Pub Date : 2026-01-14DOI: 10.1109/JFLEX.2025.3648215
Paul R. Berger
{"title":"Editorial to the First Issue of the Fifth Year of IEEE Journal on Flexible Electronics","authors":"Paul R. Berger","doi":"10.1109/JFLEX.2025.3648215","DOIUrl":"https://doi.org/10.1109/JFLEX.2025.3648215","url":null,"abstract":"","PeriodicalId":100623,"journal":{"name":"IEEE Journal on Flexible Electronics","volume":"5 1","pages":"2-2"},"PeriodicalIF":0.0,"publicationDate":"2026-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11353355","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145963438","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This work reports the fabrication and electrical characterization of fully inkjet-printed Ag/PEDOT:PSS/zinc oxide (ZnO) heterojunction devices on flexible polyimide (Kapton) substrates. All functional layers, including the bottom Ag electrode, p-type PEDOT:PSS, and n-type ZnO, are deposited exclusively by inkjet printing, enabling a scalable and low-temperature additive process compatible with large-area flexible electronics. While PEDOT:PSS/ZnO heterostructures have been widely studied for optoelectronic and diode applications, they are typically realized using partially printed or vacuum-processed layers and are not optimized for memristive operation. Here, we demonstrate that fully printed PEDOT:PSS/ZnO heterojunctions exhibit pronounced rectifying current–voltage ($I$ –$V$ ) characteristics, a clear threshold for switching, and a stable hysteretic response indicative of memristive behavior. The device response stabilizes after an initial forming cycle and maintains reproducible high and low resistance state (LRS) over repeated voltage sweeps. Furthermore, under voltage pulse sequences, the heterojunction shows short-term potentiation and depression, with the conductance depending on the history of applied pulses, mimicking synaptic plasticity. These results highlight fully inkjet-printed PEDOT:PSS/ZnO heterojunctions on flexible substrates as promising candidates for low-cost, large-area artificial synapses and printed neuromorphic circuits.
{"title":"A Fully Printed Heterojunction Based on PEDOT:PSS and ZnO With Memristive Behavior","authors":"Apostolos Apostolakis;Dimitris Barmpakos;Grigoris Kaltsas","doi":"10.1109/JFLEX.2025.3648966","DOIUrl":"https://doi.org/10.1109/JFLEX.2025.3648966","url":null,"abstract":"This work reports the fabrication and electrical characterization of fully inkjet-printed Ag/PEDOT:PSS/zinc oxide (ZnO) heterojunction devices on flexible polyimide (Kapton) substrates. All functional layers, including the bottom Ag electrode, p-type PEDOT:PSS, and n-type ZnO, are deposited exclusively by inkjet printing, enabling a scalable and low-temperature additive process compatible with large-area flexible electronics. While PEDOT:PSS/ZnO heterostructures have been widely studied for optoelectronic and diode applications, they are typically realized using partially printed or vacuum-processed layers and are not optimized for memristive operation. Here, we demonstrate that fully printed PEDOT:PSS/ZnO heterojunctions exhibit pronounced rectifying current–voltage (<inline-formula> <tex-math>$I$ </tex-math></inline-formula>–<inline-formula> <tex-math>$V$ </tex-math></inline-formula>) characteristics, a clear threshold for switching, and a stable hysteretic response indicative of memristive behavior. The device response stabilizes after an initial forming cycle and maintains reproducible high and low resistance state (LRS) over repeated voltage sweeps. Furthermore, under voltage pulse sequences, the heterojunction shows short-term potentiation and depression, with the conductance depending on the history of applied pulses, mimicking synaptic plasticity. These results highlight fully inkjet-printed PEDOT:PSS/ZnO heterojunctions on flexible substrates as promising candidates for low-cost, large-area artificial synapses and printed neuromorphic circuits.","PeriodicalId":100623,"journal":{"name":"IEEE Journal on Flexible Electronics","volume":"5 2","pages":"56-63"},"PeriodicalIF":0.0,"publicationDate":"2025-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146122775","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-15DOI: 10.1109/JFLEX.2025.3644809
G. Samuelraj Chrysolite;S. Dhanu Shree;J. Sheril Sharo Christa;G. Venika;Angeline Mathew;Manickam
The high prevalence of problems related to lordosis/kyphosis among weightlifters, athletes, wrestlers, and IT professionals highlights the need for effective posture monitoring solutions. Common sensors used for posture monitoring include accelerometers, gyroscopes, magnetometers, inertial sensors, tilt sensors, flexible pressure sensors, and flexible strain sensors. Due to constraints such as sensitivity to environmental factors, power consumption, patient comfort, and bulkiness, a flexible adhesive capacitance-based superstrate infused complementary split ring resonator (CSRR)-based antenna sensor, which uses both the antenna’s electromagnetic field and sensor’s transducing property, is proposed. The proposed printed antenna sensor is polyimide based with compact dimensions of $35times 36times 0.13$ mm3. Fractal structures are incorporated for better coverage of the posture changes in the spine region with multidirectional antenna pattern avoiding the usage of antenna array structures. Capacitive sensing is preferred to monitor physical structure changes as it is insensitive to environmental factors. When the person’s posture at kyphosis/lordosis changes beyond normal angular limits (Kyphosis-20° to 45°-Outward/Lordosis-20° to 40°-Inward), the resonant frequency of the antenna