Organic electrochemical transistors, or OECTs, have long been considered one of the most promising bridges between living tissue and electronic circuits. Unlike conventional silicon devices, they rely on soft organic materials that conduct both ions and electrons, allowing the faint ionic signals of biology to be converted directly into amplified electronic output. Yet the very property that makes them attractive—their intimate contact with salty, watery physiological fluids—has also been their undoing. A team led by Yuanwen Jiang at the University of Pennsylvania now reports in Nature Materials a solution inspired by the architecture of cell membranes themselves, and the results are striking: transistors that respond in microseconds, survive weeks in simulated body fluid, and can track dopamine release in a living rat brain in real time.
The core problem is what the researchers call the water paradox. For an OECT to work, ions from the surrounding electrolyte must penetrate the channel material, a class of compounds known as organic mixed ionic–electronic conductors, or OMIECs. This volumetric doping is what gives OECTs their exceptional amplification. But water molecules hitch a ride with the ions. Once inside, they disrupt the ordered packing of conjugated polymer chains, degrade crystalline domains that carry charge, and trigger electrochemical side reactions that chemically oxidize the polymer backbone. The consequence is a slow, degrading device: pristine PEDOT:PSS transistors in the study took roughly 87 microseconds to switch and lost more than 40 percent of their on-state current after four weeks in phosphate-buffered saline at body temperature.
Previous attempts to shield OECTs with solid-state electrolytes ran into an intrinsic trade-off. Materials that conduct ions well, such as poly(ethylene oxide) or Nafion, tend to absorb water readily; materials that block water, such as parylene C or SU-8, barely conduct ions at all. The Pennsylvania team broke this deadlock by borrowing a design principle from biology. Living cell membranes solve the same dilemma with a spatially segregated dual architecture: a water-tight lipid bilayer studded with nanoporous protein channels that ferry ions across selectively. The researchers built a synthetic analogue of that structure—a supramolecular artificial ion-channel polymer.
The material is a copolymer made by reversible addition-fragmentation chain transfer polymerization, combining two chemically distinct building blocks. The first is a crown ether derivative bearing urea groups. Crown ethers are ring-shaped molecules whose oxygen-lined cavities bind specific metal cations with high affinity; the urea groups provide hydrogen-bonding handles that drive the rings into stacked, columnar assemblies, forming continuous ion-conducting pathways. The second block is a fluorinated polymer scaffold whose hydrophobicity suppresses water uptake. The result is a microphase-separated material in which ion transport and water exclusion are handled by different domains, just as in a cell membrane.
The team synthesized four variants with different fluoroalkyl chain lengths and found that polymer 3 struck the best balance: an ionic conductivity of 2.09 microsiemens per centimetre alongside a water permeability of 5.88 × 10⁻²⁰ square metres per second per pascal at 25 degrees Celsius—figures that together outperformed conventional solid ionic conductors and passivation materials alike. Control experiments confirmed the design logic: a pure crown ether polymer, a pure fluorinated polymer, and a copolymer lacking the urea linkers all failed to resolve the ion-versus-water trade-off. Small-angle X-ray scattering, transmission electron microscopy, infrared spectroscopy and circular dichroism together verified the microphase-separated, hydrogen-bonded assembly that underpins the channels.
The ion-transport behaviour was probed with two complementary assays. In vesicle experiments using a pH-sensitive fluorescent dye, the polymer transported all alkali metal cations tested, with sodium ions moving fastest—a match for the 2.2-ångström cavity of the 15-crown-5 ring, which nearly perfectly fits the 2.04-ångström sodium ion and even drives partial stripping of its hydration shell. Removing the urea linkers roughly doubled the concentration needed for half-maximal transport, indicating that hydrogen bonding organizes the crown ethers into more continuous hopping pathways. Voltage-clamp recordings on suspended lipid bilayers showed a sodium conductance of 236 ± 17 picosiemens with a clear bimodal open-closed distribution, while the urea-free control showed no voltage response at all.
When incorporated as a thin overlayer on PEDOT:PSS transistors, the ion-channel layer transformed device performance. The modified OECTs achieved drain currents of about 14.6 milliamperes, transconductance up to 53.8 millisiemens, and switching time constants of roughly 1.3 microseconds—nearly sixty times faster than unmodified devices and equivalent to an operational bandwidth near 0.8 megahertz. Normalized transconductance exceeded 44.8 millisiemens per micrometre, surpassing even state-of-the-art vertical OECTs in the speed–gain balance. The strategy proved general: coating two n-type semiconductors, BBL and p(gNDI-T2), yielded similar gains, and crown ethers tuned for lithium and potassium each boosted performance in their matching electrolytes. High-density arrays of 100 and 960 transistors fabricated with lithography showed 99 percent yield and uniform characteristics.
