Xiaochuan Dai

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.

Poly(3,4-ethylenedioxythiophene) (PEDOT)-based polymers have emerged as the unrivaled standards for mixed ionic-electronic conduction, bridging the gap between rigid electronics and soft biological tissues. However, the long-term operational stability of PEDOT-based devices is frequently compromised by a critical material failure: the delamination of the polymer coating under electrochemical and mechanical stress. This interfacial instability is a fundamental challenge shared across broad electrochemical applications, from bioelectronics to energy storage and fuel cells, where active materials undergo recurrent volumetric oscillation. While extensive research has optimized PEDOT-based polymers' electrochemical performance, the underlying interfacial mechanics remain insufficiently addressed in the literature. This review reconciles these disparate findings by first dissecting the genesis of the interface, illustrating how specific fabrication histories dictate fundamental failure modes: the intrinsic "stress accumulation" driven by in situ electropolymerization versus the osmotic "rehydration shock" characteristic of ex situ solution processing. Against this mechanistic backdrop, we establish a systematic framework for interfacial engineering, categorizing state-of-the-art adhesion strategies into two distinct paradigms: Chemical Anchoring, which leverages composites, intermediate layers, and functionalized derivatives to engineer covalent bridges; and Physical Anchoring, which utilizes "inside-out" deposition or "outside-in" etching to maximize mechanical interlocking. Beyond synthesis, we critically evaluate the lack of standardization in adhesion metrics, surveying techniques from in vitro stress tests to in vivo functional validation. By synthesizing these disparate methodologies, we propose a 3-tier benchmarking guideline to standardize future comparative studies. With these guidelines, we aim to outline a trans-disciplinary roadmap for seaming the biotic-abiotic divide, ensuring the reliability of the next-generation bioelectronic interface.

Burst suppression is widely observed across cortical regions during reversible or pathological unconsciousness, yet its neuronal organization remains incompletely understood. Here we present an integrated Cortex-wide Optical-electrical Dual-modal Explorer (CODE) system to examine neuronal dynamics during burst suppression under isoflurane anesthesia in the mouse. We identified distinct cortex-wide neuronal ensembles that alternately associate with burst or suppression events, exhibiting dynamic neuronal recruitment and reactivation during anesthesia. Burst events were marked by highly synchronized neuronal activity early in the burst phase with high functional connectivity, whereas suppression events displayed more asynchronous, temporally distributed activity with reduced connectivity. Transitions between these states involved sequential, directionally organized propagation across cortical regions. ECoG bursts propagated from bilateral sensory cortices to motor areas within tens of milliseconds with increasing synchrony with calcium activity. Furthermore, we established a robust metric linking ECoG and calcium signals, revealing state-dependent interpretability. These findings reveal the single-neuron-to-population architecture of burst suppression and illustrate how integrated optical–electrical measurements enable high-resolution, large-scale interrogation of cortical dynamics.

Radiative cooling textiles are typically designed for specific indoor or outdoor conditions, limiting their environmental adaptability. Here, we report a continuously spun molecular interface–engineered silk (Mie-Silk) that integrates radiative and conductive cooling for effective body temperature regulation in diverse settings. The Mie-Silk has a natural silk yarn core with high mid-infrared (MIR) emissivity and a surface layer of ZrO ₂ nanoparticles (NPs) enabling strong solar scattering based on the Mie scattering principle. Natural silk fibroin acts as a robust binder, anchoring the NPs on the silk surface securely. Woven Mie-Silk achieves outdoor radiative cooling through high solar reflectivity (92.54%) and MIR emissivity (97.13%) within the atmospheric window. Indoors, where radiative cooling is less effective, its thermal conductivity (0.19 watts per meter-Kelvin) facilitated by densely packed NPs provides obvious cooling capability. This Mie-Silk, with effective cooling across varied environments, represents a promising candidate for next-generation personal thermal management clothing.

Achieving neuromodulation at subcellular scales requires stimulation electrodes that integrate micrometer-scale footprints, high spatial density, and an efficient, reliable charge-delivery capability. Here, we introduce a diffusion-tuned galvanostatic deposition strategy, guided by mass transport mediation, to uniformly and array-widely coat PEDOT:PSS onto densely packed electrodes with diameters ranging from 3 to 10 μm. The resulting Subcellular-Scale Stimulation Electrode Arrays (3SEA) exhibit robust electrochemical performance, with a tens to hundreds kilohms impedance at 1 kHz and charge-storage capacities of 22.1-54.1 mC/cm². They also achieve charge-injection capacities of 2.31-10.1 mC/cm², surpassing previously reported values of microelectrodes. Functional validation of 3SEA upon neurostimulation using calcium imaging of HT-22 neurons exhibits reliable stimulus-evoked Ca²⁺ transients, confirming subcellular-scale and efficient stimulation capability with biphasic pulses as low as 1 nC/phase. Our results establish a scalable framework for fabricating high-performance subcellular-scale stimulating bioelectronics and high-precision neural interfaces.

