A major challenge for implantable m

A major challenge for implantable medical systems is the inclusion or reliable delivery of electrical power. We use ultrasound to deliver mechanical energy through skin and liquids and demonstrate a thin implantable vibrating triboelectric generator able to effectively harvest it. The ultrasound can induce micrometer-scale displacement of a polymer thin membrane to generate electrical energy through contact electrification. We recharge a lithium-ion battery at a rate of 166 microcoulombs per second in water. The voltage and current generated ex vivo by ultrasound energy transfer reached 2.4 volts and 156 microamps under porcine tissue. These findings show that a capacitive triboelectric electret is the first technology able to compete with piezoelectricity to harvest ultrasound in vivo and to power medical implants.
This work investigated triboelectric technology as it receives US energy in liquids and soft tissues. The prototypes can generate power on the order of milliwatts, enabling recharging of capacitors and Li-ion batteries. We noted some performance variations between VI-TEG prototypes and that better controlling the thickness and tension of the membrane, and the air gap, influences the vibrations and could improve performance.