City University of Hong Kong

Super wearable electronics that are lightweight, stretchable and increase sweat permeability by 400-fold have been developed by scientists, enabling reliable long-term monitoring of biosignals for biomedical devices. Super wearable electronics that are lightweight, stretchable and increase sweat permeability by 400-fold have been developed by scientists at City University of Hong Kong (CityUHK), enabling reliable long-term monitoring of biosignals for biomedical devices. Led by Professor Yu Xinge in CityUHK's Department of Biomedical Engineering (BME), the research team has recently developed a universal method to creating these super wearable electronics that allow gas and sweat permeability, solving the most critical issue facing wearable biomedical devices. Wearable electronics play a significant role in promoting health and fitness. Continuous monitoring of physiological signals over a prolonged period is essential for gaining a comprehensive perspective on an individual's overall health status, early disease prediction, personalised therapeutics and improved management of chronic health conditions. However, the long-term signal stability could be influenced by sweat or air permeability. Professor Yu and his team have put in significant effort into addressing the need for wearable devices that can provide continuous and stable monitoring of vital signs without causing discomfort or signal disruption brought about by perspiration. Resolving this challenge, the team has developed a fundamental methodology from materials processing, device architecture and system integration for integrated permeable wearable electronics based on a nature-inspired three-dimensional liquid diode (3D LD) configuration, in which surface structures facilitate the spontaneous flow of liquids in a specific direction. The findings have recently been published in the journal Nature under the title "A three-dimensional liquid diode for soft, integrated permeable electronics." "Incorporating a 3D spatial liquid manipulation technique, we have achieved fully integrated permeable electronics that match the circuitry and functionality to state-of-the-art wearable devices, enabling superb breathability," said Professor Yu. "The 3D LD does not rely on unique materials but adopts an in-plane liquid transport layer called the horizontal liquid diode." In the study, the device that the team created can transport sweat from the skin 4,000 times more effectively than the human body can produce it, ensuring seamless monitoring even in sweating conditions, solving the issue of signal disruption caused by sweat accumulation at the device-skin interface. And because of its thin, lightweight, soft, and stretchable features, the device demonstrated exceptional compatibility with the human body, effectively adhering to the skin, maintaining a comfortable and stable interface between the device and the skin, providing high-quality signals. "Our findings provide fluid manipulation and system integration strategies for the soft, permeable wearables. We have successfully applied this technology to both advanced skin-integrated electronics and textile-integrated electronics, achieving reliable health monitoring over a weeklong duration," said Professor Yu. Currently, the team is advancing to clinical trials to confirm the effectiveness of their technology in real-world scenarios. Professor Yu is the corresponding author. Dr Zhang Binbin, Dr Li Jiyu, Zhou Jingkun, and Chow Lung are the paper's first authors. Dr Zhang and Dr Li are postdoctoral fellows in the BME and Hong Kong Centre for Cerebro-Cardiovascular Health Engineering, an InnoHK centre. Mr Zhou Jingkun and Mr Chow are PhD students under the supervision of Professor Yu.

