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10 pages, 4578 KiB

Open AccessArticle

Printing Smart Designs of Light Emitting Devices with Maintained Textile Properties

by Inge Verboven, Jeroen Stryckers, Viktorija Mecnika, Glen Vandevenne, Manoj Jose and Wim Deferme

Materials 2018, 11(2), 290; https://doi.org/10.3390/ma11020290 - 13 Feb 2018

Cited by 21 | Viewed by 5598

Abstract

To maintain typical textile properties, smart designs of light emitting devices are printed directly onto textile substrates. A first approach shows improved designs for alternating current powder electroluminescence (ACPEL) devices. A configuration with the following build-up, starting from the textile substrate, was applied [...] Read more.

To maintain typical textile properties, smart designs of light emitting devices are printed directly onto textile substrates. A first approach shows improved designs for alternating current powder electroluminescence (ACPEL) devices. A configuration with the following build-up, starting from the textile substrate, was applied using the screen printing technique: silver (10 µm)/barium titanate (10 µm)/zinc-oxide (10 µm) and poly(3,4-ethylenedioxythiophene)poly(styrenesulfonate) (10 µm). Textile properties such as flexibility, drapability and air permeability are preserved by implementing a pixel-like design of the printed layers. Another route is the application of organic light emitting devices (OLEDs) fabricated out of following layers, also starting from the textile substrate: polyurethane or acrylate (10–20 µm) as smoothing layer/silver (200 nm)/poly(3,4-ethylenedioxythiophene)poly(styrenesulfonate) (35 nm)/super yellow (80 nm)/calcium/aluminum (12/17 nm). Their very thin nm-range layer thickness, preserving the flexibility and drapability of the substrate, and their low working voltage, makes these devices the possible future in light-emitting wearables. Full article

(This article belongs to the Special Issue Stretchable and Flexible Electronic Materials & Devices)

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11 pages, 13314 KiB

Open AccessCommunication

Washable and Reliable Textile Electrodes Embedded into Underwear Fabric for Electrocardiography (ECG) Monitoring

by Amale Ankhili, Xuyuan Tao, Cédric Cochrane, David Coulon and Vladan Koncar

Materials 2018, 11(2), 256; https://doi.org/10.3390/ma11020256 - 07 Feb 2018

Cited by 93 | Viewed by 11068

Abstract

A medical quality electrocardiogram (ECG) signal is necessary for permanent monitoring, and an accurate heart examination can be obtained from instrumented underwear only if it is equipped with high-quality, flexible, textile-based electrodes guaranteeing low contact resistance with the skin. The main objective of [...] Read more.

A medical quality electrocardiogram (ECG) signal is necessary for permanent monitoring, and an accurate heart examination can be obtained from instrumented underwear only if it is equipped with high-quality, flexible, textile-based electrodes guaranteeing low contact resistance with the skin. The main objective of this article is to develop reliable and washable ECG monitoring underwear able to record and wirelessly send an ECG signal in real time to a smart phone and further to a cloud. The article focuses on textile electrode design and production guaranteeing optimal contact impedance. Therefore, different types of textile fabrics were coated with modified poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) in order to develop and manufacture reliable and washable textile electrodes assembled to female underwear (bras), by sewing using commercially available conductive yarns. Washability tests of connected underwear containing textile electrodes and conductive threads were carried out up to 50 washing cycles. The influence of standardized washing cycles on the quality of ECG signals and the electrical properties of the textile electrodes were investigated and characterized. Full article

(This article belongs to the Special Issue Stretchable and Flexible Electronic Materials & Devices)

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19 pages, 11526 KiB

Open AccessFeature PaperArticle

From Fibrils to Toughness: Multi-Scale Mechanics of Fibrillating Interfaces in Stretchable Electronics

by Olaf Van der Sluis, Tijmen Vermeij, Jan Neggers, Bart Vossen, Marc Van Maris, Jan Vanfleteren, Marc Geers and Johan Hoefnagels

Materials 2018, 11(2), 231; https://doi.org/10.3390/ma11020231 - 02 Feb 2018

Cited by 5 | Viewed by 4928

Abstract

Metal-elastomer interfacial systems, often encountered in stretchable electronics, demonstrate remarkably high interface fracture toughness values. Evidently, a large gap exists between the rather small adhesion energy levels at the microscopic scale (‘intrinsic adhesion’) and the large measured macroscopic work-of-separation. This energy gap is [...] Read more.

