Cellulose nanofibril, flexible electronics, microwave applications, radio-frequency inductor-capacitor and filters, Telecommunication, TK5101-6720, Electric apparatus and materials. Electric circuits. Electric networks, TK452-454.4

Cellulose nanofibril (CNF) substrates that are inexpensive, biodegradable, and quickly incinerable, are potential substrates for disposable RF applications. In this paper, high-performance flexible microwave lumped elements and filters fabricated on flexible CNF substrates are reported. A spiral inductor with a resonance frequency of 29.8 GHz and quality (Q) factor of 8.5 and a metal-insulator-metal (MIM) capacitor with a resonance frequency of 45 GHz and Q factor of 85.2 were achieved in a 200 μm thick CNF substrate. Meanwhile, the inductor and capacitor exhibit outstanding mechanical bendability, that is negligible performance changes were observed when they were bent to a radius as small as 15 mm. Based on the spiral inductor and MIM capacitor, a 5-GHz band-stop filter and a 4 GHz band-pass filter with excellent mechanical bendability were further demonstrated on the CNF substrate. These results indicate the potential of using CNF as substrates for broader microwave applications.