Special Issue "Flexible/Stretchable Electronics"

A special issue of Electronics (ISSN 2079-9292). This special issue belongs to the section "Microelectronics and Optoelectronics".

Deadline for manuscript submissions: 31 December 2019.

Special Issue Editor

Prof. Sunkook Kim
E-Mail Website
Guest Editor
School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, Kyunggi-do 16419, Korea
Interests: nano-devices; flexible electronics; thin-film transistor; augmented human research; display

Special Issue Information

Dear Colleagues,

Exciting achievements have been produced towards the rapid growth of flexible and stretchable electronics technology, such as rollable displays, electronic eye cameras, conformable wearable sensors, and health monitoring devices. These electronic devices are more essentially designed, with excellent mechanical deformability, possessing sensitive-to-multifunctional responses, smart human–machine interactions, and intelligent control capabilities. However, the most common and critical issue that hinders the performances of the flexible and stretchable electronics is the maintenance of device performance under external deformations. Thus, the development of material design and engineering should focus on the realization of flexibility and stretchability. Although, intrinsically flexible and stretchable materials show potential applications, their electrical performances remain incomparable with those of conventional electronic materials. Recently, hierarchical architectures inspired by nature have greatly enhanced the potential applications in novel flexible devices. Thus, innovative breakthroughs in advanced materials, through unique geometrical designs that are mechanically robust, have drawn extensive attention in the field of flexible and stretchable device engineering. Moreover, combinations of these electronic devices, with more emphasis on miniaturization, multifunctional sensing and battery-free wireless communications, enable fruitful future flexible and stretchable electronic devices.

The main aim of this Special Issue is to seek high-quality submissions that highlight emerging applications, address recent breakthroughs in flexible and stretchable electronic system-innovative geometrical designs, device architectures, facile fabrication methodologies, smart electronic devices with multifunctionalities, and battery-free wireless communication. The topics of interest include, but are not limited to:

  • Flexible and stretchable electronics for biomedical applications
  • Multifunctional smart sensors
  • Battery free, wireless electronic devices
  • Power supply, generation, and storage in stretchable electronics
  • Scalable high throughput and facile fabrication procedures for the realization of scientific technological growth and development
  • Robust and reliable novel geometrical designs for high performance stretchable electronic devices

Prof. Sunkook Kim
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Electronics is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Flexible and stretchable electronics for biomedical applications
  • Multifunctional smart sensors
  • Battery free, wireless electronic devices
  • Power supply, Generation, and Storage in stretchable electronics
  • Scalable high throughput and facile fabrication procedures for the realization of scientific technological growth and development
  • Robust and reliable novel geometrical designs for high performance stretchable electronic devices

Published Papers (6 papers)