Metal-elastomer interfacial systems, often encountered in stretchable electronics, demonstrate remarkably high interface fracture toughness values. Evidently, a large gap exists between the rather small adhesion energy levels at the microscopic scale (‘intrinsic adhesion’) and the large measured macroscopic work-of-separation. This energy gap is closed here by unravelling the underlying dissipative mechanisms through a systematic numerical/experimental multi-scale approach. This self-containing contribution collects and reviews previously published results and addresses the remaining open questions by providing new and independent results obtained from an alternative experimental set-up. In particular, the experimental studies on Cu-PDMS (Poly(dimethylsiloxane)) samples conclusively reveal the essential role of fibrillation mechanisms at the micro-meter scale during the metal-elastomer delamination process. The micro-scale numerical analyses on single and multiple fibrils show that the dynamic release of the stored elastic energy by multiple fibril fracture, including the interaction with the adjacent deforming bulk PDMS and its highly nonlinear behaviour, provide a mechanistic understanding of the high work-of-separation. An experimentally validated quantitative relation between the macroscopic work-of-separation and peel front height is established from the simulation results. Finally, it is shown that a micro-mechanically motivated shape of the traction-separation law in cohesive zone models is essential to describe the delamination process in fibrillating metal-elastomer systems in a physically meaningful way. Full article

(This article belongs to the Special Issue Stretchable and Flexible Electronic Materials & Devices)

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10 pages, 5942 KiB

Open AccessArticle

A Stretchable Alternating Current Electroluminescent Fiber

by Dan Hu, Xiuru Xu, Jingsheng Miao, Ori Gidron and Hong Meng

Materials 2018, 11(2), 184; https://doi.org/10.3390/ma11020184 - 24 Jan 2018

Cited by 46 | Viewed by 7539

Abstract

Flexible, stretchable electroluminescent fibers are of significance to meet the escalating requirements of increasing complexity and multifunctionality of smart electronics. We report a stretchable alternating current electroluminescent (ACEL) fiber by a low-cost and all solution-processed scalable process. The ACEL fiber provides high stretchability, [...] Read more.

Flexible, stretchable electroluminescent fibers are of significance to meet the escalating requirements of increasing complexity and multifunctionality of smart electronics. We report a stretchable alternating current electroluminescent (ACEL) fiber by a low-cost and all solution-processed scalable process. The ACEL fiber provides high stretchability, decent light-emitting performance, with excellent stability and nearly zero hysteresis. It can be stretched up to 80% strain. Our ACEL fiber device maintained a stable luminance for over 6000 stretch-release cycles at 50% strain. The mechanical stretchability and optical stability of our ACEL fiber device provides new possibilities towards next-generation stretchable displays, electronic textiles, advanced biomedical imaging and lighting, conformable visual readouts in arbitrary shapes, and novel health-monitoring devices. Full article

(This article belongs to the Special Issue Stretchable and Flexible Electronic Materials & Devices)

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17 pages, 2327 KiB

Open AccessArticle

A Novel Manufacturing Process for Compact, Low-Weight and Flexible Ultra-Wideband Cavity Backed Textile Antennas

by Dries Van Baelen, Sam Lemey, Jo Verhaevert and Hendrik Rogier

Materials 2018, 11(1), 67; https://doi.org/10.3390/ma11010067 - 03 Jan 2018

Cited by 14 | Viewed by 4398

Abstract

A novel manufacturing procedure for the fabrication of ultra-wideband cavity-backed substrate integrated waveguide antennas on textile substrates is proposed. The antenna cavity is constructed using a single laser-cut electrotextile patch, which is folded around the substrate. Electrotextile slabs protruding from the laser-cut patch [...] Read more.

