New fabrication method for silk fibroin microelectronics

Korean researchers have developed a novel fabrication method for the multilayer processing of silk-based microelectronics. Described in ACS Applied Materials & Interfaces, the technology for creating a biodegradable silk fibroin film allows microfabrication with polymer or metal structures manufactured from photolithography.

Silk fibroins are biocompatible, biodegradable, transparent and flexible, which makes them good candidates for implantable biomedical devices; they have also been used as biodegradable films and functional microstructures in biomedical applications. However, conventional microfabrication processes require strong etching solutions and solvents to modify the structure of silk fibroins.

To prevent the silk fibroin from being damaged during the process, Professor Hyunjoo J Lee from the Korea Advanced Institute of Science and Technology (KAIST) and her team came up with a novel process, named aluminium hard mask on silk fibroin (AMoS), which is capable of micropatterning multiple layers composed of both fibroin and inorganic materials, such as metal and dielectrics with high-precision microscale alignment.

The AMoS process can make silk fibroin patterns on devices, or make patterns on silk fibroin thin films with other materials, by using photolithography — a core technology in the current microfabrication process. The team successfully cultured primary neurons on the processed silk fibroin micropatterns, and confirmed that silk fibroin has excellent biocompatibility before and after the fabrication process and that it also can be applied to implanted biological devices.

Through this technology, the team realised the multilayer micropatterning of fibroin films on a silk fibroin substrate and fabricated a biodegradable microelectric circuit consisting of resistors and silk fibroin dielectric capacitors in a silicon wafer with large areas. They also used the technology to position the micropattern of the silk fibroin thin film closer to the flexible polymer-based brain electrode and confirmed the dye molecules mounted on the silk fibroin were transferred successfully from the micropatterns.

“This technology facilitates wafer-scale, large-area processing of sensitive materials,” said Prof Lee. “We expect it to be applied to a wide range of biomedical devices in the future. Using the silk fibroin with micropatterned brain electrodes can open up many new possibilities in research on brain circuits by mounting drugs that restrict or promote brain cell activities.”

Image caption: The cover page of ACS AMI. For a larger image, click here.

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