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Large quantities of microscopic red, green, and blue light-emitting diodes (LEDs) made of crystalline inorganic semiconductor materials micro-transfer printed in large quantities onto rigid or flexible substrates form monochrome and color displays having a wide range of sizes and interesting properties. Transfer-printed micro-LED displays promise excellent environmental robustness, brightness, spatial resolution, and efficiency. Passive-matrix and active-matrix inorganic LED displays were constructed, operated, and their attributes measured. Tests demonstrate that inorganic micro-LED displays have outstanding color, viewing angle, and transparency. Yield improvement techniques include redundancy, physical repair, and electronic correction. Micro-transfer printing enables revolutionary manufacturing strategies in which microscale LEDs are first assembled into miniaturized micro-system "light engines," and then micro-transfer printed and interconnected directly to metallized large-format panels. This paper reviews micro-transfer printing technology for micro-LED displays. FIGURE 3 -(A) Schematic illustration of a micro-transfer stamp that is rigid in horizontal directions and compliant in the vertical dimension. (B) Photograph of a stamp on a 225 × 225 mm glass back. (C) SEM of the stamp posts.FIGURE 4 -Photograph of a 50 × 50 mm stamp silicon master (A) and elastomer stamp (B). The stamp has an array of 250 by 250 posts on a 200-micron pitch with 62,500 posts. Journal of the SID 25/10, 2017 591 FIGURE 9 -Micrographs of an array of microscopic inorganic light-emitting diodes microtransfer printed to a metal-coated substrate (left) and emitting red light (right). The anodes are connected in common with a transparent aluminum zinc oxide anode.

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Rapid synthesis of ultralong silver nanowires (AgNWs) has been obtained using a one-pot polyol-mediated synthetic procedure. The AgNWs have been prepared from the base materials in less than one hour with nanowire lengths reaching 195 μm, which represents the quickest synthesis and one of the highest reported aspect ratios to date. These results have been achieved through a joint analysis of all reaction parameters, which represents a clear progress beyond the state of the art. Dispersions of the AgNWs have been used to prepare thin, flexible, transparent and conducting films using spray coating. Due to the higher aspect ratio, an improved electrical percolation network is observed. This allows a low sheet resistance (RS = 20.2 Ω/sq), whilst maintaining high optical film transparency (T = 94.7%), driving to the highest reported figure-of-merit (FoM = 338). Owing to the light-scattering influence of the AgNWs, the density of the AgNW network can also be varied to enable controllability of the optical haze through the sample. Based on the identification of the optimal haze value, organic photovoltaics (OPVs) have been fabricated using the AgNWs as the transparent electrode and have been benchmarked against indium tin oxide (ITO) electrodes. Overall, the performance of OPVs made using AgNWs sees a small decrease in power conversion efficiency (PCE), primarily due to a fall in open-circuit voltage (50 mV). This work indicates that AgNWs can provide a low cost, rapid and roll-to-roll compatible alternative to ITO in OPVs, with only a small compromise in PCE needed.

Macroporous monolithic cryogels made from poly(vinyl alcohol) (PVA) with degree of saponification 87.7% have been prepared using a crosslinking reaction with glutaraldehyde under acidic conditions at subzero temperatures. The porous structure of the monolithic cryogels from PVA (cryoPVA), analyzed using optical microscopy, scanning electron microscopy, and environmental scanning electron microscopy, revealed interconnected macropores up to 150 m in size with a noticeable microporosity of the gel walls. Differential scanning calorimetry measurement showed that more than 90% of the water in the cryoPVA monoliths was freezable water, while the amount of polymer bound water increased with increase in the polymer concentration in the cryoPVA sample. The swelling degree of cryoPVA depended on concentration of polymer in the initial reaction mixture and degree of crosslinking. The cryoPVA monoliths were elastic and spongy-like materials that can be dried, stored in dried state, and re-swelled when required. Derivatization of hydroxyl-groups of the cryoPVA monolith allowed incorporation of required functionality. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1057-1066, 200

Displays that use direct light emission from microscale inorganic light emitting diodes (ILEDs) have the potential to be very bright and also very power efficient. High-throughput assembly technologies that accurately and cost-effectively deposit large arrays of ILEDs onto display substrates with high yield are key enablers for ILED displays. Transfer-printing with elastomer stamps is a candidate assembly technology for making ILED displays. A variety of passive matrix ILED displays have been designed and fabricated using transfer-printed microscale ILEDs.

The sensitivity of a low-cost polymeric optical fibre humidity sensor based on transmittance changes due to evanescent wave absorption is reported using test measurements in an environmental chamber and of the skin. The layer-by-layer method was used to coat 30mm of the central unclad section of a multimode polymeric optical fibre with 7 layers of a hydrophilic film consisting of bilayers of poly(allylamine hydrochloride) and SiO2 mesoporous nanoparticles. Sensor characterisation shows a decrease in light transmission as relative humidity increases as a result of refractive index changes of the coating deposited onto the optical fibre which correlates with a commercial capacitive humidity sensor. The sensitivity obtained for the sensor coated with an optimum 7 layers was approximately -3.87x10 -3 and -9.61x10 -3 in transmittance percentage per RH percentage for the range of ~10% to ~75% RH and 90% to 97% RH, respectively. In addition, a response time of 1.5s can be seen for breath monitoring with the polymeric optical fibre humidity sensor. The proof of concept measurements made on the skin indicate that this sensor has the potential to be used to monitor humidity of the skin microenvironment within a wound dressing which can be used to provide better prognosis of healing.

Films and sponges of chitosan (CHI), chitosan/hyaluronic acid (CHI-HA) and chitosan/chondroitin sulphate (CHI-CHOS), were prepared by film deposition or lyophilization (sponges), avoiding the formation of interpolyelectrolyte complexes. The biological behaviour of the systems was analysed by studying the cell behaviour using a fibroblast cell line and standard biological MTT and Alamar Blue tests. The morphology of films, sponges and cell seeded samples was analysed by ESEM. The results obtained indicate that all the systems can be considered as good supports for cell adhesion and proliferation, but there is specific activation of the proliferative process in the presence of hyaluronic acid and chondroitin sulphate.