A novel manufacturing procedure for the fabrication of ultra-wideband cavity-backed substrate integrated waveguide antennas on textile substrates is proposed. The antenna cavity is constructed using a single laser-cut electrotextile patch, which is folded around the substrate. Electrotextile slabs protruding from the laser-cut patch are then vertically folded and glued to form the antenna cavity instead of rigid metal tubelets to implement the vertical cavity walls. This approach drastically improves mechanical flexibility, decreases the antenna weight to slightly more than 1 g and significantly reduces alignment errors. As a proof of concept, a cavity-backed substrate integrated waveguide antenna is designed and realized for ultra-wideband operation in the [5.15–5.85] GHz band. Antenna performance is validated in free space as well as in two on body measurement scenarios. Furthermore, the antenna’s figures of merit are characterized when the prototype is bent at different curvature radii, as commonly encountered during deployment on the human body. Also the effect of humidity content on antenna performance is studied. In all scenarios, the realized antenna covers the entire operating frequency band, meanwhile retaining a stable radiation pattern with a broadside gain above 5 dBi, and a radiation efficiency of at least 70%. Full article

(This article belongs to the Special Issue Stretchable and Flexible Electronic Materials & Devices)

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9354 KiB

Open AccessFeature PaperArticle

Electrochemical Impedance Analysis of a PEDOT:PSS-Based Textile Energy Storage Device

by Ida Nuramdhani, Argun Talat Gokceoren, Sheilla Atieno Odhiambo, Gilbert De Mey, Carla Hertleer and Lieva Van Langenhove

Materials 2018, 11(1), 48; https://doi.org/10.3390/ma11010048 - 28 Dec 2017

Cited by 20 | Viewed by 6686

Abstract

A textile-based energy storage device with electroactive PEDOT:PSS (poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate)) polymer functioning as a solid-state polyelectrolyte has been developed. The device was fabricated on textile fabric with two plies of stainless-steel electroconductive yarn as the electrodes. In this study, cyclic voltammetry and electrochemical impedance [...] Read more.

A textile-based energy storage device with electroactive PEDOT:PSS (poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate)) polymer functioning as a solid-state polyelectrolyte has been developed. The device was fabricated on textile fabric with two plies of stainless-steel electroconductive yarn as the electrodes. In this study, cyclic voltammetry and electrochemical impedance analysis were used to investigate ionic and electronic activities in the bulk of PEDOT:PSS and at its interfaces with stainless steel yarn electrodes. The complex behavior of ionic and electronic origins was observed in the interfacial region between the conductive polymer and the electrodes. The migration and diffusion of the ions involved were confirmed by the presence of the Warburg element with a phase shift of 45° (n = 0.5). Two different equivalent circuit models were found by simulating the model with the experimental results: (QR)(QR)(QR) for uncharged and (QR)(QR)(Q(RW)) for charged samples. The analyses also showed that the further the distance between electrodes, the lower the capacitance of the cell. The distribution of polymer on the cell surface also played important role to change the capacitance of the device. The results of this work may lead to a better understanding of the mechanism and how to improve the performance of the device. Full article

(This article belongs to the Special Issue Stretchable and Flexible Electronic Materials & Devices)

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1734 KiB

Open AccessArticle

Schottky Emission Distance and Barrier Height Properties of Bipolar Switching Gd:SiOx RRAM Devices under Different Oxygen Concentration Environments

by Kai-Huang Chen, Tsung-Ming Tsai, Chien-Min Cheng, Shou-Jen Huang, Kuan-Chang Chang, Shu-Ping Liang and Tai-Fa Young

Materials 2018, 11(1), 43; https://doi.org/10.3390/ma11010043 - 28 Dec 2017

Cited by 25 | Viewed by 6317

Abstract

In this study, the hopping conduction distance and bipolar switching properties of the Gd:SiOx thin film by (radio frequency, rf) rf sputtering technology for applications in RRAM devices were calculated and investigated. To discuss and verify the electrical switching mechanism in various different [...] Read more.

In this study, the hopping conduction distance and bipolar switching properties of the Gd:SiOx thin film by (radio frequency, rf) rf sputtering technology for applications in RRAM devices were calculated and investigated. To discuss and verify the electrical switching mechanism in various different constant compliance currents, the typical current versus applied voltage (I-V) characteristics of gadolinium oxide RRAM devices was transferred and fitted. Finally, the transmission electrons’ switching behavior between the TiN bottom electrode and Pt top electrode in the initial metallic filament forming process of the gadolinium oxide thin film RRAM devices for low resistance state (LRS)/high resistance state (HRS) was described and explained in a simulated physical diagram model. Full article

(This article belongs to the Special Issue Stretchable and Flexible Electronic Materials & Devices)

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24683 KiB

Open AccessArticle

A Wearable Textile 2D Touchpad Sensor Based on Screen-Printing Technology

by Josue Ferri, Jose Vicente Lidón-Roger, Jorge Moreno, Gabriel Martinez and Eduardo Garcia-Breijo

Materials 2017, 10(12), 1450; https://doi.org/10.3390/ma10121450 - 20 Dec 2017

Cited by 23 | Viewed by 8222

Abstract

Among many of the designs used in the detection of 2D gestures for portable technology, the touchpad is one of the most complex and with more functions to implement. Its development has undergone a great push due to its use in displays, but [...] Read more.