sensor changes and thereby translated as abnormal curvatures of the spine region (thoracic/lumbar). In heterogeneous medium, particle swarm optimization (PSO) is applied to the initial antenna sensor design in simulation using fractal structures, yielding performance characteristics, which has a good reflection coefficient of −14.48 dB with good impedance matching of $53~Omega $ and a directional gain of 1.3 dBi at the resonant frequency of 6.66 GHz for lordosis (inward curvature of above 45° between L3 and L4) and reflection coefficient of −17.16 dB with good impedance matching of $47~Omega $ and a directional gain of 0.33 dBi at the resonant frequency of 6.74 GHz for kyphosis (outward curvature of above 40° between T7 and T8). The proposed antenna sensor is also validated in real-time environment using a vector network analyzer (VNA) for performance characteristics measurement on few human subjects. This proposed wearable antenna sensor offers a non-invasive and efficient approach to real-time posture monitoring, contributing to spinal health improvement for individuals prone to problems related to lordosis/kyphosis, thereby enhancing the ergonomic aspects in healthcare.
{"title":"Fractal-Based Flexible Capacitive Antenna Sensor for Non-Invasive Spinal Kyphosis/Lordosis Assessment","authors":"G. Samuelraj Chrysolite;S. Dhanu Shree;J. Sheril Sharo Christa;G. Venika;Angeline Mathew;Manickam","doi":"10.1109/JFLEX.2025.3644809","DOIUrl":"https://doi.org/10.1109/JFLEX.2025.3644809","url":null,"abstract":"The high prevalence of problems related to lordosis/kyphosis among weightlifters, athletes, wrestlers, and IT professionals highlights the need for effective posture monitoring solutions. Common sensors used for posture monitoring include accelerometers, gyroscopes, magnetometers, inertial sensors, tilt sensors, flexible pressure sensors, and flexible strain sensors. Due to constraints such as sensitivity to environmental factors, power consumption, patient comfort, and bulkiness, a flexible adhesive capacitance-based superstrate infused complementary split ring resonator (CSRR)-based antenna sensor, which uses both the antenna’s electromagnetic field and sensor’s transducing property, is proposed. The proposed printed antenna sensor is polyimide based with compact dimensions of <inline-formula> <tex-math>$35times 36times 0.13$ </tex-math></inline-formula> mm<sup>3</sup>. Fractal structures are incorporated for better coverage of the posture changes in the spine region with multidirectional antenna pattern avoiding the usage of antenna array structures. Capacitive sensing is preferred to monitor physical structure changes as it is insensitive to environmental factors. When the person’s posture at kyphosis/lordosis changes beyond normal angular limits (Kyphosis-20° to 45°-Outward/Lordosis-20° to 40°-Inward), the resonant frequency of the antenna sensor changes and thereby translated as abnormal curvatures of the spine region (thoracic/lumbar). In heterogeneous medium, particle swarm optimization (PSO) is applied to the initial antenna sensor design in simulation using fractal structures, yielding performance characteristics, which has a good reflection coefficient of −14.48 dB with good impedance matching of <inline-formula> <tex-math>$53~Omega $ </tex-math></inline-formula> and a directional gain of 1.3 dBi at the resonant frequency of 6.66 GHz for lordosis (inward curvature of above 45° between L3 and L4) and reflection coefficient of −17.16 dB with good impedance matching of <inline-formula> <tex-math>$47~Omega $ </tex-math></inline-formula> and a directional gain of 0.33 dBi at the resonant frequency of 6.74 GHz for kyphosis (outward curvature of above 40° between T7 and T8). The proposed antenna sensor is also validated in real-time environment using a vector network analyzer (VNA) for performance characteristics measurement on few human subjects. This proposed wearable antenna sensor offers a non-invasive and efficient approach to real-time posture monitoring, contributing to spinal health improvement for individuals prone to problems related to lordosis/kyphosis, thereby enhancing the ergonomic aspects in healthcare.","PeriodicalId":100623,"journal":{"name":"IEEE Journal on Flexible Electronics","volume":"5 2","pages":"46-55"},"PeriodicalIF":0.0,"publicationDate":"2025-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146122779","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-28DOI: 10.1109/JFLEX.2025.3638974
Sparsh Kapar;Shubham Ranjan;Czang-Ho Lee;William S. Wong;Manoj Sachdev
Thin-film transistors (TFTs) have garnered recent research interest in the development of flexible displays, due to their low fabrication costs and high-volume production. In displays, driver circuits are typically implemented with off-panel CMOS logic, while the display pixels themselves use TFTs. This approach restricts the resolution enhancement of displays and causes significant power dissipation. Additionally, implementing CMOS-like logic with unipolar TFTs requires careful attention to power and voltage swing. The latest bootstrapped inverter technology has addressed some of these issues, demonstrating the use of unipolar TFTs in row-driver display circuits. In this article, we propose a row address decoder circuit for TFT-based displays that reduces dynamic power consumption through charge sharing on glass and flexible substrates. The impact of bending and substrate material was also investigated. Measurement results show that the proposed design-based 3-to-8 decoder under various conditions saves on average 26.0% of the power compared to a state-of-the-art TFT-based decoder.
