Publications
639 results found
Matrone GM, van Doremaele ERW, Surendran A, et al., 2024, A modular organic neuromorphic spiking circuit for retina-inspired sensory coding and neurotransmitter-mediated neural pathways., Nat Commun, Vol: 15
Signal communication mechanisms within the human body rely on the transmission and modulation of action potentials. Replicating the interdependent functions of receptors, neurons and synapses with organic artificial neurons and biohybrid synapses is an essential first step towards merging neuromorphic circuits and biological systems, crucial for computing at the biological interface. However, most organic neuromorphic systems are based on simple circuits which exhibit limited adaptability to both external and internal biological cues, and are restricted to emulate only specific the functions of an individual neuron/synapse. Here, we present a modular neuromorphic system which combines organic spiking neurons and biohybrid synapses to replicate a neural pathway. The spiking neuron mimics the sensory coding function of afferent neurons from light stimuli, while the neuromodulatory activity of interneurons is emulated by neurotransmitters-mediated biohybrid synapses. Combining these functions, we create a modular connection between multiple neurons to establish a pre-processing retinal pathway primitive.
Surgailis J, Flagg LQ, Richter LJ, et al., 2024, The Role Of Side Chains and Hydration on Mixed Charge Transport in N-Type Polymer Films., Adv Mater
Introducing ethylene glycol (EG) side chains to a conjugated polymer backbone is a well-established synthetic strategy for designing organic mixed ion-electron conductors (OMIECs). However, the impact that film swelling has on mixed conduction properties has yet to be scoped, particularly for electron-transporting (n-type) OMIECs. Here, we investigate the effect of the length of branched EG chains on mixed charge transport of n-type OMIECs based on a naphthalene-1,4,5,8-tetracarboxylic-diimide-bithiophene backbone. We use atomic force microscopy, grazing-incidence wide-angle X-ray scattering (GIWAXS), and scanning tunneling microscopy to establish the similarities between the common-backbone films in dry conditions. Electrochemical quartz crystal microbalance with dissipation monitori1ng (EQCM-D) and in situ GIWAXS measurements reveal stark changes in film swelling properties and microstructure during electrochemical doping, depending on the side chain length. We find that even in the loss of the crystallite content upon contact with the aqueous electrolyte, the films can effectively transport charges and that it is rather the high water content that harms the electronic interconnectivity within the OMIEC films. These results highlight the importance of controlling water uptake in the films to impede the charge transport in n-type electrochemical devices. This article is protected by copyright. All rights reserved.
Uguz I, Ohayon D, Yilmaz S, et al., 2024, Complementary integration of organic electrochemical transistors for front-end amplifier circuits of flexible neural implants., Sci Adv, Vol: 10
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.
Aitchison CM, Zhang Y, Lu W, et al., 2024, Photocatalytic CO2 reduction by topologically matched polymer-polymer heterojunction nanosheets., Faraday Discuss, Vol: 250, Pages: 251-262
Conversion of solar energy into chemical fuel can be achieved through a number of routes but direct conversion, via photocatalysis, is potentially the simplest and cheapest route to the transformation of low-value substances, water and CO2, to useful chemical fuels or feedstocks such as hydrogen, formate, methanol, and syngas. 2D polymers, including carbon nitrides and COFs, have emerged as one of the most promising classes of organic photocatalysts for solar fuels production due to their energetic tunability, charge transport properties and robustness. They are, however, difficult to process and so there have been limited studies into the formation of heterojunction materials incorporating these components. In this work we use our novel templating approach to combine topologically matched imine-based donor polymers with acceptor polymers formed through Knoevenagel condensation. An efficient heterojunction interface was formed by matching the isostructural nodes and linkers that make up the D1 and A1 semiconductors and this was reflected in the increased photocatalytic activity of the heterojunction material T1. Tuning of the templating synthesis route to give heterojunctions with optimised donor : acceptor ratios, as well as the photocatalytic conditions, resulted in CO production rates that were between 1.5 and 10 times higher than those of the individual polymers. A further set of polymers A5 and D5 were developed with more optimised structures for CO2 reduction including increased overpotential for the reduction reaction and the presence of co-catalyst chelating groups. These had increased activity compared to the group 1 family and again showed higher activity for CO production by the templated heterojunction, T5, than either individual component or a physical mixture of the donor and acceptor.
