Tunable Organic Active Neural Probe Enabling Near-Sensor Signal Processing.

Neural recording systems have significantly progressed to provide an advanced understanding and treatment for neurological diseases. Flexible transistor-based active neural probes exhibit great potential in electrophysiology applications due to their intrinsic amplification capability and tissue-compliant nature. However, most current active neural probes exhibit bulky back-end connectivity since the output is current, and the development of an integrated circuit for voltage output is crucial for near-sensor signal processing at the abiotic/biotic interface. Here, inkjet-printed organic voltage amplifiers are presented by monolithically integrating organic electrochemical transistors and thin-film polymer resistors on a single, highly flexible substrate for in vivo brain activity recording. Additive inkjet printing enables the seamless integration of multiple active and passive components on the somatosensory cortex, leading to significant noise reduction over the externally connected typical configuration. It also facilitates fine-tuning of the voltage amplification and frequency properties. The organic voltage amplifiers are validated 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. These results bring organic active neural probes to the forefront in applications where efficient sensory data processing is performed at sensor endpoints.

Microfabricated Ion-Selective Transistors with Fast and Super-Nernstian Response.

Transistor-based ion sensors have evolved significantly, but the best-performing ones rely on a liquid electrolyte as an internal ion reservoir between the ion-selective membrane and the channel. This liquid reservoir makes sensor miniaturization difficult and leads to devices that are bulky and have limited mechanical flexibility, which is holding back the development of high-performance wearable/implantable ion sensors. This work demonstrates microfabricated ion-selective organic electrochemical transistors (OECTs) with a transconductance of 4 mS, in which a thin polyelectrolyte film with mobile sodium ions replaces the liquid reservoir. These devices are capable of selective detection of various ions with a fast response time (≈1 s), a super-Nernstian sensitivity (85 mV dec-1 ), and a high current sensitivity (224 µA dec-1 ), comparing favorably to other ion sensors based on traditional and emerging materials. Furthermore, the ion-selective OECTs are stable with highly reproducible sensitivity even after 5 months. These characteristics pave the way for new applications in implantable and wearable electronics.