{"title":"A Flexible Decoder With Charge-Sharing Feature for TFT Display Backplanes","authors":"Sparsh Kapar;Shubham Ranjan;Czang-Ho Lee;William S. Wong;Manoj Sachdev","doi":"10.1109/JFLEX.2025.3638974","DOIUrl":"https://doi.org/10.1109/JFLEX.2025.3638974","url":null,"abstract":"Thin-film transistors (TFTs) have garnered recent research interest in the development of flexible displays, due to their low fabrication costs and high-volume production. In displays, driver circuits are typically implemented with off-panel CMOS logic, while the display pixels themselves use TFTs. This approach restricts the resolution enhancement of displays and causes significant power dissipation. Additionally, implementing CMOS-like logic with unipolar TFTs requires careful attention to power and voltage swing. The latest bootstrapped inverter technology has addressed some of these issues, demonstrating the use of unipolar TFTs in row-driver display circuits. In this article, we propose a row address decoder circuit for TFT-based displays that reduces dynamic power consumption through charge sharing on glass and flexible substrates. The impact of bending and substrate material was also investigated. Measurement results show that the proposed design-based 3-to-8 decoder under various conditions saves on average 26.0% of the power compared to a state-of-the-art TFT-based decoder.","PeriodicalId":100623,"journal":{"name":"IEEE Journal on Flexible Electronics","volume":"5 2","pages":"37-45"},"PeriodicalIF":0.0,"publicationDate":"2025-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146122778","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-14DOI: 10.1109/JFLEX.2025.3633230
Lingala Prasanthi;M. Durga Prakash
Flexible and wearable electronics demand transistor technologies that can sustain stable performance under extreme mechanical deformation. In this work, we propose a quantitative benchmarking framework for strain resilience in organic thin-film transistors (OTFTs), introducing three normalized metrics: degradation factor (DF), quantifying drain-current loss under strain; the mobility factor (MF), representing the rate of charge-transport degradation per unit strain; and the strain-stability window (SSW), defining the maximum strain range within which devices remain in the safe operating zone (DF < 15%). Using Silvaco Victory TCAD, we systematically investigate the strain-dependent behavior of single-dielectric (Al2O3) and hybrid-dielectric (Al2O3/PVP) OTFTs under both compressive (concave) and tensile (convex) bending with radii from 8 to 1 $mu $ m. Results show that hybrid-dielectric OTFTs exhibit superior strain tolerance, with a DF of only 9% under 9.85% tensile strain, compared with 25% for single-dielectric devices. Furthermore, hybrid devices show a markedly lower MF (−3%/strain compressive and −1.9%/strain tensile) compared with single-dielectric OTFTs (−6%/strain compressive and −5%/strain tensile). Beyond confirming the mechanical advantages of hybrid dielectrics, our study demonstrates that strain-stability quantifiers provide a universal method to benchmark flexible OTFT reliability, bridging device physics with practical requirements of wearable bioelectronics. These findings establish hybrid Al2O3/PVP dielectrics not only as performance enhancers but also as reliable design enablers for next-generation strain-resilient organic electronics.
