IEEE Journal on Flexible Electronics - J-FLEX

11/06/2025

The latest issue of J-FLEX (Volume 4, Issue 11) was released yesterday!

Saurabh B. Mishra et al. address flexible capacitive pressure sensors, which have simple sensing structure, zero-temperature drift, linear response, and high sensitivity, leading to applications in human healthcare, including soft and surgical robotics, human–machine interaction (HMI), and wearable devices. In this article, we present a highly compressible multilayer flexible capacitive pressure sensor based on air/vapor bubble-induced polydimethylsiloxane (PDMS) foam thin film as dielectric and polypyrrole (Ppy)-coated cotton textile as electrodes. We showcase two applications of our sensor, including mouse click and grasping of a cup. The sensor can be fabricated in different shapes and sizes for various applications of free-form electronics such as soft and surgical robotics, wearable, biomedical, and human–machine interaction.

Tien Nguyen et al. examine hypertension, which is a leading contributor to cardiovascular disease (CVD), stroke, and chronic kidney disease worldwide. However, current blood pressure (BP) monitoring techniques, whether auscultatory, oscillometric, or invasive, are constrained by episodic measurement, user variability, and limited feasibility for real-world, continuous monitoring. This article presents a noninvasive device based on dual-site photoplethysmography (PPG) signals, with calculated pulse wave velocity (PWV), that combines off-the-shelf sensors with an infrared-based dual-PPG sensor.

S. Chinmay et al. introduce methods for fabricating patterned, large-area, detachable alloy electrodes. The techniques harness droplet impact deposition and a postprocessing strategy to realize flexible micrometer-thick alloy electrode films of area ranging from a few square millimeters to several square centimeters. Further, we demonstrate free-standing reusable electrode films with simply connected and complex geometries that are relevant for wide variety of applications in electronics.

About the Cover: The cover highlights a dual-site wearable that simultaneously captures photoplethysmography signals from the finger and toe, comparing their temporal variations to track pulse wave velocity and predict blood pressure in real time. By combining simple optics with machine learning, this cuff-free system points to the future of continuous, everyday cardiovascular monitoring. Cover image created using ChatGPT by Satvik Kolla and Yihan Liu.

https://ieee-jflex.org/

J-FLEX is a joint publication of IEEE Sensors Council (SC), IEEE Electron Devices Society (EDS), and IEEE Circuits and Systems Society (CASS).

10/31/2025

Happy Halloween 🎃

10/28/2025

The latest issue of J-FLEX (Volume 4, Issue 10) was released today!

With the importance of contact resistance in organic field-effect transistors (OFETs), Fiheon Imroze et al. present the thickness of the source–drain (SD) electrode serves a pivotal role in determining the contact resistance in solution-processed bottom-gate bottom-contact (BGBC) OFETs. This study explores the impact of morphological disorder at the metal–semiconductor (M–S) interface, arising due to the thickness of SD electrodes on contact resistance, particularly in solution-processed BGBC OFETs. A 20-fold reduction in contact resistance and a twofold increase in mobility are observed in devices with a 20-nm SD electrode compared to those with an 80-nm SD electrode. TCAD simulations incorporating mobility modeling in disordered channel regions provide insights into the underlying physics governing contact resistance variations.

Mayana Yousuf Ali Khan et al. presents a novel compact xnor gate, which is fabricated using unipolar single-gate n-type oxide thin-film transistors (TFTs) at low temperatures ( ≤ 150 °C). The proposed two-input xnor gate utilizes only two driving transistors and an active load (a diode-connected transistor), significantly reducing power consumption, design complexity, and active area. In contrast, implementing a conventional two-input xnor gate with unipolar transistor technology typically requires four two-input nor gates, which need at least 12 transistors. These findings highlight that the xnor gate achieves its functionality with almost one-fourth of the circuit complexity compared to a traditional design without compromising other performance metrics, such as speed and power consumption.

