Tag Archives: Hong Kong Polytechnic University (PolyU)

Aerogel material (inspired by loofahs) uses sunlight to remove salt from seawater

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Should you be living in an area where there’s lots of salt water but not much drinking water this July 2, 2025 news item on Nanowerk is likely to be of special interest, Note: A link has been removed,

Most of Earth’s water is in the oceans and too salty to drink. Desalination plants can make seawater drinkable, but they require large amounts of energy. Now, researchers reporting in ACS Energy Letters (“Size-Insensitive Vapor Diffusion Enabled by Additive Freeze-Printed Aerogels for Scalable Desalination”) have developed a sponge-like material with long, microscopic air pockets that uses sunlight and a simple plastic cover to turn saltwater into freshwater. A proof-of-concept test outdoors successfully produced potable water in natural sunlight in a step toward low-energy, sustainable desalination.

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Caption: This isn’t a paper chain, it’s a 3D-printed material that soaks up seawater, purifying it into salt-free water. Credit: Adapted from ACS Energy Letters 2025, DOI: 10.1021/acsenergylett.5c01233

A July 2, 2025 American Chemical Society news releease (also on EurekAlert), which originated the news item, provides more information, Note: A link has been removed,

This isn’t the first time scientists have created spongy materials that use sunlight as a sustainable energy source for cleaning or desalinating water. For example, a loofah-inspired hydrogel with polymers inside its pores was tested on chromium-contaminated water and, when heated by the sun, the hydrogel quickly released a collectible, clean water vapor through evaporation. But while hydrogels are squishy and liquid-filled, aerogels are more rigid, containing solid pores that can transport liquid water or water vapor. Aerogels have been tested as a means of desalination, but they are limited by their evaporation performance, which declines as the size of the material increases. So, Xi Shen and colleagues wanted to design a porous desalination aerogel that maintained its efficiency at different sizes.

The researchers made a paste containing carbon nanotubes and cellulose nanofibers and then 3D-printed it onto a frozen surface, allowing each layer to solidify before the next was added. This process formed a sponge-like material with evenly distributed tiny vertical holes, each around 20 micrometers wide. They tested square pieces of the material, ranging in size from 0.4 inches wide (1 centimeter) to about 3 inches wide (8 centimeters), and found that the larger pieces released water through evaporation at rates as efficient as the smaller ones.

In an outdoor test, the researchers placed the material in a cup containing seawater, and it was covered by a curved, transparent plastic cover. Sunlight heated the top of the spongy material, evaporating just the water, not the salt, into water vapor. The vapor collected on the plastic cover as liquid, moving the now clean water to the edges, where it dripped into a funnel and container below the cup. After 6 hours in natural sunlight, the system generated about 3 tablespoons of potable water.

“Our aerogel allows full-capacity desalination at any size,” Shen says, “which provides a simple, scalable solution for energy-free desalination to produce clean water.”

The authors acknowledge funding from the National Natural Science Foundation of China, the Research Grants Council of Hong Kong SAR, the Environment and Conservation Fund of Hong Kong SAR, and the Hong Kong Polytechnic University.

Here’s a link to and a citation for the paper,

Size-Insensitive Vapor Diffusion Enabled by Additive Freeze-Printed Aerogels for Scalable Desalination by Xiaomeng Zhao, Yunfei Yang, Xuemin Yin, Zhuo Luo, Kit-Ying Chan, and Xi Shen. ACS Energy Letters (ACS Energy Lett.) 2025, 10, 7, 3419–3429 DOI: https://doi.org/10.1021/acsenergylett.5c01233 Published July 2, 2025 Copyright © 2025 American Chemical Society

This paper is behind a paywall.

First-of-its-kind thermally-insulated and breathable soft robotic clothing for use in extreme heat

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An August 15, 2024 news item on ScienceDaily announces research that may help make people safer in extreme heat,

As global warming intensifies, people increasingly suffer from extreme heat. For those working in a high-temperature environment indoors or outdoors, keeping thermally comfortable becomes particularly crucial. A team led by Dr Dahua SHOU, Limin Endowed Young Scholar in Advanced Textiles Technologies and Associate Professor of the School of Fashion and Textiles of The Hong Kong Polytechnic University (PolyU) has developed first-of-its-kind thermally-insulated and breathable soft robotic clothing that can automatically adapt to changing ambient temperatures, thereby helping to ensure worker safety in hot environments. Their research findings have been published in the international interdisciplinary journal Advanced Science.

