Ultrasonic receiver could power medical implants even after bending

Stable and continuous power is paramount for many implanted electronic devices. But, according to researchers at the Korea Institute of Science and Technology (KIST), conventional wireless charging methods have several limitations.

The team aimed to overcome those hurdles with a new ultrasound-based wireless charging system. The new ultrasonic receiver offers improved biocompatibility, according to a research announcement, and even maintains performance after being bent, which could happen within the body.

Conventional wireless charging methods (such as electromagnetic induction and radio frequency-based charging) used in smartphones and wireless earphones suffer from short transmission distances, low energy transfer efficiency in biological tissues, and electromagnetic interference, the KIST announcement said. Ultrasound is absorbed less by human tissues, the team said, and allows for more reliable energy transfer in implantable and skin-adherent devices.

A research team led by Dr Sunghoon Hur of the Electronic and Hybrid Materials Research Centre at KIST and Professor Hyun-Cheol Song of Korea University, both in Seoul, developed the new ultrasonic receiver. The researchers also demonstrated wireless charging of batteries by receiving ultrasonic waves – an important step towards commercialising the technology.

The team reportedly improved the power conversion efficiency compared with conventional ultrasonic receivers by using high-efficiency piezoelectric materials and a unique structural design. By creating a stretchable and biocompatible ultrasonic receiver, designed to conform closely to the curves of the human body while achieving stable power conversion, they were able to transmit 20 milliwatts (mW) of power at a distance of 3cm underwater and 7mW at 3cm beneath the skin – enough to continuously run low-power wearable devices or implantable medical devices, the announcement said.

“The findings are expected to help accelerate the commercialisation of ultrasonic-based wireless charging technology for implantable medical electronics. In particular, it is expected to provide a new paradigm for providing safe and continuous power to low-power medical devices such as implantable pacemakers, neurostimulators and wearable sensors,” it said.

Dr Hur added: “Through this research, we have demonstrated that wireless power transmission technology using ultrasound can be applied practically. We plan to conduct further research for miniaturisation and commercialisation, to accelerate the practical application of the technology.”

Similar systems could also be useful for underwater drones and marine sensors that require long-term power, the announcement added.

The research was published in Advanced Materials.