Bhawna Tiwari et al. present an electrocardiogram (ECG) monitoring system with charge redistribution noise-shaping successive approximation register analog to digital converter (CR-NS SAR ADC). The proposed system has successfully demonstrated an ECG reconstruction while preserving crucial parameters such as PR, QT, ST, QRS, RR interval, and heart rate, which are essential for analyzing ECG data. The ADC is designed using single-gate indium-gallium-zinc-oxide thin-film transistor (IGZO TFT) technology only with n-type TFTs and fabricated on a 30- μm-thick polyimide substrate. Further, this work has addressed circuit design challenges that arise due to only n-type transistor-based implementation. From measurements, this circuit shows a Walden figure-of-merit (FoMW) of 13.8 nJ/c.s, Schreier FoM ( FoMS ) of 98.298 dB, SNR of 39.23 dB, and ENOB of 6 bits. The proposed ADC operates up to a sampling frequency of 2.08 kHz with a power consumption of 1.85 mW at a supply voltage (VDD) of 4 V. This design is well suited for biomedical wearable devices because of its low-power operation and compatibility with flexible substrates.

About the Cover: The cover image highlights a flexible electrocardiogram (ECG) monitoring system realized with a charge-redistribution noise-shaping SAR ADC, fabricated entirely using n-type IGZO thin-film transistors on a flexible polyimide substrate. The design employs an energy-efficient merged capacitor switching scheme together with a first-order passive noise-shaping technique. This implementation achieves better performance with low power consumption, demonstrating its suitability for wearable biomedical applications. The work highlights the potential of flexible electronics for next-generation healthcare systems.

https://ieee-jflex.org/

J-FLEX is a joint publication of IEEE Sensors Council (SC), IEEE Electron Devices Society (EDS), and IEEE Circuits and Systems Society (CASS).

10/16/2025

The latest issue of J-FLEX (Volume 4, Issue 9) was released today!

Alexander M. Watson et al. present a stretchable RF transmission line based on a polymerized liquid metal network (Poly-LMN) patterned onto a stretchable dielectric substrate. The Poly-LMN material has metallic conductivity and notably exhibits a high degree of strain insensitivity that is uniquely well-suited to the requirements of stretchable RF devices. The fabrication and characterization of coplanar waveguide (CPW) transmission lines are presented. The Poly-LMN material maintains consistent transmission and reflection RF performance, whereas other stretchable conductors exhibit increased loss while subjecting devices to strains up to 100%. Additional characterization demonstrates the robustness of the chosen material set when subjected to 1000 cycles of strain and to extreme strains of 300%. Several applications, including highly stretchable and self-healing coaxial cables and a peel-and-stick double-stub impedance matching system are presented.

Alireza Golgouneh and Lucy E. Dunne (see cover) present the development and evaluation of a low-profile, textile-based, and biocompatible flexible sensor matrix composed of 72 sensing cells (6 × 12 configurations) with a spatial fine resolution of 1 cm2, designed for wearable applications requiring precise onbody force measurement. The goal of this article is to improve force-estimation accuracy for applications such as medical monitoring, rehabilitation, and human-computer interaction. This
study contributes a fully soft e-textile matrix together with a matching data-driven modeling framework.

Puneet Sharma et al. present This work presents a simple fabrication method for detecting human wrist pulse and respiration rate using a flexible resistive strain sensor. Two types of flexible strain sensors were fabricated; one based on polydimethylsiloxane (PDMS)- coated multiwall carbon nanotubes (MWCNTs) and the other MWCNTs/graphene nanoplatelets (GNPs) composite on a PDMS substrate. Both sensors exhibited high sensitivity, with gauge factors (GFs) of 35.37 for MWCNT-based sensors and 49.53 for MWCNTs/GNP-based sensors, and excellent stretchability, with detectable strain ranges of up to 236% and 164%, respectively. The fabricated sensors demonstrated high performance and applicability, making them suitable for use in wearable health monitoring devices.

