A research team led by Prof. Hnin Yin Yin NYEIN from the Department of Chemical and Biological Engineering at The Hong Kong University of Science and Technology (HKUST) has developed a novel wearable device named "HELP" (heteromodal epidermal liquid-metal patch). By leveraging liquid-metal technology, this soft, skin-like patch simultaneously tracks both breathing and heart activity. This comfortable, non-invasive technology marks a promising step toward a future where patients with chronic respiratory and heart conditions can receive continuous, clinical-grade health monitoring right at home.
This work was published in the journal Science Advances under the title "Intermetallic-anchored epidermal EGaIn patch with analog constriction gates for cardiorespiratory monitoring". The research was conducted entirely by a research team from the Department of Chemical and Biological Engineering at HKUST. Led by Prof. Nyein, the team includes first author Dr. LI Yue (former Postdoctoral Scholar and HKUST PhD graduate), and co-authors LIN Yu-Chun (former Research Assistant and HKUST BEng graduate), HE Anwei (current PhD student), WANG Xuejie (current PhD student), WANG Xu (current MPhil student), and Dr. Johnson Q. CUI (former Postdoctoral Research Fellow and HKUST PhD graduate).
Chronic respiratory diseases, including asthma, chronic obstructive pulmonary disease (COPD), and obstructive sleep apnea (OSA), are among the leading causes of health decline and hospitalization worldwide. Currently, managing and diagnosing these conditions relies heavily on procedures confined to specialized clinical environments. For instance, testing lung function requires spirometry, while diagnosing sleep disorders requires overnight polysomnography (PSG)-an uncomfortable test involving dozens of wired sensors attached to the patient. Because these diagnostic setups are bulky, expensive, and require trained medical personnel, they are highly impractical for daily use at home. As a result, critical nighttime breathing changes or gradual disease progression often go completely undetected until a patient's condition becomes severe.
While wearable health sensors present an ideal solution for continuous home monitoring, engineers worldwide have long struggled with a fundamental performance trade-off: designing a sensor that is highly sensitive to subtle body movements while remaining stable over extended periods of wear. Liquid metals (LMs) has been recognized as premier materials for soft electronics due to its excellent flexibility and near-zero mechanical fatigue. However, liquid metals naturally suffer from poor adhesion to standard elastic substrates. When integrated into wearable devices, this incompatibility leads to gradual baseline signal drift over time and severe signal distortion during user movement, ultimately compromising the reliability of continuous monitoring.
The HKUST research team has successfully overcame this longstanding engineering hurdle through a smart, materials-and-structure co-design. In their study, the researchers introduced a bioinspired anchoring strategy that firmly secures the liquid metal in place. By pre-depositing a network of microscopic silver nanowires (AgNWs) onto a flexible silicone base, the team mimicked the hierarchical, interlocking structures of gecko feet. This microscopic network anchors the liquid metal through both chemical and physical mechanisms, preventing it from sliding or causing signal drift. This breakthrough allows the HELP patch to maintain stable electrical performance even after undergoing 500,000 stretching cycles.
To complement this stable foundation, the team engineered a unique "analog constriction gate" architecture. By embedding graded, dome-like microbulges of varying sizes along the sensor's breathing channel, the patch mimics sequential valves. As the user's chest expands, these tiny gates constrict the liquid metal path in a progressive sequence. This design provides the sensor with extraordinary sensitivity and linearity across its entire physical range, allowing it to easily capture everything from a barely noticeable, shallow resting breath (less than 0.01% chest strain) to a deep, heavy chest expansion without any signal distortion.
The resulting HELP patch features a dual-channel design. One channel is wide and thick, specifically optimized to record clean electrocardiogram (ECG) heart signals while remaining immune to chest stretching. The other channel is a thin, U-shaped loop optimized to measure physical chest and abdominal movement. Remarkably, despite its advanced capabilities, the patch does not require expensive cleanroom fabrication or complex manufacturing equipment. The team developed a highly scalable, simple stencil-brushing process to pattern the liquid metal onto the anchored substrate, making the device cost-effective and highly amenable to mass production.
In initial pilot clinical studies, the HKUST team demonstrated the clinical utility of the HELP system on human subjects. When used for sleep monitoring, the self-applied patch showed strong agreement with traditional, gold-standard hospital PSG equipment in detecting sleep apnea events. Furthermore, the patch was applied by the patients themselves in less than a minute, eliminating the need for the dozens of wired sensors typical of traditional sleep studies. The HELP patch also successfully tracked how well asthma patients responded to their bronchodilator treatments in real-time, objectively confirming the rapid restoration and synchronization of their breathing patterns.
Most notably, the continuous monitoring capability allowed researchers to detect critical overnight physiological changes that are otherwise missed during standard clinic visits. "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 Prof. Nyein.
