Development of micropatterning process of conductive hydrogels for bioelectronics through laser-induced phase separation

□ Prof. Seung Hwan Ko (Seoul National University) and Prof. C-Yoon Kim (Konkuk University) joint research team has published their work in the world-famous scientific journal 'Science Advances' on June 8, local time in the United States.

 

□ The development of safe neural electrodes in micro-scale is essential to determine the condition of a patient suffering from central nervous system disease by reading electrical signals from a specific area of ​​the brain or to apply electrical stimulation to the brain for medical treatment. Existing neural electrodes were mainly developed using hard metals, so it was difficult to attach to the soft brain tissue, and the side effects were severe.

 

□ The micro-electrodes developed by this research team is safe and minimizes immune response when inserted into the body for a long period by using a soft, bio-friendly conducting polymer that stretches like living tissue. In addition, it can precisely read neural signals from very small cells through high electrical conductivity and pattern resolution.

 

□ The research team discovered a phase separation phenomenon in which the internal structure of the polymer is locally changed when the laser is irradiated to the conducting polymer Poly(3,4-ethylenedioxythiophene) : poly(styrenesulfonate) (PEDOT : PSS).

 

 

□ PEDOT:PSS is a biocompatible conducting polymer that has been spotlighted as a core material for bioelectronics. However, the phase distribution inside the polymer is disadvantageous for electrical conductivity and mechanical stability in aqueous solution. To solve it, phase separation processes that change the phase have been developed, led by chemical treatment techniques. Phase separated conductive polymer becomes a conductive hydrogels which are capable of maintaining electrical and mechanical properties in aqueous solution. However, since most of the chemicals used for phase separations are highly cytotoxic, a detoxification process is required before using as bioelectronic devices, and there are limitations in low electrical conductivity and additional patterning process is required.

 

□ The research team induced the phase separation of PEDOT:PSS using the photo-thermo-chemical reaction by the laser without toxic additives. Digital laser patterning that converts the desired area of PEDOT:PSS into conductive hydrogels was able to fabricate fine patterns that can maintain electrical and mechanical properties. While non-treated areas of PEDOT:PSS was dissolved in water.

 

□ This technology can produce conductive hydrogels pattern at the level of photolithography processes with much faster speed. It also can safely read brain signals and/or apply electrical stimulation due to its soft mechanical properties and high electrochemical properties when implanted into a living body.

 

□ Prof. Seung Hwan Ko, who is the corresponding author of the research, said, “It is possible to produce high resolution of conductive hydrogels pattern at the level of the photolithography processes at a dramatically reduced cost and time.”, and “It will be possible to contribute to the development of technologies in various research fields that require conductive polymer-based hydrogels.” Prof. C-Yoon Kim said, “Through the high biocompatibility of the laser process, it will be a new fundamental technology for the brain-computer interface that can collect electrophysiological signals while maintaining health when implanted into the body for long periods.”

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