@article{burgt_krauhausen_griggs_mcculloch_toonder_gkoupidenis_2024, title={Bio-inspired multimodal learning with organic neuromorphic electronics for behavioral conditioning in robotics}, url={https://doi.org/10.21203/rs.3.rs-3878146/v1}, DOI={10.21203/rs.3.rs-3878146/v1}, abstractNote={Abstract
        Biological systems interact directly with the environment and learn by receiving multimodal feedback via sensory stimuli that shape the formation of internal neuronal representations. Drawing inspiration from biological concepts such as exploration and sensory processing that eventually lead to behavioral conditioning, we present a robotic system handling objects through multimodal learning. A small-scale organic neuromorphic circuit locally integrates and adaptively processes multimodal sensory stimuli, enabling the robot to interact intelligently with its surroundings. The real-time handling of sensory stimuli via low-voltage organic neuromorphic devices with synaptic functionality forms multimodal associative connections that lead to behavioral conditioning, and thus the robot learns to avoid potentially dangerous objects. This work demonstrates that adaptive neuro-inspired circuitry with multifunctional organic materials, can accommodate locally efficient bio-inspired learning for advancing intelligent robotics.}, author={Burgt, Yoeri and Krauhausen, Imke and Griggs, Sophie and McCulloch, Iain and Toonder, Jaap and Gkoupidenis, Paschalis}, year={2024}, month={Jan} }
 @article{krauhausen_griggs_mcculloch_toonder_gkoupidenis_burgt_2024, title={Bio-inspired multimodal learning with organic neuromorphic electronics for behavioral conditioning in robotics}, url={https://doi.org/10.1038/s41467-024-48881-2}, DOI={10.1038/s41467-024-48881-2}, abstractNote={Abstract Biological systems interact directly with the environment and learn by receiving multimodal feedback via sensory stimuli that shape the formation of internal neuronal representations. Drawing inspiration from biological concepts such as exploration and sensory processing that eventually lead to behavioral conditioning, we present a robotic system handling objects through multimodal learning. A small-scale organic neuromorphic circuit locally integrates and adaptively processes multimodal sensory stimuli, enabling the robot to interact intelligently with its surroundings. The real-time handling of sensory stimuli via low-voltage organic neuromorphic devices with synaptic functionality forms multimodal associative connections that lead to behavioral conditioning, and thus the robot learns to avoid potentially dangerous objects. This work demonstrates that adaptive neuro-inspired circuitry with multifunctional organic materials, can accommodate locally efficient bio-inspired learning for advancing intelligent robotics.}, journal={Nature Communications}, author={Krauhausen, Imke and Griggs, Sophie and McCulloch, Iain and Toonder, Jaap M. J. and Gkoupidenis, Paschalis and Burgt, Yoeri}, year={2024}, month={Jun} }
 @article{colucci_koutsouras_morsbach_gkoupidenis_blom_kraft_2024, title={Organic Electrochemical Transistor-Based Immunosensors for SARS-CoV-2 Detection}, url={https://doi.org/10.1021/acsaelm.4c00260}, DOI={10.1021/acsaelm.4c00260}, abstractNote={Following the emergence of the worldwide severe respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic, the need for innovative strategies and methodologies to facilitate cost-effective and early stage diagnosis has become evident. To prevent the outbreak of such contagious diseases, an efficient approach is systematic testing of the population. Here, we introduce a planar organic electrochemical transistor (OECT)-based immunosensor for the detection of SARS-CoV-2. The gold gate electrode of the poly(3,4-ethylenedioxy-thiophene):polystyrene sulfonate (PEDOT:PSS)-based OECTs was functionalized with SARS-CoV-2 antibodies. The detection mechanism is based on the specific interaction of the antibodies with the spike protein of the virus, allowing its direct detection and not requiring the prior formation of antibodies in the patient's body. As a proof of concept, the ability of the immunosensor to detect the SARS-CoV-2 spike protein is assessed. The sensor exhibits a remarkably low limit of detection (LOD) of 10–17 M, with an incubation time of 30 min. Furthermore, the sensors demonstrate selectivity when exposed to similar proteins and stability, retaining their LOD after 20 days of storage. Lastly, the functionalization protocol may easily be adapted for other pathogens/biomarkers, enabling not only a point-of-care device for SARS-CoV-2 detection but also a versatile platform for biosensing applications.}, journal={ACS Applied Electronic Materials}, author={Colucci, Renan and Koutsouras, Dimitrios A. and Morsbach, Svenja and Gkoupidenis, Paschalis and Blom, Paul W. M. and Kraft, Ulrike}, year={2024}, month={Apr} }
 @article{belleri_tarres_mcculloch_blom_kovacs-vajna_gkoupidenis_torricelli_2024, title={Unravelling the operation of organic artificial neurons for neuromorphic bioelectronics}, volume={15}, ISSN={["2041-1723"]}, url={https://doi.org/10.1038/s41467-024-49668-1}, DOI={10.1038/s41467-024-49668-1}, abstractNote={Abstract Organic artificial neurons operating in liquid environments are crucial components in neuromorphic bioelectronics. However, the current understanding of these neurons is limited, hindering their rational design and development for realistic neuronal emulation in biological settings. Here we combine experiments, numerical non-linear simulations, and analytical tools to unravel the operation of organic artificial neurons. This comprehensive approach elucidates a broad spectrum of biorealistic behaviors, including firing properties, excitability, wetware operation, and biohybrid integration. The non-linear simulations are grounded in a physics-based framework, accounting for ion type and ion concentration in the electrolytic medium, organic mixed ionic-electronic parameters, and biomembrane features. The derived analytical expressions link the neurons spiking features with material and physical parameters, bridging closer the domains of artificial neurons and neuroscience. This work provides streamlined and transferable guidelines for the design, development, engineering, and optimization of organic artificial neurons, advancing next generation neuronal networks, neuromorphic electronics, and bioelectronics.}, number={1}, journal={NATURE COMMUNICATIONS}, author={Belleri, Pietro and Tarres, Judith Pons i and McCulloch, Iain and Blom, Paul W. M. and Kovacs-Vajna, Zsolt M. and Gkoupidenis, Paschalis and Torricelli, Fabrizio}, year={2024}, month={Jun} }
 @article{shao_li_yang_he_wang_fu_fu_ling_gkoupidenis_yan_et al._2023, title={A Reconfigurable Optoelectronic Synaptic Transistor with Stable Zr‐CsPbI<sub>3</sub> Nanocrystals for Visuomorphic Computing}, volume={35}, ISSN={0935-9648 1521-4095}, url={http://dx.doi.org/10.1002/adma.202208497}, DOI={10.1002/adma.202208497}, abstractNote={AbstractReconfigurable phototransistor memory attracts considerable attention for adaptive visuomorphic computing, with highly efficient sensing, memory, and processing functions integrated onto a single device. However, developing reconfigurable phototransistor memory remains a challenge due to the lack of an all‐optically controlled transition between short‐term plasticity (STP) and long‐term plasticity (LTP). Herein, an air‐stable Zr‐CsPbI3 perovskite nanocrystal (PNC)‐based phototransistor memory is designed, which is capable of broadband photoresponses. Benefitting from the different electron capture ability of Zr‐CsPbI3 PNCs to 650 and 405 nm light, an artificial synapse and non‐volatile memory can be created on‐demand and quickly reconfigured within a single device for specific purposes. Owing to the optically reconfigurable and wavelength‐aware operation between STP and LTP modes, the integrated blue feature extraction and target recognition can be demonstrated in a homogeneous neuromorphic vision sensor array. This work suggests a new way in developing perovskite optoelectronic transistors for highly efficient in‐sensor computing.}, number={12}, journal={Advanced Materials}, publisher={Wiley}, author={Shao, He and Li, Yueqing and Yang, Wei and He, Xiang and Wang, Le and Fu, Jingwei and Fu, Mingyang and Ling, Haifeng and Gkoupidenis, Paschalis and Yan, Feng and et al.}, year={2023}, month={Feb} }
