiques qui comprennent les vannes microfluidiques destructibles. Dans un exemple, une vanne microfluidique destructible peut comprendre un canal microfluidique, un matériau de génération de gaz solide positionné pour bloquer l'écoulement de fluide à travers le canal microfluidique et un initiateur électrique adjacent au matériau de génération de gaz solide. Le matériau de génération de gaz solide peut être converti en un gaz par réaction chimique ou sublimation. L'initiateur électrique peut être conçu pour initier une réaction chimique ou une sublimation du matériau de génération de gaz solide pour convertir le matériau de génération de gaz solide en un gaz et permettre au fluide de s'écouler à travers le canal microfluidique.
PCT/US2021/021664 2021-03-10 2021-03-10 Vannes microfluidiques destructibles WO2022191830A1 (fr)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2004050242A2 (fr) * 2002-12-04 2004-06-17 Spinx, Inc. Dispositifs et procedes de manipulation de fluides programmable a petite echelle
US20070092409A1 (en) * 2005-10-21 2007-04-26 Beatty Christopher C Reconfigurable valve using optically active material
EP1884284A1 (fr) * 2006-08-04 2008-02-06 Samsung Electronics Co., Ltd. Unité de soupape à fermeture et appareil de réaction avec soupape à fermeture
WO2018223033A1 (fr) * 2017-06-02 2018-12-06 Northwestern University Systèmes microfluidiques pour échantillonnage et détection épidermiques

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2004050242A2 (fr) * 2002-12-04 2004-06-17 Spinx, Inc. Dispositifs et procedes de manipulation de fluides programmable a petite echelle
US20070092409A1 (en) * 2005-10-21 2007-04-26 Beatty Christopher C Reconfigurable valve using optically active material
EP1884284A1 (fr) * 2006-08-04 2008-02-06 Samsung Electronics Co., Ltd. Unité de soupape à fermeture et appareil de réaction avec soupape à fermeture
WO2018223033A1 (fr) * 2017-06-02 2018-12-06 Northwestern University Systèmes microfluidiques pour échantillonnage et détection épidermiques

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