Research Team Led by SNU Professor Sang Ken Kauh Makes Direct-Writing of Liquid Metal Patterns on Uneven Surfaces for Wearable Devices Possible

- Published as Cover Article of Advanced Materials Technologies


▲ Professor Sang Ken Kauh of SNU Department of Mechanical and Aerospace Engineering

 
SNU College of Engineering (Dean Kookheon Char) announced on 15^th that research team led by Professor Sang Ken Kauh of the Department of Mechanical and Aerospace Engineering (including Ph.D. Candidate Young Yoon) has developed a technology that writes liquid metal patterns on uneven surfaces. Thus, development of wearable devices that freely bend or fold is now possible.
 
The recent rising interest on flexible and wearable devices have led to active researches on flexible electrical circuits that maintain their performance when bent or stretched. The candidates that allow such circuits are electronic textiles like graphene and carbon nanotube, but they share a limitation to be vulnerable against heat; thus, large-scale production is difficult.
 
As an alternative to electronic textiles, printing and patterning using liquid metal, specifically gallium mixture, have been developed. However, even patterning faced difficulties when it came across uneven surfaces of wearable devices worn on hands, elbow, ear, etc.
 
Hence, Kauh’s team designed a new system that could write liquid-metal patterns on not only flat surfaces, but also curvatures. A wearable sensing glove was made to detect the movement of fingers by implementing touch sensors to saddle-shaped curves. This device drew a random circuit using its two-axes horizontal automatic stage and wrote consistent liquid-metal patterns regardless of the height of circuit board using its vertical stage and laser distance measurer.
 
In addition, by using a horizontal rotational stage, the laser distance measurer collected the range before the needle. Thus, a safety distance could be kept between the needle and board based on the collected range. This completed the patterning system that drew liquid-metal circuits on uneven surfaces.
 
Professor Kauh states, “Just with a simple system, liquid-metal patterns can be drawn freely on not just flat or sloped surfaces but also curved surfaces. This research will be a wide groundwork for development of tailored wearables and application of liquid-metal.”
 
The research findings were published on Advanced Materials Technolgies as the cover article of February issue under the title of “Wearable Electronics: Four Degrees-of-Freedom Direct Writing of Liquid Metal Patterns on Uneven Surfaces.” The research was conducted with the support of the Individual Basic Science and Engineering Research Program of the Ministry of Science and ICT and the National Research Foundation of Korea.
 
[Reference]
Research Paper: https://doi.org/10.1002/admt.201800379
Y. Yoon, S. Kim, D. Kim, S. K. Kauh, and J. Lee, “Four Degrees-of-Freedom Direct Writing of Liquid Metal Patterns on Uneven Surfaces,” Adv. Mater. Technol., vol. 4, no. 2, p. 1800379, 2018
 
Cover Page of Advanced Materials Technologies: https://doi.org/10.1002/admt.201970011