 @article{krauhausen_coen_spolaor_gkoupidenis_van de burgt_2023, title={Brain‐Inspired Organic Electronics: Merging Neuromorphic Computing and Bioelectronics Using Conductive Polymers}, volume={10}, ISSN={1616-301X 1616-3028}, url={http://dx.doi.org/10.1002/adfm.202307729}, DOI={10.1002/adfm.202307729}, abstractNote={AbstractNeuromorphic computing offers the opportunity to curtail the huge energy demands of modern artificial intelligence (AI) applications by implementing computations into new, brain‐inspired computing architectures. However, the lack of fabrication processes able to integrate several computing units into monolithic systems and the need for new, hardware‐tailored training algorithms still limit the scope of application and performance of neuromorphic hardware. Recent advancements in the field of organic transistors present new opportunities for neuromorphic systems and smart sensing applications, thanks to their unique properties such as neuromorphic behavior, low‐voltage operation, and mixed ionic‐electronic conductivity. Organic neuromorphic transistors push the boundaries of energy efficient brain‐inspired hardware AI, facilitating decentralized on‐chip learning and serving as a foundation for the advancement of closed‐loop intelligent systems in the next generation. The biocompatibility and dual ionic‐electronic conductivity of organic materials introduce new prospects for biointegration and bioelectronics. Their ability to sense and regulate biosystems, as well as their neuro‐inspired functions can be combined with neuromorphic computing to create the next‐generation of bioelectronics. These systems will be able to seamlessly interact with biological systems and locally compute biosignals in a relevant matter.}, journal={Advanced Functional Materials}, publisher={Wiley}, author={Krauhausen, Imke and Coen, Charles‐Théophile and Spolaor, Simone and Gkoupidenis, Paschalis and van de Burgt, Yoeri}, year={2023}, month={Oct} }
 @article{tzouvadaki_gkoupidenis_vassanelli_wang_prodromakis_2023, title={Interfacing Biology and Electronics with Memristive Materials}, url={https://doi.org/10.1002/adma.202210035}, DOI={10.1002/adma.202210035}, abstractNote={AbstractMemristive technologies promise to have a large impact on modern electronics, particularly in the areas of reconfigurable computing and artificial intelligence (AI) hardware. Meanwhile, the evolution of memristive materials alongside the technological progress is opening application perspectives also in the biomedical field, particularly for implantable and lab‐on‐a‐chip devices where advanced sensing technologies generate a large amount of data. Memristive devices are emerging as bioelectronic links merging biosensing with computation, acting as physical processors of analog signals or in the framework of advanced digital computing architectures. Recent developments in the processing of electrical neural signals, as well as on transduction and processing of chemical biomarkers of neural and endocrine functions, are reviewed. It is concluded with a critical perspective on the future applicability of memristive devices as pivotal building blocks in bio‐AI fusion concepts and bionic schemes.}, journal={Advanced Materials}, author={Tzouvadaki, Ioulia and Gkoupidenis, Paschalis and Vassanelli, Stefano and Wang, Shiwei and Prodromakis, Themis}, year={2023}, month={Aug} }
 @article{cucchi_parker_stavrinidou_gkoupidenis_kleemann_2023, title={In Liquido Computation with Electrochemical Transistors and Mixed Conductors for Intelligent Bioelectronics}, volume={2}, ISSN={0935-9648 1521-4095}, url={http://dx.doi.org/10.1002/adma.202209516}, DOI={10.1002/adma.202209516}, abstractNote={Next‐generation implantable computational devices require long‐term‐stable electronic components capable of operating in, and interacting with, electrolytic surroundings without being damaged. Organic electrochemical transistors (OECTs) emerged as fitting candidates. However, while single devices feature impressive figures of merit, integrated circuits (ICs) immersed in common electrolytes are hard to realize using electrochemical transistors, and there is no clear path forward for optimal top‐down circuit design and high‐density integration. The simple observation that two OECTs immersed in the same electrolytic medium will inevitably interact hampers their implementation in complex circuitry. The electrolyte's ionic conductivity connects all the devices in the liquid, producing unwanted and often unforeseeable dynamics. Minimizing or harnessing this crosstalk has been the focus of very recent studies. Herein, the main challenges, trends, and opportunities for realizing OECT‐based circuitry in a liquid environment that could circumnavigate the hard limits of engineering and human physiology, are discussed. The most successful approaches in autonomous bioelectronics and information processing are analyzed. Elaborating on the strategies to circumvent and harness device crosstalk proves that platforms capable of complex computation and even machine learning (ML) can be realized in liquido using mixed ionic–electronic conductors (OMIECs).}, journal={Advanced Materials}, publisher={Wiley}, author={Cucchi, Matteo and Parker, Daniela and Stavrinidou, Eleni and Gkoupidenis, Paschalis and Kleemann, Hans}, year={2023}, month={Feb}, pages={2209516} }
 @article{gkoupidenis_zhang_kleemann_ling_santoro_fabiano_salleo_burgt_2023, title={Organic mixed conductors for bioinspired electronics}, url={https://doi.org/10.1038/s41578-023-00622-5}, DOI={10.1038/s41578-023-00622-5}, journal={Nature Reviews Materials}, author={Gkoupidenis, P. and Zhang, Y. and Kleemann, H. and Ling, H. and Santoro, F. and Fabiano, S. and Salleo, A. and Burgt, Y.}, year={2023}, month={Dec} }
 @article{lieberth_pavlou_harig_blom_gkoupidenis_torricelli_2023, title={Real‐Time Monitoring of Cellular Barrier Functionality with Dynamic‐Mode Current‐Driven Organic Electrochemical Transistor}, volume={8}, ISSN={2365-709X 2365-709X}, url={http://dx.doi.org/10.1002/admt.202201697}, DOI={10.1002/admt.202201697}, abstractNote={AbstractCellular barriers control fundamental physiological functions in animals and plants. Accurate detection of barrier dysfunction requires real‐time monitoring. Organic electrochemical transistors are a promising bioelectronic platform to monitoring cellular barriers. However, current approaches are not ideally suited for direct and real‐time measurements: they require off‐line model‐based data analysis or slow measurement operation to achieve equilibrium conditions. Herein, dynamic‐mode current‐driven organic electrochemical transistors are proposed for direct real‐time monitoring of cellular barrier functionality. In contrast to current approaches, the organic electrochemical transistor is operated under nonequilibrium conditions. The approach shows a sensitivity larger than 350 × 10−6 V (Ω cm2)−1 with an operating range of 13–640 Ω cm2. The sensitivity can be optimized on‐line by simply changing the dynamic conditions and real‐time monitoring of reversible barrier functionality is demonstrated by using a tight‐junction modulator with a concentration as‐low‐as 122 × 10−6 m. The theoretical foundation of the method is provided. The analysis shows the general applicability of the approach, opening opportunities for precision in vitro bioelectronics and medical diagnostic.}, number={10}, journal={Advanced Materials Technologies}, publisher={Wiley}, author={Lieberth, Katharina and Pavlou, Aristea and Harig, Daria and Blom, Paul W. M. and Gkoupidenis, Paschalis and Torricelli, Fabrizio}, year={2023}, month={Feb} }
 @article{zhu_li_yelemulati_deng_li_wang_li_li_gkoupidenis_tai_2022, title={An artificial remote tactile device with 3D depth-of-field sensation}, url={https://doi.org/10.1126/sciadv.abo5314}, DOI={10.1126/sciadv.abo5314}, abstractNote={Flexible tactile neuromorphic devices are becoming important as the impetus for the development of human-machine collaboration. However, accomplishing and further transcending human intelligence with artificial intelligence still confront many barriers. Here, we present a self-powered stretchable three-dimensional remote tactile device (3D-RTD) that performs the depth-of-field (DOF) sensation of external mechanical motions through a conductive-dielectric heterogeneous structure. The device can build a logic relationship precisely between DOF motions of an external active object and sensory potential signals of bipolar sign, frequency, amplitude, etc. The sensory mechanism is revealed on the basis of the electrostatic theory and multiphysics modeling, and the performance is verified via an artificial-biological hybrid system with micro/macroscale interaction. The feasibility of the 3D-RTD as an obstacle-avoidance patch for the blind is systematically demonstrated with a rat. This work paves the way for multimodal neuromorphic device that transcends the function of a biological one toward a new modality for brain-like intelligence.}, journal={Science Advances}, author={Zhu, Shanshan and Li, Yuanheng and Yelemulati, Huoerhute and Deng, Xinping and Li, Yongcheng and Wang, Jingjing and Li, Xiaojian and Li, Guanglin and Gkoupidenis, Paschalis and Tai, Yanlong}, year={2022}, month={Oct} }
 @article{sarkar_lieberth_pavlou_frank_mailaender_mcculloch_blom_torricelli_gkoupidenis_2022, title={An organic artificial spiking neuron for in situ neuromorphic sensing and biointerfacing}, url={https://doi.org/10.1038/s41928-022-00859-y}, DOI={10.1038/s41928-022-00859-y}, abstractNote={AbstractThe effective mimicry of neurons is key to the development of neuromorphic electronics. However, artificial neurons are not typically capable of operating in biological environments, which limits their ability to interface with biological components and to offer realistic neuronal emulation. Organic artificial neurons based on conventional circuit oscillators have been created, but they require many elements for their implementation. Here we report an organic artificial neuron that is based on a compact nonlinear electrochemical element. The artificial neuron can operate in a liquid and is sensitive to the concentration of biological species (such as dopamine or ions) in its surroundings. The system offers in situ operation and spiking behaviour in biologically relevant environments—including typical physiological and pathological concentration ranges (5–150 mM)—and with ion specificity. Small-amplitude (1–150 mV) electrochemical oscillations and noise in the electrolytic medium shape the neuronal dynamics, whereas changes in ionic (≥2% over the physiological baseline) and biomolecular (≥ 0.1 mM dopamine) concentrations modulate the neuronal excitability. We also create biohybrid interfaces in which an artificial neuron functions synergistically and in real time with epithelial cell biological membranes.}, journal={Nature Electronics}, author={Sarkar, Tanmoy and Lieberth, Katharina and Pavlou, Aristea and Frank, Thomas and Mailaender, Volker and McCulloch, Iain and Blom, Paul W. M. and Torricelli, Fabrizio and Gkoupidenis, Paschalis}, year={2022}, month={Nov} }
