University of California, San Diego engineers have developed a new wearable ultrasound device that can provide long-term, wireless monitoring of muscle activity with potential applications in healthcare and human-machine interfaces. The work was a collaborative project with Jinghong Li, a pulmonologist, intensive care specialist, and professor of medicine at UC San Diego Health.

The research team was led by Sheng Xu, a professor and Jacobs Faculty Scholar in the Aiiso Yufeng Li Family Department of Chemical and Nano Engineering at UC San Diego. The work was published on October 31 in Nature Electronics. 

The device is designed to stick to the skin with a layer of adhesive and is powered by a battery. It enables high-resolution tracking of muscle function without invasive procedures.

This wearable ultrasound technology may offer a promising alternative to electromyography (EMG), which involves applying metal electrodes on the skin to record electrical muscle activity. Ultrasound provides high-resolution imaging by penetrating deep tissues, offering detailed insights into muscle function. 

The ultrasound technology that Xu’s team and their collaborators developed is compact, wireless, and low-power. 

The device is housed in a flexible silicone elastomer casing, consisting of three main components: a single transducer for sending and receiving ultrasound waves; a custom-designed wireless circuit that controls the transducer, records data, and wirelessly transmits the data to a computer; and a lithium-polymer battery that can power the system for at least three hours.

In tests, the device was worn over the rib cage to monitor diaphragm motion and thickness, which are useful for assessing respiratory health.

 “By tracking diaphragm activity, the technology could potentially support patients with respiratory conditions and those reliant on mechanical ventilation,” said Joseph Wang, a distinguished professor in the Aiiso Yufeng Li Family Department of Chemical and Nano Engineering who is a co-author of the study.

“This technology could potentially be worn by individuals during their daily routines for continuous, long-term monitoring,” said study co-first author Xiangjun Chen, a Ph.D candidate in the Materials Science and Engineering program at UC San Diego.

Researchers also used the device on the forearm to capture hand and wrist muscle activity, which enabled its use as a human-machine interface to control a robotic arm and play a virtual game.

In the future, researchers plan to improve the technology’s accuracy, portability, energy efficiency, and computational capabilities.

Photo: Muyang Lin