(Invited) Self-Powered Wearable and Implantable Electrical Stimulation Devices for Biomedical Applications

Abstract

Electrical stimulation (ES) is a widely used therapeutic treatment strategy. It showed significantly positive results in treating a variety of diseases, biological disorders, and neurological problems. Today, the emergence of wearable devices is rapidly reshaping the development of medical devices, pushing them from conventional bulky and rigid silicon electronics to flexible and primarily polymer-based systems. Among many types of functions, nanogenerators are developed as a unique device for converting biomechanical energy into electrical pulses. This talk will fist introduce the application of flexible nanogenerators as an implantable power source and its biosafety and compatibility. In addition, the pulsed electricity from nanogenerators can be applied directly as a ES signal for therapeutic treatment. In our recent research, we successfully implemented such an electromechanical system for skin wound healing, hair growth, and vagus nerve stimulation for obesity control. An electrical stimulation bandage was developed by integrating a flexible nanogenerator and a pair of dressing electrodes on a flexible substrate. Rat studies demonstrated rapid closure of a full-thickness rectangular skin wound within 3 days as compared to 12 days of usual contraction-based healing processes in rodents. From in vitro studies, the accelerated skin wound healing was attributed to the electric field-facilitated fibroblast migration, proliferation and transdifferentiation. Via a similar design, the electrical pulses were applied to stimulate hair growth. Significantly facilitated hair regeneration results were obtained from Sprague-Dawley rats and nude mice, which was attributed to the improved secretion of vascular endothelial growth factor and keratinocyte growth factor. In another work, an implanted vagus nerve stimulation system was developed. The device comprises a flexible and biocompatible nanogenerator that is attached on the surface of stomach. It generates biphasic electric pulses in responsive to the peristalsis of stomach. The electric signals generated by this device stimulates the vagal afferent fibers to reduce food intake and achieve weight control. This strategy is successfully demonstrated on rat models. Within 100 days, the average body weight is controlled at 350 g, 38% less than the control groups. All the results bring a new concept in electrical therapeutic technology that is battery-free, self-activated and directly responsive to body activities. Keywords: Nanogenerator; Implantable medical devices; Wearable devices; Self-powered systems; Electrical stimulation;