 @article{artificial neurons emulate biological counterparts to enable synergetic operation_2022, volume={5}, ISSN={2520-1131}, url={http://dx.doi.org/10.1038/s41928-022-00862-3}, DOI={10.1038/s41928-022-00862-3}, number={11}, journal={Nature Electronics}, publisher={Springer Science and Business Media LLC}, year={2022}, month={Nov}, pages={721–722} }
 @article{granelli_alessandri_gkoupidenis_vassalini_kovács‐vajna_blom_torricelli_2022, title={High‐Performance Bioelectronic Circuits Integrated on Biodegradable and Compostable Substrates with Fully Printed Mask‐Less Organic Electrochemical Transistors}, volume={18}, ISSN={1613-6810 1613-6829}, url={http://dx.doi.org/10.1002/smll.202108077}, DOI={10.1002/smll.202108077}, abstractNote={AbstractOrganic electrochemical transistors (OECTs) rely on volumetric ion‐modulation of the electronic current to provide low‐voltage operation, large signal amplification, enhanced sensing capabilities, and seamless integration with biology. The majority of current OECT technologies require multistep photolithographic microfabrication methods on glass or plastic substrates, which do not provide an ideal path toward ultralow cost ubiquitous and sustainable electronics and bioelectronics. At the same time, the development of advanced bioelectronic circuits combining bio‐detection, amplification, and local processing functionalities urgently demand for OECT technology platforms with a monolithic integration of high‐performance iontronic circuits and sensors. Here, fully printed mask‐less OECTs fabricated on thin‐film biodegradable and compostable substrates are proposed. The dispensing and capillary printing methods are used for depositing both high‐ and low‐viscosity OECT materials. Fully printed OECT unipolar inverter circuits with a gain normalized to the supply voltage as high as 136.6 V−1, and current‐driven sensors for ion detection and real‐time monitoring with a sensitivity of up to 506 mV dec−1, are integrated on biodegradable and compostable substrates. These universal building blocks with the top‐performance ever reported demonstrate the effectiveness of the proposed approach and can open opportunities for next‐generation high‐performance sustainable bioelectronics.}, number={26}, journal={Small}, publisher={Wiley}, author={Granelli, Roberto and Alessandri, Ivano and Gkoupidenis, Paschalis and Vassalini, Irene and Kovács‐Vajna, Zsolt M. and Blom, Paul W. M. and Torricelli, Fabrizio}, year={2022}, month={Jun} }
 @article{zhang_ye_van der pol_dong_van doremaele_krauhausen_liu_gkoupidenis_portale_song_et al._2022, title={High‐Performance Organic Electrochemical Transistors and Neuromorphic Devices Comprising Naphthalenediimide‐Dialkoxybithiazole Copolymers Bearing Glycol Ether Pendant Groups}, volume={32}, ISSN={1616-301X 1616-3028}, url={http://dx.doi.org/10.1002/adfm.202201593}, DOI={10.1002/adfm.202201593}, abstractNote={AbstractOrganic electrochemical transistors (OECTs) have emerged as building blocks for low power circuits, biosensors, and neuromorphic computing. While p‐type polymer materials for OECTs are well developed, the choice of high‐performance n‐type polymers is limited, despite being essential for cation and metabolite biosensors, and crucial for constructing complementary circuits. N‐type conjugated polymers that have efficient ion‐to‐electron transduction are highly desired for electrochemical applications. In this contribution, three non‐fused, planar naphthalenediimide (NDI)‐dialkoxybithiazole (2Tz) copolymers, which systematically increase the amount of polar tri(ethylene glycol) (TEG) side chains: PNDI2OD‐2Tz (0 TEG), PNDIODTEG‐2Tz (1 TEG), PNDI2TEG‐2Tz (2 TEG), are reported. It is demonstrated that the OECT performance increases with the number of TEG side chains resulting from the progressively higher hydrophilicity and larger electron affinities. Benefiting from the high electron mobility, excellent ion conduction capability, efficient ion‐to‐electron transduction, and low‐lying lowest unoccupied molecular orbital energy level, the 2 TEG polymer achieves close to 105 on‐off ratio, fast switching, 1000 stable operation cycles in aqueous electrolyte, and has a long shelf life. Moreover, the higher number TEG chain substituted polymer exhibits good conductance state retention over two orders of magnitudes in electrochemical resistive random‐access memory devices, highlighting its potential for neuromorphic computing.}, number={27}, journal={Advanced Functional Materials}, publisher={Wiley}, author={Zhang, Yanxi and Ye, Gang and van der Pol, Tom P. A. and Dong, Jingjin and van Doremaele, Eveline R. W. and Krauhausen, Imke and Liu, Yuru and Gkoupidenis, Paschalis and Portale, Giuseppe and Song, Jun and et al.}, year={2022}, month={Apr} }
 @inproceedings{gkoupidenis_2022, title={Organic neuromorphic electronics for bio-inspired processing and local sensorimotor learning in robotics}, url={http://dx.doi.org/10.1117/12.2636040}, DOI={10.1117/12.2636040}, abstractNote={Artificial intelligence applications have demonstrated their enormous potential for complex processing over the last decade. However, they are mainly based on digital operating principles while being part of an analogue world. Moreover, they still lack the efficiency and computing capacity of biological systems. Neuromorphic electronics emulate the analogue information processing of biological nervous systems. Neuromorphic electronics based on organic materials have the ability to emulate efficiently and with fidelity a wide range of bio-inspired functions. A prominent example of a neuromorphic device is based on organic mixed conductors (ionic-electronic). Neuromorphic devices based on organic mixed conductors show volatile, non-volatile and tunable dynamics suitable for the emulation of synaptic plasticity and neuronal functions, and for the mapping of artificial neural networks in physical circuits. Finally, small-scale organic neuromorphic circuits enable the local sensorimotor control and learning in robotics.}, booktitle={Organic and Hybrid Sensors and Bioelectronics XV}, publisher={SPIE}, author={Gkoupidenis, Paschalis}, editor={Shinar, Ruth and Kymissis, Ioannis and List-Kratochvil, Emil J.Editors}, year={2022}, month={Oct} }
 @article{sarkar_lieberth_pavlou_frank_mailaender_mcculloch_blom_torricelli_gkoupidenis_2022, title={Publisher Correction: An organic artificial spiking neuron for in situ neuromorphic sensing and biointerfacing}, url={https://doi.org/10.1038/s41928-022-00894-9}, DOI={10.1038/s41928-022-00894-9}, abstractNote={sentence "The OEND consists of two OECTs, namely, T 1 and T 2 , that are connected via the R 1 = 5 kΩ and R}, journal={Nature Electronics}, author={Sarkar, Tanmoy and Lieberth, Katharina and Pavlou, Aristea and Frank, Thomas and Mailaender, Volker and McCulloch, Iain and Blom, Paul W. M. and Torricelli, Fabrizio and Gkoupidenis, Paschalis}, year={2022}, month={Nov} }
 @article{koutsouras_amiri_blom_torricelli_asadi_gkoupidenis_2021, title={An Iontronic Multiplexer Based on Spatiotemporal Dynamics of Multiterminal Organic Electrochemical Transistors}, url={https://doi.org/10.1002/adfm.202011013}, DOI={10.1002/adfm.202011013}, abstractNote={AbstractThe seamless integration of electronics with biology requires new bio‐inspired approaches that, analogously to nature, rely on the presence of electrolytes for signal multiplexing. On the contrary, conventional multiplexing schemes mostly rely on electronic carriers and require peripheral circuitry for their implementation, which imposes severe limitations toward their adoption in bio‐applications. Here, a bio‐inspired iontronic multiplexer based on spatiotemporal dynamics of organic electrochemical transistors (OECTs), with an electrolyte as the shared medium of communication, is shown. The iontronic system discriminates locally random‐access events with no need of peripheral circuitry or address assignment, thus deceasing significantly the integration complexity. The form factors of OECTs that allow for intimate biointerfacing as well as the electrochemical nature of the communication medium, open new avenues for unconventional multiplexing in the emerging fields of bioelectronics, wearables, and neuromorphic computing or sensing.}, journal={Advanced Functional Materials}, author={Koutsouras, Dimitrios A. and Amiri, Morteza Hassanpour and Blom, Paul W. M. and Torricelli, Fabrizio and Asadi, Kamal and Gkoupidenis, Paschalis}, year={2021}, month={May} }