Zhong Y, Lopez-Larrea N, Alvarez-Tirado M, et al., 2024, Eutectogels as a Semisolid Electrolyte for Organic Electrochemical Transistors., Chem Mater, Vol: 36, Pages: 1841-1854, ISSN: 0897-4756
Organic electrochemical transistors (OECTs) are signal transducers offering high amplification, which makes them particularly advantageous for detecting weak biological signals. While OECTs typically operate with aqueous electrolytes, those employing solid-like gels as the dielectric layer can be excellent candidates for constructing wearable electrophysiology probes. Despite their potential, the impact of the gel electrolyte type and composition on the operation of the OECT and the associated device design considerations for optimal performance with a chosen electrolyte have remained ambiguous. In this work, we investigate the influence of three types of gel electrolytes-hydrogels, eutectogels, and iongels, each with varying compositions on the performance of OECTs. Our findings highlight the superiority of the eutectogel electrolyte, which comprises poly(glycerol 1,3-diglycerolate diacrylate) as the polymer matrix and choline chloride in combination with 1,3-propanediol deep eutectic solvent as the ionic component. This eutectogel electrolyte outperforms hydrogel and iongel counterparts of equivalent dimensions, yielding the most favorable transient and steady-state performance for both p-type depletion and p-type/n-type enhancement mode transistors gated with silver/silver chloride (Ag/AgCl). Furthermore, the eutectogel-integrated enhancement mode OECTs exhibit exceptional operational stability, reflected in the absence of signal-to-noise ratio (SNR) variation in the simulated electrocardiogram (ECG) recordings conducted continuously over a period of 5 h, as well as daily measurements spanning 30 days. Eutectogel-based OECTs also exhibit higher ECG signal amplitudes and SNR than their counterparts, utilizing the commercially available hydrogel, which is the most common electrolyte for cutaneous electrodes. These findings underscore the potential of eutectogels as a semisolid electrolyte for OECTs, particularly in applications demanding robust and prolonged physio
Paulsen BD, Meli D, Moser M, et al., 2024, Enhancement of Conjugated Polymer Microstructure and Mixed-Conducting Properties via Chalcogenophene Heteroatom Substitution, Chemistry of Materials, Vol: 36, Pages: 1818-1830, ISSN: 0897-4756
Heteroatom substitution is a powerful tool to tune the intra- and intermolecular structure of conjugated polymers as well as their resulting optoelectronic and electrochemical properties. A series of oligoethylene glycol bithiophene chalcogenophene polymers (p(g3T2-X)) with systematically varied furan, thiophene, selenophene, and tellurophene comonomers have been synthesized for mixed ionic-electronic conducting applications. Their microstructures have been thoroughly characterized ex situ and in situ with X-ray scattering, and their mixed conducting properties have been probed in electrochemical transistor testbeds. Chalcogenophene heteroatom choice was found to clearly dictate the polymer microstructure (crystallite dimensionality and orientation) and tune mixed conducting properties. Proceeding down Group 16, from O to Se systematically directed the molecular ordering of 2D polymer crystallites from face-on (O) to mixed (S) to edge-on (Se) orientations, with Te driving the polymer to form well-oriented edge-on 3D crystallites. Heteroatom dictated crystallite quality, and orientation tuned relative ionic transport by 2 orders of magnitude. Hole mobility (μhole) and mixed conducting figure of merit (μC*) were each tuned over an order of magnitude depending on heteroatom choice, with the Te-containing polymer reaching μhole = 3.60 cm2 V-1 s-1 and μC* = 483 F cm-1 V-1 s-1, due to improved molecular ordering. Insights from this polymer series highlight target microstructures for enhanced mixed conduction in future conjugated polymers.
