researchers develop cooling ceramic tiles that mimic the whiteness of beetle to deflect heat

City University of Hong Kong replicate Cyphochilus beetle

Researchers at the City University of Hong Kong have developed cooling ceramic tiles that replicate the bio-whiteness of the Cyphochilus beetle to deflect heat, reduce home air-conditioning usage, and combat global warming. The ability of their cooling ceramic tiles to repel heat depends on how they interact with light, and they can be effective in two ranges of light, namely the solar range, which comes from the sun, and the mid-infrared range. 

In the solar range, the tiles reflect a lot of light to minimize heating from the sun, while in the mid-infrared range, they emit a lot of heat, helping to cool down the material. Another component of the cooling ceramic tiles that the researchers at the City University of Hong Kong add is alumina or aluminum oxide.

This ingredient has a high band gap, which means it doesn’t easily absorb sunlight, making it an ideal element to keep a space cool. Tiles are only one of the many potential products and shapes that the cooling ceramic can take form since the cooling ceramic can also be applied to several industries (more on this below).

images by the City University of Hong Kong

researchers’ cooling ceramic tiles have 99% solar reflectivity

The researchers at the City University of Hong Kong reproduce the color of the Cyphochilus beetle, which has a quality known as bio-whiteness, meaning the insect appears very white. White paint on the surface of a house can help decrease heat, as some research found, and by emulating the color of the Cyphochilus beetle and its bio-whiteness, the cooling ceramic tiles may achieve the same. The ceramic’s structure is designed to scatter sunlight, and this takes place by optimizing the arrangement of pores in the ceramic. 

After that, the material can reflect almost all sunlight that hits it. With the same process applied in the experiment conducted by the researchers at the City University of Hong Kong for their cooling ceramic tiles, they share that they achieve 99.6 percent solar reflectivity, meaning the tiles deflect almost all of the sunlight they receive. In the mid-infrared range, the cooling ceramic tiles emit thermal heat radiation, which achieves a high thermal emission of 96.5 percent, meaning that they release a significant amount of heat.

the researchers come up with cooling ceramic tiles that replicate the bio-whiteness of the cyphochilus beetle

withstanding temperatures exceeding 1,000 °C

Professor Edwin Tso Chi-yan, an Associate Professor in the School of Energy and Environment (SEE) at the City University of Hong Kong and one of the corresponding authors of the paper, says that ‘the cooling ceramic is made of alumina, which provides the desired UV resistance degradation, which is a concern typical of most polymer-based PRC designs. It also exhibits outstanding fire resistance by withstanding temperatures exceeding 1,000 °C, which surpasses the capabilities of most polymer-based or metal-based PRC materials. 

He shares as well that the beauty of the cooling ceramic tiles is that they fulfill the requirements for both high-performance PRC and applications in real-life settings. He also adds that the cooling ceramic tiles can even be added with a layered color while maintaining their anti-heat properties. 

Professor Tso and the researchers at the City University of Hong Kong found in their experiment that applying their cooling ceramic tiles on a house roof can achieve more than 20 percent electricity for space cooling, ‘which confirms the great potential of cooling ceramic in reducing people’s reliance on traditional active cooling strategies and provides a sustainable solution for avoiding electricity grid overload, greenhouse gas emissions, and urban heat islands,’ the professor comments.

the city university of hong kong’s researchers say another color can be added on top of their cooling ceramic tiles

The researchers claim too that their cooling ceramic tiles can withstand outdoor conditions for a long time so that they won’t degrade easily because of the weather, chemicals, or wear and tear. If these tiles are faced with extreme high temperatures, they become super hydrophilic, meaning water droplets spread out immediately on their surface, still keeping their ability to cool the surface down. Because of their porous structure, these tiles quickly absorb water droplets too, which is handy for a rapid cooling effect.

As of publishing the story, Professor Tso says that the researchers intend to further the passive thermal management strategies based on the findings of their study. They plan to explore the application of their cooling ceramic tiles to several surfaces and industries and see if they can improve energy efficiency, promote sustainability, and increase the accessibility and applicability of passive radiative cooling technologies in various sectors, including textiles, energy systems, and transportation.

application test of the beetle-inspired cooling ceramic tiles by the researchers of the City University of Hong Kong

researchers (from left) Lin Kaixin, Professor Edwin Tso Chi-yan, and Chen Siru

project info:

name: Cooling ceramic tiles

institution: City University of Hong Kong

researchers: Chi Yan Tso, Kaixin Lin, Siru Chen, Yijun Zeng, Tsz Chung Ho, Yihao Zhu, Xiong Wang, Fayu Liu, Baoling Huang, Christopher Yu-Hang Chao, Zuankai Wang