{"title":"Design and Analysis of Enhanced Strain Tolerance in Organic Thin-Film Transistors With Hybrid Al2O3/PVP Dielectrics for Flexible Electronics","authors":"Lingala Prasanthi;M. Durga Prakash","doi":"10.1109/JFLEX.2025.3633230","DOIUrl":"https://doi.org/10.1109/JFLEX.2025.3633230","url":null,"abstract":"Flexible and wearable electronics demand transistor technologies that can sustain stable performance under extreme mechanical deformation. In this work, we propose a quantitative benchmarking framework for strain resilience in organic thin-film transistors (OTFTs), introducing three normalized metrics: degradation factor (DF), quantifying drain-current loss under strain; the mobility factor (MF), representing the rate of charge-transport degradation per unit strain; and the strain-stability window (SSW), defining the maximum strain range within which devices remain in the safe operating zone (DF < 15%). Using Silvaco Victory TCAD, we systematically investigate the strain-dependent behavior of single-dielectric (Al<sub>2</sub>O<sub>3</sub>) and hybrid-dielectric (Al<sub>2</sub>O<sub>3</sub>/PVP) OTFTs under both compressive (concave) and tensile (convex) bending with radii from 8 to 1 <inline-formula> <tex-math>$mu $ </tex-math></inline-formula>m. Results show that hybrid-dielectric OTFTs exhibit superior strain tolerance, with a DF of only 9% under 9.85% tensile strain, compared with 25% for single-dielectric devices. Furthermore, hybrid devices show a markedly lower MF (−3%/strain compressive and −1.9%/strain tensile) compared with single-dielectric OTFTs (−6%/strain compressive and −5%/strain tensile). Beyond confirming the mechanical advantages of hybrid dielectrics, our study demonstrates that strain-stability quantifiers provide a universal method to benchmark flexible OTFT reliability, bridging device physics with practical requirements of wearable bioelectronics. These findings establish hybrid Al<sub>2</sub>O<sub>3</sub>/PVP dielectrics not only as performance enhancers but also as reliable design enablers for next-generation strain-resilient organic electronics.","PeriodicalId":100623,"journal":{"name":"IEEE Journal on Flexible Electronics","volume":"5 1","pages":"26-35"},"PeriodicalIF":0.0,"publicationDate":"2025-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145963439","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Metasurfaces enable subwavelength electromagnetic control with transformative wavefront engineering potential. We demonstrate a scalable, cost-effective fabrication route for high-performance metasurface collimators by printing silver nanostructures onto paper using silver halide photochemistry, eliminating complex inks and post-processing whilst enabling roll-to-roll compatibility. A two-layer uniform periodic array excited by a single-patch antenna achieves 6.87 dB simulated gain improvement at 4 GHz. Experimentally, we observe 6.1-dB gain enhancement with 2.56-mg/cm${}^{mathrm {^{2}}}$ silver loading, precisely controlled through print iterations and quantified via inductively coupled plasma optical emission spectroscopy (ICP-OES). The printed structures exhibit 40-$mu $ m dimensional accuracy ($!lt !lambda $ /100 at 4 GHz) with uniform square elements yielding maximal collimator efficiency. The paper-based metasurface antenna displays high gain with exceptional polarization purity and can be considered for demanding applications, such as satellite, radar, and advanced wireless systems.
{"title":"Desktop Inkjet Printing of Foldable Metasurface Antenna on Paper Substrates","authors":"Rupesh Pawar;Soumya Chakravarty;Tapas Chakravarty;Venugopal Santhanam","doi":"10.1109/JFLEX.2025.3630107","DOIUrl":"https://doi.org/10.1109/JFLEX.2025.3630107","url":null,"abstract":"Metasurfaces enable subwavelength electromagnetic control with transformative wavefront engineering potential. We demonstrate a scalable, cost-effective fabrication route for high-performance metasurface collimators by printing silver nanostructures onto paper using silver halide photochemistry, eliminating complex inks and post-processing whilst enabling roll-to-roll compatibility. A two-layer uniform periodic array excited by a single-patch antenna achieves 6.87 dB simulated gain improvement at 4 GHz. Experimentally, we observe 6.1-dB gain enhancement with 2.56-mg/cm<inline-formula> <tex-math>${}^{mathrm {^{2}}}$ </tex-math></inline-formula> silver loading, precisely controlled through print iterations and quantified via inductively coupled plasma optical emission spectroscopy (ICP-OES). The printed structures exhibit 40-<inline-formula> <tex-math>$mu $ </tex-math></inline-formula>m dimensional accuracy (<inline-formula> <tex-math>$!lt !lambda $ </tex-math></inline-formula>/100 at 4 GHz) with uniform square elements yielding maximal collimator efficiency. The paper-based metasurface antenna displays high gain with exceptional polarization purity and can be considered for demanding applications, such as satellite, radar, and advanced wireless systems.","PeriodicalId":100623,"journal":{"name":"IEEE Journal on Flexible Electronics","volume":"5 1","pages":"14-25"},"PeriodicalIF":0.0,"publicationDate":"2025-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145963437","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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