Hybrid‐Piezoelectret Based Highly Efficient Ultrasonic Energy Harvester for Implantable Electronics

Abstract Implantable ultrasonic energy harvesters that scavenge wireless mechanic energy from ultrasound own remarkable potential in advanced medical protocols for neuroprosthetics, wireless power, biosensor, etc. The main challenge for this kind of device is to achieve high‐efficiency energy conversion in a weak ultrasonic pressure field. Here, a multilayered piezoelectret with strain enhanced piezoelectricity by introducing a parallel‐connected air hole array in an interdielectric layer sandwiched between a pair of electrets for an efficient ultrasonic energy harvester is presented. This device delivers a remarkable peak output power around 13.13 mW and short‐circuits current around 2.2 mA when implanted into tissues at 5~10 mm under an ultrasonic probe setup at 25 mW cm⁻², which is higher than the required power threshold of bioelectronic devices and current threshold of nerve stimulation. Furthermore, the feasibility of supplying power to implantable bioelectronics and working as neuroproteins for peripheral nerve stimulation are both demonstrated. It is anticipated that this highly efficient, easily fabricated, and biocompatible device will potentially enable applications for multifunctional and advanced implantable bioelectronics in the next generation of diagnosis and therapy.