The research teams of Hyunjoo Lee, a professor in the School of Electrical Engineering, and Nakwon Choi, a doctor at the Korea Institute of Science and Technology (KIST), have collaborated to develop a multilayer microfabrication process called aluminum hard mask on silk fibroin (AMoS) that can micropattern wafers made of silk fibroins, metals, and dielectrics. The process employs ultraviolet photolithography, a conventional micropatterning technique, and has high throughput, allowing the potential mass production of silk fibroin-based microelectronic devices. PhD candidate Geon Kook and KIST PhD candidate Sohyeon Jung were the lead authors of the paper, which was featured in the January 16 edition of ACS AMI: ACS Applied Materials & Interfaces as the cover paper.

Silk fibroin is a substrate widely used in implantable devices due to its properties of biocompatibility, controllable biodegradability, transparency, and flexibility. Previously, silk fibroins had been limited in multilayer fabrication use, as conventional micropatterning techniques utilized strong etching solutions and solvents that could distort the structure of biopolymers like silk fibroin. AMoS utilizes UV photolithography to first micropattern an aluminum layer, which acts as a mask, allowing the silk fibroin layer beneath to remain intact.

In order to test the biocompatibility of the fabricated silk fibroin, primary neurons were cultivated on the surface of a micropatterned silk fibroin sample, indicating the potential use of this technology in the production of implantable devices. Using AMoS, the researchers demonstrated the technique’s large scale production capabilities by micropatterning a biodegradable, large area microcircuit composed of a resistor and capacitor on multiple layers of metals and silk fibroins. Potential applications of the silk fibroin microelectronic circuit include the control of neurons via a silk fibroin-based brain electrode and a microdroplet-mounted microcircuit that could be utilized in drug delivery experiments studying brain circuitry.

Professor Lee stated, “Large area micropatterning fabrication of sensitive biomaterials, which was previously deemed impossible, has become feasible, much like that of silicon,” and expressed, “[He] expects this technology has potential to be utilized in a wide range of biomedical device applications”.

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