Chemically derived graphene quantum dots for high-strain sensing

Graphene quantum dots (GQDs) refer to graphene fragments with a lateral dimension typically less than 100 nm, which possess unique electrical and optical properties due to the quantum confinement effect. In this study, we demonstrate that chemically derived graphene quantum dots show great potential for making highly stretchable and cost-effective strain sensors via an electron tunneling mechanism. Stretchable strain sensors are critical devices for the field of flexible or wearable electronics which are expected to maintain function up to high strain values (> 30%). However, strain sensors based on conventional materials (i.e. metal or semiconductors) or metal nanoparticles (e.g. gold or silver nanoparticles) only work within a small range of strain (i.e. the former have a working range < 1% and the latter < 3%). In this study, by simply dropcasting solution-processed GQDs between the interdigitated electrodes on polydimethylsiloxane, we obtained devices that can function in the range from 0.06% to over 50% tensile strain with both the sensitivity and working range conveniently adjustable by the concentration of GQDs applied. This study provides a new concept for practical applications of GQDs, revealing the potential of this material for smart applications such as artificial skin, human-machine interfaces, and health monitoring.