Digital thermal metasurface with arbitrary infrared thermogram

Abstract

An object exhibits the infrared thermogram of another object, which is called thermal illusion as extensively investigated in the field of thermal metamaterials. However, almost all the existing thermal illusion behaviors were theoretically designed by using unconventional thermal conductivities, which means that the conductivities must be anisotropic, graded, or even singular due to the analytical methods in use. This problem largely limits fabrications for applications. By suggesting two discretization steps, here we put forward a numerical method instead to design thermal illusion, for which unconventional conductivities are no longer needed. In the meantime, more importantly, we reveal different thermal illusion behaviors. By tailoring the joint effects of thermal conduction and convection, we design a thermal pixel of cuboidal shape. We show that the assembly of such pixels into different two-dimensional arrays could generate infrared thermograms of different objects, which is thus called the digital thermal metasurface. Also, the metasurface is reconfigurable, and it can apparently produce all the existing thermal illusion behaviors reported in the literature. Finally, we experimentally fabricate a prototype. This work opens a door for applying conventional thermal conductivities of commercially available materials to thermal illusion, and we expect it to stimulate more exciting developments in electromagnetic disguise and confrontation.

Transforming heat transfer with thermal metamaterials and devices

“…However, the devices often have bulky and rigid metal structures, which may not be conveniently applicable and require further optimization. The idea of using thermal conduction to manipulate the surface temperature and thereby the radiation was also demonstrated to generate arbitrary infrared thermogram without relying on transformation 55 .…”

Designing nonlinear thermal devices and metamaterials under the Fourier law: A route to nonlinear thermotics

“…12(a-b) to approximate the continuous change of thermal properties required by transformation theory. Another method to do a digitization of thermal conductivity distribution is griding the space with squares, which has been applied in linear conduction [173][174][175]. Recently, inspire by the LEGO bricks, Kang et al [176] built a new type of temperature-responsive metamaterials assembled from tunable unit cells as an extension of their previous work [173].…”

Metamaterials-Enabled Sensing for Human-Machine Interfacing

“…Hand movement was first detected by the sensor array, and then examined by a video camera. More than gesture recognition, Shang et al designed a digital thermal metasurface to generate the infrared thermograms of the human body [ 116 ]. They extracted an infrared image with 31 × 51 = 1581 pixels, which correspond to 1581 different thermal conductivities.…”

“…( c ) experimental infrared image of the digital metasurface to show the thermograms of a human body. Reproduced with permission from [ 116 ]. Copyright 2018, American Institute of Physics.…”