Biodegradable silicon transistors from wood-based nanomaterial

CELLULOSE nanofibrillated fiber (CNF), a transparent, flexible biodegradable substrate made from inexpensive wood, could drive the future of green, low-cost portable electronic devices.

Researchers from the University of Wisconsin-Madison have recently demonstrated the feasibility of making microwave biodegradable thin-film transistors from CNF. They describe the biodegradable device in a paper published recently in the Applied Physics Letters from AIP Publishing.

 Zhenqiang Ma, team leader and a professor of electrical and computer engineering at the UW-Madison, and his group used silicon nanomembranes as the active material in the transistor peeled from the bulk crystal and then transferred and glued onto the cellulose nanofibrill substrate. To ensure the biodegradable transistor can operate at microwave frequencies, the working range of most portable and wireless devices, they conducted a series of experiments, including measuring the current-voltage characteristics to study the device's functional performance. Results confirmed the biodegradable transistor has superior microwave-frequency operation capabilities comparable to existing semiconductor transistors

According to Ma, "We found that cellulose nanofibrillated fiber-based transistors exhibit superior performance as that of conventional silicon-based transistors. The bio-based transistors are so safe that you can put them in the forest, and fungus will quickly degrade them. They become as safe as fertilizer."

The team plans to use the biodegradable transistors to develop more complicated circuit systems.

A candidate for making green, portable electronics, wood-based CNF is a sustainable, strong, transparent nanomaterial unlike other polymers such as plastics. It has relatively low thermal expansion coefficient, which means it will not change shape as the temperature changes. 

 Cellulose nanofibrillated fiber films have the potential to be used as electronic substrates in future devices, replacing non-renewable, non-biodegradable silicon wafers that are highly purified, expensive, and rigid. This could then help arrest the growing electronic waste accumulated from devices being discarded as users upgrade to stay abreast of new technologies. A 2012 U.S. Environmental Protection Agency report indicated only 10% of about 152 million mobile devices discarded every year are recycled.

 According to Ma, "Biodegradable electronics provide a new solution for environmental problems brought by consumers' pursuit of quickly upgraded portable devices. It can be anticipated that future electronic chips and portable devices will be much greener and cheaper than that of today."