# US 11,992,842 B2 · Control of evaporation in digital microfluidics > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,992,842 B2 - Document ID: US11992842B2 - Status: Granted - Kind: B2 - Application number: 17/088,572 - Filed: 2020-11-03 - Published: 2021-03-11 - Granted: 2024-05-28 - Earliest claimed: 2018-05-23 - Assignees: mirOculus Inc. - Applicants: mirOculus Inc. - Inventors: Mais Jehan Jebrail; Mathieu Gabriel-Emmanuel Chauleau; Poornasree Kumar; Eduardo Cervantes; Foteini Christodoulou; Nikolay Sergeev; Spencer Seiler; Alejandro Tocigl Domeyko; Ana Eugenia Carvajal - Web page: https://patentgrep.com/patent/US11992842B2 ## CPC - B01L 3/502792: {for moving individual droplets on a plate, e.g. by locally altering surface tension} - B01L 3/502707: {characterised by the manufacture of the container or its components} - B01L 3/50273: {characterised by the means or forces applied to move the fluids} - B01L 7/52: {with provision for submitting samples to a predetermined sequence of different temperatures, e.g. for treating nucleic acid samples} - C12M 23/16: {Microfluidic devices; Capillary tubes (integrated microfluidic structures B01L3/5027; microreactors B01J19/0093)} - G01N 27/44791: {Microapparatus (sample containers with integrated microfluidic structures B01L3/5027)} - B01L 2200/027: for microfluidic devices - B01L 2200/0673: Handling of plugs of fluid surrounded by immiscible fluid - B01L 2200/142: Preventing evaporation - B01L 2300/042: Caps; Plugs - B01L 2300/0816: Cards, e.g. flat sample carriers usually with flow in two horizontal directions - B01L 2300/0848: Specific forms of parts of containers - B01L 2300/0874: Three dimensional network - B01L 2300/0887: Laminated structure - B01L 2300/1822: using Peltier elements - B01L 2300/1827: using resistive heater - B01L 2400/0415: electrical forces, e.g. electrokinetic - B01L 2400/0427: Electrowetting - B01L 2400/086: using baffles or other fixed flow obstructions - B01L: CHEMICAL OR PHYSICAL LABORATORY APPARATUS FOR GENERAL USE - C12M: APPARATUS FOR ENZYMOLOGY OR MICROBIOLOGY; {APPARATUS FOR CULTURING MICROORGANISMS FOR PRODUCING BIOMASS, FOR GROWING CELLS OR FOR OBTAINING FERMENTATION OR METABOLIC PRODUCTS, i.e. BIOREACTORS OR FERMENTERS} - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) ## Abstract Air-matrix digital microfluidics (DMF) apparatuses and methods of using them. These methods and apparatuses may include the use of a liquid wax coating material and/or pinning the encapsulated reaction droplet within the air gap using pinning features. Any of these methods may also include separating the liquid wax from an encapsulated aqueous droplet, e.g., using an oil absorbent wick to selectively separate the liquid oil or wax from the aqueous droplet by adsorbing and/or absorbing the liquid wax into the absorbent wick while leaving the aqueous droplet behind. ## Claims ### Claim 1 A digital microfluidics method, the method comprising: driving a droplet within an air gap of an air-matrix digital microfluidic (DMF) apparatus to a sub-region of the air gap by electrowetting; coating the droplet with a liquid wax material within the air gap; pinning the droplet within the sub-region by contacting the droplet with two or more protrusions extending from an upper surface of the air gap into the air gap, wherein the two or more protrusions extend only partially into the air gap; vortexing a plurality of magnetic beads within the coated droplet within a thermal zone; and performing one or more manipulations on the pinned droplet. ### Claim 2 (depends on 1) The method of claim 1, wherein pinning the droplet comprises pinning at least the liquid wax coating material coating the droplet. ### Claim 3 (depends on 1) The method of claim 1, wherein performing one or more manipulations comprises heating the sub-region of the air gap including the droplet. ### Claim 4 (depends on 1) The method of claim 1, further comprising driving the droplet away from the sub-region and off of the protrusions by electrowetting. ### Claim 5 (depends on 1) The method of claim 1, wherein the two or more protrusions comprise three to ten protrusions. ### Claim 6 (depends on 1) The method of claim 1, wherein each of the two or more protrusions have a cylindrical or rectangular shape. ### Claim 7 (depends on 1) The method of claim 1, wherein each of the two or more protrusions have a lateral dimension on the upper surface of the air gap between 0.5 mm to 2.8 mm. ### Claim 8 (depends on 1) The method of claim 1, wherein each of the two or more protrusions have a vertical dimension extending into the air gap of 1% to 90% of a vertical dimension of the air gap. ### Claim 9 (depends on 1) The method of claim 1, wherein each of the two or more protrusions have a vertical dimension extending into the