 @article{seufert_hassanpouramiri_gkoupidenis_asadi_2021, title={Crossbar Array of Artificial Synapses Based on Ferroelectric Diodes}, volume={7}, ISSN={2199-160X 2199-160X}, url={http://dx.doi.org/10.1002/aelm.202100558}, DOI={10.1002/aelm.202100558}, abstractNote={AbstractTwo terminal devices that exhibit resistance switching in response to an external voltage are interesting for neuromorphic computing applications. Owing to its simple device structure, a crossbar array of two‐terminal resistance switching devices is highly desired for application as artificial neural network weights. Here, ferroelectric diodes that show resistance switching in their forward bias are presented. The resistance can be set to a high‐ and a low‐resistance state or any state between these limits. It is demonstrated that the ferroelectric diodes can function as an artificial synapse. An array of the ferroelectric diodes with two bit and two row lines (2 × 2) is demonstrated. The resistance of every bit is independently tuned, and spike‐time‐dependent plasticity is shown for the array.}, number={12}, journal={Advanced Electronic Materials}, publisher={Wiley}, author={Seufert, Laura and HassanpourAmiri, Morteza and Gkoupidenis, Paschalis and Asadi, Kamal}, year={2021}, month={Oct} }
 @article{lieberth_romele_torricelli_koutsouras_brückner_mailänder_gkoupidenis_blom_2021, title={Current‐Driven Organic Electrochemical Transistors for Monitoring Cell Layer Integrity with Enhanced Sensitivity}, volume={10}, ISSN={2192-2640 2192-2659}, url={http://dx.doi.org/10.1002/adhm.202100845}, DOI={10.1002/adhm.202100845}, abstractNote={AbstractIn this progress report an overview is given on the use of the organic electrochemical transistor (OECT) as a biosensor for impedance sensing of cell layers. The transient OECT current can be used to detect changes in the impedance of the cell layer, as shown by Jimison et al. To circumvent the application of a high gate bias and preventing electrolysis of the electrolyte, in case of small impedance variations, an alternative measuring technique based on an OECT in a current‐driven configuration is developed. The ion‐sensitivity is larger than 1200 mV V‐1dec‐1 at low operating voltage. It can be even further enhanced using an OECT based complementary amplifier, which consists of a p‐type and an n‐type OECT connected in series, as known from digital electronics. The monitoring of cell layer integrity and irreversible disruption of barrier function with the current‐driven OECT is demonstrated for an epithelial Caco‐2 cell layer, showing the enhanced ion‐sensitivity as compared to the standard OECT configuration. As a state‐of‐the‐art application of the current‐driven OECT, the in situ monitoring of reversible tight junction modulation under the effect of drug additives, like poly‐l‐lysine, is discussed. This shows its potential for in vitro and even in vivo toxicological and drug delivery studies.}, number={19}, journal={Advanced Healthcare Materials}, publisher={Wiley}, author={Lieberth, Katharina and Romele, Paolo and Torricelli, Fabrizio and Koutsouras, Dimitrios A. and Brückner, Maximilian and Mailänder, Volker and Gkoupidenis, Paschalis and Blom, Paul W. M.}, year={2021}, month={Jul} }
 @article{koutsouras_torricelli_gkoupidenis_blom_2021, title={Efficient Gating of Organic Electrochemical Transistors with In‐Plane Gate Electrodes}, volume={6}, ISSN={2365-709X 2365-709X}, url={http://dx.doi.org/10.1002/admt.202100732}, DOI={10.1002/admt.202100732}, abstractNote={AbstractOrganic electrochemical transistors (OECTs) are electrolyte‐gated transistors, employing an electrolyte between their gate and channel instead of an insulating layer. For efficient gating, non‐polarizable electrodes, for example, Ag/AgCl, are typically used but unfortunately, this simple approach limits the options for multiple gate integration. Patterned polarizable Au gates on the other hand, show strongly reduced gating due to a large voltage drop at the gate/electrolyte interface. Here, an alternative, simple yet effective method for efficient OECT gating by scalable in‐plane gate electrodes, is demonstrated. The fact that poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) exhibits a volumetric capacitance in an electrolyte is made use of. As a result, the capacitance of PEDOT:PSS‐based gates can be strongly enhanced by increasing their thickness, thereby reducing the voltage loss at the gate/electrolyte interface. By combining spin coating and electrodeposition, planar electrodes of various thicknesses are created on a multi‐gated OECT chip and their effect on the gating efficiency, examined. It is shown that the gating performed by an in‐plane PEDOT:PSS electrode can be tuned to be comparable to the one obtained by a Ag/AgCl electrode. Overall, the realization of efficient gating with in‐plane electrodes paves the way toward integration of OECT‐based biosensors and “organ‐on‐a‐chip” platforms.}, number={12}, journal={Advanced Materials Technologies}, publisher={Wiley}, author={Koutsouras, Dimitrios A. and Torricelli, Fabrizio and Gkoupidenis, Paschalis and Blom, Paul W. M.}, year={2021}, month={Aug} }
 @misc{torricelli_romele_gkoupidenis_koutsouras_lieberth_kovács-vajna_blom_2021, title={Integrated amplifier with complementary organic electrochemical transistors for high-sensitivity ion detection and real-time monitoring}, url={http://dx.doi.org/10.1117/12.2583428}, DOI={10.1117/12.2583428}, abstractNote={Ions are fundamental biological regulators enabling the communication between cells, regulating metabolic and bioenergetic processing and playing a key role in pH regulation and hydration. The in-situ quantification of the ion concentration is gathering relevant interest in biomedical diagnostics and healthcare. State-of-art transistor-based ion sensors show an intrinsic trade-off between sensitivity, operating range and supply voltage. To overcome these limitations, here we focus on ion sensor amplifiers where complementary OECTs are integrated in a push-pull configuration, providing sensitivity larger than 1 V/dec at a supply voltage down to 0.5 V and operating in the physiological range. Ion detection over a range of five orders of magnitude and real-time monitoring of variations two orders of magnitude lower than the detected concentration are achieved. The ion-sensitive amplifier sets a new benchmark for ion-sensing devices, opening possibilities for predictive diagnostics and personalized medicine.}, journal={Integrated Sensors for Biological and Neural Sensing}, publisher={SPIE}, author={Torricelli, Fabrizio and Romele, Paolo and Gkoupidenis, Paschalis and Koutsouras, Dimitrios A. and Lieberth, Katharina and Kovács-Vajna, Zsolt M. and Blom, Paul W. M.}, editor={Mohseni, HoomanEditor}, year={2021}, month={Mar} }
 @article{lieberth_brückner_torricelli_mailänder_gkoupidenis_blom_2021, title={Monitoring Reversible Tight Junction Modulation with a Current‐Driven Organic Electrochemical Transistor}, volume={6}, ISSN={2365-709X 2365-709X}, url={http://dx.doi.org/10.1002/admt.202000940}, DOI={10.1002/admt.202000940}, abstractNote={AbstractThe barrier functionality of a cell layer regulates the passage of nutrients into the blood. Modulating the barrier functionality by external chemical agents like poly‐l‐lysine (PLL) is crucial for drug delivery. The ability of a cell layer to impede the passage of ions through it and therefore to act as a barrier, can be assessed electrically by measuring the resistance across the cell layer. Here, an organic electrochemical transistor (OECT) is used in a current‐driven configuration for the evaluation of reversible modulation of tight junctions in Caco‐2 cells over time. Exposure to low and medium concentrations of PLL initiates reversible modulation, whereas a too high concentration induces an irreversible barrier disruption due to nonfunctional tight junction proteins. The results demonstrate the suitability of OECTs to in situ monitor temporal barrier modulation and recovery, which can offer valuable information for drug delivery applications.}, number={5}, journal={Advanced Materials Technologies}, publisher={Wiley}, author={Lieberth, Katharina and Brückner, Maximilian and Torricelli, Fabrizio and Mailänder, Volker and Gkoupidenis, Paschalis and Blom, Paul W. M.}, year={2021}, month={Apr} }
 @article{krauhausen_koutsouras_melianas_keene_lieberth_ledanseur_sheelamanthula_giovannitti_torricelli_mcculloch_et al._2021, title={Organic neuromorphic electronics for sensorimotor integration and learning in robotics}, volume={7}, ISSN={2375-2548}, url={http://dx.doi.org/10.1126/sciadv.abl5068}, DOI={10.1126/sciadv.abl5068}, abstractNote={A robot learns to follow a path to exit a maze through sensorimotor learning that is induced by an organic neuromorphic circuit.}, number={50}, journal={Science Advances}, publisher={American Association for the Advancement of Science (AAAS)}, author={Krauhausen, Imke and Koutsouras, Dimitrios A. and Melianas, Armantas and Keene, Scott T. and Lieberth, Katharina and Ledanseur, Hadrien and Sheelamanthula, Rajendar and Giovannitti, Alexander and Torricelli, Fabrizio and Mcculloch, Iain and et al.}, year={2021}, month={Dec} }