Aitchison CM, McCulloch I, 2024, Organic Photovoltaic Materials for Solar Fuel Applications: A Perfect Match?, Chem Mater, Vol: 36, Pages: 1781-1792, ISSN: 0897-4756
This work discusses the use of donor and acceptor materials from organic photovoltaics in solar fuel applications. These two routes to solar energy conversion have many shared materials design parameters, and in recent years there has been increasing overlap of the molecules and polymers used in each. Here, we examine whether this is a good approach, where knowledge can be translated, and where further consideration to molecular design is required.
McCulloch I, Stingelin N, Anthopoulos TD, 2024, In Recognition of the Instrumental Contribution of Donal Bradley to the Field of Condensed Matter and Applied Physics., Adv Mater
Uguz I, Ohayon D, Arslan V, et al., 2024, Flexible switch matrix addressable electrode arrays with organic electrochemical transistor and pn diode technology., Nat Commun, Vol: 15
Due to their effective ionic-to-electronic signal conversion and mechanical flexibility, organic neural implants hold considerable promise for biocompatible neural interfaces. Current approaches are, however, primarily limited to passive electrodes due to a lack of circuit components to realize complex active circuits at the front-end. Here, we introduce a p-n organic electrochemical diode using complementary p- and n-type conducting polymer films embedded in a 15-μm -diameter vertical stack. Leveraging the efficient motion of encapsulated cations inside this polymer stack and the opposite doping mechanisms of the constituent polymers, we demonstrate high current rectification ratios ([Formula: see text]) and fast switching speeds (230 μs). We integrate p-n organic electrochemical diodes with organic electrochemical transistors in the front-end pixel of a recording array. This configuration facilitates the access of organic electrochemical transistor output currents within a large network operating in the same electrolyte, while minimizing crosstalk from neighboring elements due to minimized reverse-biased leakage. Furthermore, we use these devices to fabricate time-division-multiplexed amplifier arrays. Lastly, we show that, when fabricated in a shank format, this technology enables the multiplexing of amplified local field potentials directly in the active recording pixel (26-μm diameter) in a minimally invasive form factor with shank cross-sectional dimensions of only 50×8 [Formula: see text].
Shahi M, Le VN, Alarcon Espejo P, et al., 2024, The organic electrochemical transistor conundrum when reporting a mixed ionic-electronic transport figure of merit., Nat Mater, Vol: 23, Pages: 2-8
Guo K, Grünberg R, Ren Y, et al., 2023, SpyDirect: A Novel Biofunctionalization Method for High Stability and Longevity of Electronic Biosensors., Adv Sci (Weinh)
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.
Liu T, Heimonen J, Zhang Q, et al., 2023, Ground-state electron transfer in all-polymer donor:acceptor blends enables aqueous processing of water-insoluble conjugated polymers., Nat Commun, Vol: 14
Water-based conductive inks are vital for the sustainable manufacturing and widespread adoption of organic electronic devices. Traditional methods to produce waterborne conductive polymers involve modifying their backbone with hydrophilic side chains or using surfactants to form and stabilize aqueous nanoparticle dispersions. However, these chemical approaches are not always feasible and can lead to poor material/device performance. Here, we demonstrate that ground-state electron transfer (GSET) between donor and acceptor polymers allows the processing of water-insoluble polymers from water. This approach enables macromolecular charge-transfer salts with 10,000× higher electrical conductivities than pristine polymers, low work function, and excellent thermal/solvent stability. These waterborne conductive films have technological implications for realizing high-performance organic solar cells, with efficiency and stability superior to conventional metal oxide electron transport layers, and organic electrochemical neurons with biorealistic firing frequency. Our findings demonstrate that GSET offers a promising avenue to develop water-based conductive inks for various applications in organic electronics.
