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Transparent and Flexible Electronics Assembled with Metallic Nanowire-Layered Non-drying Glycerogel
摘要： There has been increasing demand for transparent and mechanically durable electrical conductors for their uses in wearable electronic devices. It is common to layer metallic nanowires on transparent but stiff polydimethylsiloxane (PDMS) or stretchable but opaque EcoflexTM-based substrates. Here, we hypothesized that layering metallic nanowires on a stretchable and hygroscopic gel would allow us to assemble a transparent, stretchable, and durable conductor. The hygroscopic property of the gel was attained by partially replacing water in the pre-formed polyacrylamide hydrogel with glycerol. The resulting gel, denoted as a glycerogel, could remain hydrated for over 6 months in air by taking up water molecules from the air. The glycerogel was tailored to be stretchable up to 8 times its original length by tuning the amount of cross-linker and acrylamide. The resulting glycerogel allowed for deposition of wavy silver nanowires using the pre-strain method up to 400 % pre-strain, without causing kinks and interfacial cracks often found with nanowires layered onto PDMS. With a pre-strain of 100%, the resulting nanowire-gel conductor exhibited optical transparency (85%) and electrical conductivity (17.1 ohm/sq) even after 5,000 cycles of deformation. The results of this study would broadly be useful to improve the performance of the next generation of flexible electronic devices.
关键词： glycerol,toughness,hydration,stretchable hydrogel,flexible electronics
更新于2025-09-23 15:21:01
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All 3D Printed Flexible ZnO UV Photodetector on Ultraflat Substrate
摘要： An all 3D printed flexible ZnO ultraviolet (UV) photodetector is demonstrated, where the 3D printing method is used not only for the electrode and photosensitive material but also for creating a substrate. An ultra-flat and flexible substrate capable of serving as the backbone layer is developed using a water-dissolvable polymer layer for surface planarization. A two layered printing followed by surface treatment is demonstrated for the substrate preparation. As a mechanical support but flexible, a thick and sparse thermoplastic polyurethane layer is printed. On its surface, a thin and dense polyvinyl alcohol (PVA) is then printed. A precise control of PVA reflow using micro-water droplet results in a flexible and extremely uniform substrate. A Cu-Ag nanowire network is directly 3D-printed on the flexible substrate for the conducting layer, followed by ZnO for photosensitive material. Unlike the planar two-dimensional printing that provides thin films, 3D printing allows the electrode to have a step height, which can be made like a dam to accommodate a thick film of ZnO. Photosentivity as a function of various ZnO thickness values was investigated to establish an optimal thickness for UV response. The device was also tested in natural sunlight along with stability and reliability.
关键词： ultraviolet radiation,UV detector,UV sensor,Printed electronics,3D printing,additive manufacturing
更新于2025-09-23 15:21:01
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[IEEE 2020 Pan Pacific Microelectronics Symposium (Pan Pacific) - HI, USA (2020.2.10-2020.2.13)] 2020 Pan Pacific Microelectronics Symposium (Pan Pacific) - Qualification of NIR, UV and Laser Irradiation as Alternative Photonic Sintering Methods for Printed Electronics
摘要： Printed Electronics creates new areas of applications with a new manner of manufacturing electronics. Due to its technical and 3D design freedom, new markets and innovative products arise that were initially unthinkable. However, the focus of research is currently on mastering and improving the printing process. The subsequent process step of drying and densifying the printed structures to achieve high conductivities in the shortest possible time is up to now hardly considered. This paper treats the inquiry of fitted and optimized parameters of alternative promising photonic sintering methods for printed electronics compared to the much more time-intensive state of the art sintering process in a furnace. These photonic sintering methods comprise the near infrared, ultraviolet light as well as laser irradiation of the printed structures. Photonic sintering promises faster and more efficient curing and sintering due to the direct and selective application of energy to the printing structures without damaging the temperature-sensitive substrates. As substrate materials ABS and PC-ABS, as well as a glass material were used. Both polymer materials are standard and technical thermoplastics which are available at the market in huge quantities at low price. For the manufacture of printed circuits, a dispense printer was used, in order to process a low-cost silver-based micro particle paste. The evaluation of the sintering result was carried out based on the electrical conductivity of the printed conductor path and the adhesion strength on the substrate. In addition, the sintering time required for the curing of the structures as well as impacts on the substrate or the printed tracks due to photonic treatment were taken into account. To perform the experiments, two different print layouts were set up in order to be able to assess the electrical properties on the first layout and the adhesion on the second layout. To obtain a detailed statement on the exploration on the photonic sintering methods, a fully factorial design plan was conducted. For the near-infrared irradiation, the important parameters were the irradiation duration and the irradiation power. While sintered by ultraviolet light, the parameters were irradiation time, as well as the distance between the sample surface and the UV emitter. In the treatment by means of laser radiation, laser power and the motion speed were identified as the relevant parameters. In order to be able to draw a comparison to the mainly used sintering method, samples were also sintered in a furnace. The results show a significant reduction of the sintering time to a few seconds with comparable and even significantly better electrical and mechanical properties.
