Biological tissues are in a constant state of complex deformation, driven by heartbeats, respiration, and everyday movements. Meanwhile, the body's weak electrophysiological signals are prone to interference from noise. In dynamic physiological settings, mechanical disruptions at the interface between tissues and devices, along with system noise during signal transmission and acquisition, can compromise the quality and reliability of signal recordings. A key challenge for implantable bioelectronic devices is how to reliably capture high-quality signals within the soft, moist, and constantly changing in vivo environment. In response, Professor Lei Ting's team from the School of Materials Science and Engineering at Peking University has introduced a novel collaborative design strategy that integrates "materials-interface-circuit" and has successfully developed a strain-insensitive elastic organic electrochemical transistor (OECT) amplifier. This amplifier can adapt to dynamic biological tissues and amplify weak electrophysiological signals directly at the moving tissue interface, thereby enhancing the quality of signal recordings.

The research has led to the creation of a new high-performance, stretchable, and stable n-type OECT material, P(bgTDPP-TVT-CN2), which retains stable electrical performance even under significant strain, providing a vital material foundation for constructing elastic complementary OECT circuits. Additionally, the research team improved the interfacial adhesion between the polymer semiconductor and gold electrodes using a benzylthiol self-assembled monolayer, boosting the device's stability under humid and repeatedly stretched conditions.

At the circuit level, the research team combined highly stretchable n-type and p-type OECT materials to build an elastic complementary OECT logic circuit for biosignal amplification. Unlike single transistors or load-diode-type circuits, the complementary circuit leverages the synergistic response of n-type and p-type devices during deformation to compensate for each other, effectively minimizing signal drift and performance degradation caused by mechanical deformation. Performance tests revealed that the elastic OECT amplifier can achieve high-gain amplification with an operating voltage of less than 1.0 V, reaching a maximum voltage gain of approximately 140 V/V. It maintains stable gain and switching threshold under different stretching strains, achieving the highest level of comprehensive performance among similar devices. Moreover, the device remained functional after being immersed in plasma for 14 days and in PBS solution for 24 days, indicating excellent long-term operational stability in physiological environments.

To meet the demands of implantable applications, the research team conducted systematic biocompatibility and in vivo performance evaluations. Cell experiments showed that P(bgTDPP-TVT-CN2) has low cytotoxicity; histological results indicated that, compared to traditional PI-based flexible devices, the elastic device elicited a lower immune response post-implantation. In comparison to passive electrodes, the elastic amplifier significantly enhanced signal quality, achieving a signal-to-noise ratio (SNR) of 25.12 ± 3.20 dB, markedly higher than the 11.08 ± 2.62 dB of passive electrodes. Furthermore, the research achieved over 10-fold signal amplification in epicardial electrophysiological recordings in rabbits, further validating the application potential of the elastic OECT amplifier in various in vivo electrophysiological scenarios.

This study overcomes the challenges of achieving mechanical stability, signal amplification, and high-SNR recording simultaneously in moist and dynamic in vivo environments for elastic bioelectronic devices through the use of highly stretchable n-type OECT materials, interface regulation, and complementary circuit compensation strategies. It paves the way for a new technological approach to next-generation implantable electrophysiological monitoring devices, flexible bioelectronic interfaces, and long-term in vivo health monitoring systems.