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Research

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Open AccessArticle
Gold/Polyimide-Based Resistive Strain Sensors
Electronics 2019, 8(5), 565; https://doi.org/10.3390/electronics8050565 - 22 May 2019
Abstract
This paper presents the fabrication and implementation of novel resistive sensors that were implemented for strain-sensing applications. Some of the critical factors for the development of resistive sensors are addressed in this paper, such as the cost of fabrication, the steps of the [...] Read more.
This paper presents the fabrication and implementation of novel resistive sensors that were implemented for strain-sensing applications. Some of the critical factors for the development of resistive sensors are addressed in this paper, such as the cost of fabrication, the steps of the fabrication process which make it time-consuming to complete each prototype, and the inability to achieve optimised electrical and mechanical characteristics. The sensors were fabricated via magnetron sputtering of thin-film chromium and gold layer on the thin-film substrates at defined thicknesses. Sticky copper tapes were attached on the two sides of the sensor patches to form the electrodes. The operating principle of the fabricated sensors was based on the change in their responses with respect to the corresponding changes in their relative resistance as a function of the applied strain. The strain-induced characteristics of the patches were studied with different kinds of experiments, such as consecutive bending and pressure application. The sensors with 400 nm thickness of gold layer obtained a sensitivity of 0.0086 Ω/ppm for the pressure ranging between 0 and 400 kPa. The gauge factor of these sensors was between 4.9–6.6 for temperatures ranging between 25 °C and 55 °C. They were also used for tactile sensing to determine their potential as thin-film sensors for industrial applications, like in robotic and pressure-mapping applications. The results were promising in regards to the sensors’ controllable film thickness, easy operation, purity of the films and mechanically sound nature. These sensors can provide a podium to enhance the usage of resistive sensors on a higher scale to develop thin-film sensors for industrial applications. Full article
(This article belongs to the Special Issue Flexible/Stretchable Electronics)
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Open AccessArticle
Ultra-Short Pulsed Laser Annealing Effects on MoS2 Transistors with Asymmetric and Symmetric Contacts
Electronics 2019, 8(2), 222; https://doi.org/10.3390/electronics8020222 - 17 Feb 2019
Abstract
The ultra-short pulsed laser annealing process enhances the performance of MoS2 thin film transistors (TFTs) without thermal damage on plastic substrates. However, there has been insufficient investigation into how much improvement can be brought about by the laser process. In this paper, [...] Read more.
The ultra-short pulsed laser annealing process enhances the performance of MoS2 thin film transistors (TFTs) without thermal damage on plastic substrates. However, there has been insufficient investigation into how much improvement can be brought about by the laser process. In this paper, we observed how the parameters of TFTs, i.e., mobility, subthreshold swing, Ion/Ioff ratio, and Vth, changed as the TFTs’ contacts were (1) not annealed, (2) annealed on one side, or (3) annealed on both sides. The results showed that the linear effective mobility (μeff_lin) increased from 13.14 [cm2/Vs] (not annealed) to 18.84 (one side annealed) to 24.91 (both sides annealed). Also, Ion/Ioff ratio increased from 2.27 × 10 5 (not annealed) to 3.14 × 10 5 (one side annealed) to 4.81 × 10 5   (both sides annealed), with Vth shifting to negative direction. Analyzing the main reason for the improvement through the Y function method (YFM), we found that both the contact resistance (Rc) and the channel interface resistance (Rch) improves after the pulsed laser annealings under different conditions. Moreover, the Rc enhances more dramatically than the Rch does. In conclusion, our picosecond laser annealing improves the performance of TFTs (especially, the Rc) in direct proportion to the number of annealings applied. The results will contribute to the investigation about correlations between the laser annealing process and the performance of devices. Full article
(This article belongs to the Special Issue Flexible/Stretchable Electronics)
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Open AccessFeature PaperArticle
Meander Microwave Bandpass Filter on a Flexible Textile Substrate
Electronics 2019, 8(1), 11; https://doi.org/10.3390/electronics8010011 - 21 Dec 2018
Cited by 2
Abstract
This paper presents an alternative process to fabricate flexible bandpass filters by using an embroidered yarn conductor on an electronic textile. The novelty of the proposed miniaturized filter is its complete integration on the outfit, with benefits in terms of compressibility, stretchability, and [...] Read more.
This paper presents an alternative process to fabricate flexible bandpass filters by using an embroidered yarn conductor on an electronic textile. The novelty of the proposed miniaturized filter is its complete integration on the outfit, with benefits in terms of compressibility, stretchability, and high geometrical accuracy opening the way to develop textile filters for wearable applications in sport and medicine. The proposed design consists of a fully embroidered microstrip topology with a length equal to quarter wavelength (λ/4) to develop a bandpass filter frequency response. A drastic reduction in the size of the filter was achieved by taking advantage of a simplified architecture based on meandered-line stepped impedance resonator. The e-textile microstrip filter was designed, simulated, fabricated, and measured with experimental validation at a 7.58 GHz frequency. The insertion loss obtained by simulation of the filter was substantially small. The return loss was greater than 20 dB for bands. To explore the relations between the physical parameters and filter performance characteristics, a theoretical equivalent circuit model of the filter constituent components was studied. The bending effect of the e-textile filter was also studied. The results showed that by raising the radius of bending to 40 mm, the resonance frequency was raised to 4.25 MHz/mm. Full article
(This article belongs to the Special Issue Flexible/Stretchable Electronics)
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Open AccessArticle
Human Limb Motion Detection with Novel Flexible Capacitive Angle Sensor Based on Conductive Textile
Electronics 2018, 7(9), 192; https://doi.org/10.3390/electronics7090192 - 11 Sep 2018
Cited by 3
Abstract
In recent years, many sensors made of hard materials have been designed to detect human body movements in physical exercises. However, hard materials usually cause extra dyskinesia for body movements. To detect human limb motion with less dyskinesia in physical exercise, a novel [...] Read more.
In recent years, many sensors made of hard materials have been designed to detect human body movements in physical exercises. However, hard materials usually cause extra dyskinesia for body movements. To detect human limb motion with less dyskinesia in physical exercise, a novel flexible capacitive angle sensor (NFCAS) based on a conductive textile was designed in this paper. The NFCAS has two non-parallel plates, namely, an exciting plate and a sensing plate, which can be fixed onto the inner forearm and the inner upper arm. Thus, the angle between the two plates of the NFCAS can be used to represent the angle of medial elbow, and its variation can lead to changes in the sensor’s capacitance at the same time. A push-ups experiment and pull-ups experiment were conducted to evaluate the designed NFCAS’s performance. Experimental results showed that the NFCAS could detect the main processes of push-ups and pull-ups. Besides high measurement precision, the NFCAS is also soft, thin, lightweight, and easily made. Therefore, it can be widely applied for detecting human limb motion with less dyskinesia in physical exercises. Full article
(This article belongs to the Special Issue Flexible/Stretchable Electronics)
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Open AccessFeature PaperArticle
Flexible PI-Based Plant Drought Stress Sensor for Real-Time Monitoring System in Smart Farm
Electronics 2018, 7(7), 114; https://doi.org/10.3390/electronics7070114 - 16 Jul 2018
Cited by 4
Abstract
Plant growth and development are negatively affected by a wide range of external stresses, including water deficits. Especially, plants generally reduce the stomatal aperture to decrease transpiration levels upon drought stress. Advanced technologies, such as wireless communications, the Internet of things (IoT), and [...] Read more.
Plant growth and development are negatively affected by a wide range of external stresses, including water deficits. Especially, plants generally reduce the stomatal aperture to decrease transpiration levels upon drought stress. Advanced technologies, such as wireless communications, the Internet of things (IoT), and smart sensors have been applied to practical smart farming and indoor planting systems to monitor plants’ signals effectively. In this study, we develop a flexible polyimide (PI)-based sensor for real-time monitoring of water conditions in tobacco plants. The stoma response, by which a plant adjusts to drought stress to maintain homeostasis, can be confirmed through the examination of evaporated water. Using a flexible PI-based sensor, a plant’s response variation is translated into an electrical signal. The sensors are integrated with a Bluetooth (BLE) module and a processing module and show potential as smart real-time water sensors in smart farms. Full article
(This article belongs to the Special Issue Flexible/Stretchable Electronics)
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Review