关键词： Printed Electronics,Polymer,Photonic Sintering,Conductivity,Alternative Sintering
更新于2025-09-23 15:21:01
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Inorganic Printed LEDs for Wearable Technology
摘要： A new form of inorganic printed electronics has been developed that allows for high speed production of solid-state lighting on flexible substrates. Light emitting diodes (LED) become more efficient as their size is decreased. However, the difficulties in making the electrical connection to micro LEDs has previously prevented these benefits being exploited outside the laboratory. Standard InGaN film, grown on a defined substrate (heteroepitaxy), was fabricated into micro LEDs (approx. 27 μm) and dispersed in a carrier fluid to form an ink, which can then be printed using established printing technologies. During printing and curing, the geometry of the individual micro LEDs causes them to orientate into a single preferential direction. Connections can then be made via further printed layers of conductive and dielectric ink to create flexible lamps consisting of areas of discrete LEDs. These lamps have low power consumption and high light output making them ideal for incorporating into garments and for packaging. The “Thunderstorm” dress (a Rainbow Winters project) was developed for the “Wired to Wear” exhibition in the Museum of Science and Industry, Chicago (MSI) to demonstrate the potential of this technology. The concept was to turn the wearer into a living representation of a thunderstorm. The concept had previously been realised in 2010 using electroluminescent elements (EL) to create a lightning flash in the panels of the dress. However, this required the wearer to carry high voltage devices, bulky electronics and heavy batteries. Instead, using inorganic printed LEDs afforded the potential to create a truly wearable piece of haute couture, using low voltages, miniature electronics and small batteries. The work reported here describes the fabrication technique used to create the micro LED lamps and the issues related to their integration into a piece of wearable technology. The lamps could be driven in such a way as to create a more realistic flash compared to the EL version. Other potential applications such as smart packaging, are also discussed.
关键词： wearable technology,inorganic LEDs,printed electronics
更新于2025-09-23 15:21:01
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Unraveling Doping Capability of Conjugated Polymers for Strategic Manipulation of Electric Dipole Layer toward Efficient Charge Collection in Perovskite Solar Cells
摘要： Developing electrical organic conductors is challenging because of the difficulties involved in generating free charge carriers through chemical doping. To devise a novel doping platform, the doping capabilities of four designed conjugated polymers (CPs) are quantitatively characterized using an AC Hall-effect device. The resulting carrier density is related to the degree of electronic coupling between the CP repeating unit and 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ), and doped PIDF-BT provides an outstanding electrical conductivity, exceeding 210 S cm?1, mainly due to the doping-assisted facile carrier generation and relatively fast carrier mobility. In addition, it is noted that a slight increment in the electron-withdrawing ability of the repeating unit in each CP diminishes electronic coupling with F4-TCNQ, and severely deteriorates the doping efficiency including the alteration of operating doping mechanism for the CPs. Furthermore, when PIDF-BT with high doping capability is applied to the hole transporting layer, with F4-TCNQ as the interfacial doping layer at the interface with perovskite, the power conversion efficiency of the perovskite solar cell improves significantly, from 17.4% to over 20%, owing to the ameliorated charge-collection efficiency. X-ray photoelectron spectroscopy and Kelvin probe analyses verify that the improved solar cell performance originates from the increase in the built-in potential because of the generation of electric dipole layer.
关键词： conjugated polymers,conducting polymers,doping,molecular electronics,solar cells
更新于2025-09-23 15:21:01
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Solution-processed upconversion photodetectors based on quantum dots
摘要： Upconversion photodetectors convert photons from the infrared to the visible light spectrum and are of use in applications such as infrared detection and imaging. High-performance upconversion devices are, however, typically based on vacuum-deposited materials, which are expensive and require high operating voltages, which limits their implementation in flexible systems. Here we report solution-processed optical upconversion photodetectors with a high photon-to-photon conversion efficiency of 6.5% and a low turn-on voltage of 2.5 V. Our devices consist of a colloidal lead sulfide quantum dot layer for harvesting infrared light that is monolithically coupled to a cadmium selenide/zinc selenide quantum dot layer for visible-light emission. We optimized the charge-extraction layers in these devices by incorporating silver nanoparticles into the electron transport layers to enable carrier tunnelling. Our photodetectors exhibit a low dark current, high detectivity (6.4 × 1012 Jones) and millisecond response time, and are compatible with flexible substrates. We also show that the devices can be used for in vitro bioimaging.
