Fig. 1. Metadevice design. (a) Schematic diagram of the structure and operation principle of the metadevice. By applying a deposition voltage (−2.5  V), a Cu film is electrodeposited on the working electrode, and the metadevice exhibits the low-emissivity state. By applying a dissolution voltage (2.5 V) to dissolve the deposited Cu film, the metadevice can return to the initial high-emissivity state. In addition, the sandwich structure of FSS with JC structure, BaF2 substrate, and electrodes formed an absorber with wideband microwave absorption performance. (b) Schematic of the geometrical parameters of the metadevice structure. (c) Simulated reflection spectra of the metadevice in the dissolved and deposited states, and the dashed line indicates the simulated reflection spectra of the metal-based device without the FSS structure.

Fig. 2. Metadevice dynamic IR regulation mechanism. (a) SEM images of the Pt film and (b) deposited Cu film. (c) IR optical constants (refractive indices “n” and extinction coefficients “k”) of the Pt film, (d) deposited Cu film, and (e) BaF2 substrate. (f) Simulated IR spectral response (reflection, absorption, and transmission) of the Pt films with a thickness of ∼4  nm at 2.5–40 μm. (g) IR spectral response of Cu electrodeposited Pt films with different deposited Cu thicknesses at 8 μm. (h) Calculated reflection spectra of the working electrode (including BaF2 substrate) with different deposited Cu thicknesses.

Fig. 3. Metadevice wideband microwave absorption mechanism. Dependence of the simulation reflection spectra of the metadevice in (a) dissolved and (b) deposited states on the electrolyte layer thickness (d2). (c) Calculated impedance results of the metadevice in the deposited state. (d) Distributions of electric field, (e) magnetic field, (f) surface current, and (g) power loss density of the metadevice in the deposited state at the resonant frequency of 10.28 GHz and (h)–(k) 17.2 GHz.

Fig. 4. Metadevice performance. (a) “Real-time” IR emissivity spectra of the metadevice during the electrodeposition process at 3–14 μm. (b) IR images of the metadevice during the electrodeposition and dissolution processes. (c) Photograph of the fabricated metadevice for dynamic IR regulation performance testing. (d) Measurement setup in a microwave anechoic chamber. (e) Micrograph of the etched FSS with JC structure. To improve the identification of the etched structure, its edges were depicted. (f) Photograph of the metadevice in the dissolved state. (g) Photograph of the metadevice in the deposited state. (h) Measured microwave reflection spectra of the metadevice in the deposited and dissolved states under normal incidence at 8–22 GHz.

Fig. 5. Adaptive IR camouflage demonstration. (a) The IR radiation of the device is adjusted by applying a bias voltage to blend into cold and (c) hot backgrounds, respectively. (b) Time trace of the apparent temperature of the device and background during the blending of the device into cold and (d) hot backgrounds.

Fig. 6. (a) Ellipsometric parameters (Phi, Delta) of the Pt film, (b) deposited Cu film, and (c) BaF2 substrate. (d) Transmission parameter of the BaF2 substrate.

Fig. 7. (a) Dependence of the simulated reflection spectra of the metadevice in the deposited state on incident wave polarization angle, and (b) incidence angle for TM- and (c) TE-polarized incident waves. (d)–(i) Dependence of the simulated reflection spectra of the metadevice in the deposited state on the structural parameters: geometrical parameters of the JC structure (d) l, (e) s, and (f) w, (g) thickness of the barium fluoride substrate d1, (h) sheet resistance of the JC structure Rs−FSS, and (i) sheet resistance of the Pt film Rs−Pt.

Fig. 8. (a) “Real-time” IR reflection spectra of the metadevice during the electrodeposition process. Dashed line represents the calculated results. (b) “Real-time” IR emissivity spectra of the RME IR electrochromic device without FSS during the electrodeposition process.

Fig. 9. (a)–(c) Measured geometric parameters of the fabricated metadevice. (See Table 3 for detailed comparison.) (d) Measured microwave reflection spectra of the metadevice in the deposited and dissolved states under normal incidence. [Same as Fig. 4(h), repeated for comparison.] (e) Simulated microwave reflection spectra of the metadevice in the deposited and dissolved states under normal incidence according to measured parameters. It can be seen that the simulation results are in good agreement with the measurements.