On-site or in-sensor biosignal transduction and amplification can offer several benefits such as improved signal quality, reduced redundant data transmission, and enhanced system integration. Ambipolar organic electrochemical transistors (OECTs) are promising for this purpose due to their high transconductance, low operating voltage, biocompatibility, and suitability for miniaturized amplifier design. However, limitations in material performance and stability have hindered their application in biosignal amplification. Here, we propose using high-spin, hydrophilic conjugated polymers and a computational screening approach to address this challenge. We designed a high-spin polymer, namely P(TII-2FT), which exhibits satisfactory, stable, and balanced ambipolar OECT performance. The figure-of-merits achieved by the P(TII-2FT) devices surpass those of the current leading materials by 5 to 20 times, resulting in remarkable voltage gains while maintaining a compact form factor. Based on this amplifier, we have successfully achieved on-site capture and amplification of various electrophysiological signals with greatly enhanced signal quality.

The advancement of biomedical imaging technology has significantly enhanced our understanding of complex physiological processes and the diagnosis of various health issues.^{1 – 3} Understanding the cerebral hemodynamics in rodents is a crucial question of interest in the fields of neuroscience, physiology, psychology, and imaging.^4,5 The vast majority of traditional imaging techniques require the subject animals to remain still or be anesthetized to ensure image quality and stability, classic optical imaging setups for mouse brains typically involve fixing the mouse’s head beneath the lens, and throughout the imaging process, gas anesthetics are delivered to the mouse through a tube and a mask. These setups are widely used in two-photon microscopy,⁶ photoacoustic imaging,⁷ and optical coherence tomography (OCT).⁸ However, under anesthesia, multiple physiological indicators can be affected, leading to research results that may not fully represent the true physiological state.⁹ Therefore, there is a growing awareness of the necessity to image the brain under fully awake conditions.

Hydrogels are an attractive category of biointerfacing materials with adjustable mechanical properties, diverse biochemical functions, and good ionic conductivity. Despite these advantages, their application in electronics has been restricted because of their lack of semiconducting properties, and they have traditionally only served as insulators or conductors. We developed single- and multiple-network hydrogels based on a water-soluble n-type semiconducting polymer, endowing conventional hydrogels with semiconducting capabilities. These hydrogels show good electron mobilities and high on/off ratios, enabling the fabrication of complementary logic circuits and signal amplifiers with low power consumption and high gains. We demonstrate that hydrogel electronics with good bioadhesive and biocompatible interface can sense and amplify electrophysiological signals with enhanced signal-to-noise ratios.

Significance: Manipulating materials with atomic-scale precision is essential for the development of a next-generation material design toolbox. Tremendous efforts have been made to advance the compositional, structural, and spatial accuracy of material deposition and patterning. Here, we presented a new reaction pathway to implement the conversions of two-dimensional materials within the atomic-layer thickness at room temperature for electrical dipole manipulation. Not only could various Janus monolayer transition metal dichalcogenides with vertical dipole be realized, but also some heterostructures, including the dipole-nondipole heterostructures (MoS₂-MoSSe) and multiheterostructures (MoS₂-MoSSe-MoSeS-MoSe₂) within the same monolayer host structure are developed, in which the dipoles can be selectively patterned to be zero (MoS₂, MoSe₂), positive (MoSSe), and negative (MoSeS).

Electron transport in biological and inorganic systems is mediated through distinct mechanisms and pathways. Their fundamental mismatch in structural and thermodynamic properties has imposed significant challenge on the effective coupling at the biotic/abiotic interface, which is central to the design and development of bioelectronic devices and their translation towards various engineering applications. Using electrochemically active bacteria, such as G. sulfurreducens, as a model system, here we report a bottom-up, bio-synthetic approach to synergize the electron transport and significantly enhance the coupling at the heterogeneous junction. In particular, graphene oxide was exploited as the respiratory electron acceptors, which can be directly reduced by G. sulfurreducens through extracellular electron transfer, closely coupled with outer membrane cytochromes in electroactive conformation, and actively “wire” the redox centers to external electrical contacts. Through this strategy, the contact resistance at the biofilm-electrode interface can be effectively reduced by 90%. Furthermore, the cyclic voltammetry reveals that the electron transfer of DL-1 biofilm transformed from a low-current (~0.36 µA), rate-limited profile to a high-current (~5µA), diffusion-limited profile. These results suggested that the integration of rGO can minimize the charge transfer barriers at the biofilm-electrode interface. The more transparent contact at DL-1/electrode interface also enables unambiguous characterization of the inherent electron transport kinetics across the electroactive biofilm independent of cell-electrode interactions. The current work represents a strategically new approach toward the seamless integration of biological and artificial electronics, which is expected to provide critical insights into the fundamentals of biological electron transport and open up new opportunities for applications in biosensing, biocomputing and bioenergy conversion.