Conformable Piezoelectric Devices and Systems for Advanced Wearable and Implantable Biomedical Applications.

With increasing demands for continuous health monitoring remotely, wearable and implantable devices have attracted considerable interest. To fulfill such demands, novel materials and device structures have been investigated, since commercial biomedical devices are not compatible with flexible and conformable form factors needed for soft tissue monitoring and intervention. Among various materials, piezoelectric materials have been widely adopted for multiple applications including sensing, energy harvesting, neurostimulation, drug delivery, and ultrasound imaging owing to their unique electromechanical conversion properties. In this review, we provide a comprehensive overview of piezoelectric-based wearable and implantable biomedical devices. We first provide the basic principles of piezoelectric devices and device design strategies for wearable and implantable form factors. Then, we discuss various state-of-the-art applications of wearable and implantable piezoelectric devices and their design strategies. Finally, we demonstrate several challenges and outlooks for designing piezoelectric-based conformable biomedical devices.