Among many of the designs used in the detection of 2D gestures for portable technology, the touchpad is one of the most complex and with more functions to implement. Its development has undergone a great push due to its use in displays, but it is not widely used with other technologies. Its application on textiles could allow a wide range of applications in the field of medicine, sports, etc. Obtaining a flexible, robust touchpad with good response and low cost is one of the objectives of this work. A textile touchpad based on a diamond pattern design using screen printing technology has been developed. This technology is widely used in the textile industry and therefore does not require heavy investments. The developed prototypes were analyzed using a particular controller for projected capacitive technologies (pro-cap), which is the most used in gesture detection. Two different designs were used to obtain the best configuration, obtaining a good result in both cases. Full article

(This article belongs to the Special Issue Stretchable and Flexible Electronic Materials & Devices)

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4349 KiB

Open AccessArticle

Bipolar Switching Properties of Neodymium Oxide RRAM Devices Using by a Low Temperature Improvement Method

by Kai-Huang Chen, Ming-Cheng Kao, Shou-Jen Huang and Jian-Zhi Li

Materials 2017, 10(12), 1415; https://doi.org/10.3390/ma10121415 - 12 Dec 2017

Cited by 10 | Viewed by 4953

Abstract

Bipolar resistive switching properties and endurance switching behavior of the neodymium oxide (Nd₂O₃) thin films resistive random access memory (RRAM) devices for a high resistive status/low resistive status (HRS/LRS) using a low temperature supercritical carbon dioxide fluid (SCF) improvement [...] Read more.

Bipolar resistive switching properties and endurance switching behavior of the neodymium oxide (Nd₂O₃) thin films resistive random access memory (RRAM) devices for a high resistive status/low resistive status (HRS/LRS) using a low temperature supercritical carbon dioxide fluid (SCF) improvement post-treatment process were investigated. Electrical and physical properties improvement of Nd₂O₃ thin films were measured by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and current versus voltage (I-V) measurement. The metal-like behavior of ohmic conduction mechanism and metallic cluster reaction of hopping conduction mechanism in initial metallic filament path forming process of the SCF-treated thin films RRAM devices was assumed and discussed. Finally, the electrical conduction mechanism of the thin films RRAM derives for set/reset was also discussed and verified in filament path physical model. Full article

(This article belongs to the Special Issue Stretchable and Flexible Electronic Materials & Devices)

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5499 KiB

Open AccessArticle

Structural, Electrical, Magnetic and Resistive Switching Properties of the Multiferroic/Ferroelectric Bilayer Thin Films

by Ming-Cheng Kao, Hone-Zern Chen, San-Lin Young, Kai-Huang Chen, Jung-Lung Chiang and Jen-Bin Shi

Materials 2017, 10(11), 1327; https://doi.org/10.3390/ma10111327 - 20 Nov 2017

Cited by 9 | Viewed by 4036

Abstract

Bi_0.8Pr_0.2Fe_0.95Mn_0.05O₃/Bi_3.96Gd_0.04Ti_2.95W_0.05O₁₂ (BPFMO/BGTWO) bilayer thin films with Multiferroic/Ferroelectric (MF/FE) structures were deposited onto Pt(111)/Ti/SiO₂/Si(100) substrates by using the sol-gel method with rapid thermal [...] Read more.

