Indentation Deformation-based Triboelectric Pressure Sensor for High Accurate Sleep Monitoring

The sensitivity of triboelectric pressure sensors is primarily enhanced by leveraging the compressive deformation of elastomeric microstructures to increase contact-electrification area. However, the effective contact area of such elastomeric microstructures is limited to the cross-sectional area, which severely restricts further enhancement of the sensitivity. In this work, we propose an indentation deformation mechanism-based strategy that transforms the effective contact area from cross-sectional area to lateral area. This is achieved by fabricating a positive layer with microstructures of relatively high Young's modulus and a negative layer with low Young's modulus. To further enhance the contact area between the two triboelectric layers, a polyvinyl alcohol-phytic acid hydrogel electrode with a lower Young's modulus is employed. The force-electric coupling model confirms that indentation deformation increases the effective contact area. Benefiting from this improvement, the sensitivity pressure ranges of 0.248–1.26 kPa and 1.26–25 kPa is 2.58 and 4.94 times higher than that under compression deformation, reaching 7.42 V/kPa and 1.53 V/kPa, respectively, which are among the leading rank. By combining a bidirectional gated recurrent unit network with bimodal information, the accuracy of diagnosing obstructive sleep apnea-hypopnea syndrome reaches 98.9 %, with an average identification time of 22.3 s.