air gap of 1% to 20% of a vertical dimension of the air gap. ### Claim 10 (depends on 1) The method of claim 1, wherein performing one or more manipulations comprises performing at least one of: vortexing a plurality of magnetic beads within the pinned droplet, cooling the sub-region of the air gap including the pinned droplet, detecting the pinned droplet; driving the pinned droplet to a channel hole within the sub-region of the air gap; aspirating the droplet into a channel of the channel hole; and driving the droplet from the sub-region by electrowetting. ### Claim 11 A digital microfluidic (DMF) method comprising: coating an aqueous reaction droplet with a liquid wax material within an air gap formed between a first hydrophobic layer of a first plate and a second hydrophobic layer of a second plate of a DMF apparatus; pinning the liquid wax coating of the aqueous reaction droplet to at least two protrusions within a sub-region of the air gap, thereby distributing the liquid wax around the reaction droplet; heating at least the sub-region of the air gap including the coated aqueous reaction droplet, whereby the liquid wax coating limits or prevents evaporation from the aqueous reaction droplet; and vortexing a plurality of magnetic beads within the coated reaction droplet within a thermal zone. ### Claim 12 (depends on 11) The method of claim 11, wherein pinning comprises pinning the liquid wax coating to the at least two protrusions disposed adjacent to the second hydrophobic layer of the second plate. ### Claim 13 (depends on 11) The method of claim 11, wherein the at least two protrusions comprise two to ten protrusions. ### Claim 14 (depends on 11) The method of claim 11, wherein each of the at least two protrusions has a cylindrical or rectangular shape. ### Claim 15 (depends on 11) The method of claim 11, wherein each of the at least two protrusions has a lateral dimension between 0.5 mm to 2.8 mm. ### Claim 16 (depends on 11) The method of claim 11, wherein each of the at least two protrusions has a vertical dimension extending into the air gap of 1% to 90% of a vertical dimension of the air gap. ### Claim 17 (depends on 11) The method of claim 11, wherein each of the at least two protrusions has a vertical dimension into the air gap extending less than 40% of a vertical dimension of the air gap. ### Claim 18 (depends on 11) The method of claim 11, wherein each of the at least two protrusions has a vertical dimension extending into the air gap between 1% to 20% of a vertical dimension of the air gap. ### Claim 19 (depends on 11) The method of claim 11, further comprising moving the coated aqueous reaction droplet away from the sub-region of the air gap after completing heating. ### Claim 20 (depends on 19) The method of claim 19, wherein moving comprises driving the coated aqueous reaction droplet by energizing a sub-set of a plurality of driving electrodes adjacent to the first hydrophobic layer of the first plate of the DMF apparatus. ### Claim 21 (depends on 19) The method of claim 19, wherein moving further comprises withdrawing at least a portion of the coated aqueous reaction droplet from a surface of the air gap of the DMF apparatus before energizing a sub-set of the plurality of driving electrodes; and reintroducing the at least portion of the coated aqueous reaction droplet back to the surface of the air gap of the DMF apparatus as a front of the aqueous reaction droplet exits the sub-region. ### Claim 22 (depends on 21) The method of claim 21, wherein withdrawing comprises withdrawing the at least portion of the coated reaction droplet via a channel from a surface of the second hydrophobic layer of the second plate to at least partially through the second plate. ### Claim 23 (depends on 11) The method of claim 11, wherein the first plate comprises a bottom plate of a cartridge configured to be seated on a seating surface of the DMF apparatus comprising a plurality of actuation electrodes. ### Claim 24 A digital microfluidic (DMF) method comprising: coating an aqueous reaction droplet with a liquid wax material within an air gap formed between a first hydrophobic layer of a first plate and a second hydrophobic layer of a second plate of a DMF apparatus, wherein the first plate comprises a bottom plate of a cartridge configured to be seated on a seating surface of the DMF apparatus comprising a plurality of actuation electrodes; pinning the liquid wax coating of the aqueous reaction droplet to at least two protrusions within a sub-region of the air gap, thereby distributing the liquid wax around the reaction droplet; and heating at least the sub-region of the air gap including the coated aqueous reaction droplet, whereby the liquid wax coating limits or prevents evaporation from the aqueous reaction droplet.