▲ Professor Jung Ki Park

Professors Jung Ki Park and Hee Tak Kim of the KAIST Department of Chemical and Biomolecular Engineering and Professor Seung Woo Lee of SKKU (Sungkyunkwan University) Advanced Institute of Nanotechnology have developed the world’s first auto-repairing electric circuit that reconnects its short-circuited part when exposed to a laser light.

By using an ordinary presentation laser pointer, one can fix the short-circuited parts of the newly developed electric circuit. The circuit is put on top of a flexible board, which allows it to be twisted, folded, or bent and used in flexible electronics or wearable computers as well as electrical wires for humanoid robots.

Electronic devices with thin and flexible integrated circuits may be short-circuited when excess force is applied. Since fixing the short-circuited portion of the integrated circuit is difficult, the entire module has to be replaced, a process that is both costly and wasteful.

The research team coated flexible ductile films with azo polymers, which move parallel to the direction of polarization of the illuminated light. Then the flexible electric circuit was completed by coating silver nanowires, which have good electric conductivity and can be easily synthesized.

To test the electric circuit, the research team short-circuited the circuit at a specific site, and then shone a laser light with an intensity of 500 mW/cm2 at the short-circuited site. The azo polymers moved in parallel to the direction of polarization of the illuminated light, and the silver nanowires moved in conjunction with the azo polymers, thereby fixing the short-circuited site.

Professor Park said, “Our research presented a potential method to solve the problem of short-circuiting in flexible electric devices.”

Professor Lee said, “We removed the need for complex restoration processes, such as the use of high temperature or toxic solvents, necessary for conventional auto-repairing electric circuit technology. We developed an electric circuit that can be easily fixed with an ordinary laser pointer.”

The research was led by Kang Hong-suk, a doctorate degree candidate at KAIST, supervised by Professors from KAIST and SKKU, and funded by the National Research Foundation of Korea. It was published in the journal Advanced Functional Materials.

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