High-sensitivity capacitive pressure sensor based on novel and bio-inspired hybrid dielectric layer for medical exercise rehabilitation

Abstract

Flexible pressure sensors are widely used in the fields of medical health, sports health, and smart homes. However, it remains challenging for these sensors to have high sensitivity across a wide pressure range. Here, inspired by the structure of a rigid human finger bone embedded in muscle, we report on a capacitance sensor using a soft-rigid (force transfer layer)–soft-hybrid dielectric layer to monitor the physical activity of unconscious patients during rehabilitation exercises. First, as the soft layer, a soft thermoplastic polyurethane/Ni (TPNi) film with micro-cone array is prepared using the external magnetic field induction method. The obtained spirulina-based gel consisting of a compact cross-linking network, which is force transmission bridge of the sensor. Owing to the sudden changes in dielectric constant of the TPNi with micro-cone structure during compression, and the mechanical difference between soft and hard layers, the capacitive sensor simultaneously have a high increase in the relative capacitance (sensitivity of 5.6355 kPa⁻¹ for 10 kPa–125 kPa), a wider sensing range and excellent environmental stability. The pressure sensors are used in real-time condition monitoring systems with a waveform display and pressure distribution to analyze the rehabilitation process of patients, including the gradual growth and disappearance of hematomas, the wearing method of splints, and leg movements. This diagnostic capability will not only serve as a proactive measure to prevent potential joint damage but also alert healthcare professionals promptly to any impending risks.