Wireless Power Transmission for Implantable Medical Devices Using Focused Ultrasound and a Miniaturized 1-3 Piezoelectric Composite Receiving Transducer.

Wireless power transmission (WPT) using ultrasound is a promising way for wirelessly recharging implantable medical devices (IMDs). However, the transmitted power using ultrasound so far is insufficient for driving the existing IMDs. Moreover, the size of the receiving transducer is larger, which is not suitable for implantation. To increase the output power and reduce the size of the implantable receiver, this article presents a method of combining focused ultrasound with a miniaturized 1-3 piezoelectric composite receiving transducer to produce higher electrical power. An analytical fluid-structure interaction model is constructed to fully understand the operating mechanism of the receiving transducer under ultrasonic force. In our experiments, a miniaturized 1-3 piezoelectric composite receiving transducer with a diameter of 3.7 mm was used. The output power generated from the receiving transducer reached 60 mW at a distance of 150 mm. In vitro and in vivo animal experiments proved that the miniaturized transducer could successfully receive focused ultrasonic energy and convert it to electrical power. The method presented and the electrical power that we obtained can provide a valuable reference for wirelessly charging of IMDs.

Fabrication of Lipid Nanotubules by Ultrasonic Drag Force.

This work reports a new method of fabricating lipid nanotubules using ultrasonic Stokes drag force in theory and experiment. Ultrasonic Stokes drag force generated using a planar piezoelectric ultrasonic transducer in a remotely controllable way is introduced. When ultrasonic Stokes drag force is applied on lipid vesicles, the lipid nanotubules attached can be dragged out from the lipid film. In order to demonstrate the formation mechanism of the lipid nanotubules produced by ultrasonic drag force clearly, a theoretical kinetic model is developed. In the experiments, the lipid nanotubules can be rapidly and efficiently fabricated using this ultrasonic transducer both in deionized water and NaCl solutions with different concentrations. The stretching speed of the lipid nanotubules can reach 33 µm/s, approximately 10 times faster than that of the existing methods. The formed lipid nanotubules have a diameter of 600 ± 100 nm (>80%). The length can reach the millimeter level. This work provided a remotely controllable, highly efficient, high-velocity, and solution environment-independent approach for fabricating lipid nanotubules.