Researchers at the University of California, Irvine and Columbia University in New York have embedded transistors in a soft, conformable material to create a biocompatible sensing implant that monitors neurological functions through successive phases of a patient’s development.
In an article recently published in Nature CommunicationsUC Irvine scientists describe their construction of internal, ion-activated, complementary organic electrochemical transistors that are more chemically, biologically, and electronically responsive to living tissues than rigid silicon-based technologies. The medical device based on these transistors can work on sensitive parts of the body and adapt to the organ structures even as they grow.
“Advanced electronics have been developing for several decades, so there is a large repository of circuit designs available. The problem is that most of these transistor and amplifier technologies are not compatible with our physiology,” said co-author Dion Khodagholy, Henry Samueli Professor of Teaching Excellence in the Department of Electrical Engineering and Computer Science at UC Irvine. “For our innovation, we used organic polymer materials that are inherently closer to us biologically, and we designed it to interact with ions, because the language of the brain and body is ionic, not electronic.”
In standard bioelectronics, complementary transistors have been composed of different materials to account for different signal polarities, which, in addition to being rigid and cumbersome, present the risk of toxicity when implanted in sensitive areas. The team of researchers from UC Irvine and Columbia University solved this problem by creating their transistors in an asymmetric shape that allows them to operate using a single biocompatible material.
“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 dedoping of the channel,” said first author Duncan Wisniewski, Ph.D. from Columbia University. .D. candidate during the project who is now a visiting scholar in the Department of Electrical Engineering and Computer Science at UC Irvine. “By designing devices with asymmetric contacts, we can control the location of doping in the channel and shift the focus from negative potential to positive potential. This design approach allows us to fabricate a complementary device using a single material.”
He added that arranging the transistors in a smaller, single-polymer material greatly simplifies the manufacturing process, allowing for large-scale manufacturing and opportunities to expand the technology beyond the original neurological application to almost any biopotential process.
Khodagholy, who directs the UC Irvine Translational Neuroelectronics Laboratory, which recently moved to Irvine from Columbia University, said his team’s work has the added benefit of scalability: “You can make devices of different sizes and still thus maintaining this complementarity, and you can even change the material, which makes this innovation applicable in multiple situations.”
Another notable advantage in Nature Communications The role is that the device can be implanted in a developing animal and resist transitions in tissue structures as the organism grows, something that is not possible with hard, silicone-based implants.
“This feature will make the device particularly useful in pediatric applications,” said co-author Jennifer Gelinas, associate professor of anatomy and neurobiology and pediatrics at UC Irvine, who is also a physician at Children’s Hospital of Orange County.
“We demonstrate our ability to create robust complementary integrated circuits that are capable of acquiring and processing high-quality biological signals,” Khodagholy said. Complementary, internal, ion-activated organic electrochemical transistors “will substantially expand the application of bioelectronics to devices that have traditionally relied on bulky, non-biocompatible components.”
Joining Khodagholy, Gelinas, and Wisniewski on this project were Claudia Cea, Liang Ma, Alexander Ranschaert, Onni Rauhala, and Zifang Zhao from Columbia University. The work was supported by the National Institutes of Health and the National Science Foundation.