 @misc{gkoupidenis_2021, title={Organic neuromorphic electronics: bio-inspired functions and applications}, url={http://dx.doi.org/10.1117/12.2595049}, DOI={10.1117/12.2595049}, abstractNote={The seamless integration of electronics with biology requires new bio-inspired approaches that, analogously to nature, rely on the presence of electrolytes for signal multiplexing. On the contrary, conventional multiplexing schemes mostly rely on electronic carriers and require peripheral circuitry for their implementation, which imposes limitations toward their adoption in bio-applications. Here we show an iontronic multiplexer based on spatiotemporal dynamics of organic electrochemical transistors (OECTs), with an electrolyte as the shared medium of communication. The iontronic system discriminates locally random-access events with no need of peripheral circuitry, thus deceasing significantly the integration complexity. The form factors of OETCs, open new avenues for unconventional multiplexing in the emerging fields of bioelectronics and neuromorphic sensors. Examples of organic neuromorphic electronics for local learning in applications with energy restrictions are also showcased.}, journal={Organic and Hybrid Sensors and Bioelectronics XIV}, publisher={SPIE}, author={Gkoupidenis, Paschalis}, editor={Shinar, Ruth and Kymissis, Ioannis and List-Kratochvil, Emil J.Editors}, year={2021}, month={Aug} }
 @article{koutsouras_lieberth_torricelli_gkoupidenis_blom_2021, title={Selective Ion Detection with Integrated Organic Electrochemical Transistors}, volume={6}, ISSN={2365-709X 2365-709X}, url={http://dx.doi.org/10.1002/admt.202100591}, DOI={10.1002/admt.202100591}, abstractNote={AbstractAccurate sensing of ion concentrations in body fluids is of importance to monitor cell functions, and any deviation of the concentration serves as a warning sign of pathophysiological conditions. Here, a fabrication approach for an integrated device consisting of two electrochemical transistors, capable of selective simultaneous detection between potassium and sodium ions in an analyte is demonstrated. A common in‐plane gate electrode is integrated in the substrate, enabling the fabrication of micro‐scale ion sensors for biomedical applications. The approach is versatile and can be extended to include numerous ion‐selective transistors on a chip in order to meet the demand for simultaneous sensing of multiple ions.}, number={12}, journal={Advanced Materials Technologies}, publisher={Wiley}, author={Koutsouras, Dimitrios A. and Lieberth, Katharina and Torricelli, Fabrizio and Gkoupidenis, Paschalis and Blom, Paul W. M.}, year={2021}, month={Aug} }
 @article{jeong_gkoupidenis_asadi_2021, title={Solution‐Processed Perovskite Field‐Effect Transistor Artificial Synapses}, volume={33}, ISSN={0935-9648 1521-4095}, url={http://dx.doi.org/10.1002/adma.202104034}, DOI={10.1002/adma.202104034}, abstractNote={AbstractMetal halide perovskites are distinctive semiconductors that exhibit both ionic and electronic transport and are promising for artificial synapses. However, developing a 3‐terminal transistor artificial synapse with the perovskite channel remains elusive due to the lack of a proper technique to regulate mobile ions in a non‐volatile manner. Here, a solution‐processed perovskite transistor is reported for artificial synapses through the implementation of a ferroelectric gate. The ferroelectric polarization provides a non‐volatile electric field on the perovskite, leading to fixation of the mobile ions and hence modulation of the electronic conductance of the channel. Multi‐state channel conductance is realized by partial ferroelectric polarization. The ferroelectric‐gated perovskite transistor is successfully used as an artificial synapse that emulates basic synaptic functions such as long‐term plasticity with excellent linearity, short‐term as well as spike‐timing‐dependent plasticity. The strategy to regulate ion dynamics in the perovskites using the ferroelectric gate suggests a generic route to employ perovskites for synaptic electronics.}, number={52}, journal={Advanced Materials}, publisher={Wiley}, author={Jeong, Beomjin and Gkoupidenis, Paschalis and Asadi, Kamal}, year={2021}, month={Oct} }
 @article{wang_li_wang_xu_fu_liu_lin_ling_gkoupidenis_yi_et al._2021, title={Thin-film transistors for emerging neuromorphic electronics: fundamentals, materials, and pattern recognition}, url={https://doi.org/10.1039/D1TC01660A}, DOI={10.1039/D1TC01660A}, abstractNote={This review paper provides an overview of the recent successful simulation of pattern recognition with TFT-based artificial synapses from device- to system-level.}, journal={Journal of Materials Chemistry C}, publisher={Royal Society of Chemistry (RSC)}, author={Wang, Conglin and Li, Yuanzhe and Wang, Yucong and Xu, Xiangdong and Fu, Mingyang and Liu, Yuyu and Lin, Zongqiong and Ling, Haifeng and Gkoupidenis, Paschalis and Yi, Mingdong and et al.}, year={2021} }
 @article{hassanpour amiri_heidler_müllen_gkoupidenis_asadi_2020, title={Designing Multi‐Level Resistance States in Graphene Ferroelectric Transistors}, volume={30}, ISSN={1616-301X 1616-3028}, url={http://dx.doi.org/10.1002/adfm.202003085}, DOI={10.1002/adfm.202003085}, abstractNote={AbstractConventional memory elements code information in the Boolean “0” and “1” form. Devices that exceed bistability in their resistance are useful as memory for future data storage due to their enhanced memory capacity, and are also a necessity for contemporary applications such as neuromorphic computing. Here, with the aid of an experimentally validated device model, design rules are outlined and more than two stable resistance states in a graphene ferroelectric field‐effect transistor are experimentally demonstrated. The design methodology can be extrapolated for on‐demand introduction of multiple resistance states in ferroelectric transistors for applications both in data storage and neuromorphic computing.}, number={34}, journal={Advanced Functional Materials}, publisher={Wiley}, author={Hassanpour Amiri, Morteza and Heidler, Jonas and Müllen, Klaus and Gkoupidenis, Paschalis and Asadi, Kamal}, year={2020}, month={Jun} }
 @article{ling_koutsouras_kazemzadeh_burgt_yan_gkoupidenis_2020, title={Electrolyte-gated transistors for synaptic electronics, neuromorphic computing, and adaptable biointerfacing}, url={https://doi.org/10.1063/1.5122249}, DOI={10.1063/1.5122249}, abstractNote={Functional emulation of biological synapses using electronic devices is regarded as the first step toward neuromorphic engineering and artificial neural networks (ANNs). Electrolyte-gated transistors (EGTs) are mixed ionic–electronic conductivity devices capable of efficient gate-channel capacitance coupling, biocompatibility, and flexible architectures. Electrolyte gating offers significant advantages for the realization of neuromorphic devices/architectures, including ultralow-voltage operation and the ability to form parallel-interconnected networks with minimal hardwired connectivity. In this review, the most recent developments in EGT-based electronics are introduced with their synaptic behaviors and detailed mechanisms, including short-/long-term plasticity, global regulation phenomena, lateral coupling between device terminals, and spatiotemporal correlated functions. Analog memory phenomena allow for the implementation of perceptron-based ANNs. Due to their mixed-conductivity phenomena, neuromorphic circuits based on EGTs allow for facile interfacing with biological environments. We also discuss the future challenges in implementing low power, high speed, and reliable neuromorphic computing for large-scale ANNs with these neuromorphic devices. The advancement of neuromorphic devices that rely on EGTs highlights the importance of this field for neuromorphic computing and for novel healthcare technologies in the form of adaptable or trainable biointerfacing.}, journal={Applied Physics Reviews}, author={Ling, Haifeng and Koutsouras, Dimitrios A. and Kazemzadeh, Setareh and Burgt, Yoeri and Yan, Feng and Gkoupidenis, Paschalis}, year={2020}, month={Mar} }
 @article{romele_gkoupidenis_koutsouras_lieberth_kovács-vajna_blom_torricelli_2020, title={Multiscale real time and high sensitivity ion detection with complementary organic electrochemical transistors amplifier}, url={https://doi.org/10.1038/s41467-020-17547-0}, DOI={10.1038/s41467-020-17547-0}, abstractNote={AbstractIons are ubiquitous biological regulators playing a key role for vital processes in animals and plants. The combined detection of ion concentration and real-time monitoring of small variations with respect to the resting conditions is a multiscale functionality providing important information on health states. This multiscale functionality is still an open challenge for current ion sensing approaches. Here we show multiscale real-time and high-sensitivity ion detection with complementary organic electrochemical transistors amplifiers. The ion-sensing amplifier integrates in the same device both selective ion-to-electron transduction and local signal amplification demonstrating a sensitivity larger than 2300 mV V−1 dec−1, which overcomes the fundamental limit. It provides both ion detection over a range of five orders of magnitude and real-time monitoring of variations two orders of magnitude lower than the detected concentration, viz. multiscale ion detection. The approach is generally applicable to several transistor technologies and opens opportunities for multifunctional enhanced bioelectronics.}, journal={Nature Communications}, author={Romele, Paolo and Gkoupidenis, Paschalis and Koutsouras, Dimitrios A. and Lieberth, Katharina and Kovács-Vajna, Zsolt M. and Blom, Paul W. M. and Torricelli, Fabrizio}, year={2020}, month={Jul} }
