Thermally Degradable Split-Ring Resonator Made on a Gelatin Substrate with Enhanced Dielectric and Conductive Properties

Abstract

Ingestible electronics, taken orally for monitoring organs, bacteria, and cells, are innovative wireless diagnostic and therapeutic technologies. Whereas residual in-body devices may require surgical removal, food-based sensors are seen as a way of ensuring safety. This study reports a split-ring resonator (SRR) whose resonance can be observed wirelessly. It is fabricated on a thermoresponsive gelatin substrate with a collaged edible metal leaf. Gelatin is a highly water-absorbing material, which may affect the resonator performance. According to high-frequency structural simulations, this resonator requires a low dielectric loss, <0.05, and high conductivity, >106 S/m. We found that these targets were achieved by completely drying the gelatin film and transferring multiple stacked metal leaves onto the film. Thin metal sheets were glued using an oleogel made of beeswax and olive oil, and the use of a hydrophobic material also aided in the transfer. Thus, we gained insights into the criteria for fabricating transient resonators with thermodegradability. SRRs made with edible materials are a technology that works in harmony with people and the environment and could lead to wireless devices or micromachines for the healthcare, agriculture, and livestock industries.