Xudong Tao

Cutaneous electrophysiology is a fundamental non-invasive technique for assessing electrically active organs such as the brain, heart, and muscles. Standard approaches, however, are limited in spatial resolution, reducing sensitivity to certain pathological features. The development of body surface potential mapping using electrode arrays has helped overcome these limitations, enhancing the diagnostic power of cutaneous recordings, yet clinical adoption remains constrained by challenges in electrode performance, wiring complexity, wearability, data transmission, and interpretability. Here, we present a hybrid e-textile electrode array system that overcomes these barriers, enabling simultaneous mapping of electrical activity along the cortico-muscular axis. The system combines application-specific conducting polymer coatings to improve electrode performance, a flexible fabrication process for robust connectivity and wearability, and interpretable machine learning algorithms for data analysis. In controlled single-subject experiments, we demonstrate reliable muscle and brain recordings, enabling classification of grasped object shapes and somatosensory stimuli. Simultaneous multi-site recordings along the cortico-muscular axis provide spatial maps of reaction time distributions and allow prediction of muscle activation patterns from cortical activity. This platform establishes a framework for wearable, multi-modal electrophysiological mapping and non-invasive study of cortico-muscular dynamics, representing a step towards practical brain–body interfaces with applications in neurorehabilitation, prosthetics, and human–machine interaction.

Cutaneous electrogastrography (EGG) is a non‐invasive diagnostic technique critical for assessing gastrointestinal (GI) function, particularly in monitoring chronic disorders and abnormalities in gastric motility. However, traditional EGG technologies are limited by low spatiotemporal resolution, poor electrode stability, static configurations, and reliance on disposable silver/silver chloride (Ag/AgCl) electrodes with gel electrolytes that dehydrate over time. These factors increase costs and confine high‐resolution EGG to clinical settings, limiting its utility for long‐term and point‐of‐care (POC) applications. Here, a fabrication technique for soft, 3D‐protruded and conducting eutectogel array of electrodes is reported. The PEDOT eutectogel interlayer interface was engineered to enhance conductivity, reduce skin‐electrode impedance, and improve dehydration resistance compared to Ag/AgCl electrodes. Long‐term stability was assessed under extended ambient drying conditions. A 16‐circular electrode array was fabricated and optimized through a transfer function analysis, yielding electrodes with a 15 mm diameter and a 30 mm interelectrode spacing. High‐resolution EGG signals were successfully recorded from the epigastrium using the electrode array before and after a meal, providing spatially resolved information. This work presents a promising solution for low‐cost, stable, and long‐term gastric monitoring with high spatial resolution, advancing wearable gastrointestinal diagnostics and enabling point‐of‐care monitoring of chronic gastrointestinal disorders.

Direct‐current (DC) sputtering combined with roll‐to‐roll processing offers a highly competitive approach for scaling up the manufacturing of flexible functional thin films. However, its application to less‐conductive functional materials, such as semiconductors, remains limited due to charge buildup and arcing on the target. This study investigates the intrinsic relationships between DC sputtering power and the surface topography, elemental composition, crystallography, and thermoelectric properties of flexible thin‐film semiconductors. We explore low‐level DC power for room‐temperature roll‐to‐roll sputtering of Bi‐Te thermoelectric films, identifying an optimal power window that avoids charge‐buildup effects on the semiconductor target. Low‐power DC sputtering enables controlled crystallographic, microstructural, and compositional characteristics, thereby modulating electrical transport properties and, consequently, thermoelectric performance. As a result, a room‐temperature figure of merit of ∼0.1 is achieved at an optimal power of 0.22 kW while maintaining high‐throughput roll‐to‐roll manufacturability. Device‐level validation is demonstrated using a flexible thermoelectric generator, showing output performance consistent with COMSOL simulations.

Fabricating flexible bioelectronics remains an ongoing challenge in pursuing a cost‐effective, efficient, scalable, and environmentally friendly approach for research and commercial applications. The current dominant method, lithography, presents challenges due to its incompatibility with solvent‐sensitive biomaterials and the phase mismatch between the photoresist and flexible substrates, such as elastomers. This study proposes a simplified, cleanroom‐free toolkit as a potential alternative to lithography for fabricating intricate bioelectronics on flexible substrates with submicron resolution. This technique integrates a two‐photon laser writing mask, mask transfer, and multi‐layer/material patterning processes, enabling batch‐to‐batch processing and making it suitable for scalable production. With excellent conformal patterning capability, different functional and encapsulation biomaterials can be patterned on flexible substrates, including elastomers, parylene‐C, polymer sheets, skin, fabric, and plant leaves. The versatility of this toolkit is validated by fabricating various prototypes of wearable and implantable bioelectronics, demonstrating excellent performance.

In recent years, microfluidic systems have evolved to incorporate increasingly complex multi-layer and multi-material structures. While conventional 2-dimensional microfluidic systems are typically fabricated with lithographic techniques, the increase in system complexity necessitates a more versatile set of fabrication techniques. Similarly, although 3D printing can easily produce intricate microfluidic geometries, integrating multiple membranes and electrode components remains challenging. This study proposes a toolkit for fabricating free-standing 3-dimensional microfluidic systems for biomedical devices, incorporating flow channels, electrodes, and membranes. The fabrication techniques include molding separation using 3D printed molds, laser-based processing, and component assembly, each achieving micron resolution. Here, we introduce a novel approach to integrate membranes into microfluidics by directly curing elastomer-based microfluidics with the membrane through replica molding, while preserving membrane functionality by effectively removing elastomer residues through reactive ion etching. The resulting membrane-elastomer microfluidic component significantly simplifies the assembly of intricate microfluidic systems, reducing the device size to millimeter dimensions, suitable for implantable applications. The toolkit’s versatility is demonstrated by a redox flow iontophoretic drug delivery prototype at the millimeter scale, featuring two electrodes, four membranes, and four microfluidic channels.

