In Situ Growth of Laser-Induced Graphene on Flexible Substrates for Wearable Sensors

Advances in healthcare monitoring, human–machine interfaces, and soft robots require the development of wearable sensors that are efficient, scalable, and facile to prepare. Although laser-induced graphene (LIG) has recently attracted considerable attention in the fabrication of patterned graphene-based wearable sensors, the transfer process is inevitable due to the limited stretchability of carbon precursors. In this work, we proposed a strategy for in situ growth, transfer-free LIG on various flexible substrates (poly(dimethylsiloxane) (PDMS), poly(ethylene terephthalate) (PET), and paper). This was achieved by coating a biobased liquid carbon precursor (PGE-fa) on target substrates followed by laser irradiation under ambient conditions. After encapsulation, the fabricated flexible sensors were obtained. Based on the advantage of LIG in patterning, designs with different shapes and geometrical parameters were systematically investigated to optimize the sensing performance. The resulting LIG/PDMS sensor had a wide working range of ∼30% and demonstrated an ultrahigh sensitivity of 68,238.5 as well as outstanding stability over 10,000 cycles. Additionally, the sensor responded well to external stimuli at different bending angles. The potential applications of the sensor were further demonstrated by monitoring human motions, from subtle signals, including vocal cords, to large movements of the fingers and elbow joints.