Graphene/Au Hybrid Antenna Coil Exfoliated with Multi‐Stacked Graphene Flakes for Ultra‐Thin Biomedical Devices

Abstract

Flexible electronics with organic substrates have been developed for bio‐conformable devices and soft robotics. Although biodegradable polymers are preferred substrates for biomedical applications, they have poor heat durability, which precludes printing of conductive lines that require annealing at high temperatures (>250 °C). The fabrication of an ultra‐flexible, inkjet‐printed antenna coil with a resistivity of 4.30 × 10−5 Ω‐cm is reported. It involves annealing of a graphene/Au antenna coil printed on a glass substrate and transferring onto a 182‐nm‐thick poly(D, L‐lactic acid) nanosheet by exfoliation of multi‐stacked graphene flakes. Then, a light‐emitting device, powered wirelessly, even in the rounded, twisted, or attached states, is fabricated by mounting a blue LED chip on the nanosheet antenna coil. The self‐deploying device is also stored in a water‐soluble capsule, injected into a silicone bag, released from the dissolved capsule, and operated wirelessly. This work facilitates the hybridization of conductive lines and biodegradable polymers on ultra‐flexible biomaterials for the biomedical application of flexible electronics.

Ultra‐Deformable and Tissue‐Adhesive Liquid Metal Antennas with High Wireless Powering Efficiency

“…This value was within a range of those of typical commercially available coils that operate at similar frequencies ( q = 10–30) [ 37 ] and higher than those of previously reported thin‐film antennas made of finely‐patterned Cu wire ( q < 19), [ 11 ] 2D‐patterned liquid metal ( q < 5), [ 25 ] and inkjet‐printed Au/graphene ( q < 5). [ 16 ]…”

“…[ 4 ] 2D printing technologies permitted creating ultraconformable antenna based on sub‐micrometer‐thick conductive patterns on such polymeric ultrathin substrates. [ 16,17 ] However, 2D‐printed ultrathin antennas tend to be yet unsuitable for use on the wet and dynamic tissues in terms of limited electromechanical properties (i.e., poor stretchability and high resistance of the printed conductive patterns). Hence, to minimize the interference with the electrical and ionic conditions of the living physiological systems to the wireless operation, the integrated circuit must be sealed with an insulating layer (e.g., 50 μm‐thick silicone rubber sheet [ 16 ] ), which compromises the flexibility and conformability of the whole device.…”

Flexible Induction Heater Based on the Polymeric Thin Film for Local Thermotherapy

“…We previously reported the transference of Au printed wirings to PDLLA thin film by utilizing the interlayer release of multistacked graphene flakes. [ 27 ] In this study, the printed wiring was directly transferred to the PDLLA thin film without using graphene. Our unique approach can lead to new fabrication methods of transferring metal particles onto various types of polymer thin films.…”

“…We recently reported that a poly(D, L‐lactic acid) (PDLLA) nanosheet (thickness: 182 nm) can be employed as a base material of a wirelessly powered device. [ 27 ] PDLLA is a type of polymer that has biocompatibility, biodegradability, and heat resistance, [ 28 ] which has an ideal property in the fabrication process as well as practical application for hyperthermia. In this study, we developed a wirelessly operated, implantable IH device by layering thin‐film Au wiring (1.5 µm) and a biodegradable polymer thin film (5 µm) with a simple structure without consideration of the shape of the antenna, and the insertion of a resonant circuit ( Figure ).…”

High‐Resolution 3D Printing for Electronics

“…Tetsu et al developed an ultra-flexible antenna coil through graphene/Au hybrid inkjet printing. [176] The graphene/gold bilayer spiral antenna coil is 24.96 cm in length and 5.5 turns in total, which was inkjet-printed into the glass substrate and transferred to polymer nanosheets, which is possible because graphene flakes are piled up with weak Van der Waals forces. [177] The electro-mechanical properties of the nanosheet antenna coil were evaluated through bending tests.…”