David Ohayon

Abiotic redox‐active materials are increasingly used to interface with electroactive microorganisms, yet their influence on cellular regulation remains poorly understood. Here, Shewanella oneidensis MR‐1 was coupled with the electron‐transporting conjugated polymer poly(benzodifurandione) (PBFDO) to examine how material interfaces reshape inward extracellular electron transfer (EET). PBFDO‐coated carbon electrodes enhanced electron uptake and fumarate reduction, producing over two orders of magnitude higher current density and up to a twelvefold increase in succinate production than polymer‐free controls. Integrated electrochemical, transcriptomic, metabolomic, and protein analyses reveal coordinated physiological remodeling associated with the polymer‐supported interface rather than passive conductivity alone. PBFDO exposure is associated with transcriptional enrichment of genes linked to the Mtr‐CymA electron‐transfer conduit, energy metabolism, and biofilm formation. Metabolomics revealed altered intracellular redox and metabolite profiles consistent with enhanced fumarate respiration, alongside elevated NADH/NAD ⁺ and ATP/ADP ratios indicative of altered cellular redox and energetic states. Beyond transcriptional regulation, polymer‐responsive small RNAs (sRNAs) revealed a post‐transcriptional regulatory layer linked to the biohybrid interface. Delivery of individual sRNAs into control cells partially recapitulated the polymer‐induced phenotype, increasing current output up to threefold while altering intracellular redox balance. These findings establish sRNA‐mediated regulation as a previously unrecognized mechanism linking biohybrid interfaces to enhanced microbial electrosynthesis.

Despite the development of various pseudocapacitive materials, full-cell pseudocapacitors have yet to surpass the power density of conventional electric double layer capacitors, primarily due to the lack of high-rate positive pseudocapacitive materials. This work reports a solid-state conjugated polyelectrolyte that achieves high-rate charge storage as a positive electrode, facilitated by a co-ion desorption mechanism. The conjugated polyelectrolyte retains 70% of its capacitance at 100 A g⁻¹ with a mass loading of 2.8 mg cm⁻² and exhibits a long cycling life of 100,000 cycles in a Swagelok cell configuration. Increasing the electrode thickness fourfold has minimal impact on ion diffusivity and accessibility, yielding a high areal capacitance of 915 mF cm⁻². When paired with a high-rate negative pseudocapacitive electrode Ti₃C₂T_x, the device leverages the redox-active potentials of both materials, achieving a device voltage of 1.5 V and supports operation rates up to 10 V s⁻¹ or 50 A g⁻¹. This configuration enables the pseudocapacitor to deliver an areal power of 160 mW cm⁻², while significantly increasing the areal energy (up to 71 μWh cm⁻²). The high areal performance, combined with the additive-free and water-based fabrication process, makes pseudocapacitors promising for on-chip and wearable energy storage applications.

Living biophotovoltaics represent a potentially green and sustainable method to generate bio-electricity by harnessing photosynthetic microorganisms. However, barriers to electron transfer across the abiotic/biotic interface hinder solar-to-electricity conversion efficiencies. Herein, we report on a facile method to improve interfacial electron transfer by combining the photosynthetic cyanobacterium Synechococcus elongatus PCC 7942 (S. elongatus) with a conjugated polyelectrolyte (CPE) atop indium tin oxide (ITO) charge-collecting electrodes. By self-assembly of the CPE with S. elongatus, soft and semitransparent S. elongatus/CPE biocomposites are formed with three-dimensional (3D) conductive networks that exhibit mixed ionic-electronic conduction. This specific architecture enhances both the natural and mediated exoelectrogenic pathway from cells to electrodes, enabling improved photocurrent output compared to bacteria alone. Electrochemical studies confirm the improved electron transfer at the biotic-abiotic interface through the CPE. Furthermore, microscopic photocurrent mapping of the biocomposites down to the single-cell level reveals a ~ 0.2 nanoampere output per cell, which translates to a 10-fold improvement relative to that of bare S. elongatus, corroborating efficient electron transport from S. elongatus to the electrode. This synergistic combination of biotic and abiotic materials underpins the improved performance of biophotovoltaic devices, offering broader insights into the electron transfer mechanisms relevant to photosynthesis and bioelectronic systems.

This work presents a charge storage device based on polymeric mixed conductors and a solid-state ionic liquid electrolyte, featuring minimized self-discharge and enhanced stability thanks to an integrated barrier against water and oxygen.

Electron transporting (n-type) polymeric mixed conductors are an exciting class of materials for devices with aqueous electrolyte interfaces, such as bioelectronic sensors, actuators, and soft charge storage systems. However, their charge transport performance falls short of their p-type counterparts, primarily due to electrochemical side reactions such as the oxygen reduction reaction (ORR). To mitigate ORR, a common strategy in n-type organic semiconductor design focuses on lowering the lowest unoccupied molecular orbital (LUMO) level. Despite empirical observations suggesting a correlation between deep LUMO levels, low ORR, and enhanced electrochemical cycling stability in water, this relationship lacks robust evidence. In this work, we delve into the electrochemical reactions of n-type polymeric mixed conductors with varying LUMO levels and assess the impact of ORR on charge storage performance and organic electrochemical transistor (OECT) operation. Our results reveal a limited correlation between LUMO levels and ORR currents, as well as the electrochemical operational stability of the films. While ORR currents minimally contribute to OECT channel currents under fixed biasing conditions, n-type films self-discharge rapidly at floating potentials in a capacitor-like configuration. The density functional theory analysis, complemented by X-ray photoelectron spectroscopy, underscores the critical role of backbone chemistry in controlling O₂-related degradation pathways and device performance losses. These findings highlight the persistent challenge posed by ORR in n-type semiconductor design and advocate for shifting the focus toward exploring chemical moieties with limited O₂ interactions to enhance operational stability and performance at n-type film/water interfaces.