 @misc{keene_gkoupidenis_burgt_2021, title={Neuromorphic computing systems based on flexible organic electronics}, ISBN={9780128188903}, url={http://dx.doi.org/10.1016/b978-0-12-818890-3.00018-7}, DOI={10.1016/b978-0-12-818890-3.00018-7}, abstractNote={Today software systems known as neural networks are at the basis of numerous artificial intelligence applications and are successfully implemented to translate languages, classify images, recognize diseases, and form the basis of the spur in autonomous driving. However, these algorithms require a substantial amount of computer resources and energy. The brain on the other hand, operates in a highly parallel fashion, connecting neurons via synapses, rendering it compact and highly efficient in recognizing patterns, speech, and images. Neuromorphic engineering takes advantage of the efficiency of the brain by mimicking and implementing essential concepts such as neurons and synapses in hardware. In this chapter we review the development of organic neuromorphic devices. We highlight efforts to mimic essential brain functions, such as spiking phenomena, spatiotemporal processing, homeostasis, and functional connectivity and demonstrate related applications. Next, we review important metrics for implementing low-power and reliable neuromorphic computing, such as state retention and conductance tuning. Finally, we give an outlook on future directions and potential applications, with a particular focus on interfacing with biological environments.}, journal={Organic Flexible Electronics}, publisher={Elsevier}, author={Keene, Scott T. and Gkoupidenis, Paschalis and Burgt, Yoeri van de}, year={2021}, pages={531–574} }
 @article{van de burgt_gkoupidenis_2020, title={Organic materials and devices for brain-inspired computing: From artificial implementation to biophysical realism}, volume={45}, ISSN={0883-7694 1938-1425}, url={http://dx.doi.org/10.1557/mrs.2020.194}, DOI={10.1557/mrs.2020.194}, abstractNote={Abstract}, number={8}, journal={MRS Bulletin}, publisher={Springer Science and Business Media LLC}, author={van de Burgt, Yoeri and Gkoupidenis, Paschalis}, year={2020}, month={Aug}, pages={631–640} }
 @article{tuchman_mangoma_gkoupidenis_van de burgt_john_mathews_shaheen_daly_malliaras_salleo_2020, title={Organic neuromorphic devices: Past, present, and future challenges}, volume={45}, ISSN={0883-7694 1938-1425}, url={http://dx.doi.org/10.1557/mrs.2020.196}, DOI={10.1557/mrs.2020.196}, abstractNote={Abstract}, number={8}, journal={MRS Bulletin}, publisher={Springer Science and Business Media LLC}, author={Tuchman, Yaakov and Mangoma, Tanyaradzwa N. and Gkoupidenis, Paschalis and van de Burgt, Yoeri and John, Rohit Abraham and Mathews, Nripan and Shaheen, Sean E. and Daly, Ronan and Malliaras, George G. and Salleo, Alberto}, year={2020}, month={Aug}, pages={619–630} }
 @inproceedings{gkoupidenis_2019, title={Biological plausibility in organic neuromorphic devices: from global phenomena to synchronization functions}, url={http://dx.doi.org/10.1117/12.2526392}, DOI={10.1117/12.2526392}, abstractNote={It is now well recognized that traditional computing systems based on von Neumann architecture are not efficient enough to manipulate and process the massive amount of data produced by the contemporary information technologies. A shifting paradigm from the traditional computing systems is the emulation of the brain computational efficiency at the hardware-based level, a field that is also known as neuromorphic computing. Although neuromorphic computing with inorganic materials has been advanced over the past years, nevertheless biological plausibility is questionable in many cases of solid-state technologies. In the brain, for instance, neural populations are immersed in a common electrolyte or cerebrospinal fluid and this fact equips the brain with more efficient features in processing when compared to electronic devices or circuits. Due to this topology in biological neural networks, higher order phenomena exist such as global regulation of neural activity and communication between different regions in the brain mediated by the presence of the global electrolyte. In this work, device concepts will be presented that lead to biological plausibility in organic neuromorphic devices, including global phenomena and synchronization functions. Introducing this level of biological plausibility, paves the way for new concepts of neuromorphic communication between different subunits in a circuit.}, booktitle={Organic and Hybrid Sensors and Bioelectronics XII}, publisher={SPIE}, author={Gkoupidenis, Paschalis}, editor={Shinar, Ruth and Kymissis, Ioannis and List-Kratochvil, Emil J.Editors}, year={2019}, month={Sep} }
 @article{lingstedt_ghittorelli_lu_koutsouras_marszalek_torricelli_crăciun_gkoupidenis_blom_2019, title={Effect of DMSO Solvent Treatments on the Performance of PEDOT:PSS Based Organic Electrochemical Transistors}, volume={5}, ISSN={2199-160X 2199-160X}, url={http://dx.doi.org/10.1002/aelm.201800804}, DOI={10.1002/aelm.201800804}, abstractNote={AbstractThe conductivity of poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonic acid) (PEDOT:PSS) can be strongly enhanced by treatment with high boiling solvents as dimethyl sulfoxide (DMSO). The effect of various DMSO solvent treatment methods on the performance of organic electrochemical transistors (OECTs) based on PEDOT:PSS is studied. The treatments include mixing PEDOT:PSS with DMSO before film deposition, exposing a deposited PEDOT:PSS film to a saturated DMSO vapor, and dipping a PEDOT:PSS film in a DMSO bath. Compared to dry PEDOT:PSS, operating in the OECT configuration causes a significant reduction of its conductivity for all treatments, due to the swelling of PEDOT:PSS by the direct contact of the conductive channel with the electrolyte. The dipping method gives rise to the highest OECT performance, reflected in the highest on/off ratio and transconductance. The improved conductivity and device performance after dipping arise from an enhanced charge carrier mobility due to enhanced structural order.}, number={3}, journal={Advanced Electronic Materials}, publisher={Wiley}, author={Lingstedt, Leona V. and Ghittorelli, Matteo and Lu, Hao and Koutsouras, Dimitrios A. and Marszalek, Tomasz and Torricelli, Fabrizio and Crăciun, N. Irina and Gkoupidenis, Paschalis and Blom, Paul W. M.}, year={2019}, month={Feb} }
 @article{koutsouras_prodromakis_malliaras_blom_gkoupidenis_2019, title={Functional Connectivity of Organic Neuromorphic Devices by Global Voltage Oscillations}, url={https://doi.org/10.1002/aisy.201900013}, DOI={10.1002/aisy.201900013}, abstractNote={Global oscillations in the brain synchronize neural populations and lead to dynamic binding between different regions. This functional connectivity reconfigures as needed for the architecture of the neural network, thereby transcending the limitations of its hardwired structure. Despite the fact that it underlies the versatility of biological computational systems, this concept is not captured in current neuromorphic device architectures. Herein, functional connectivity in an array of organic neuromorphic devices connected through an electrolyte is demonstrated. The output of these devices is shown to be synchronized by a global oscillatory input despite the fact that individual inputs are stochastic and independent. This temporal coupling is induced at a specific phase of the global oscillation in a way that is reminiscent of phase locking of neurons to brain oscillations. This demonstration provides a pathway toward new neuromorphic architectural paradigms, where dynamic binding transcends the limitations of structural connectivity, and could enable architectural concepts of hierarchical information flow.}, journal={Advanced Intelligent Systems}, author={Koutsouras, Dimitrios A. and Prodromakis, Themis and Malliaras, George G. and Blom, Paul W. M. and Gkoupidenis, Paschalis}, year={2019}, month={May} }
 @article{lingstedt_ghittorelli_brückner_reinholz_crăciun_torricelli_mailänder_gkoupidenis_blom_2019, title={Monitoring of Cell Layer Integrity with a Current‐Driven Organic Electrochemical Transistor}, volume={8}, ISSN={2192-2640 2192-2659}, url={http://dx.doi.org/10.1002/adhm.201900128}, DOI={10.1002/adhm.201900128}, abstractNote={AbstractThe integrity of CaCo‐2 cell barriers is investigated by organic electrochemical transistors (OECTs) in a current‐driven configuration. Ion transport through cellular barriers via the paracellular pathway is modulated by tight junctions between adjacent cells. Rupturing its integrity by H2O2 is monitored by the change of the output voltage in the transfer characteristics. It is demonstrated that by operating the OECT in a current‐driven configuration, the sensitive and temporal resolution for monitoring the cell barrier integrity is strongly enhanced as compared to the OECT transient response measurement. As a result, current‐driven OECTs are useful tools to assess dynamic and critical changes in tight junctions, relevant for clinical applications as drug targeting and screening.}, number={16}, journal={Advanced Healthcare Materials}, publisher={Wiley}, author={Lingstedt, Leona V. and Ghittorelli, Matteo and Brückner, Maximilian and Reinholz, Jonas and Crăciun, N. Irina and Torricelli, Fabrizio and Mailänder, Volker and Gkoupidenis, Paschalis and Blom, Paul W. M.}, year={2019}, month={Jul} }
