Stretchable Ink Printed Graphene Device with Weft-Knitted Fabric Substrate Based on Thermal-Acoustic Effect

Thermal-acoustic devices have great potential as flexible ultrathin sound sources. However, stretchable sound sources based on a thermal-acoustic mechanism remain elusive, as realizing stable resistance in a reasonable range is challenging. In this study, a stretchable thermal-acoustic device based on graphene ink is fabricated on a weft-knitted fabric. After optimization of the graphene ink concentration, the device resistance changes by 8.94% during 4000 cycles of operation in the unstretchable state. After multiple cycles of bending, folding, prodding, and washing, the sound pressure level (SPL) change of the device is within 10%. Moreover, the SPL has an increase with the strain in a specific range, showing a phenomenon similar to the negative differential resistance (NDR) effect. This study sheds light on the use of stretchable thermal-acoustic devices for e-skin and wearable electronics.