Highly Sensitive and Tunable Organic Voltage Amplifiers Based on Inkjet-Printed Organic Electrochemical Transistors for In Vivo Recordings of Brain Activity

Organic electrochemical transistors (OECTs) exhibit great potential in electrophysiology signal-recording applications. Their mechanism of operation leverages mixed ionic/electronic conduction, and this makes them amplifying transducers that offer a high signal-to-noise ratio. However, the output of OECTs is current and this makes them incompatible with most electrophysiology data acquisition systems. To maximize their utilization, a circuit converting their output to the voltage without bulky back-end connectivity would be highly desirable. Here, we present inkjet-printed organic voltage amplifiers by integrating active and passive electrical components on a single, highly flexible substrate for in vivo brain activity recording. Drop-on-demand printing facilitates fine-tuning of the voltage amplification properties while monolithic integration of the printed circuit achieves significant noise reduction. Finally, we validate the conformable brain-integrated organic voltage amplifiers as electrocorticography devices in a rat in vivo model, showing their ability to record local field potentials in an experimental model of spontaneous and epileptiform activity in rats. Our results pave the way for the use of OECT-based circuits toward the seamless interface between biology and electronics.