 @article{koutsouras_lingstedt_lieberth_reinholz_mailänder_blom_gkoupidenis_2019, title={Probing the Impedance of a Biological Tissue with PEDOT:PSS‐Coated Metal Electrodes: Effect of Electrode Size on Sensing Efficiency}, url={https://doi.org/10.1002/adhm.201901215}, DOI={10.1002/adhm.201901215}, abstractNote={AbstractElectrodes coated with poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) have been employed to measure the integrity of cellular barriers. However, a systematic experimental study of the correlation between tissue integrity and impedance of the sensing device has not yet been conducted. Using impedance spectroscopy, how the impedance ratio of the biological tissue to the recording device affects the recording ability of the latter is investigated. PEDOT:PSS‐coated electrodes of various dimensions are employed and the effect of their size to their sensing efficiency is examined. The biotic/abiotic ensemble is modeled with a simple equivalent circuit and an analytical expression of the total impedance as a function of frequency is extracted. The results reveal a critical impedance ratio of the biological tissue to the sensor which allows for efficient sensing of the tissue integrity. This work provides the ground rules for improved impedance‐based biosensors with optimized sensitivity.}, journal={Advanced Healthcare Materials}, author={Koutsouras, Dimitrios A. and Lingstedt, Leona V. and Lieberth, Katharina and Reinholz, Jonas and Mailänder, Volker and Blom, Paul W. M. and Gkoupidenis, Paschalis}, year={2019}, month={Dec} }
 @article{van doremaele_gkoupidenis_van de burgt_2019, title={Towards organic neuromorphic devices for adaptive sensing and novel computing paradigms in bioelectronics}, volume={7}, ISSN={2050-7526 2050-7534}, url={http://dx.doi.org/10.1039/c9tc03247a}, DOI={10.1039/c9tc03247a}, abstractNote={We present an overview of the latest studies on organic neuromorphic and smart sensing devices and highlight the potential of these concepts to enhance the interaction efficiency between electronics and biological substances.}, number={41}, journal={Journal of Materials Chemistry C}, publisher={Royal Society of Chemistry (RSC)}, author={van Doremaele, Eveline R. W. and Gkoupidenis, Paschalis and van de Burgt, Yoeri}, year={2019}, pages={12754–12760} }
 @article{koutsouras_malliaras_gkoupidenis_2018, title={Emulating homeoplasticity phenomena with organic electrochemical devices}, volume={8}, ISSN={2159-6859 2159-6867}, url={http://dx.doi.org/10.1557/mrc.2018.53}, DOI={10.1557/mrc.2018.53}, abstractNote={Biologic neural networks are immersed in common electrolyte environment, and homeoplasticity or global factors of this environment are forcing specific normalization functions that regulate the overall network behavior. In this work, a common electrolyte is used to gate a grid of organic electrochemical devices. The electrolyte functions as a global parameter that controls collectively the device grid. Statistical analysis of the grid and the subsequent definition of global metrics reveal that the grid behaves similarly to a single device. This global control modulates the gain of the device grid, a phenomenon analog to multiplicative scaling in biologic networks. This work demonstrates the potential use of electrolytes as homeostatic media in neuromorphic device architectures.}, number={2}, journal={MRS Communications}, publisher={Springer Science and Business Media LLC}, author={Koutsouras, Dimitrios A. and Malliaras, George G. and Gkoupidenis, Paschalis}, year={2018}, month={Apr}, pages={493–497} }
 @article{rezaei‐mazinani_ivanov_proctor_gkoupidenis_bernard_malliaras_ismailova_2018, title={Monitoring Intrinsic Optical Signals in Brain Tissue with Organic Photodetectors}, volume={3}, ISSN={2365-709X 2365-709X}, url={http://dx.doi.org/10.1002/admt.201700333}, DOI={10.1002/admt.201700333}, abstractNote={AbstractStudies of the living tissue via optical means are able to monitor biological activities such as metabolism, gene expression, and variations in ionic concentration. Organic optoelectronic devices have numerous advantages over traditional inorganic technologies, yet limited examples of their capabilities exist in biomedical applications. An organic photodetector (OPD) with a simple structure acts as a highly sensitive optical sensor for detecting intrinsic optical signals of a living brain tissue. The signals are related to cell volume variations and are essential in detecting biological events, such as metabolism and hypoxia. This work demonstrates for the first time the capability of OPDs to assess biooptical events in neuroscience. Their simple fabrication and the capability for selective absorption of an optical event via tunable chemistry pave the way for their integration in biomedical prostheses with broad applications in bioelectronics.}, number={5}, journal={Advanced Materials Technologies}, publisher={Wiley}, author={Rezaei‐Mazinani, Shahab and Ivanov, Anton I. and Proctor, Christopher M. and Gkoupidenis, Paschalis and Bernard, Christophe and Malliaras, George G. and Ismailova, Esma}, year={2018}, month={Feb} }
 @inproceedings{gkoupidenis_koutsouras_malliaras_2018, title={Neuromorphic devices based on organic mixed conductors}, url={http://dx.doi.org/10.1117/12.2320100}, DOI={10.1117/12.2320100}, abstractNote={Neuromorphic devices and architectures offer novel ways of data manipulation and processing, especially in data intensive applications. At a single device level, various forms of neuroplasticity have been emulated over the past years, mainly with inorganic devices. The implementation of neuroplasticity functions with these devices also enabled applications at a circuit level related to machine learning such as feature or pattern recognition. Although the field of organic-based neuromorphic devices and circuits is still at its infancy, organic materials may offer attractive features for neuromorphic engineering. Over the past years for example, a few simple neuromorphic functions have been demonstrated with biological substances and bioelectronic devices. In this work various neuromorphic devices will be presented that are based on organic mixed conductors, materials that are traditionally used in organic bioelectronics. A prominent example of a device in bioelectronics that exploits mixed conductivity phenomena is the organic electrochemical transistor (OECT). Devices based on OECTs show volatile and tunable dynamics suitable for the emulation of short-term synaptic plasticity functions. Chemical synthesis allows for the introduction of non-volatile phenomena suitable for long-term memory functions. The device operation in common electrolyte permits the definition of spatially distributed multiple inputs at a single device level. The presence of a global electrolyte in an array of devices also allows for the homeostatic or global control of the array. Global electrical oscillations can be used as global clocks that frequency-lock the local activity of individual devices in analogy to the global oscillations in the brain. Finally, “soft” interconnectivity through the electrolyte can be defined, a feature that paves the way for parallel interconnections between devices with minimal hard-wired connections.}, booktitle={Organic and Hybrid Sensors and Bioelectronics XI}, publisher={SPIE}, author={Gkoupidenis, Paschalis and Koutsouras, Dimitrios K. and Malliaras, George G.}, editor={Shinar, Ruth and Kymissis, Ioannis and Torsi, Luisa and List-Kratochvil, Emil J.Editors}, year={2018}, month={Sep} }
 @article{koutsouras_gkoupidenis_stolz_subramanian_malliaras_martin, title={Impedance Spectroscopy of Spin-Cast and Electrochemically Deposited PEDOT:PSS Films on Microfabricated Electrodes with Various Areas}, url={http://dx.doi.org/10.1002/celc.201700297}, DOI={10.1002/celc.201700297}, abstractNote={AbstractWe have examined the electrochemical impedance spectroscopy (EIS) of PEDOT:PSS‐coated gold electrodes in various electrolytes as a function of temporal frequency (from 0.1 to 104 Hz) by using a custom‐designed microfabricated substrate. The electrode areas were systematically varied over a broad range in nominal size from 10×10 μm (100 μm2) to 500×500 μm (2.5×105 μm2). Comparisons were made between spin‐cast PEDOT:PSS crosslinked with GOPS and electrochemically deposited PEDOT:PSS films with similar thicknesses. The impedance spectra of the PEDOT:PSS‐coated electrodes with various sizes could all be reasonably well described by a two‐element equivalent circuit model with a solution resistance Rs and a film capacitance C. These two parameters together define a characteristic temporal frequency fc=1/(2πRsC). By normalizing the impedance with respect to Rs (Zn=|Z|/Rs) and the frequency with respect to fc (fn=f/fc), we found that all of the experimental Bode curves could be collapsed onto a single master plot of Zn vs. fn. In addition, analytical formulas that allow the estimation of the film impedance magnitude |Z| and phase ϕ were derived and experimentally validated. These results are of fundamental interest and are also anticipated to be important for the design, characterization, and optimization of conjugated polymer films for interfacing biomedical devices with living tissue.}, journal={ChemElectroChem}, author={Koutsouras, Dimitrios A. and Gkoupidenis, Paschalis and Stolz, Clemens and Subramanian, Vivek and Malliaras, George G. and Martin, David C.}, pages={n/a-n/a} }