The Selective Metallization Technique shows promise for roll-to-roll in-line patterning of flexible electronics using evaporated metals, but challenges arise when applied to sputtering functional materials. This study overcomes these challenges with simultaneous sputtering of Bi-Sb-Te and evaporation of metal (Ag or Cu) for thermoelectric layers when using Selective Metallization Technique. Large-scale manufacturing is demonstrated through roll-to-roll processing of a 0.8 m wide polymer web at 25 m/min, achieving high-throughput production of functional thin-film patterns with nanometer thickness. The room-temperature-deposited material system exhibits significantly enhanced thermoelectric performance and facilitates an n-type-to-p-type transition in the Cu- or Ag-containing Bi-Sb-Te-based composite film. Here, we show that while applying Selective Metallization Technique, the evaporation of metal modifies the impact of residual oil on Bi-Sb-Te, which can be effectively removed with a few seconds of plasma exposure, and the fabricated thermoelectric devices are validated in wearable applications utilizing a coiled-up wristband design.

Electrode arrays that interface with peripheral nerves are used in the diagnosis and treatment of neurological disorders; however, they require complex placement surgeries that carry a high risk of nerve injury. Here we leverage recent advances in soft robotic actuators and flexible electronics to develop highly conformable nerve cuffs that combine electrochemically driven conducting-polymer-based soft actuators with low-impedance microelectrodes. Driven with applied voltages as small as a few hundreds of millivolts, these cuffs allow active grasping or wrapping around delicate nerves. We validate this technology using in vivo rat models, showing that the cuffs form and maintain a self-closing and reliable bioelectronic interface with the sciatic nerve of rats without the use of surgical sutures or glues. This seamless integration of soft electrochemical actuators with neurotechnology offers a path towards minimally invasive intraoperative monitoring of nerve activity and high-quality bioelectronic interfaces.

The High Target Utilisation Sputtering technique (HiTUS) is of interest for industrial processes, including in roll‐to‐roll manufacturing. This study marks the first application of HiTUS to thermoelectric materials, exemplified by bismuth telluride. The HiTUS technique separates the sputtering power into the plasma power and the target power, with additional kinetic energy in the sputtering particles from the applied electrical field, thus enabling a much wider sputter parameter space to modify the film performance. This study investigates how plasma power, target power, and substrate bias in HiTUS intricately influence crystal orientation/size, elemental composition, surface morphology, and other film properties. These factors subsequently affect carrier density/mobility, and consequently the thermoelectric performance of the bismuth telluride film. These deposited films reach a power factor of 6.5 × 10⁻⁴ W m⁻¹ K⁻² with a figure of merit ≈0.14 at room temperature, the highest value for room‐temperature sputtered un‐doped bismuth telluride. Subsequent post‐deposition annealing significantly enhances the crystallinity of the film (highly polycrystalline), further improving the power factor to 23.5 × 10⁻⁴ W m⁻¹ K^‐2, with a figure of merit ≈0.45 at room temperature. The excellent performance of the HiTUS fabricated thermoelectric film opens opportunities for the large‐area manufacture of thin‐film thermoelectric materials and devices.

Drug delivery into the brain and spinal cord is fundamentally limited by the blood‐brain barrier which impedes the use of the vast majority of drugs. Implants based on iontophoresis use an applied voltage to deliver charged drug molecules, allowing solvent‐free delivery directly into the site of interest and overcoming issues associated with systemic exposure to the drug. However, during continuous delivery over long periods, electrochemical reactions occur at the electrodes leading to corrosive gas formation. Here, the concept of redox flow iontophoresis is presented, where a redox mediator solution is used to control electrode reactions and sustain continuous delivery for theoretically unlimited duration. As a proof‐of‐concept, a redox flow iontophoresis‐based brain implant that can continuously deliver the cancer drug doxorubicin at stable rates exceeding 2 nmol min⁻¹ is demonstrated. This new concept enables the continuous delivery of various potent drugs into the brain and spinal cord and therefore has the potential to improve treatment options for various diseases.

Organic thin-film transistors (OTFTs) with ideal behavior are highly desired, because nonideal devices may overestimate the intrinsic property and yield inferior performance in applications. In reality, most polymer OTFTs reported in the literature do not exhibit ideal characteristics. Supported by a structure-property relationship study of several low-disorder conjugated polymers, here, we present an empirical selection rule for polymer candidates for textbook-like OTFTs with high reliability factors (100% for ideal transistors). The successful candidates should have low energetic disorder along their backbones and form thin films with spatially uniform energetic landscapes. We demonstrate that these requirements are satisfied in the semicrystalline polymer PffBT4T-2DT, which exhibits a reliability factor (~100%) that is exceptionally high for polymer devices, rendering it an ideal candidate for OTFT applications. Our findings broaden the selection of polymer semiconductors with textbook-like OTFT characteristics and would shed light upon the molecular design criteria for next-generation polymer semiconductors.