A self-powered portable spherical grip sensor based on flexible PZT piezoelectric composites for rehabilitation self-monitoring

Grip strength is a critical health indicator for evaluating the rehabilitation progress of patients with hand dysfunction. However, for these patients, grip strength values and variability are often significantly limited by their physical condition. Therefore, grip sensors must exhibit high performance in terms of detection threshold, sensitivity, and portability to meet clinical demands. This study presents a compact, highly sensitive, and portable spherical grip strength sensor designed using flexible PZT piezoelectric composite materials. With a diameter of 78 mm, the sensor responds rapidly to force and frequency changes, achieving a response time of just 90 ms. When subjected to forces between 2 N and 23.78 N, the sensor generates output voltage peak-to-peak values ranging from 0.43 V to 6.1 V. It achieves a sensitivity of 0.264 V/N, representing a significant 87 % improvement over conventional grip strength sensors, and demonstrates remarkable stability over 4000 cycles. The results of grip strength measurements on subjects of different genders indicate that the sensor can distinguish grip levels by gender based on grip strength values. Additionally, it possesses self-powering capabilities, converting the mechanical energy generated by grip strength into electrical energy through the piezoelectric effect. This enables it to recharge itself and significantly reduces its reliance on external power sources.