Wearable Patch Tracks Sleep Apnea and Chronic Respiratory Disease

Obstructive sleep apnea (OSA) requires overnight polysomnography, a test that uses many wired sensors and is difficult to repeat at home. Chronic respiratory diseases such as asthma, chronic obstructive pulmonary disease (COPD), and OSA can worsen between clinic visits. Bulky and costly monitoring systems may miss nighttime breathing changes until disease becomes severe. Researchers have now developed a skin-like wearable patch that aims to support continuous cardiorespiratory monitoring outside specialized clinical settings.

The technology is called HELP, or heteromodal epidermal liquid-metal patch. A team from the Department of Chemical and Biological Engineering at The Hong Kong University of Science and Technology (HKUST) developed the device. The soft, noninvasive patch simultaneously tracks breathing and heart activity using liquid-metal technology.

The HELP patch addresses a key materials problem in wearable sensors. Liquid metals are flexible and resist mechanical fatigue, but they adhere poorly to standard elastic substrates. The researchers used a bioinspired anchoring strategy by depositing microscopic silver nanowires onto a flexible silicone base, which secures the liquid metal and helps prevent baseline signal drift and signal distortion during movement.

The device also uses an analog constriction gate architecture to measure breathing. Graded, dome-like microbulges along the breathing channel act like sequential valves as the chest expands. This allows the sensor to detect shallow resting breaths involving less than 0.01% chest strain while also capturing deeper chest expansion without signal distortion.

The patch has two channels. One wide, thick channel records electrocardiogram heart signals while remaining unaffected by chest stretching. A second thin, U-shaped loop measures chest and abdominal movement. The team also developed a stencil-brushing process to pattern the liquid metal onto the anchored substrate.

In pilot clinical studies with human subjects, the HELP system showed strong agreement with hospital polysomnography equipment in detecting sleep apnea events. Patients applied the patch themselves in less than one minute. The patch also tracked real-time responses in asthma patients after bronchodilator treatment and detected overnight physiological changes in COPD patients that daytime checks can miss. The work was published in Science Advances under the title “Intermetallic-anchored epidermal EGaIn patch with analog constriction gates for cardiorespiratory monitoring.”

“What is particularly rewarding about our clinical pilot results is seeing how continuous home monitoring can capture hidden symptoms. In COPD patients, for example, daytime spot-checks often show normal oxygen levels because the body actively compensates while awake. Our patch unmasks these physiological changes as the body relaxes during sleep, enabling proactive rather than reactive care,” said Hnin Yin Yin Nyein, a professor in the Department of Chemical and Biological Engineering at The Hong Kong University of Science and Technology.

Related Links
HKUST