High-performance strain sensors using flexible micro-porous 3D-graphene with conductive network synergy†

Despite the advancement of flexible electronics, particularly wearable devices, soft robots, and human–machine interaction, flexible sensor designs have predominantly concentrated on uniaxial stimuli detection, which constrains their capability to discern the intricate multidimensional strains inherent in multi-degree-of-freedom motions. This study utilized plasma-enhanced chemical vapor deposition (PECVD) to in situ grow wafer-scale three-dimensional graphene (3D-graphene) on a silicon (Si) substrate, complemented by femtosecond laser cutting for precise patterning. The as-fabricated flexible strain sensor exhibits anisotropic electromechanical properties, driven by the porous and cross-linked nature of 3D-graphene, which significantly enhances the sensitivity and durability. Through tensile testing in both parallel and perpendicular orientations to the longitudinal axis of the graphene strip, distinct gauge factors (GF_‖ = 413 and GF_⊥ = 22) were observed, demonstrating the sensor's efficacy in the as-fabricated in-plane omnidirectional strain detection. Subsequent evaluations, including tensile, bending, and strain response tests, highlight exceptional performance characteristics: the sensor maintains integrity under 180-degree bending and demonstrates a rapid response time of 0.7 s. Such capabilities enable the sensor to monitor various human physiological activities across different scales, including eyelid blinks, facial muscle movements, respiratory cycles, and joint or cervical spine dynamics. This unique combination positions it as a promising candidate for next-generation wearable electronics and intelligent robotic systems.