High-gain and broadband in vivo amplifiers enabled by matched materials

In-sensor biosignal amplification could enable superior signal quality, lower data transmission redundancy, and enhanced device integration. Organic electrochemical transistor (OECT)-based circuits offer an attractive candidate due to their low-voltage operation, high transduction efficiency, and seamless interfacing with biological tissues. However, the fundamental design principles governing high-performance OECT-based amplifiers, particularly the coupling between material design and circuit-level performance, remain insufficiently understood. Here, we present a matched n-p material system to elucidate the design principles and in-sensor amplification capability of complementary OECT circuits. Specifically, we develop a high-performance, low-operation-voltage n-type polymer, P(lgFTDPP-2FT), and integrate it with a complementary p-type DPP polymer. The resulting inverter-based amplifier can operate at low voltage while demonstrating a high gain exceeding 800 V V^-1, a bandwidth above 600 Hz at 0.6 V, and an ultralow power consumption down to 0.57 nW at 0.2 V. We further demonstrate in vivo amplification of mouse electrocorticographic (ECoG) signal with good biocompatibility and superior signal quality. This work establishes a general material-device-circuit framework and design guidelines for OECT-based amplifiers.