About the Cover: The cover image illustrates a soft, textile-based force sensing matrix engineered to address the longstanding challenge of accurate on-body force estimation on curved and compliant surfaces. Conventional flexible sensors often mis-estimate forces when conformed to body geometries due to deformation and hysteresis. By integrating a biocompatible e-textile matrix with advanced data-driven modeling, including recurrent neural networks, this work achieves precise and robust force sensing under realistic body conditions, with applications spanning healthcare, rehabilitation, and wearable robotics. Cover image created by Alireza Golgouneh and Lucy E. Dunne.

https://ieee-jflex.org/

J-FLEX is a joint publication of IEEE Sensors Council (SC), IEEE Electron Devices Society (EDS), and IEEE Circuits and Systems Society (CASS).

08/28/2025

The latest issue of J-FLEX (Volume 4, Issue 7) was released yesterday!

A.M. Sonagara et al. proposes an MIMO antenna for the first time that satisfies all the requirements for the RSN applications, such as a flexible and an ultrathin profile, a very low volume, and an endfire beam with a downward tilt to cover all UEs present below the deployed radio stripes. A spoof surface plasmon polariton (SSPP)-based structure is used over a flexible substrate to achieve a flexible and ultrathin MIMO antenna. The MIMO antenna has a maximum gain of 7.4 dBi with an impedance bandwidth of 42.2%, isolation up to 26.7 dB, and envelope correlation coefficient (ECC) below 0.19. Besides its ultrathin flexible profile and extremely low volume, the proposed MIMO antenna has a tilted beam and wideband operation, making it an excellent choice for beyond fifth-generation (5G) RSN applications.

R. Al-Haidari et. al. investigate the use of magnetically aligned anisotropic conductive epoxy (MA-ACE) as a versatile interconnection technology for flexible and stretchable electronics is explored. The MA-ACE leverages magnetically induced self-assembly of vertically conductive columns within a polymer matrix. Additionally, it offers low curing temperatures and pressure-less assembly while providing strong adhesion to a wide range of materials. The results showed that the MA-ACE exhibited a high yield of 86%–100%, strong adhesion to all surfaces, low contact resistance (~50–150 m Ω per connection), and high x–y isolation ( >10^11 Ω ).

Yi Zhou et al. present a proof-of-concept inkjet-printed microstrip line on a 3-D-printed polypropylene (PP) substrate designed and fabricated, with metallization thicknesses of three, six, and nine layers. Cyclic mandrel bending tests up to 12500 cycles are conducted and results show that six-layer samples offer the best balance between electrical performance and mechanical reliability for 5G and mm-wave applications.

About the Cover: The cover image introduces magnetically aligned anisotropic conductive particles in epoxy for interconnecting mechanically different components in flexible and stretchable electronics. A 3-D micro X-ray tomography image illustrates the ferromagnetic conductive particles aligned along the z-axis, forming vertical conductive pathways. This alignment bridges ultra-soft polymerized liquid metal with a stretchable E-textile.

https://ieee-jflex.org/

J-FLEX is a joint publication of IEEE Sensors Council (SC), IEEE Electron Devices Society (EDS), and IEEE Circuits and Systems Society (CASS):

07/30/2025

The latest issue of J-FLEX (Volume 4, Issue 6) was released today!

S. Siddique et al. employ coaxially electrospun hollow nanofibers characterized by a high surface-to-volume ratio, enhanced air gaps, and densely packed microstructure-nanostructure to fabricate a highly sensitive capacitive pressure sensor. Systematic characterization across varying pressure ranges revealed that the sensor achieved superior sensitivity in the low-pressure range (0.2–2 kPa), outperforming sensors fabricated using traditional electrospun nanofiber dielectric layers.

L. Purnal et. al. investigate the impact of the changing device parameters due to applied strain on the generated Joule heat and resulting temperature change. A fully automated spray-coating-based stencil-printing method of Galinstan is used to achieve reproducible and reliable devices. Results show the combined effects of when stretching. Finally, using custom cyclic stretch testers, we report the robustness of stretchable devices surviving at least 400000 cycles at 25% strain. Several prototypes of wearable devices, smart patches, and sensors are presented.