 @article{neuromorphic device architectures with global connectivity through electrolyte gating_2017, url={https://www.nature.com/articles/ncomms15448}, journal={Nature Communications 8,15448}, year={2017} }
 @inproceedings{gkoupidenis_koutsouras_lonjaret_rezaei-mazinani_ismailova_fairfield_malliaras_2017, title={Organic neuromorphic devices based on electrochemical concepts}, url={http://dx.doi.org/10.1117/12.2272693}, DOI={10.1117/12.2272693}, abstractNote={Neuroinspired device architectures offer the potential of higher order functionalities in information processing beyond their traditional microelectronic counterparts. In the actual neural environment, neural processing takes place in a complex and interwoven network of neurons and synapses. In addition, this network is immersed in a common electrochemical environment and global parameters such as ionic concentrations and concentrations of various hormones regulate the overall behaviour of the network. Here, various concepts of organic neuromorphic devices are presented based on organic electrochemical transistors (OECTs). Regarding the implementation of neuromorphic devices, the key properties of the OECT that resemble the neural environment are also presented. These include the operation in liquid electrolyte environment, low power consumption and the ability of formation of massive interconnections through the electrolyte continuum. Showcase examples of neuromorphic functions with OECTs are demonstrated, including short-, long-term plasticity and spatiotemporal or distributed information processing.}, booktitle={Hybrid Memory Devices and Printed Circuits 2017}, publisher={SPIE}, author={Gkoupidenis, Paschalis and Koutsouras, Dimitrios and Lonjaret, Thomas and Rezaei-Mazinani, Shahab and Ismailova, Esma and Fairfield, Jessamyn A. and Malliaras, George G.}, editor={List-Kratochvil, Emil J.Editor}, year={2017}, month={Sep} }
 @article{pedot:pss microelectrode arrays for hippocampal cell culture electrophysiological recordings_2017, url={https://www.cambridge.org/core/journals/mrs-communications/article/pedotpss-microelectrode-arrays-for-hippocampal-cell-culture-electrophysiological-recordings/B69B098DC9629881E5478FD48D07E4DB}, journal={MRS Communications, 7, 2, 259-265}, year={2017} }
 @article{kapetanakis_gkoupidenis_saltas_douvas_dimitrakis_argitis_beltsios_kennou_pandis_kyritsis_et al._2016, title={Direct Current Conductivity of Thin-Film Ionic Conductors from Analysis of Dielectric Spectroscopic Measurements in Time and Frequency Domains}, volume={120}, DOI={10.1021/acs.jpcc.6b06979}, abstractNote={A method is developed for extracting the direct current conductivity (σdc) of ion-conducting materials from frequency- and time-domain dielectric spectroscopy measurements. This method exploits the electrode polarization effects arising from the charging of an ion-blocking capacitor and provides a useful way of obtaining σdc for ionic conductors that do not exhibit a frequency- (time-) independent conductivity plateau; the latter absence of plateau is often encountered in the case of thin-film materials. It allows, by proper design of the test cells, the estimation of σdc independently of the specimen thickness, as demonstrated herein for SiO2 blocking layers and electrolyte systems made of a polyoxometalate (POM) molecule embedded in poly(methyl methacrylate) (PMMA) polymeric matrices. For different postpreparation and measurement conditions, the σdc values obtained for thick (8 μm) POM–PMMA layers are in good agreement not only with the observed conductivity plateaus but also with the values determined ...}, number={38}, journal={The Journal of Physical Chemistry C}, publisher={American Chemical Society (ACS)}, author={Kapetanakis, Eleftherios and Gkoupidenis, Paschalis and Saltas, Vassilios and Douvas, Antonios M. and Dimitrakis, Panagiotis and Argitis, Panagiotis and Beltsios, Konstantinos and Kennou, Stella and Pandis, Christos and Kyritsis, Apostolos and et al.}, year={2016}, month={Sep}, pages={21254–21262} }
 @article{gkoupidenis_koutsouras_lonjaret_fairfield_malliaras_2016, title={Orientation selectivity in a multi-gated organic electrochemical transistor}, volume={6}, DOI={10.1038/srep27007}, abstractNote={AbstractNeuromorphic devices offer promising computational paradigms that transcend the limitations of conventional technologies. A prominent example, inspired by the workings of the brain, is spatiotemporal information processing. Here we demonstrate orientation selectivity, a spatiotemporal processing function of the visual cortex, using a poly(3,4ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) organic electrochemical transistor with multiple gates. Spatially distributed inputs on a gate electrode array are found to correlate with the output of the transistor, leading to the ability to discriminate between different stimuli orientations. The demonstration of spatiotemporal processing in an organic electronic device paves the way for neuromorphic devices with new form factors and a facile interface with biology.}, journal={Scientific Reports}, publisher={Springer Nature}, author={Gkoupidenis, Paschalis and Koutsouras, Dimitrios A. and Lonjaret, Thomas and Fairfield, Jessamyn A. and Malliaras, George G.}, year={2016}, month={Jun}, pages={27007} }
 @article{gkoupidenis_rezaei-mazinani_proctor_ismailova_malliaras_2016, title={Orientation selectivity with organic photodetectors and an organic electrochemical transistor}, volume={6}, DOI={10.1063/1.4967947}, abstractNote={Neuroinspired device architectures offer the potential of higher order functionalities in information processing beyond their traditional microelectronic counterparts. Here we demonstrate a neuromorphic function of orientation selectivity, which is inspired from the visual system, with a combination of organic photodetectors and a multi-gated organic electrochemical transistor based on poly(3,4ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS). The device platform responds preferably to different orientations of light bars, a behaviour that resembles orientation selectivity of visual cortex cells. These results pave the way for organic-based neuromorphic devices with spatially correlated functionalities and potential applications in the area of organic bioelectronics.}, number={11}, journal={AIP Advances}, publisher={AIP Publishing}, author={Gkoupidenis, Paschalis and Rezaei-Mazinani, Shahab and Proctor, Christopher M. and Ismailova, Esma and Malliaras, George G.}, year={2016}, month={Nov}, pages={111307} }
 @article{gkoupidenis_schaefer_garlan_malliaras_2015, title={Neuromorphic Functions in PEDOT:PSS Organic Electrochemical Transistors}, volume={27}, DOI={10.1002/adma.201503674}, abstractNote={UNLABELLED
Depressive short-term synaptic plasticity functions are implemented with a simple polymer poly(3,4ethylenedioxythiophene):poly(styrene sulfonate) (


PEDOT
PSS) organic electrochemical transistor device. These functions are a first step toward the realization of organic-based neuroinspired platforms with spatiotemporal information processing capabilities.}, number={44}, journal={Advanced Materials}, publisher={Wiley-Blackwell}, author={Gkoupidenis, Paschalis and Schaefer, Nathan and Garlan, Benjamin and Malliaras, George G.}, year={2015}, month={Oct}, pages={7176–7180} }
 @article{gkoupidenis_schaefer_strakosas_fairfield_malliaras_2015, title={Synaptic plasticity functions in an organic electrochemical transistor}, url={https://doi.org/10.1063/1.4938553}, DOI={10.1063/1.4938553}, abstractNote={Synaptic plasticity functions play a crucial role in the transmission of neural signals in the brain. Short-term plasticity is required for the transmission, encoding, and filtering of the neural signal, whereas long-term plasticity establishes more permanent changes in neural microcircuitry and thus underlies memory and learning. The realization of bioinspired circuits that can actually mimic signal processing in the brain demands the reproduction of both short- and long-term aspects of synaptic plasticity in a single device. Here, we demonstrate the implementation of neuromorphic functions similar to biological memory, such as short- to long-term memory transition, in non-volatile organic electrochemical transistors (OECTs). Depending on the training of the OECT, the device displays either short- or long-term plasticity, therefore, exhibiting non von Neumann characteristics with merged processing and storing functionalities. These results are a first step towards the implementation of organic-based neuromorphic circuits.}, journal={Applied Physics Letters}, author={Gkoupidenis, Paschalis and Schaefer, Nathan and Strakosas, Xenofon and Fairfield, Jessamyn A. and Malliaras, George G.}, year={2015}, month={Dec} }