Nano electromechanical approach for flexible piezoresistive sensor

Flexible sensor with superior sensitivity and widened working range is urgently demanded to cater for the rapid progress of wearable electronics and mechnosensational human-machine interfaces. However, the manufacturing of the wearable sensor with promising sensitivity in a broad working range is a challenge for the soft property of the sensing materials. Introducing a porous insulating spacer between the sensing and electrode materials recently demonstrated an effective and energy-conservation approach. In this study we directly employed the bio-derived leaf vein as the first avoiding layer to partially separate the sensing component and electrode part, along with the ultralong MnO₂ nanowires (NWs) as the second spacer inside the graphite flakes (GFs), to significantly improve the sensitivity from 4.7 kPa⁻¹ to 8.6 kPa⁻¹ as well as the broader working range of 28.9 kPa. The in situ transmission electron microscope (TEM) and scanning electron microscope (SEM) was respectively used to further quantitatively analyze the sensing mechanism and deformation process for GFs and MnO₂ NWs at nano scale. These results demonstrated the flexibility and imperative roles of the GFs’ intrinsic deformation-induced current change on the improvement of sensitivity and the fracture behavior of MnO₂ NW. Further, the flexible sensor on the potential applications of health monitoring and human-machine interfaces were successfully demonstrated. We thus strongly believe our work, based on the bio-derived spacing layer and advanced in situ electromechanical characterizations of GFs and MnO₂ NWs for the wearable sensor, could profoundly guide people to explore more opportunities to develop new-concept sensor device and smart systems.