关键词： quantum dots,infrared detection,bioimaging,flexible electronics,upconversion photodetectors
更新于2025-09-23 15:21:01
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High-selectivity bandpass filter using six pairs of quarter-wavelength coupled lines
摘要： We present a 16-channel readout integrated circuit (ROIC) with nanosecond-resolution time to digital converter (TDC) for pixelated Cadmium Telluride (CdTe) gamma-ray detectors. The pixel array ROIC is the proof of concept of the pixel array readout ASIC for positron-emission tomography (PET) scanner, positron-emission mammography (PEM) scanner, and Compton gamma camera. The electronics of each individual pixel integrates an analog front-end with switchable gain, an analog to digital converter (ADC), configuration registers, and a 4-state digital controller. For every detected photon, the pixel electronics provides the energy deposited in the detector with 10-bit resolution, and a fast trigger signal for time stamp. The ASIC contains the 16-pixel matrix electronics, a digital controller, five global voltage references, a TDC, a temperature sensor, and a band-gap based current reference. The ASIC has been fabricated with TSMC m mixed-signal CMOS technology and occupies an area of mm. The TDC shows a resolution mm of 95.5 ps, a precision of 600 ps at full width half maximum W. In acquisition (FWHM), and a power consumption of mode, the total power consumption of every pixel is W. An equivalent noise charge (ENC) of at maximum gain and negative polarity conditions has been measured at room temperature.
关键词： positron emission tomography,low-power electronics,semiconductor radiation detectors,application specific integrated circuits,gamma-ray detectors,Analog-digital conversion,energy resolution
更新于2025-09-23 15:21:01
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Doped Layer Characterization Using Accurate Optical Modelling of Mid-Infrared Spectrometry
摘要： We present a 16-channel readout integrated circuit (ROIC) with nanosecond-resolution time to digital converter (TDC) for pixelated Cadmium Telluride (CdTe) gamma-ray detectors. The pixel array ROIC is the proof of concept of the pixel array readout ASIC for positron-emission tomography (PET) scanner, positron-emission mammography (PEM) scanner, and Compton gamma camera. The electronics of each individual pixel integrates an analog front-end with switchable gain, an analog to digital converter (ADC), con?guration registers, and a 4-state digital controller. For every detected photon, the pixel electronics provides the energy deposited in the detector with 10-bit resolution, and a fast trigger signal for time stamp. The ASIC contains the 16-pixel matrix electronics, a digital controller, ?ve global voltage references, a TDC, a temperature sensor, and a band-gap based current reference. The ASIC has been fabricated with TSMC m mixed-signal CMOS technology and occupies an area of mm. The TDC shows a resolution mm of 95.5 ps, a precision of 600 ps at full width half maximum W. In acquisition (FWHM), and a power consumption of mode, the total power consumption of every pixel is W. An equivalent noise charge (ENC) of at maximum gain and negative polarity conditions has been measured at room temperature.
关键词： positron emission tomography,low-power electronics,application speci?c integrated circuits,semiconductor radiation detectors,gamma-ray detectors,Analog-digital conversion,energy resolution
更新于2025-09-23 15:21:01
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[SpringerBriefs in Applied Sciences and Technology] Air-Stable Inverted Organic Light-Emitting Diodes ||
摘要： We introduce the importance of air stability on the basis of the principles and the history of organic light-emitting diodes (OLEDs), and the way of realising air-stable OLEDs finally. OLEDs are current-driven self-emitting devices that, in principle, have the features of lightness and thinness. Therefore OLEDs are expected to have unprecedented flexibility. However, it is difficult to achieve air stability in OLEDs, which is the key property for the realisation of flexible devices, because it has been essential to use air-active materials in consideration of the operational mechanism.
关键词： organic electronics,air stability,OLEDs,encapsulation,flexibility
更新于2025-09-23 15:21:01
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Continuous-Wave Laser-Induced Transfer of Metal Nanoparticles to Arbitrary Polymer Substrates
摘要： Laser-induced forward transfer (LIFT) and selective laser sintering (SLS) are two distinct laser processes that can be applied to metal nanoparticle (NP) ink for the fabrication of a conductive layer on various substrates. A pulsed laser and a continuous-wave (CW) laser are utilized respectively in the conventional LIFT and SLS processes; however, in this study, CW laser-induced transfer of the metal NP is proposed to achieve simultaneous sintering and transfer of the metal NP to a wide range of polymer substrates. At the optimum laser parameters, it was shown that a high-quality uniform metal conductor was created on the acceptor substrate while the metal NP was sharply detached from the donor substrate, and we anticipate that such an asymmetric transfer phenomenon is related to the di?erence in the adhesion strengths. The resultant metal electrode exhibits a low resistivity that is comparable to its bulk counterpart, together with strong adhesion to the target polymer substrate. The versatility of the proposed process in terms of the target substrate and applicable metal NPs brightens its prospects as a facile manufacturing scheme for ?exible electronics.
关键词： selective laser sintering,flexible electronics,metal nanoparticle ink,laser-induced forward transfer
更新于2025-09-23 15:21:01