Thermally-actuated devices and use thereof

1. A device comprising:

(i) at least one substrate;

(ii) a ceiling;

(iii) one or more flow channels disposed between said substrate and said ceiling and configured to contain an actuation liquid;

(iv) one or more recesses distributed throughout at least said substrate and open to said flow channel and configured to contain a fluid;

wherein 50% to 80% of the flow channel liquid-substrate interface, interfaces with said fluid within said recesses, and

(v) at least one heating element, configured to heat one or more portions of the actuation liquid and generate a temperature gradient within said actuation liquid; and

wherein said ceiling or said substrate comprises any one of (i) a plate having one or more transparencies configured to allow light to shine through in a defined pattern; and (ii) a film or a plate characterized by light absorbance over a defined range of wavelengths selected from the infra-red (IR) spectrum, the visible spectrum, or in the ultraviolet (UV) spectrum.

2. The device of claim 1 , wherein any one of: (i) said recesses are microsized; (ii) said temperature gradient generates a pressure distribution or a velocity field in the actuation liquid; (iii) at least one of said flow channels is interposed between said substrate and said ceiling; (iv) said fluid is selected from a gas or a liquid characterized by a viscosity of up to 100 Cp.

3. The device of claim 1 , being in the form of a closed chamber.

4. The device of claim 1 , wherein said actuation liquid is characterized by any one of: (i) a viscosity of 0.1 Cp to 100 Cp; (ii) an interfacial tension of 0.1 mN/m to 75 mN/m; (iii) a thermal conductivity of 0.015 W/mK to 0.3 W/mK; and (iv) a liquid selected from Newtonian liquid and a non-Newtonian liquid.

5. The device of claims 1 , wherein said substrate is characterized by a thermal conductivity of 0.015 W/mK to 2 W/mK.

6. The device of claim 1 , wherein a vertical distance between said ceiling and said substrate is 5 μm to 1 cm.

7. The device of claim 1 , wherein any one of: (i) said recesses are characterized by a depth of 5 to 100 μm; and (ii) a volume of said recesses varies within less than ±30%.

8. The device of claim 1 , wherein said substrate is selected from any one of: (i) a substrate characterized by a thickness of 100 to 1000 μm; (ii) a superhydrophobic substrate; (iii) a substrate characterized by a static water contact angle of at least 100°; and (iv) a substrate having attached thereto light-absorbing particles, characterized by a light absorbance efficiency of at least 1%.

9. The device of claim 8 , wherein said superhydrophobic substrate comprises a material selected from the group consisting of: silicon, glass, Poly(dimethylsiloxane) (PDMS), parylene, Poly(methylmethacrylate), polyethylene, and any combination thereof.

10. The device of claim 1 , wherein said ceiling is selected from (i) a ceiling comprising a superhydrophobic material; and (ii) a ceiling comprising an elastic sheet.

11. The device of claim 10 , wherein said elastic sheet is selected from: (i) a sheet characterized by E*h 3 having a value of 10 −13 to 10 −9 N*m, wherein “E” is Young's modulus of said membrane, and “h” is a thickness of said membrane; and (ii) a sheet in fluid communication with said actuating liquid and is configured to deform in response to a flow of said actuating liquid.

12. The device of claim 1 , wherein said actuation liquid, comprises light-absorbing particles, characterized by a light absorbance efficiency of at least 1%.

13. The device of claim 1 , wherein said recesses are selected from gas-containing recesses and recesses substantially devoid of liquid.

14. The device of claim 1 , wherein said heating element is selected from (i) a plurality of electrodes, disposed proximately to an interface of said flow channel on said substrate; and (ii) illumination means.

15. The device of claim 1 , wherein said flow channel is characterized by a width of between 50 um to 5 cm.

16. The device of claim 1 , further comprising a control unit configured to provide a predetermined and/or variable heat toward one or more regions of said actuation liquid.

17. A device comprising:

(i) at least one substrate;

(ii) a ceiling comprising an elastic sheet;

(iii) one or more flow channels disposed between said substrate and said ceiling and configured to contain an actuation liquid;

(iv) one or more recesses distributed throughout at least said substrate and open to said flow channel and configured to contain a fluid;

wherein 50% to 80% of the flow channel liquid-substrate interface, interfaces with said fluid within said recesses, and

(v) at least one heating element, configured to heat one or more portions of the actuation liquid and generate a temperature gradient within said actuation liquid;

wherein said elastic sheet is selected from: (i) a sheet characterized by E*h 3 having a value of 10 −13 to 10 −9 N*m, wherein “E” is Young's modulus of said membrane, and “h” is a thickness of said membrane; and (ii) a sheet in fluid communication with said actuating liquid and is configured to deform in response to a flow of said actuating liquid.

18. A method comprising the steps of:

(a) providing a device having:

(i) at least one substrate;

(ii) a ceiling;

(iii) one or more flow channels disposed between said substrate and said ceiling and containing an actuation liquid; and

(iv) one or more recesses distributed throughout at least said substrate and open to said flow channel and containing a fluid;

wherein 50% to 80% of the flow channel liquid-substrate interface, interfaces with said fluid within said recesses, and

(b) providing thermal energy to a portion of said actuation liquid so as to establish a temperature gradient to said actuation liquid, thereby generating pressure distribution or a velocity field in the actuation liquid;

wherein said ceiling has an elastic film, and wherein said pressure distribution of said actuating liquid deforms a defined region of said elastic film upon providing thermal energy.