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.

Thermally Degradable Water Diffusion Barrier Assembled by Gelatin and Beeswax toward Edible Electronics

“…Figure a depicts the procedure transferring metal patterns (edible silver leaf) to the gel films. The metal pattern is created on the basis of our previous work, , and to briefly explain it here, silver foils are pasted together using beeswax/vegetable oil Oleogel as an adhesive. Figure b shows the transfer result of a complex metal leaf trace pattern.…”

“…The hydrophobic particles acted as a water diffusion barrier and the film could gradually be degraded by the gelatin’s sol―gel changes. Furthermore, we patterned an edible resonator on the film by using gelatin’s good metal pattern transferability and demonstrated its operation in an abdominal phantom environment in order to gain insight into criteria for making transient electronics . In particular, by integrating the water diffusion barrier in the film, we expected that the water penetration time of the device could be extended.…”

“…Furthermore, we patterned an edible resonator on the film by using gelatin's good metal pattern transferability and demonstrated its operation in an abdominal phantom environment in order to gain insight into criteria for making transient electronics. 42 In particular, by integrating the water diffusion barrier in the film, we expected that the water penetration time of the device could be extended. Our proposal suggests that this edible water diffusion barrier film for electronic devices will open up new possibilities for minimally invasive and wireless monitoring technology for human and environmental healthcare.…”

Degradable Superhydrophobic Coatings Using the Solid–Liquid Transition of a Multilayer Structure near Body Temperature

“…For example, in drug delivery, contents are released in response to pH, temperature, light, and redox . Recent advances have led to edible smart surfaces with hydrophobic natural waxes, which are approved by the U.S. Food and Drug Administration, and the brittleness of these coatings has been decreased , with a diatom shell, chitosan, cellulose, ectin, oils, and attapulgite. , Although these coatings would be useful as protective films for drug delivery and edible electronics, , their wax materials have high melting points, e.g., approximately 61–65 °C for beeswax, and cannot be dissolved in the body. Thus, what is needed is a film designed to be degradable in the body.…”