Vertical electrochemical transistor shows biomedical sensing potential

Researchers at Northwestern University have developed a transistor that is claimed to be ideal for lightweight, flexible, high-performance bioelectronics.

The vertical electrochemical transistor is based on a new kind of electronic polymer and a vertical, instead of planar, architecture
The vertical electrochemical transistor is based on a new kind of electronic polymer and a vertical, instead of planar, architecture - Northwestern University

The electrochemical transistor is said to be compatible with blood and water and can amplify important signals, making it useful for biomedical sensing. In use, the transistor could enable wearable devices for onsite signal processing at the biology-device interface. Potential applications include measuring heartbeat and levels of sodium and potassium in blood as well as eye motion for studying sleep disorders.

The study detailing the electrochemical transistor and an accompanying News & Views article have been published in Nature.

“All modern electronics use transistors, which rapidly turn current on and off,” said Tobin J. Marks, a co-corresponding author of the study. “Here we use chemistry to enhance the switching. Our electrochemical transistor takes performance to a totally new level. You have all the properties of a conventional transistor but far higher transconductance, ultra-stable cycling of the switching properties, a small footprint that can enable high density integration, and easy, low-cost fabrication.”

Marks led the research team along with Antonio Facchetti, research professor of chemistry at Northwestern’s Weinberg College of Arts and Sciences; Wei Huang, now a professor at the University of Electronic Science and Technology of China; and Jonathan Rivnay, professor of biomedical engineering at Northwestern’s McCormick School of Engineering.


The electrochemical transistor – which conducts electricity and ions and is stable in air - is based on a new kind of electronic polymer and a vertical architecture.

“This exciting new type of transistor allows us to speak the language of both biological systems, which often communicate via ionic signalling, and electronic systems, which communicate with electrons,” Rivnay said in a statement. “The ability of the transistors to work very efficiently as ‘mixed conductors’ makes them attractive for bioelectronic diagnostics and therapies.”

“With their vertical architecture, our electrochemical transistors can be stacked one on top of another,” Facchetti said. “Thus, we can make very dense electrochemical complementary circuits, which is impossible for the conventional planar electrochemical transistors.”

To make more reliable and powerful electronic circuits, p-type and n-type transistors are needed but the challenge faced by researchers is that n-type transistors are difficult to build and are typically unstable.

According to Northwestern, this is the first work to demonstrate electrochemical transistors with similar and very high performance for both types (p+n) electrochemical transistors, which resulted in the fabrication of very efficient electrochemical complementary circuits.