A. Scholz et al. present a secure hybrid system, which contains a custom-designed, thinned application-specific integrated circuit (ASIC) in foil, as well as two printed temperature sensing elements that are seamlessly embedded in an industrial process fabricated automotive coolant hose and an inkjet-printed unique identifier in the form of a physically unclonable function (PUF) to derive the system’s authenticity. We show the obtained temperature response and the unique identification by generating the challenge-response pairs (CRPs) of the PUF over 1000 repetitions. The security circuit shows only 0.0084% of flipped bits at T=25 ∘ C, which makes it well-suited to be used as PUF.

About the Cover: Liquid metal-based stretchable electronics offer high performance and conformability, specifically in the field of on-skin electronics, as soft sensors and actuators. These devices consist of liquid metal conductors encapsulated in an elastomeric material. Most recent production techniques allow for integration of rigid electronic components as well as reliable interconnections using specially designed flexible circuits. With regard to wearer comfort, the joule heating of such devices can be predicted and thus managed using modeling and design adaptation.

https://ieee-jflex.org/

J-FLEX is a joint publication of IEEE Sensors Council (SC), IEEE Electron Devices Society (EDS), and IEEE Circuits and Systems Society (CASS):

07/10/2025

In this historical age in which electronics and human life go along side-by-side toward a digital transformation of our society and know-how, a rising concern related to the environmental impact of the electronics industry is dramatically posed to our society. The extensive usage of rare-Earth elements or hardly accessible materials in key and rapidly expanding sectors (i.e., renewable energy, electric vehicles, and robotics) represents a key issue. The environmental costs and carbon footprint related to chips and systems manufacturing, relying on water, gas, and energy consumption, as well as energy demanding fabrication protocols, are constantly growing since the last decades. In addition, once our electronic device reaches their end-of-life, another key aspect is represented by the surge of waste—often referred as e-waste—generated in our countries, which are rarely recycled or properly collected.

In response to this technological framework, the scientific community is largely investing time, resources, and effort to find and establish innovative materials, methods, and strategies to bridge the gap between the required functionalities of any electronic system (reliability, durability, and so on) and its environmental footprint. This leads to the scope of this Special Issue (SI), aiming at works on a wide plethora of topics regarding sustainable and environmentally-friendly electronics: from functional and sustainable materials, to fabrication strategies, electronic devices, and applications. The widespread of these results can result in multidisciplinary applications, ranging from edible electronics, to health monitoring, robotics, and the Internet of Things (IoTs).

This SI in IEEE Journal on Flexible Electronics (J-FLEX) contains a collection of six articles.

A special thanks to our guest editors, Giuseppe Cantarella (lead), Sara Carniello, Clara Santato and Prakash Tiwari.

About the Cover: The graphical cover page underscores a commitment to guiding the evolution of the electronics industry while simultaneously promoting environmental sustainability. It emphasizes a nature to-nature approach as the primary challenge for the future—a strategy in which the raw materials and elements used in sensors, transistors, and circuits can be reintegrated into the ecosystem, achieving a net-zero environmental footprint across every stage of an electronic device’s lifecycle. The cover art was conceptualized and designed by Enrique Sahagún from Scixel.

https://ieee-jflex.org/

J-FLEX is a joint publication of IEEE Sensors Council (SC), IEEE Electron Devices Society (EDS), and IEEE Circuits and Systems Society (CASS):

06/23/2025

The latest issue of J-FLEX (Volume 4, Issue 4) was released last week!

H. Lei et al. present flexible antennas additively manufactured via screen printing of copper conductive inks. Antennas, such as straight dipoles, meandering dipoles, and circular disk monopoles, are designed for operation at 24 GHz and then manufactured on a variety of flexible substrates. A resolution of 50 μm width and spacing was obtained at a printing speed of 10000 mm2/s. A minimum bend radius of 6.25 mm was achieved for the flexible antennas. Measurement and simulation were in agreement. This is the first report of a flexible screen-printed 24-GHz antenna on ceramics with copper metallization.

