Chung-Ang University researchers demonstrate paper electrode-based crawling soft robots

Biological systems have inspired the development of next-generation soft robotic systems with diverse motions and functions. Such versatility in soft robots—in terms of rapid and efficient crawling—can be achieved via asymmetric bending through bilayer-type actuators that combine responsive liquid crystal elastomers (LCEs) with flexible substrates. This, in turn, requires temperature-responsive LCEs with accurate temperature regulation via elaborate Joule heating configurations.

However, it is a complicated task owing to the difficulty in generating asymmetric motions using isotropic thermal distributions, necessitating simple temperature gradient patterning and bilayer fabrication technologies.

Addressing these challenges, a team of researchers from the Department of Chemical Engineering at Chung-Ang University, led by Professor Suk Tai Chang and Assistant Professor Changyeon Lee, have proposed a facile electroless plating method for patterning asymmetric temperature gradients on paper substrates, ultimately resulting in the development of innovative caterpillar-inspired soft robots. Their findings were made available online and published in the journal Advanced Functional Materials on 30 July 2025.

Prof. Chang sheds light on the motivation behind their research. “Our motivation for this work comes from the fascinating world of nature, specifically the crawling motion of caterpillars. We were intrigued by how such a simple organism could achieve highly efficient locomotion through sequential bending and stretching. I wanted to replicate this elegant mechanism in a soft robotic system, but without the complexity of traditional methods that often require intricate heating configurations.”

With this vision in mind, the researchers chose cellulose-based paper—a common and eco-friendly material—as the substrate for the soft robots. Furthermore, instead of complex circuit designs, they turned to printing-based electrode patterning technology to dramatically simplify the fabrication process.

“Cellulose-based paper substrates provide distinct advantages due to their porous structure, which enables facile electrode deposition via solution-based processes and offers high mechanical deformability,” remarks Prof. Lee.

In this study, the team deposited Cu electrodes asymmetrically on paper substrates by changing electrode widths. This variation caused electrical resistance gradients, producing significant temperature gradients across the substrate. This process finally resulted in energy-efficient soft robots capable of directional crawling at a low actuation voltage value via paper substrate integration with LCEs in a bilayer architecture.

“In this way, we successfully achieved asymmetric bending motion, which is a difficult feat for conventional soft robots. By precisely controlling the temperature gradient on the paper-based electrode, we were able to induce differential bending, which mimics the natural crawling motion of a caterpillar. This novel mechanism enables directional and controlled movement for soft robots,” points out Prof. Chang.

The lightweight and thin crawling robot presented in this work could be used for environmental monitoring or performing special tasks in environments that are difficult for humans to reach, whether due to physical constraints or safety concerns.

Overall, the simplicity and cost-effectiveness of the electrode patterning process, in combination with the abundance and eco-friendly nature of paper-based actuators, is a promising approach for the scalable and sustainable fabrication of real-life soft robots, paving the way for the widespread integration of soft robots into our daily lives.

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Reference
DOI: 10.1002/adfm.202512328

About Chung-Ang University
Chung-Ang University is a private comprehensive research university located in Seoul, South Korea. It was started as a kindergarten in 1916 and attained university status in 1953. It is fully accredited by the Ministry of Education of Korea. Chung-Ang University conducts research activities under the slogan of “Justice and Truth” Its new vision for completing 100 years is “The Global Creative Leader” Chung-Ang University offers undergraduate, postgraduate, and doctoral programs, which encompass a law school, management program, and medical school; it has 16 undergraduate and graduate schools each. Chung-Ang University’s culture and arts programs are considered the best in Korea

Website: https://neweng.cau.ac.kr/index.do

About Suk Tai Chang from Chung-Ang University
Suk Tai Chang is a Professor of the Department of Chemical Engineering at Chung-Ang University. He received his Ph.D. degree in Chemical and Biomolecular Engineering from North Carolina State University and worked as a Postdoctoral Fellow at Sandia National Laboratories, USA. His research topics are focused on thin film deposition and micropatterning, microfluidic synthesis of microfibers and microcapsules, and wearable physical sensors. Currently, his research group is developing paper-based energy storage devices and soft actuators.

Website: https://scholarworks.bwise.kr/cau/researcher-profile?ep=759

About Changyeon Lee from Chung-Ang University
Changyeon Lee is an assistant professor of Chemical Engineering at Chung-Ang University. His research group focuses on developing stimuli-responsive polymers, such as liquid crystal polymers, for applications in soft robotics, sensors, energy devices, and beyond. His group is also researching semiconducting polymers. Before his position at Chung-Ang University, he conducted research in Prof. Chinedum Osuji’s group at the University of Pennsylvania. He earned his Ph.D. in Chemical and Biomolecular Engineering from the Korea Advanced Institute of Science and Technology (KAIST) in 2018.

Website: https://scholarworks.bwise.kr/cau/researcher-profile?ep=139