Xu J, Späth A, Gruber W, et al., 2023, Tailoring doped organic nanoparticles as selective hole transporters for printed non-fullerene organic solar cells, Nano Energy, Vol: 118, ISSN: 2211-2855
Most interface materials for organic solar cells (OSCs) were originally optimized for fullerene-based systems and are now being adapted for non-fullerene acceptor (NFA) based solar cells. This reliance on established interface materials results in a limited choice of interface materials for NFA based OSCs. For vacuum processed organic devices, the concept of doped interface materials is exceptionally successful, but has not yet been translated to modern NFA based devices due to solution processing constraints requiring orthogonal solubility. Herein, we report a novel concept for the development of solution-processed HTL in inverted n-i-p architecture OSCs using doped organic nanoparticles (D-NPs), overcoming solvent compatibility limitations and enabling scalable production processes. We demonstrate that the functional key interface properties of D-NPs HTLs can be tailored independently over a wide regime. Specifically, conductivity and work function can be optimized separately by varying the dopant concentration and the material system. By using D-NPs as HTL in the n-i-p architecture, power conversion efficiencies (PCE) of over 12 % are achieved for PM6:Y6 based devices. The D-NPs HTL concept is successfully applied to a variety of organic semiconductors used in photovoltaics and opens a new class of tailorable interface materials for solution-processed HTL materials.
Zhong Y, Nayak PD, Wustoni S, et al., 2023, Ionic Liquid Gated Organic Electrochemical Transistors with Broadened Bandwidth., ACS Appl Mater Interfaces
The organic electrochemical transistor (OECT) is a biosignal transducer known for its high amplification but relatively slow operation. Here, we demonstrate that the use of an ionic liquid as the dielectric medium significantly improves the switching speed of a p-type enhancement-mode OECT, regardless of the gate electrode used. The OECT response time with the ionic liquid improves up to ca. 41-fold and 46-fold for the silver/silver chloride (Ag/AgCl) and gold (Au) gates, respectively, compared with devices gated with the phosphate buffered saline (PBS) solution. Notably, the transistor gain remains uncompromised, and its maximum is reached at lower voltages compared to those of PBS-gated devices with Ag/AgCl as the gate electrode. Through ultraviolet-visible spectroscopy and etching X-ray photoelectron spectroscopy characterizations, we reveal that the enhanced bandwidth is associated with the prediffused ionic liquid inside the polymer, leading to a higher doping level compared to PBS. Using the ionic liquid-gated OECTs, we successfully detect electrocardiography (ECG) signals, which exhibit a complete waveform with well-distinguished features and a stable signal baseline. By integrating nonaqueous electrolytes that enhance the device bandwidth, we unlock the potential of enhancement-mode OECTs for physiological signal acquisition and other real-time biosignal monitoring applications.
Craighero M, Guo J, Zokaei S, et al., 2023, Impact of Oligoether Side-Chain Length on the Thermoelectric Properties of a Polar Polythiophene, ACS APPLIED ELECTRONIC MATERIALS
Ling Z, Nugraha MI, Hadmojo WT, et al., 2023, Over 19% Efficiency in Ternary Organic Solar Cells Enabled by n-Type Dopants, ACS ENERGY LETTERS, Vol: 8, Pages: 4104-4112, ISSN: 2380-8195
Druet V, Ohayon D, Petoukhoff CE, et al., 2023, A single n-type semiconducting polymer-based photo-electrochemical transistor., Nat Commun, Vol: 14
Conjugated polymer films, which can conduct both ionic and electronic charges, are central to building soft electronic sensors and actuators. Despite the possible interplay between light absorption and the mixed conductivity of these materials in aqueous biological media, no single polymer film has been utilized to create a solar-switchable organic bioelectronic circuit that relies on a fully reversible and redox reaction-free potentiometric photodetection and current modulation. Here we demonstrate that the absorption of light by an electron and cation-transporting polymer film reversibly modulates its electrochemical potential and conductivity in an aqueous electrolyte, which is harnessed to design an n-type photo-electrochemical transistor (n-OPECT). By controlling the intensity of light incident on the n-type polymeric gate electrode, we generate transistor output characteristics that mimic the modulation of the polymeric channel current achieved through gate voltage control. The micron-scale n-OPECT exhibits a high signal-to-noise ratio and an excellent sensitivity to low light intensities. We demonstrate three direct applications of the n-OPECT, i.e., a photoplethysmogram recorder, a light-controlled inverter circuit, and a light-gated artificial synapse, underscoring the suitability of this platform for a myriad of biomedical applications that involve light intensity changes.
