IGT-based gates conform to the surface of orchid petals. Scale bar, 1 cm. Source: Jennifer Gelinas, Columbia University
Bioelectronic systems deployed in medical applications require components to record and process body signals, pinpoint patterns and deliver electrical or chemical stimulation to address problems. Transistors are needed to amplify or switch electronic signals on circuits, but the design of safe, reliable and long service life devices has eluded researchers.
A team from Columbia University and Columbia University Medical Center has engineered a biocompatible internal-ion-gated organic electrochemical transistor (IGT) fast enough to enable real-time signal sensing and stimulation of brain signals. The development could lead to safer, smaller and smarter bioelectronic devices, such as brain-machine interfaces, wearable electronics and responsive therapeutic stimulation devices, for long-term implantation.
Mobile ions contained within a conducting polymer channel enable both volumetric capacitance (ionic interactions involving the entire bulk of the channel) and shortened ionic transit time. The IGT has a large amplification rate and high speed, and can be independently gated and microfabricated to produce scalable conformable integrated circuits. The design improves the speed of the transistor by an order of magnitude compared to other silicon-based ionic devices of the same size.
The translational capacity of the IGT was demonstrated with an electroencephalography platform. Used to record human brain waves from the surface of the scalp, the IGT local amplification directly at the device-scalp interface was shown to enable the contact size to be decreased by five orders of magnitude. The resulting device easily fits between hair follicles, simplifying placement without the need for adhesives, and could also be easily manipulated by hand to improve mechanical and electrical stability.
The research is published in Science Advances.
