Danqing Liu © TU Eindhoven
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Danqing Liu, assistant professor at the Department of Chemical Engineering and Chemistry of TU Eindhoven, is receiving more than 400,000 euros in order to develop smart surfaces that can secrete fluids and absorb them n response to light or to electric fields from their environment. These surfaces will be used to study friction during motion, for self-cleaning systems, and for robotic and health care applications.

The Dutch Research Council (NWO) has awarded three million euros to seven early-stage researchers in physics and chemistry through the START-UP program. Liu is one of them.

Secretion is a common phenomenon in nature. Human skin secretes oil to defend our bodies against bacteria and sweat to regulate our body temperature. Fish secrete mucus from their skin so as to protect against parasites and reduce friction from water in order to swim faster. Inspired by the skins of living creatures, Danqing Liu develops smart surfaces that can repeatedly release and reabsorb substances under environmental stimuli such as light and electricity.

Controlled release of liquid from surface areas is important for self-cleaning systems, where the released lubricant modifies surface moisture and repels attachment of various contaminants. Also, it can be used for biomedical purposes, such as skin patches, in controlling humidity and slowly release antibiotics to cure wounds. And, in a not too distant future, smart surfaces could even be used as ‘artificial skins’ for robots.

The body produces heat

Walking, exercising, lifting objects or simply standing still. Every time we use our muscles, they produce heat as a by-product. The more we use them, the more they have to be actively cooled down. This is why we sweat. By sweating, water is pumped out of our bodies, and as that water evaporates, it cools us down.

In robots, especially in humanoid robots which place high torque demands on their motors, generated heat presents a major constraint on their performance. Currently, engineers solve this problem by using fans or bulky radiators, which take up space and add mass. In the future, the smart surfaces developed by Liu might be used to develop artificial skins which could ‘make robots sweats, cool down and perform better’.

Responsive materials

With a broad background in various disciplines ranging from electrical to mechanical and chemical engineering, Liu attempts to fill the gap between molecular sciences – such as synthetic organic chemistry – and material science. “I develop new materials like silicons, hydrogels and liquid crystal polymers, on sub-micrometric scales,”  she explains. These materials are ‘responsive’, meaning that they can sense external stimuli and adapt to those via built-in sensory systems. The latter are either intrinsically present in the material itself or they can be integrated as optical, electrical or chemical sensors.