Stability was equally dramatic. After four weeks in phosphate-buffered saline at 37 degrees Celsius, the protected transistors retained 96 percent of their initial on-state current and a fast 9.5-microsecond response, while unprotected devices fell to 59 percent of their current and slowed to 417 microseconds. The protected devices also endured at least 6,000 electrochemical doping cycles with 97 percent current retention. Mechanistic studies explained why. Grazing-incidence X-ray diffraction showed that bare PEDOT:PSS lamellae swelled from 13.2 to 20.7 ångströms under bias as water flooded in, whereas coated films expanded only to 13.7 ångströms; profilometry revealed 247 percent swelling in the bare film versus 19 percent in the protected one. Electrochemical quartz crystal microbalance measurements delivered the most vivid number: in pristine PEDOT:PSS, each injected sodium ion dragged roughly 86 water molecules into the film. With the ion-channel layer, that ratio collapsed to about 5, even though a similar amount of charge was injected. Volumetric capacitance and apparent carrier mobility both rose in the coated devices, from 86 to 108 farads per cubic centimetre and from 2.29 to 7.47 square centimetres per volt-second, respectively.
To demonstrate real-world utility, the team fabricated a miniaturized, flexible four-channel OECT array on a polyimide substrate and implanted it in the ventral tegmental area of anaesthetized rats, 8 millimetres below the dura. Dopamine is oxidized at the gate electrode, producing a Faradaic current that modulates the transistor in a concentration-dependent manner. The sensors showed excellent linearity across physiologically relevant dopamine concentrations from 10 nanomolar to 0.2 millimolar, a detection limit of 0.244 nanomolar, and a temporal resolution of 4.4 milliseconds for phasic dopamine transients—outperforming both passive electrochemistry and microdialysis. Electrical stimulation of the medial forebrain bundle evoked immediate, spatially localized dopamine signals, and control experiments moving either the stimulator or the sensor abolished the signal, confirming its biological origin. Immunostaining for tyrosine hydroxylase and c-Fos verified activation of dopaminergic neurons, and reproducible recordings persisted over a full week of implantation, whereas unprotected devices lost their amplification within days.
By decoupling ion transport from water transport within a single, solution-processable material, the supramolecular ion-channel polymer resolves a bottleneck that has constrained organic bioelectronics for years. The researchers suggest the platform could enable closed-loop adaptive neuromodulation, in which devices both sense and correct pathological neural activity, and could feed into biohybrid computing architectures that merge living signalling with synthetic circuits. With a provisional patent filed by the University of Pennsylvania covering the materials and transistor technology, the work also carries clear translational ambition. For a field whose devices have historically drowned in the fluids they were built to sense, a membrane-inspired fix that keeps the ions flowing while shutting the water out may prove to be the turning point.
Subject of Research: Supramolecular artificial ion-channel materials for fast, water-stable organic electrochemical transistors used in in vivo neurotransmitter monitoring
Article Title: Rapid-responsive and water-stable organic electrochemical transistors enabled by supramolecular artificial ion channels
Article References: Wang, Y., Cao, B., Zou, Y., Lu, T.-C., Huang, Y., Gao, Y., Wang, Y., Ye, Y., Liu, J., Zhang, T., Li, J., Geng, Y., Ping, Y., Wang, Z., Han, J., Sha, B., Hu, C., Chen, X., Zhang, C., … Jiang, Y. (2026). Rapid-responsive and water-stable organic electrochemical transistors enabled by supramolecular artificial ion channels. Nature Materials. https://doi.org/10.1038/s41563-026-02745-w
Image Credits: AI Generated
DOI: 10.1038/s41563-026-02745-w
Keywords: organic electrochemical transistors, supramolecular ion channels, crown ethers, organic mixed ionic-electronic conductors, PEDOT:PSS, bioelectronics, dopamine sensing, neural implants, water permeability, fluorinated polymers, hydrogen-bonded assembly, Nature Materials
News Source: Denise Maddox. (October 8, 2026). Artificial Ion Channels Make Organic Transistors Fast and Waterproof. Scienmag.
