In Situ Co-transformation of Reduced Graphene Oxide Embedded in Laser-Induced Graphene and Full-Range On-Body Strain Sensor

On-body strain information provides various indicators such as heart rate, physiological pulse, voice waveform, respiratory rate, and body motion status. Recent advances in wearable strain sensors using nanomaterials have significantly enhanced sensor performance with regard to sensitivity, detectable range, and response time. However, it is still challenging to obtain all types of body strain information, from small vibrations to joint movements, using one type of sensor. Herein, a full-range on-body strain (FROS) sensor covering ultrasmall-to-large strains such as vocal vibration and joint movement is reported. To achieve an ultrawide detectable range, reduced graphene oxide (rGO)-embedded laser-induced graphene (LIG) is synthesized by laser engraving on a graphene oxide (GO)-embedded polyimide (PI) complex film. An rGO-LIG homostructure based on sp²-carbons is photothermally reconstructed from the GO-PI heterostructure in a complex film by in situ co-transformation and then transferred to an elastomer substrate. The fabricated FROS sensor successfully performs on-body strain monitoring of various indicators, such as physiological pulse, vocal sound waveform, and body movement, as well as American sign language translation. Furthermore, it is believed that this rGO-LIG homostructure-based material synthesized by in situ co-transformation can potentially provide novel functionalities in fields such as wearable electronics, humanoid, soft robotics, and intelligent prosthetics.