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Open AccessReview
Wearable and Flexible Textile Electrodes for Biopotential Signal Monitoring: A review
Electronics 2019, 8(5), 479; https://doi.org/10.3390/electronics8050479 - 29 Apr 2019
Abstract
Wearable electronics is a rapidly growing field that recently started to introduce successful commercial products into the consumer electronics market. Employment of biopotential signals in wearable systems as either biofeedbacks or control commands are expected to revolutionize many technologies including point of care [...] Read more.
Wearable electronics is a rapidly growing field that recently started to introduce successful commercial products into the consumer electronics market. Employment of biopotential signals in wearable systems as either biofeedbacks or control commands are expected to revolutionize many technologies including point of care health monitoring systems, rehabilitation devices, human–computer/machine interfaces (HCI/HMIs), and brain–computer interfaces (BCIs). Since electrodes are regarded as a decisive part of such products, they have been studied for almost a decade now, resulting in the emergence of textile electrodes. This study presents a systematic review of wearable textile electrodes in physiological signal monitoring, with discussions on the manufacturing of conductive textiles, metrics to assess their performance as electrodes, and an investigation of their application in the acquisition of critical biopotential signals for routine monitoring, assessment, and exploitation of cardiac (electrocardiography, ECG), neural (electroencephalography, EEG), muscular (electromyography, EMG), and ocular (electrooculography, EOG) functions. Full article
(This article belongs to the Special Issue Flexible/Stretchable Electronics)
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