Complementary Internal Ion-Gated Organic Electrochemical Transistors (C-IGT)

Bioelectronic devices capable of accurately and safely interfacing with physiological systems for the capture, monitoring, processing, and stimulation of neural systems are required in both medicine and research. Because of the ionic flux-based communication system used by neurons in the brain tissue signal transduction is required for devices to observe neural activity through an electrical interface. This creates the need for organic mixed-conducting based transistors and sensors for measurement and recording of neuronal signals and systems. To use these sensors effectively conformable and scalable systems must be created for interfacing with both biology and existing technology. Current integrated circuit technology relies on a complementary approach of balanced N-type and P-type devices for improvements in power efficiency and scalability. Here we demonstrate a method to create transistors with N-type functionality, transistor action in the first quadrant and resistor like in the third quadrant, from P-type materials which usually express the opposite behavior, modulating in the third quadrant and acting as a resistor in the first quadrant. These opposing behaviors enabled a complementary logic device with an output voltage range similar to the input voltage dynamics. Additionally, similar channel material and geometry resulted in equal impedances between the two transistors yielding a higher power efficiency and fabrication density. To create these devices the transistor geometry was analyzed in terms of relative size to establish performance thresholds for different types of operation, including N-type, P-type, high power, and high speed. Transistors were characterized in terms of asymmetry, voltage required for complementary operation, speed, and gain. Using designs informed by the characterization of channel contact asymmetry we then fabricated circuits including amplifiers and logic gates for digital systems. These CIGT circuit designs have a broad range of applications in bioelectronics including wearable electronics, neural interfacing, and therapeutic implants.