Bi_0.8Pr_0.2Fe_0.95Mn_0.05O₃/Bi_3.96Gd_0.04Ti_2.95W_0.05O₁₂ (BPFMO/BGTWO) bilayer thin films with Multiferroic/Ferroelectric (MF/FE) structures were deposited onto Pt(111)/Ti/SiO₂/Si(100) substrates by using the sol-gel method with rapid thermal annealing. The BPFMO/BGTWO thin films exhibited well-saturated ferromagnetic and ferroelectric hysteresis loops because of the electro-magnetic coupling induced by the MF/FE structure. The remnant magnetization (2Mr) and remnant polarization (2Pr) were 4.6 emu/cm³ and 62 μC/cm², respectively. Moreover, the bipolar I-V switching curves of BPFMO/BGTWO bilayer thin films resistive random access memory (RRAM) devices were discussed, and investigated for LRS/HRS. Full article

(This article belongs to the Special Issue Stretchable and Flexible Electronic Materials & Devices)

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3806 KiB

Open AccessArticle

Eco-Friendly and Biodegradable Biopolymer Chitosan/Y₂O₃ Composite Materials in Flexible Organic Thin-Film Transistors

by Bo-Wei Du, Shao-Ying Hu, Ranjodh Singh, Tsung-Tso Tsai, Ching-Chang Lin and Fu-Hsiang Ko

Materials 2017, 10(9), 1026; https://doi.org/10.3390/ma10091026 - 03 Sep 2017

Cited by 42 | Viewed by 6580

Abstract

The waste from semiconductor manufacturing processes causes serious pollution to the environment. In this work, a non-toxic material was developed under room temperature conditions for the fabrication of green electronics. Flexible organic thin-film transistors (OTFTs) on plastic substrates are increasingly in demand due [...] Read more.

The waste from semiconductor manufacturing processes causes serious pollution to the environment. In this work, a non-toxic material was developed under room temperature conditions for the fabrication of green electronics. Flexible organic thin-film transistors (OTFTs) on plastic substrates are increasingly in demand due to their high visible transmission and small size for use as displays and wearable devices. This work investigates and analyzes the structured formation of aqueous solutions of the non-toxic and biodegradable biopolymer, chitosan, blended with high-k-value, non-toxic, and biocompatible Y₂O₃ nanoparticles. Chitosan thin films blended with Y₂O₃ nanoparticles were adopted as the gate dielectric thin film in OTFTs, and an improvement in the dielectric properties and pinholes was observed. Meanwhile, the on/off current ratio was increased by 100 times, and a low leakage current was observed. In general, the blended chitosan/Y₂O₃ thin films used as the gate dielectric of OTFTs are non-toxic, environmentally friendly, and operate at low voltages. These OTFTs can be used on surfaces with different curvature radii because of their flexibility. Full article

(This article belongs to the Special Issue Stretchable and Flexible Electronic Materials & Devices)

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1833 KiB

Open AccessArticle

Thermoelectric Properties of Flexible PEDOT:PSS/Polypyrrole/Paper Nanocomposite Films

by Jun Li, Yong Du, Runping Jia, Jiayue Xu and Shirley Z. Shen

Materials 2017, 10(7), 780; https://doi.org/10.3390/ma10070780 - 11 Jul 2017

Cited by 26 | Viewed by 5365

Abstract

Flexible poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/polypyrrole/paper (PEDOT:PSS/PPy/paper) thermoelectric (TE) nanocomposite films were prepared by a two-step method: first, PPy/paper nanocomposite films were prepared by an in situ chemical polymerization process, and second, PEDOT:PSS/PPy/paper TE composite films were fabricated by coating the as-prepared PPy/paper nanocomposite films using a [...] Read more.

Flexible poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/polypyrrole/paper (PEDOT:PSS/PPy/paper) thermoelectric (TE) nanocomposite films were prepared by a two-step method: first, PPy/paper nanocomposite films were prepared by an in situ chemical polymerization process, and second, PEDOT:PSS/PPy/paper TE composite films were fabricated by coating the as-prepared PPy/paper nanocomposite films using a dimethyl sulfoxide-doped PEDOT:PSS solution. Both the electrical conductivity and the Seebeck coefficient of the PEDOT:PSS/PPy/paper TE nanocomposite films were greatly enhanced from 0.06 S/cm to ~0.365 S/cm, and from 5.44 μV/K to ~16.0 μV/K at ~300 K, respectively, when compared to the PPy/paper TE nanocomposite films. The thermal conductivity of the PEDOT:PSS/PPy/paper composite film (0.1522 Wm⁻¹K⁻¹ at ~300 K) was, however, only slightly higher than that of the PPy/paper composite film (0.1142 Wm⁻¹K⁻¹ at ~300 K). As a result, the ZT value of the PEDOT:PSS/PPy/paper composite film (~1.85 × 10⁻⁵ at ~300 K) was significantly enhanced when compared to that of the PPy/paper composite film (~4.73 × 10⁻⁷ at ~300 K). The as-prepared nanocomposite films have great potential for application in flexible TE devices. Full article