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An August 14, 2024 Hong Kong Polytechnic University press release (also on EurekAlert but published on August 15, 2024), which originated the news item, elaborates on the issue and on the proposed solution,

Maintaining a constant body temperature is one of the most critical requirements for living and working. High-temperature environments elevate energy consumption, leading to increased heat stress, thus exacerbating chronic conditions such as cardiovascular disease, diabetes, mental health issues and asthma, while also increasing the risk of infectious disease transmission. According to the World Health Organisation, globally, there were approximately 489,000 heat-related deaths annually between 2000 and 2019, with 45% occurring in Asia and 36% in Europe.

Thermal protective clothing is essential to safeguard individuals in extreme high-temperature environments, such as firefighters who need to be present at fires [sic] scenes and construction workers who work outdoors for extended periods. However, traditional gear has been limited by statically fixed thermal resistance, which can lead to overheating and discomfort in moderate conditions, while its heat insulation may not offer sufficient protection in extreme fire events and other high-temperature environments. To address this issue, Dr Shou and his team have developed intelligent soft robotic clothing for automatic temperature adaptation and thermal insulation in hot environments, offering superior personal protection and thermal comfort across a range of temperatures.

Their research was inspired by biomimicry in nature, like the adaptive thermal regulation mechanism in pigeons, which is mainly based on structural changes. Pigeons use their feathers to trap a layer of air surrounding their skin to reduce heat loss to the environment. When the temperature drops, they fluff up their feathers to trap a significant amount of still air, thereby increasing thermal resistance and retaining warmth.

The protective clothing developed by the team uses soft robotic textile for dynamic adaptive thermal management. Soft actuators, designed like a human network-patterned exoskeleton and encapsulating a non-toxic, non-flammable, low-boiling-point fluid, were strategically embedded within the clothing. This thermo-stimulated system turns the fluid from a liquid into a gas when the ambient temperature rises, causing expansion of soft actuators and thickening the textile matrix, thereby enhancing the gap of still air and doubling the thermal resistance from 0.23 to 0.48 Km²/W. The protective clothing can also keep the inner surface temperatures at least 10°C cooler than conventional heat-resistant clothing, even when the outer surface reaches 120°C.

This unique soft robotic textile, made by thermoplastic polyurethane, is soft, resilient and durable. Notably, it is far more skin-friendly and conformable than temperature-responsive clothing embedded with shape-memory alloys and is adjustable for a wide range of protective clothing. The soft actuators have exhibited no signs of leakage after undergoing rigorous standard washing tests. The porous, spaced knitting structure of the material can also significantly reduce convective heat transfer while maintaining high moisture breathability. Not relying on thermoelectric chips or circulatory liquid cooling systems for cooling or heat conduction, the light-weighted, soft robotic clothing can effectively regulate temperature itself without any energy consumption.

Dr Shou said, “Wearing heavy firefighting gear can feel extremely stifling. When firefighters exit a fire scene and remove their gear, they are sometimes drained nearly a pound of sweat from their boots [sic]. This has motivated me to develop a novel suit capable of adapting to various environmental temperatures while maintaining excellent breathability. Our soft robotic clothing can seamlessly adapt to different seasons and climates, multiple working and living conditions, and transitions between indoor and outdoor environments to help users experience constant thermal comfort under intense heat.”

Looking forward, Dr Shou finds the innovation to have a wide range of potential applications, from activewear, winter jackets, healthcare apparel and outdoor gear, to sustainable textile-based insulation for construction and buildings, contributing to energy-saving efforts. Supported by the Innovation and Technology Commission and the Hong Kong Research Institute of Textiles and Apparel, Dr Shou and his team have also extended the thermo-adaptive concept to develop inflatable, breathable jackets and warm clothing. This soft robotic clothing is suitable for low-temperature environments or sudden temperature drops to aid those who are stranded in the wilderness to maintain normal body temperature.

