Advanced electronics have been in development for several decades, resulting in a vast collection of circuit designs. However, most of these transistor and amplifier technologies are incompatible with human physiology. In traditional bioelectronics, complementary transistors are made from different materials to handle the varying polarities of signals. These designs, while functional, are often rigid and cumbersome and present a risk of toxicity when implanted in sensitive areas. Now, researchers have developed a biocompatible sensor implant by embedding transistors in a soft, conformable material to monitor neurological functions through successive stages of a patient’s development.

In a paper published in Nature Communications, scientists from the University of California, Irvine (Irvine, CA, USA) and Columbia University (New York, NY, USA) described their creation of complementary, internal, ion-gated, organic electrochemical transistors. These transistors are more chemically, biologically, and electronically compatible with living tissues compared to rigid, silicon-based technologies. Medical devices based on these transistors can function in delicate parts of the body and adapt to organ structures, even as they grow. The asymmetric design of the transistors allows them to operate using a single, biocompatible material.

By arranging the transistors into a smaller, single-polymer material, the fabrication process is greatly simplified, enabling large-scale production. This innovation opens up possibilities to expand the technology beyond its initial use in neurology to virtually any biopotential process. Additionally, the device can be implanted in a developing animal and can withstand changes in tissue structures as the organism grows—something that rigid, silicon-based implants cannot do. Complementary, internal, ion-gated, organic electrochemical transistors will significantly broaden the scope of bioelectronics, enabling the development of devices that traditionally relied on bulky, non-biocompatible components.

“A transistor is like a simple valve that controls the flow of current. In our transistors, the physical process that controls this modulation is governed by the electrochemical doping and de-doping of the channel,” said first author Duncan Wisniewski, Columbia University Ph.D. “By designing devices with asymmetrical contacts, we can control the doping location in the channel and switch the focus from negative potential to positive potential. This design approach allows us to make a complementary device using a single material.” 

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