(This article belongs to the Special Issue Stretchable and Flexible Electronic Materials & Devices)

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2211 KiB

Open AccessArticle

Investigation of Rapid Low-Power Microwave-Induction Heating Scheme on the Cross-Linking Process of the Poly(4-vinylphenol) for the Gate Insulator of Pentacene-Based Thin-Film Transistors

by Ching-Lin Fan, Ming-Chi Shang, Shea-Jue Wang, Mao-Yuan Hsia, Win-Der Lee and Bohr-Ran Huang

Materials 2017, 10(7), 742; https://doi.org/10.3390/ma10070742 - 03 Jul 2017

Cited by 3 | Viewed by 3695

Abstract

In this study, a proposed Microwave-Induction Heating (MIH) scheme has been systematically studied to acquire suitable MIH parameters including chamber pressure, microwave power and heating time. The proposed MIH means that the thin indium tin oxide (ITO) metal below the Poly(4-vinylphenol) (PVP) film [...] Read more.

In this study, a proposed Microwave-Induction Heating (MIH) scheme has been systematically studied to acquire suitable MIH parameters including chamber pressure, microwave power and heating time. The proposed MIH means that the thin indium tin oxide (ITO) metal below the Poly(4-vinylphenol) (PVP) film is heated rapidly by microwave irradiation and the heated ITO metal gate can heat the PVP gate insulator, resulting in PVP cross-linking. It is found that the attenuation of the microwave energy decreases with the decreasing chamber pressure. The optimal conditions are a power of 50 W, a heating time of 5 min, and a chamber pressure of 20 mTorr. When suitable MIH parameters were used, the effect of PVP cross-linking and the device performance were similar to those obtained using traditional oven heating, even though the cross-linking time was significantly decreased from 1 h to 5 min. Besides the gate leakage current, the interface trap state density (Nit) was also calculated to describe the interface status between the gate insulator and the active layer. The lowest interface trap state density can be found in the device with the PVP gate insulator cross-linked by using the optimal MIH condition. Therefore, it is believed that the MIH scheme is a good candidate to cross-link the PVP gate insulator for organic thin-film transistor applications as a result of its features of rapid heating (5 min) and low-power microwave-irradiation (50 W). Full article

(This article belongs to the Special Issue Stretchable and Flexible Electronic Materials & Devices)

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2410 KiB

Open AccessArticle

An All Oxide-Based Imperceptible Thin-Film Transistor with Humidity Sensing Properties

by Kyung Su Kim, Cheol Hyoun Ahn, Won Jun Kang, Sung Woon Cho, Sung Hyeon Jung, Dae Ho Yoon and Hyung Koun Cho

Materials 2017, 10(5), 530; https://doi.org/10.3390/ma10050530 - 13 May 2017

Cited by 18 | Viewed by 5841

Abstract

We have examined the effects of oxygen content and thickness in sputtered InSnO (ITO) electrodes, especially for the application of imperceptible amorphous-InGaZnO (a-IGZO) thin-film transistors (TFTs) in humidity sensors. The imperceptible a-IGZO TFT with 50-nm ITO electrodes deposited at Ar:O [...] Read more.

We have examined the effects of oxygen content and thickness in sputtered InSnO (ITO) electrodes, especially for the application of imperceptible amorphous-InGaZnO (a-IGZO) thin-film transistors (TFTs) in humidity sensors. The imperceptible a-IGZO TFT with 50-nm ITO electrodes deposited at Ar:O₂ = 29:0.3 exhibited good electrical performances with V_th of −0.23 V, SS of 0.34 V/dec, µ_FE of 7.86 cm²/V∙s, on/off ratio of 8.8 × 10⁷, and has no degradation for bending stress up to a 3.5-mm curvature. The imperceptible oxide TFT sensors showed the highest sensitivity for the low and wide gate bias of −1~2 V under a wide range of relative humidity (40–90%) at drain voltage 1 V, resulting in low power consumption by the sensors. Exposure to water vapor led to a negative shift in the threshold voltage (or current enhancement), and an increase in relative humidity induced continuous threshold voltage shift. In particular, compared to conventional resistor-type sensors, the imperceptible oxide TFT sensors exhibited extremely high sensitivity from a current amplification of >10³. Full article