Here’s a link to and a citation for the paper,

Soft Robotic Textiles for Adaptive Personal Thermal Management by Xiaohui Zhang, Zhaokun Wang, Guanghan Huang, Xujiang Chao, Lin Ye, Jintu Fan, Dahua Shou. Volume 11, Issue 21 June 5, 2024 2309605 First published online: 26 March 2024 DOI: https://doi.org/10.1002/advs.202309605

This paper is open access.

A new ink for energy storage devices from the Hong Kong Polytechnic University

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Energy storage is not the first thought that leaps to mind when ink is mentioned. Live and learn, eh? A Sept. 23, 2015 news item on Nanowerk describes the connection (Note: A link has been removed),

 The Department of Applied Physics of The Hong Kong Polytechnic University (PolyU) has developed a simple approach to synthesize novel environmentally friendly manganese dioxide ink by using glucose (“Aqueous Manganese Dioxide Ink for Paper-Based Capacitive Energy Storage Devices”).

The MnO2 ink could be used for the production of light, thin, flexible and high performance energy storage devices via ordinary printing or even home-used printers. The capacity of the MnO2 ink supercapacitor is more than 30 times higher than that of a commercial capacitor of the same weight of active material (e.g. carbon powder), demonstrating the great potential of MnO2 ink in significantly enhancing the performances of energy storage devices, whereas its production cost amounts to less than HK$1.

A Sept. 23, 2015 PolyU media release, which originated the news item, expands on the theme,

MnO2 is a kind of environmentally-friendly material and it is degradable. Given the environmental compatibility and high potential capacity of MnO2, it has always been regarded as an ideal candidate for the electrode materials of energy storage devices. The conventional MnO2 electrode preparation methods suffer from high cost, complicated processes and could result in agglomeration of the MnO2 ink during the coating process, leading to the reduction of electrical conductivity. The PolyU research team has developed a simple approach to synthesize aqueous MnO2 ink. Firstly, highly crystalline carbon particles were prepared by microwave hydrothermal method, followed by a morphology transmission mechanism at room temperature. The MnO2 ink can be coated on various substrates, such as conductive paper, plastic and glass. Its thickness and weight can also be controlled for the production of light, thin, transparent and flexible energy storage devices. Substrates coated by MnO2 ink can easily be erased if required, facilitating the fabrication of electronic devices.

PolyU researchers coated the MnO2 ink on conductive A4 paper and fabricated a capacitive energy storage device with maximum energy density and power density amounting to 4 mWh•cm-3 and 13 W•cm-3 respectively. The capacity of the MnO2 ink capacitor is more than 30 times higher than that of a commercial capacitor of the same weight of active material (e.g. carbon powder), demonstrating the great potential of MnO2 ink in significantly enhancing the performances of energy storage devices. Given the small size, light, thin, flexible and high energy capacity properties of the MnO2 ink energy storage device, it shows a potential in wide applications. For instance, in wearable devices and radio-frequency identification systems, the MnO2 ink supercapacitor could be used as the power sources for the flexible and “bendable” display panels, smart textile, smart checkout tags, sensors, luggage tracking tags, etc., thereby contributing to the further development of these two areas.

The related paper has been recently published on Angewandte Chemie International Edition, a leading journal in Chemistry. The research team will work to further improve the performance of the MnO2 ink energy storage device in the coming two years, with special focus on increasing the voltage, optimizing the structure and synthesis process of the device. In addition, further tests will be conducted to integrate the MnO2 ink energy storage device with other energy collection systems.

Here’s a link to and a citation for the paper,

Aqueous Manganese Dioxide Ink for Paper-Based Capacitive Energy Storage Devices by Jiasheng Qian, Huanyu Jin, Dr. Bolei Chen, Mei Lin, Dr. Wei Lu, Dr. Wing Man Tang, Dr. Wei Xiong, Prof. Lai Wa Helen Chan, Prof. Shu Ping Lau, and Dr. Jikang Yuan. Angewandte Chemie International Edition Volume 54, Issue 23, pages 6800–6803, June 1, 2015 DOI: 10.1002/anie.201501261 Article first published online: 17 APR 2015

© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This paper is behind a paywall.