Lightweight porous silica foams with extreme-low dielectric permittivity and loss for future 6G wireless communication technologies

In the next generation wireless communication systems operating at near terahertz frequencies, dielectric substrates with the lowest possible permittivity and loss factor are becoming essential. In this work, highly porous (98.9% +/- 0.1%) and lightweight silica foams (0.025 +/- 0.005 g/cm(3)), that have extremely low relative permittivity (epsilon(r) = 1.018 +/- 0.003 at 300 GHz) and corresponding loss factor (tan delta< 3 x 10(-4) at 300 GHz) are synthetized by a template-assisted sol-gel method. After dip-coating the slabs of foams with a thin film of cellulose nanofibers, sufficiently smooth surfaces are obtained, on which it is convenient to deposit electrically conductive planar thin films of metals important for applications in electronics and telecommunication devices. Here, micropatterns of Ag thin films are sputtered on the substrates through a shadow mask to demonstrate double split-ring resonator metamaterial structures as radio frequency filters operating in the sub-THz band.

Automated summary

In this study, highly porous and lightweight silica foams with extremely low permittivity and loss factor were synthesized by a template-assisted sol-gel method for applications in next generation wireless communication systems. Micropatterns of electrically conductive metals, such as Ag thin films, were successfully deposited on the smooth surfaces of the foams for radio frequency filter structures.