(This article belongs to the Special Issue Stretchable and Flexible Electronic Materials & Devices)

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2500 KiB

Open AccessArticle

Mechanical Properties of ZTO, ITO, and a-Si:H Multilayer Films for Flexible Thin Film Solar Cells

by Claudia Hengst, Siegfried B Menzel, Gayatri K Rane, Vladimir Smirnov, Karen Wilken, Barbara Leszczynska, Dustin Fischer and Nicole Prager

Materials 2017, 10(3), 245; https://doi.org/10.3390/ma10030245 - 01 Mar 2017

Cited by 22 | Viewed by 7172

Abstract

The behavior of bi- and trilayer coating systems for flexible a-Si:H based solar cells consisting of a barrier, an electrode, and an absorption layer is studied under mechanical load. First, the film morphology, stress, Young’s modulus, and crack onset strain (COS) were analyzed [...] Read more.

The behavior of bi- and trilayer coating systems for flexible a-Si:H based solar cells consisting of a barrier, an electrode, and an absorption layer is studied under mechanical load. First, the film morphology, stress, Young’s modulus, and crack onset strain (COS) were analyzed for single film coatings of various thickness on polyethylene terephthalate (PET) substrates. In order to demonstrate the role of the microstructure of a single film on the mechanical behavior of the whole multilayer coating, two sets of InSnOx (indium tin oxide, ITO) conductive coatings were prepared. Whereas a characteristic grain–subgrain structure was observed in ITO-1 films, grain growth was suppressed in ITO-2 films. ITO-1 bilayer coatings showed two-step failure under tensile load with cracks propagating along the ITO-1/a-Si:H-interface, whereas channeling cracks in comparable bi- and trilayers based on amorphous ITO-2 run through all constituent layers. A two-step failure is preferable from an application point of view, as it may lead to only a degradation of the performance instead of the ultimate failure of the device. Hence, the results demonstrate the importance of a fine-tuning of film microstructure not only for excellent electrical properties, but also for a high mechanical performance of flexible devices (e.g., a-Si:H based solar cells) during fabrication in a roll-to-roll process or under service. Full article

(This article belongs to the Special Issue Stretchable and Flexible Electronic Materials & Devices)

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Review

Jump to: Research

21 pages, 1180 KiB

Open AccessReview

Fabrication Approaches to Interconnect Based Devices for Stretchable Electronics: A Review

by Steven Nagels and Wim Deferme

Materials 2018, 11(3), 375; https://doi.org/10.3390/ma11030375 - 03 Mar 2018

Cited by 29 | Viewed by 9632

Abstract

Stretchable electronics promise to naturalize the way that we are surrounded by and interact with our devices. Sensors that can stretch and bend furthermore have become increasingly relevant as the technology behind them matures rapidly from lab-based workflows to industrially applicable production principles. [...] Read more.

Stretchable electronics promise to naturalize the way that we are surrounded by and interact with our devices. Sensors that can stretch and bend furthermore have become increasingly relevant as the technology behind them matures rapidly from lab-based workflows to industrially applicable production principles. Regardless of the specific materials used, creating stretchable conductors involves either the implementation of strain reliefs through insightful geometric patterning, the dispersion of stiff conductive filler in an elastomeric matrix, or the employment of intrinsically stretchable conductive materials. These basic principles however have spawned a myriad of materials systems wherein future application engineers need to find their way. This paper reports a literature study on the spectrum of different approaches towards stretchable electronics, discusses standardization of characteristic tests together with their reports and estimates matureness for industry. Patterned copper foils that are embedded in elastomeric sheets, which are closest to conventional electronic circuits processing, make up one end of the spectrum. Furthest from industry are the more recent circuits based on intrinsically stretchable liquid metals. These show extremely promising results, however, as a technology, liquid metal is not mature enough to be adapted. Printing makes up the transition between both ends, and is also well established on an industrial level, but traditionally not linked to creating electronics. Even though a certain level of maturity was found amongst the approaches that are reviewed herein, industrial adaptation for consumer electronics remains unpredictable without a designated break-through commercial application. Full article

(This article belongs to the Special Issue Stretchable and Flexible Electronic Materials & Devices)

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