Photothermal trap

Patent metadata

Field	Value
Publication number	US-11441817-B2
Application number	US-201817048205-A
Country	US
Kind code	B2
Filing date	Nov 9, 2018
Priority date	Apr 19, 2018
Publication date	Sep 13, 2022
Grant date	Sep 13, 2022

Abstract

Articles, systems, and methods in which electromagnetic energy is converted to heat (e.g., for the purpose of inducing or inhibiting phase change of a material disposed over a surface) are generally described.

First claim

What is claimed is:

1. A photothermal trap, comprising:
a thermal spreader; and
an absorber over the thermal spreader, the absorber configured to absorb electromagnetic radiation;
wherein:
the photothermal trap is configured such that at least a portion of the electromagnetic radiation absorbed by the absorber is converted to heat that is transferred to the thermal spreader, and
the photothermal trap has a thermal response time constant of less than or equal to 800 seconds.

2. The photothermal trap of claim 1 , further comprising a thermal insulator under the thermal spreader.

3. The photothermal trap of claim 1 , further comprising a hydrophobic surface on or over the absorber.

4. The photothermal trap of claim 1 , wherein the thermal spreader is a thermally conductive solid.

5. The photothermal trap of claim 1 , wherein the thermal spreader is a heat pipe.

6. The photothermal trap of claim 1 , wherein the absorber has an absorptivity of at least 50% with respect to at least one wavelength of electromagnetic radiation within a band of wavelengths from 200 nm to 1 μm.

7. The photothermal trap of claim 1 , wherein the absorber has an emissivity of less than or equal to 50% at a temperature of 25° C. with respect to at least one wavelength of electromagnetic radiation within a band of wavelengths from 200 nm to 1 μm.

8. The photothermal trap of claim 1 , wherein the absorber has a broadband emissivity of less than or equal to 50% at a temperature of 25° C.

9. The photothermal trap of claim 1 , wherein the thermal spreader has a thermal conductivity in a lateral direction of at least 50 W m −1 K −1 at 25° C.

10. The photothermal trap of claim 1 , wherein there is a thermal transfer rate of at least 0.1 W between a first location and a second location in the thermal spreader separated in a lateral direction by a distance of at least 100 times the thickness of the thermal spreader, when the first and second locations have a difference in temperature of 1 Kelvin.

11. The photothermal trap of claim 1 , further comprising a material disposed over the absorber, wherein the material undergoes a phase change in the temperature range of from −20° C. to 50° C.

12. The photothermal trap of claim 1 , wherein the thermal spreader is in the form of a layer.

13. The photothermal trap of claim 1 , wherein the absorber is in the form of a layer.

14. A photothermal trap, comprising:
a first region having a thermal conductivity in a lateral direction of at least 50 W m −1 K −1 at 25° C.; and
a second region, over the first region, the second region having an absorptivity of at least 50% with respect to at least one wavelength of electromagnetic radiation within a band of wavelengths from 200 nm to 1 μm;
wherein the photothermal trap has a thermal response time constant of less than or equal to 800 seconds.

15. The photothermal trap of claim 14 , further comprising a third region, under the first region, having a thermal conductivity in a transverse direction of less than or equal to 1 W m −1 K −1 at 25° C.

16. The photothermal trap of claim 14 , further comprising a hydrophobic surface on or over the second region.

17. The photothermal trap of claim 14 , wherein the first region is a solid.

18. The photothermal trap of claim 14 , wherein the first region is a heat pipe.

19. A method of inducing or inhibiting a phase change of a material disposed over a photothermal trap comprising a thermal spreader, an absorber over the thermal spreader that is configured to absorb electromagnetic radiation, a thickness, and a lateral dimension perpendicular to the thickness, the method comprising:
exposing the photothermal trap to electromagnetic radiation such that the electromagnetic radiation is absorbed by a first area of the photothermal trap that is part of the absorber and converted to heat that is transported along the lateral dimension of the photothermal trap via the thermal spreader to a second area of the photothermal trap resulting in the inducing or inhibiting of the phase change of the material over the second area of the photothermal trap,
wherein the photothermal trap has a thermal response time constant of less than or equal to 800 seconds.

Assignees

• Massachusetts Inst Technology

Inventors

• Varanasi Kripa K
• Dash Susmita
• De Ruiter Jolet

Classifications

• F24S80/56

  characterised by means for preventing heat loss · CPC title

• F28D15/0275

  Arrangements for coupling heat-pipes together or with other structures, e.g. with base blocks; Heat pipe cores · CPC title

• Y02E10/50

  Photovoltaic [PV] energy · CPC title

• F24S70/20

  characterised by absorbing coatings; characterised by surface treatment for increasing absorption · CPC title

• F24S20/61 Primary

  Passive solar heat collectors, e.g. operated without external energy source · CPC title