Nerraj and Navneet Gupta show the investigations on optimal dielectric material for self-powered flexible pressure sensors (SPFPSs) based on triboelectric nanogenerators (TENGs) using multiple criteria decision-making (MCDM) methods, specifically TOPSIS and VIKOR. Several materials attributes, such as surface charge density, coefficient of friction, and dielectric constant, are examined to find out the best dielectric material. Determined polydimethylsiloxane (PDMS) is the most suitable dielectric material for TENG-based SPFPSs.

R. Aigner et al. present a fully textile capacitive touch sensor that provides an additional electrode for implementing driven (or active) shielding, which can considerably improve signal-to-noise ratio (SNR) and guard from parasitic capacitance. Using an enameled copper wire as a bobbin thread in computerized machine embroidery, both sensor and shield electrodes are applied in a single sequence, eliminating manual intermediate or finishing steps and harnessing the design flexibility provided by the embroidery technique. A major finding is that the impact of density seems minor, while adjustments of the pattern layout seem to adequately compensate for a lower stitch density, with a grid layout yielding the best results.

About the Cover: Using enameled wire as a bobbin (lower) thread in computerized machine embroidery offers a scalable and versatile approach for attaching electrodes to the backside of fabrics, protecting them from mechanical wear. Both sensing and shielding electrodes are fabricated in a single-step process. Shield electrodes can be used to implement driven shielding to enhance the device’s signal-to-noise ratio and sensing range. Cover art credit: Roland Aigner, Elisabeth Gschaider.

https://ieee-jflex.org/

J-FLEX is a joint publication of IEEE Sensors Council (SC), IEEE Electron Devices Society (EDS), and IEEE Circuits and Systems Society (CASS):

06/19/2025

IEEE J-FLEX has reached the stars and is now a fully established technical journal for the field of flexible electronics.

And we are going to reach even higher...

06/14/2025

05/16/2025

The latest issue of J-FLEX (Volume 4, Issue 3) was just released!

A. Grover et al. present a study that aims to design and enhance the performance of lead-free methylammonium (MA) and formamidinium (FA) compound (FAMASnGeI3)-based flexible perovskite solar cell (FPSC) by utilizing the solar cell capacitance simulator 1-D (SCAPS-1D). We have obtained Voc of 0.87 V, Jsc of 45.7 mA/cm2, fill factor (FF) of 75.3%, and PCE of 29.9%. The obtained results were compared with similar existing research based on various absorber layers. It was found that the selected absorber layer improves the performance of FPSCs.

R. Govind et al. demonstrate an approach to achieve smart performance using flexible conducting electrodes based on graphene nanoplatelets (GNPs)/poly(3,4-ethylenedioxythiophene):poly (styrenesulfonate) (PEDOT:PSS) nanocomposite by the incorporation of machine learning methods. Applications of the electrodes as smart electrothermal heater and touch panel have been demonstrated with intelligent performance. The integration of machine learning methods ensures smart functioning and helps to achieve better functionalities in both applications. This work paves the way for significant advancements in flexible electronics and touchscreen technology with the assistance of machine learning strategies.

J. Corona et al. show that to understand the influence of the printing process, we build upon our previous work, where a noncontact optical technique, known as modulated photothermal radiometry (MPTR), was used to measure the thermal conductivity of aerosol-jet-printed thin films. In this work, we use the method to study the thermal properties of extrusion-printed silver on glass and alumina substrates. A noise resistant data analysis fitting technique is applied using a 2-D heat transfer model. The thermal conductivity measurement is validated using the Weidemann-Franz (WF) relationship from measured electrical conductivity values.

About the Cover: This next-generation photovoltaic technology offers high efficiency with mechanical adaptability. The image symbolizes a step forward in wearable and portable solar energy solutions. It reflects the synergy of innovation, materials science, and sustainable energy research. See “Design and Enhancing Performance of Lead-Free Flexible Perovskite Solar Cells: A Numerical Approach,” p. 109.

https://ieee-jflex.org/

J-FLEX is a joint publication of IIEEE Sensors Council(SC), IIEEE Electron Devices Society(EDS), and IIEEE Circuits and Systems Society(CASS):