Researchers have developed a sensor array design technology inspired by the human auditory system. By mimicking the human ear's ability to distinguish sounds through tonotopy, this innovative sensor array approach could optimize the application of sensor arrays in fields such as robotics, aviation, healthcare, and industrial machinery. Researchers from The Hong Kong University of Science and Technology (HKUST) have developed a sensor array design technology inspired by the human auditory system. By mimicking the human ear's ability to distinguish sounds through tonotopy, this innovative sensor array approach could optimize the application of sensor arrays in fields such as robotics, aviation, healthcare, and industrial machinery. Traditional sensor arrays face challenges such as complex wiring, limited reconfigurability, and low damage resistance. The design developed by the HKUST team, led by Associate Professor YANG Zhengbao from the Department of Mechanical & Aerospace Engineering, addresses these challenges by assigning a unique frequency to each sensor unit and using the sensor unit signal to modulate the amplitude of the frequency signal, similar to the distinct frequencies processed by hair cells in the human cochlea. These amplitude-modulated signals of different frequencies are then superimposed onto a single conductor, and a Fast Fourier Transform algorithm is finally used to decipher the individual signals. This design allows the reduction of a large number of output wires from the conventional row-column setup to a single wire, without sacrificing functionality. This innovative method allows the decoding system to process information from all sensor units simultaneously, which is a stark contrast to the existing implementation of time-division multiplexing for sensor array decoding. The research team leverages a redundancy design in the sensor connection network to ensure continuous operation, even when parts of the array's connection network are damaged. This design feature is inspired by the multiple synaptic connections between hair cells in the internal ear and neurons, providing a backup should one pathway fail. This redundant design not only enhances the system's damage tolerance but also enables greater reconfigurability, a feature that is particularly useful in rapidly changing environments such as responsive robotics or adaptable wearable devices. The Lego-style modular design could also lead to cost savings in maintenance, as it is easier to repair than traditional multi-wire sensor arrays. The proposed sensor array technology offers a multitude of potential applications. Its flexibility and robustness make it ideally suited for integration into curved surfaces and operation in harsh environments. It can adapt to the shape and multimodal sensing requirements of the surface while providing real-time data. In practical terms, the team has demonstrated the sensor array's functionality in two primary applications -- a pressure sensor array and a pressure-temperature multimodal sensor array. The latter is particularly noteworthy for its potential to monitor critical parameters in medical prosthetics, thereby enhancing comfort and safety for users. The team has also underscored the technology's potential for monitoring strain distribution in airplane wings, which could contribute to the development of safer and more fuel-efficient aircraft. Despite its many advantages, this sensor array design does encounter some limitations. The number of sensor units in the array is constrained by the operational bandwidth of the circuits, and the potential for miniaturization is limited by the size of the off-the-shelf electronic components required for each sensor unit. Looking ahead, the HKUST team aims to further simplify the sensor array's design and seek commercial partnerships to bring this technology to the market. The team's findings, realized in collaboration with City University of Hong Kong, were recently published in the journal Science Advances in an article titled "One-wire reconfigurable and damage-tolerant sensor matrix inspired by the auditory tonotopy." Dr. LONG Zhihe and Mr. LIN Weikang are the first authors of this work.

Starting a new year, many people pledge to enact self-care routines that improve their appearance. And facial sheet masks soaked in skin care ingredients provide an easy way to do this. However, these wet masks and their waterproof packaging often contain plastics and preservatives. Now, a study reports a dry-packaged hydrating facial mask that is made of biobased and sustainable materials. Starting a new year, many people pledge to enact self-care routines that improve their appearance. And facial sheet masks soaked in skin care ingredients provide an easy way to do this. However, these wet masks and their waterproof packaging often contain plastics and preservatives. Now, a study in ACS Applied Materials & Interfaces reports a dry-packaged hydrating facial mask that is made of biobased and sustainable materials. Consumers in the beauty industry are increasingly concerned about the sustainability and sourcing of personal care items, in terms of both products' ingredients and packaging. Facial sheet masks are popular cosmetic products advertised to benefit and enhance the skin. But they are typically made with plastic backing fabrics and are packaged with wet ingredients, requiring preservatives and disposable water-tight pouches. A more environmentally friendly option would be to package the facial masks dry. So, Jinlain Hu and coworkers aimed to design a facial sheet mask with biobased materials that could be enveloped in paper and later activated to deliver moisture and nutrients. The researchers developed a facial mask with a sheet of plant-based polylactic acid (PLA), which could repel water, and they coated it in a layer of gelatin mixed with hyaluronic acid and green tea extract. They deposited the top layer as either tiny fibers or microspheres, using electrospinning or electrospray, respectively, and tested how well the masks could transfer moisture. They found: Finally, the team investigated how its mask's ingredients impacted mouse cells as a proxy for reactions on skin. Fewer cells showed signals of aging when grown on the mask compared with cells grown in control conditions; the researchers attribute this to the antioxidant properties of the green tea extracts. The team says the beneficial properties of the natural ingredients and the one-way moisture-delivery design make this mask a promising alternative with a lesser environmental impact compared to traditional, wet-packed products. The authors acknowledge funding from the City University of Hong Kong, the National Natural Science Foundation of China, and Shenzhen-Hong Kong-Macau Science & Technology Fund.