Thermal signature control structures

Patent metadata

Field	Value
Publication number	US-11208568-B2
Application number	US-201815981354-A
Country	US
Kind code	B2
Filing date	May 16, 2018
Priority date	May 17, 2017
Publication date	Dec 28, 2021
Grant date	Dec 28, 2021

Abstract

Subwavelength conducting particles can be arranged on conducting surfaces to provide arbitrary thermal emissivity spectra. For example, a thermal emissivity spectrum can be tailored to suppress a thermal signature of an object without sacrificing radiative cooling efficiency.

First claim

What is claimed is:

1. An apparatus, comprising:
a conducting surface;
a plurality of conducting particles arranged on the conducting surface, each particle having a flat surface and forming a planar gap region between the conducting surface and the conducting particle;
wherein the plurality of conducting particles is arranged according to a specific arrangement selected to provide a predetermined thermal emissivity spectrum for the apparatus with respect to a specific radiative cooling efficiency for the apparatus and either or both a size and a shape of each of the plurality of conducting particles are selected to provide the predetermined thermal emissivity spectrum for the apparatus.

2. The apparatus of claim 1 , wherein the predetermined thermal emissivity spectrum is a thermal emissivity spectrum that reduces a thermal signature of the apparatus by a first factor and reduces a radiative cooling efficiency of the apparatus by a second factor that is substantially smaller than the first factor.

3. The apparatus of claim 2 , wherein the thermal signature corresponds to thermal radiance integrated over a selected spectral range of infrared wavelengths.

4. The apparatus of claim 2 , wherein the radiative cooling efficiency corresponds to thermal radiance integrated over all infrared wavelengths.

5. The apparatus of claim 1 , wherein the predetermined thermal emissivity spectrum provides:
an apparent temperature of the apparatus that is substantially less than an actual temperature of the apparatus; and
an actual radiative cooling rate that is substantially greater than an apparent radiative cooling rate.

6. The apparatus of claim 5 , wherein the apparent temperature corresponds to a temperature of a blackbody having a blackbody thermal radiance in a selected spectral range equivalent to an actual thermal radiance of the apparatus in the selected spectral range.

7. The apparatus of claim 1 , wherein each of the conducting particles has a resonant wavelength selected from a set of resonant wavelengths, the set of resonant wavelengths corresponding to a set of sizes of the conducting particles.

8. The apparatus of claim 7 , wherein the set of sizes of the conducting particles is a set of lengths of planar gap regions between the plurality of conducting particles and the conducting surface.

9. The apparatus of claim 7 , wherein the selected thermal emissivity spectrum includes:
one or more spectral ranges of enhanced thermal emissivity that include the set of resonant wavelengths;
one or more spectral ranges of suppressed thermal emissivity that exclude the set of resonant wavelengths.

10. The apparatus of claim 9 , wherein the one or more spectral ranges of suppressed thermal emissivity include a selected spectral range, and the set of resonant wavelengths includes one or more resonant wavelengths below a lower wavelength limit of the selected spectral range or above an upper wavelength limit of the selected spectral range.

11. The apparatus of claim 1 , wherein the plurality of conducting particles is a colloidal assembly of conducting particles on the conducting surface.

12. The apparatus of claim 1 , wherein the plurality of conducting particles is a lithographically-defined arrangement of conducting particles on the conducting surface.

13. The apparatus of claim 3 , wherein the selected spectral range is a range of atmospheric transmission of thermal infrared radiation.

14. The apparatus of claim 3 , wherein the selected spectral range is a range of detector response for a thermal infrared detector.

15. The apparatus of claim 1 , further comprising:
a layer of infrared-transparent material covering the conducting surface and the conducting particles.

16. The apparatus of claim 15 , wherein the layer of infrared-transparent material includes ZnO or FeO particles.

17. A method of fabricating an apparatus, comprising:
arranging a plurality of conducting particles on a conducting surface according to a specific arrangement, each particle having a flat surface and forming a planar gap region between the conducting surface and the conducting particle, wherein the specific arrangement and either or both a size and a shape of each of the plurality of conducting particles are selected to provide a predetermined thermal emissivity spectrum for the apparatus with respect to a specific radiative cooling efficiency for the apparatus.

18. The method of claim 17 , further comprising:
placing a flexible layer on a substrate; and
depositing the conducting surface as a metal layer on the flexible layer.

19. The method of claim 18 , further comprising:
after arranging the plurality of conducting particles, peeling the flexible layer off of the substrate.

20. The method of claim 18 , further comprising:
depositing a spacer layer on the conducting surface.

21. The method of claim 17 , wherein the arranging of the plurality of conducting particles includes:
colloidally assembling the conducting particles on the conducting surface.

22. The method of claim 17 , wherein the arranging of the plurality of conducting particles includes:
photolithographically arranging the plurality of conducting particles on the conducting surface.

23. The method of claim 22 , wherein the photolithographic arranging is a photolithographic arranging by a lift-off process.

24. The method of claim 17 , further comprising:
covering the arranged plurality of conducting particles with an infrared-transparent material.

25. The apparatus of claim 6 , wherein the selected spectral range is a range of atmospheric transmission of thermal infrared radiation.

26. The apparatus of claim 6 , wherein the selected spectral range is a range of detector response for a thermal infrared detector.

27. The apparatus of claim 10 , wherein the selected spectral range is a range of atmospheric transmission of thermal infrared radiation.

28. The apparatus of claim 10 , wherein the selected spectral range is a range of detector response for a thermal infrared detector.

29. The apparatus of claim 1 , wherein the specific radiative cooling efficiency is about 50% of a radiative cooling efficiency of the apparatus absent the plurality of conducting particles arranged on the conducting surface.

Assignees

• Elwha Llc

Inventors

• Akselrod Gleb M
• Josberger Erik Edward
• Weidman Mark C

Classifications

• F41H3/00 Primary

  Camouflage, i.e. means or methods for concealment or disguise (for vessels B63G8/34, B63G13/02 {; sound camouflage, i.e. simulating gun fire noise, F41A33/04; dummy or decoy targets F41J; chaff per se F41J2/00; ammunition for dispensing chaff F42B5/15, F42B12/70; radar absorbing fabrics H01Q17/005}) · CPC title

• G02B1/118

  having sub-optical wavelength surface structures designed to provide an enhanced transmittance, e.g. moth-eye structures · CPC title

• G02B5/204

  in which spectral selection is performed by means of a conductive grid or array, e.g. frequency selective surfaces (for use with wavelengths longer than the infrared light H01Q15/0006) · CPC title

• G02B1/002

  made of materials engineered to provide properties not available in nature, e.g. metamaterials · CPC title

• C09D5/32 Primary

  Radiation-absorbing paints {(protection against X-, gamma- or corpuscular radiation G21F)} · CPC title