Maciej Gryszel

Polymer‐based organic mixed ion‐electron conductors (OMIECs) are a class of materials offering unique coupled dual charge transport characteristics along with appealing properties including mechanical softness, biocompatibility, tunability, volumetric capacitance, and stability. These features have been exploited in devices including organic electrochemical transistors (OECTs), neuromorphic computing, energy storage, sensors, neural electrodes, and actuators. Conventionally, OMIEC polymers are prepared through chemical, vapor‐phase, electrochemical, or enzymatic polymerization, typically relying on oxidants, metal catalysts, and/or organic solvents, significantly limiting their scalability, sustainability, and biocompatibility. Here, we introduce an initiator‐free, visible‐light‐induced polymerization of water‐soluble conducting polymer precursors, enabling facile formation of high‐performance and inherently biocompatible OMIECs. This novel approach allows direct photopatterning and seamless film deposition and manufacturing of OECTs across rigid, flexible, and biological substrates, exemplified by glass, textiles, and mouse skin (in vivo). Through careful optimization of the photopolymerization process, resulting OMIECs possess state‐of‐the‐art electrical, electrochemical, and device properties along with exceptional compatibility and conformability with various flexible and biological surfaces. Finally, we demonstrate the utility of these photopatterned electrodes, manufactured directly on mouse skin in vivo, where they significantly enhance the recording efficacy and signal‐to‐noise ratio of low‐frequency brain activity in anesthetized mice.

Polymer‐based organic mixed ion‐electron conductors (OMIECs) are a class of materials offering unique coupled dual charge transport characteristics along with appealing properties including mechanical softness, biocompatibility, tunability, volumetric capacitance, and stability. These features have been exploited in devices including organic electrochemical transistors (OECTs), neuromorphic computing, energy storage, sensors, neural electrodes, and actuators. Conventionally, OMIEC polymers are prepared through chemical, vapor‐phase, electrochemical, or enzymatic polymerization, typically relying on oxidants, metal catalysts, and/or organic solvents, significantly limiting their scalability, sustainability, and biocompatibility. Here, we introduce an initiator‐free, visible‐light‐induced polymerization of water‐soluble conducting polymer precursors, enabling facile formation of high‐performance and inherently biocompatible OMIECs. This novel approach allows direct photopatterning and seamless film deposition and manufacturing of OECTs across rigid, flexible, and biological substrates, exemplified by glass, textiles, and mouse skin (in vivo). Through careful optimization of the photopolymerization process, resulting OMIECs possess state‐of‐the‐art electrical, electrochemical, and device properties along with exceptional compatibility and conformability with various flexible and biological surfaces. Finally, we demonstrate the utility of these photopatterned electrodes, manufactured directly on mouse skin in vivo, where they significantly enhance the recording efficacy and signal‐to‐noise ratio of low‐frequency brain activity in anesthetized mice.

A novel approach is reported for obtaining ambipolar electroactive polymers via in situ electropolymerization for vertical organic electrochemical transistor (vOECT) applications. It is shown that electropolymerization is a practical and efficient method to obtain copolymers without contamination from chemical polymerization processes. To this end, two monomers, G‐DTP‐Bu‐NDI and G‐DTP‐G‐NDI, are proposed, comprising naphthalene diimide (NDI) as the acceptor core and dithienopyrrole (DTP) as the donor unit, capable of forming carbon–carbon bonds under the influence of an electric current. The incorporation of oligo(oxyethylene) (OEG) side groups ensures their amphiphilicity. Both compounds underwent successful electrochemical polymerization, resulting in thin, porous, uniform polymer layers on the electrode surface. The synthesized polymers are further examined using electrochemical and spectroelectrochemical techniques in both organic and aqueous electrolytes. Regardless of the electrolyte medium (aqueous or non‐aqueous), poly(G‐DTP‐Bu‐NDI), and poly(G‐DTP‐G‐NDI) exhibit stable electroactivity, as demonstrated by numerous scans showing ambipolar redox behavior. Both polymers are tested as components of vertical OECTs, following in situ electrochemical deposition within a 350 nm channel. The recorded transfer characteristics suggest that the fabricated donor–acceptor (D‐A) compounds hold promise for developing a new generation of ambipolar ECT devices.

