IEEE Journal on Flexible Electronics - J-FLEX

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):

05/01/2025

The latest issue of J-FLEX (Volume 4, Issue 2) was just released!

With great pleasure, I introduce the invited review paper, “Flexible Sensors for IoT-Based Health Monitoring.”

The cover artwork is emblematic of this IoT health monitoring system:

"Flexible sensors conform naturally to the body for comfortable, long-term wear—seamlessly tracking vital signs throughout daily life. Integrated with the Internet of Things (IoT), they provide continuous, real-time health data to users and healthcare providers. This fusion of ergonomic design and smart connectivity empowers remote monitoring, timely alerts, and personalized, proactive care tailored to individual needs."

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

https://ieee-jflex.org/

04/26/2025

Scientific publications are always a moving target, new innovations and new challenges.

Always an informative meeting for the annual IEEE Panel of Editors, representing IEEE Journal on Flexible Electronics (J-FLEX), as the current and founding Editor-in-Chief (Paul Berger).

Wonderful interactions with friends and colleagues.

04/25/2025

The latest issue of J-FLEX (Volume 4, Issue 1) was just released!

With great pleasure, I introduce the publication in IEEE Journal on Flexible Electronics (J-FLEX) of the extended papers from the 2024 IEEE International Conference on Flexible, Printable Sensors and Systems (IEEE FLEPS), held in Tampere, Finland.

I wish to thank our authors, reviewers and especially our guest editors, who are Matti Mäntysalo, Gaetano Marrocco, Shweta Saxena Agarwala, Gerd Grau, and Wei Gao.

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

https://ieee-jflex.org/

03/29/2025

The latest issue of J-FLEX (Volume 3, Issue 12) was just released!

This covers a Cross Society Special Issue (IFETC & ISCAS) on Flexible Hybrid Electronics: Advancing Next-Generation Applications. This Special Issue showcases pioneering research in flexible circuit designs, with a focus on thin-film transistors and printed materials tailored for thermal and microwave applications. The following articles exemplify the innovative strides being made in this field.

In Zhang et al. introduce a bidirectional biomedical pixel interface circuit based on low-temperature polycrystalline silicon thin-film transistors (LTPS-TFTs), designed specifically for large-area medical applications. Key performance metrics include a 40-dB gain, an input noise of 86.2 µV/√Hz, and an effective number of bits (ENOB) of 9.13, with stability confirmed via statistical tests on 20 chips.

In Ranjan et al. delve into the design of low-power digital circuits using hydrogenated amorphous silicon thin-film transistors (a-Si:H TFTs), with an emphasis on unipolar TFT logic gates on flexible substrates. A 3-to-8 decoder—implemented on both glass and flexible substrates—demonstrates an average total power reduction of 46.5% across various operating conditions.

In Ersan et al. explore the fabrication of X-band (8–12 GHz) frequency selective surfaces (FSSs) on glass fiber fabrics using an optimized screen-printing process. The work focuses on how the size and morphology of conductive particles influence electromagnetic performance, offering critical insights into the design of high-performance FSS structures.

In Govind et al. investigate the development of graphene-based phase-change thermal interface nanocomposites and heat sinks to advance thermal management in integrated circuits (ICs). By integrating graphene into paraffin, the resulting nanocomposites exhibit markedly enhanced thermal conductivity.

About the Cover: This is a conceptual bandage-like wearable FHE sensing system, using advanced printing and thin silicon techniques. It will have printed sensors/sensor peripherals, as simple as temperature/EEG/ECG/EMG, glucose, lactate, biomarkers integrated with multiplexing circuitry and amplifier to perform readout and amplification. Also, printed super cap for power supply and printed antenna for RF communication. Ultra-thin and light FHE can achieve wear and forget; and provide continuous monitoring; and the whole system as indicated can be partially disposable and partially reusable.

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):

03/02/2025

The latest issue of J-FLEX (Volume 3, Issue 11) was just released!

In this Special Issue, we celebrate the invention of the transistor, over 75 years ago, in 1947 by physicists John Bardeen, Walter Brattain, and William Shockley at AT&T Bell Labs in Murray Hill, New Jersey in USA [1-3], who all shared in the 1956 Nobel Prize in Physics. This first working transistor, a point-contact transistor, is widely considered to have launched the modern-day electronics age. But even predating Bardeen, Brattain and Shockley, Julius Edgar Lilienfeld, recently immigrated to USA from what is now known as Lviv, Ukraine, to the Boston area of Massachusetts, proposed the concept of a field-effect transistor (FET) through a US patent application in 1926 [4], almost 100 years ago, although he never attempted to build a working prototype.

Today, the thin film transistor (TFT) has evolved from these discoveries to revolutionize the field of display technology, driving the extinction of cathode ray tube (CRT) and plasma displays. For every flat panel display commercially sold in retail stores now, whether a television, a computer monitor, a laptop, a tablet, or a phone, etc., each pixel is driven by a TFT to control greyscale and color. At the core, TFTs are deposited onto a substrate, any substrate, whether crystalline or amorphous, while still producing functional transistors, unlike advanced silicon CMOS for digital computing, high-speed III-V transistors for communications, or high-voltage wide bandgap transistors for the electrification of motors, where those classes of transistors are created by crystalline transistors atop crystalline substrates, often by epitaxy, keeping the deposited layers in registry with the crystalline substrate template. The advent of TFT technology, largely non-crystalline atop glass, has permitted electronics to permeate new vistas, particularly large area applications, like displays.

By unlocking a pathway for efficacious TFTs atop a range of substrates, this also provided a pathway for reduced temperature processing, allowing a range of softer and flexible substrates, like Corning’s Willow® glass and various plastics, to be accessed too. Thus, this Special Issue examines some key evolution within the flexible electronics community on transistors, including TFTs, but also the nascent organic bipolar transistor, which could be poised for great future impact.

So, it gives this Guest Editorial team great pleasure to introduce the following contributions to this very unique Special Issue on flexible electronics transistors during these key anniversary years.

About the Cover: The advent of thin-film transistors (TFT) began in earnest with its evolution from the first field-effect transistor proposed in a patent application in 1926 and the first working transistor, a point contact transistor, developed at AT&T Bell Labs in 1947. The image conveys a timeline from those nascent discoveries and inventions at the beginning of the 20th Century through to the end of the 20th Century, when flat-panel displays displaced bulky displays whereby TFTs were literally the driving force behind red–green–blue (RGB) pixelated displays. In the 21st Century, TFT evolution is now transforming these flat-panel displays into flexible displays and opening vistas for completely new use cases, like medical wearables in the form of electronic tattoos.

The Lilienfeld patent ( #1,745,175, filed on October 8, 1926) image was obtained from sources related to the www.uspto.gov website.
The AT&T Bell Labs point contact transistor image was obtained with permission from the Bell System Memorial website (https://memorial.bellsystem.com/) from their “History of the Transistor” section.

The cover art for this special issue was designed by Mr. Enrique Sahagún from Scixel.

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):