Living biophotovoltaics represents a potentially green and sustainable method to generate bio-electricity through rewiring of photosynthetic electron transport chains (P-ETCs) to interconnect photosynthetic bacteria to electrodes. However, barriers to electron transfer across the abiotic/biotic interface hinders solar-to-electricity conversion efficiencies. Herein, we report on a facile method to improve interfacial electron transfer by combining the photosynthetic cyanobacterium Synechococcus elongatus PCC 7942 (Syne) with a conjugated polyelectrolyte (CPE) atop indium tin oxide (ITO) charge-collecting electrodes. By self-assembly of the CPE with Syne, soft and semitransparent Syne/CPE biocomposites are formed with three-dimensional conductive networks that exhibit mixed ionic-electronic conduction. These specific structures rewire an artificial P-ETC from bacteria to electrodes, allowing for improved and sustained photocurrent output compared to the performance of bacteria alone. Electrochemical studies confirmed the enhanced interfacial electron transport efficiency via the artificial P-ETC. Furthermore, microscopic photocurrent mapping for the biocomposites down to the single-cell level revealed a ~0.2 nanoampere output per cell, which translates to a 10-fold improvement relative to that of bare Syne, corroborating highly efficient long-range electron transport from Syne to the electrode via the three-dimensional CPE structure. This synergistic combination of biotic and abiotic materials underpins the significantly improved performance of biophotovoltaic devices, providing broader insights into the electron transfer mechanisms in a variety of bio-hybrid systems within semi-artificial photosynthesis and bioelectronic devices.

The ability to amplify, translate, and process small ionic potential fluctuations of neural processes directly at the recording site is essential to improve the performance of neural implants. Organic front-end analog electronics are ideal for this application, allowing for minimally invasive amplifiers owing to their tissue-like mechanical properties. Here, we demonstrate fully organic complementary circuits by pairing depletion- and enhancement-mode p- and n-type organic electrochemical transistors (OECTs). With precise geometry tuning and a vertical device architecture, we achieve overlapping output characteristics and integrate them into amplifiers with single neuronal dimensions (20 micrometers). Amplifiers with combined p- and n-OECTs result in voltage-to-voltage amplification with a gain of >30 decibels. We also leverage depletion and enhancement-mode p-OECTs with matching characteristics to demonstrate a differential recording capability with high common mode rejection rate (>60 decibels). Integrating OECT-based front-end amplifiers into a flexible shank form factor enables single-neuron recording in the mouse cortex with on-site filtering and amplification.

Electronic immunosensors are indispensable tools for diagnostics, particularly in scenarios demanding immediate results. Conventionally, these sensors rely on the chemical immobilization of antibodies onto electrodes. However, globular proteins tend to adsorb and unfold on these surfaces. Therefore, self‐assembled monolayers (SAMs) of thiolated alkyl molecules are commonly used for indirect gold–antibody coupling. Here, a limitation associated with SAMs is revealed, wherein they curtail the longevity of protein sensors, particularly when integrated into the state‐of‐the‐art transducer of organic bioelectronics—the organic electrochemical transistor. The SpyDirect method is introduced, generating an ultrahigh‐density array of oriented nanobody receptors stably linked to the gold electrode without any SAMs. It is accomplished by directly coupling cysteine‐terminated and orientation‐optimized spyTag peptides, onto which nanobody‐spyCatcher fusion proteins are autocatalytically attached, yielding a dense and uniform biorecognition layer. The structure‐guided design optimizes the conformation and packing of flexibly tethered nanobodies. This biolayer enhances shelf‐life and reduces background noise in various complex media. SpyDirect functionalization is faster and easier than SAM‐based methods and does not necessitate organic solvents, rendering the sensors eco‐friendly, accessible, and amenable to scalability. SpyDirect represents a broadly applicable biofunctionalization method for enhancing the cost‐effectiveness, sustainability, and longevity of electronic biosensors, all without compromising sensitivity.

A subclass of organic semiconductors known as conjugated polyelectrolytes (CPEs) is characterized by a conjugated backbone with ionic pendant groups. The water solubility of CPEs typically hinders applications of thin films in aqueous media. Herein, it is reported that films of an anionic CPE, namely CPE‐K, drop cast from water produces single‐component solid‐state pseudocapacitive electrodes that are insoluble in aqueous electrolyte. That X‐ray diffraction experiments reveal a more structurally ordered film, relative to the as‐obtained powder from chemical synthesis, and dynamic light scattering measurements show an increase in aggregate particle size with increasing [KCl] indicate that CPE‐K films are insoluble because of tight interchain contacts and electrostatic screening by the electrolyte. CPE‐K film electrodes can maintain 85% of their original capacitance (84 F g⁻¹) at 500 A g⁻¹ and exhibit excellent cycling stability, where a capacitance retention of 93% after 100 000 cycles at a current density of 35 A g⁻¹. These findings demonstrate that it is possible to use initially water soluble ionic‐organic materials in aqueous electrolytes, by increasing the electrolyte concentration. This strategy can be applied to the application of conjugated polyelectrolytes in batteries, organic electrochemical transistors, and electrochemical sensors, where fast electron and ion transport are required.