Simatos D, Jacobs IE, Dobryden I, et al., 2023, Effects of Processing-Induced Contamination on Organic Electronic Devices, SMALL METHODS, ISSN: 2366-9608
Savva A, Hama A, Herrera-Lopez G, et al., 2023, Photo-Chemical Stimulation of Neurons with Organic Semiconductors, ADVANCED SCIENCE
Keene ST, Laulainen JEM, Pandya R, et al., 2023, Hole-limited electrochemical doping in conjugated polymers, NATURE MATERIALS, Vol: 22, Pages: 1121-+, ISSN: 1476-1122
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Siemons N, 2023, Controlling swelling in mixed transport polymers through alkyl side-chain physical cross-linking, Proceedings of the National Academy of Sciences of USA, Vol: 120, ISSN: 0027-8424
Semiconducting conjugated polymers bearing glycol side chains can simultaneously transport both electronic and ionic charges with high charge mobilities, making them ideal electrode materials for a range of bioelectronic devices. However, heavily glycolated conjugated polymer films have been observed to swell irreversibly when subjected to an electrochemical bias in an aqueous electrolyte. The excessive swelling can lead to the degradation of their microstructure, and subsequently reduced device performance. An effective strategy to control polymer film swelling is to copolymerize glycolated repeat units with a fraction of monomers bearing alkyl side chains, although the microscopic mechanism that constrains swelling is unknown. Here we investigate, experimentally and computationally, a series of archetypal mixed transporting copolymers with varying ratios of glycolated and alkylated repeat units. Experimentally we observe that exchanging 10% of the glycol side chains for alkyl leads to significantly reduced film swelling and an increase in electrochemical stability. Through molecular dynamics simulation of the amorphous phase of the materials, we observe the formation of polymer networks mediated by alkyl side-chain interactions. When in the presence of water, the network becomes increasingly connected, counteracting the volumetric expansion of the polymer film.
Le VN, Bombile JH, Rupasinghe GS, et al., 2023, New Chemical Dopant and Counterion Mechanism for Organic Electrochemical Transistors and Organic Mixed Ionic-Electronic Conductors, ADVANCED SCIENCE
Almulla L, Inal S, Petoukhoff CE, et al., 2023, Soft Photosensitive Polymers as Water-Compatible Photodetectors, MATSUS Fall 2023 Conference, Publisher: FUNDACIO DE LA COMUNITAT VALENCIANA SCITO
Chen Y, Wang H, Chen H, et al., 2023, Quasi-1D Polymer Semiconductor - Diarylethene Blends: High Performance Optically Switchable Transistors, ADVANCED FUNCTIONAL MATERIALS, ISSN: 1616-301X
LeCroy G, Cendra C, Quill TJ, et al., 2023, Role of aggregates and microstructure of mixed-ionic-electronic-conductors on charge transport in electrochemical transistors, MATERIALS HORIZONS, Vol: 10, Pages: 2568-2578, ISSN: 2051-6347
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Turetta N, Danowski W, Cusin L, et al., 2023, A photo-responsive organic electrochemical transistor, JOURNAL OF MATERIALS CHEMISTRY C, Vol: 11, Pages: 7982-7988, ISSN: 2050-7526
Kaienburg P, Bristow H, Jungbluth A, et al., 2023, Vacuum-Deposited Donors for Low-Voltage-Loss Nonfullerene Organic Solar Cells, ACS APPLIED MATERIALS & INTERFACES, Vol: 15, Pages: 31684-31691, ISSN: 1944-8244
McCulloch I, Chabinyc M, Brabec C, et al., 2023, Sustainability considerations for organic electronic products, NATURE MATERIALS, ISSN: 1476-1122
Wu R, Paulsen BD, Ma Q, et al., 2023, Quantitative Composition and Mesoscale Ion Distribution in p-Type Organic Mixed Ionic-Electronic Conductors, ACS APPLIED MATERIALS & INTERFACES, Vol: 15, Pages: 30553-30566, ISSN: 1944-8244
Moruzzi F, Zhang W, Purushothaman B, et al., 2023, Solution-processable polymers of intrinsic microporosity for gas-phase carbon dioxide photoreduction, NATURE COMMUNICATIONS, Vol: 14
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