Vertical organic electrochemical transistor platforms enable facile channel formation by electropolymerization. The improved deposition control and resulting high performance is demonstrated here with the trimer ETE-COONa.

Visible‐light‐driven semiconductor photoelectrodes are promising new devices for on‐demand photocathodic generation of hydrogen peroxide. Herein, the fabrication of organic polymeric photocathodes employing poly(4,7‐di(thiophen‐2‐yl)benzo[c][1,2,5]thiadiazole) (pThBTD), and comparatively seven other related derivatives is reported. The monomer dithienobenzodithiazole can be directly polymerized on an electrode via two methods: electropolymerization or iodine‐vapor‐assisted polymerization. Both give polymers with wide visible light absorption and suitable stability for photoelectrodes. These methods yield different active layer morphologies, with electropolymerization yielding photocathodes with better performance. Critical issues affecting oxygen reduction photocurrents are evaluated, namely thickness, wettability, and pH. Photocathodic oxygen reduction currents, as well as photovoltages, are among the highest reported for an organic photoelectrocatalyst, and pThBTD films can stably produce H₂O₂ with high faradaic yield over at least 8 h. This study shows that single‐component organic semiconductor devices can be highly competitive versus more complex heterostructures and that such low‐bandgap organic polymers can afford remarkable stability.

Bioelectronic devices such as neural stimulation and recording devices require stable low‐impedance electrode interfaces. Various forms of nitridated titanium are used in biointerface applications due to robustness and biological inertness. In this work, stoichiometric TiN thin films are fabricated using a dual Kaufman ion‐beam source setup, without the necessity of substrate heating. These layers are remarkable compared to established forms of TiN due to high degree of crystallinity and excellent electrical conductivity. How this fabrication method can be extended to produce structured AlN, to yield robust AlN/TiN bilayer micropyramids, is described. These electrodes compare favorably to commercial TiN microelectrodes in the performance metrics important for bioelectronics interfaces: higher conductivity (by an order of magnitude), lower electrochemical impedance, and higher capacitive charge injection with lower faradaicity. These results demonstrate that the Kaufman ion‐beam sputtering method can produce competitive nitride ceramics for bioelectronics applications at low deposition temperatures.

The archetypical conducting polymer poly(3,4-ethylenedioxythiophene) can be equipped with a glycol side-chain, which favorably tunes its electrochemical properties and opens new processability options.

Increasing the electrochemical surface area of noble metal electrodes is vital for many applications, including catalysis and bioelectronics. Herein, a method is presented for obtaining porous noble metal thin films via reactive magnetron sputtering of noble metal oxides, MO_x, followed by their reduction using chemical reducers or electrochemical current. Variation of reduction conditions yields a range of different electrochemical and morphological properties. This method for obtaining porous noble metals is rapid, facile, and compatible with microfabrication processes. The resulting metallic films are porous and have competitively high capacitance and low impedance.

Organic semiconductors are gaining increasing attention as promising active materials in aqueous electrochemical and photoelectrochemical applications. Controlling the semiconductor/electrolyte interface is a critical aspect. The aim of this work is to increase the electrochemical surface area of an archetypical polymeric semiconductor, poly(3-hexylthiophene), P3HT. Here we use a technique of blending with polystyrene, phase separation, followed by selective removal of polystyrene to obtain various nano/microstructures of P3HT. We evaluate how three-dimensional structuring of P3HT affects electrochemical capacitance, photovoltage generation, and photoelectrochemical currents. The aqueous wettability of the exposed surface is critical, and it can be significantly modified by employing oxygen plasma treatment. Structured and plasma-hydrophilized P3HT samples demonstrate higher photoelectrochemical currents for the oxygen reduction reaction. We find that regardless of structuring and photocurrent performance, the oxygen reduction on P3HT always proceeds to produce H₂O₂ with 90%+ faradaic efficiency. The results of our efforts are demonstrations of how to tune and to increase both electrochemical capacitive and faradaic behavior of P3HT layers. Our findings indicate some limitations imposed by the P3HT itself, including low photovoltages and photochemical bleaching. Overall, these findings answer several open questions in the field of P3HT photoelectrochemical interfaces, and provide some general guidelines that can be applied to other organic semiconducting materials.

Hydrogen peroxide (H2O2) is an important oxidant, used in various fields of industry, such as paper manufacturing, production of polymers, detergents, and cosmetics. Considering that the molecule d ...