Flexible microelectronics: New application for thin‐film transistors in fingerprint sensors

Abstract— Thin‐film transistors (TFTs) are field‐effect transistors that can be used to create large‐scale‐integrated (LSI) circuits. The combination of high‐performance TFTs and transfer technology of the TFTs has the potential to foster the rise of a new flexible microelectronics industry. This paper discusses the current status of flexible microelectronics, using a TFT fingerprint sensor (FPS) as an example. Technology used in active‐matrix displays can easily be applied to the TFT FPS. TFT technology should not be confined to the display industry; its use should be expanded into the semiconductor industry. With the result presented in this paper, we declare a new era of flexible microelectronics open.     

Flexible microelectronics becoming a reality with Suftla transfer technology

Abstract— Suftla is a technology that is used to transfer polycrystalline silicon (polysilicon) thin‐film‐transistor (TFT) circuits from an original glass substrate to a plastic sheet. The electronic devices in the next generation will be thin, lightweight, and will handle huge amounts of data, yet consume less energy. Suftla technology, together with high‐performance polysilicon TFTs, meets all these requirements because we have developed a variety of smart flexible electronic devices, such as thin paperback‐sized displays and microprocessors. Suftla will usher in a new era of life‐enhancing flexible microelectronics.     

Method for simultaneous imaging of endogenous low molecular weight metabolites in mouse brain using TiO2 nanoparticles in nanoparticle-assisted laser desorption/ionization-imaging mass spectrometry

We report the detection of a group of endogenous low molecular weight metabolites (LMWM) in mouse brain (80-500 Da) using TiO(2) nanoparticles (NPs) in nanoparticle-assisted laser desorption/ionization-imaging mass spectrometry (Nano-PALDI-IMS) without any washing and separation step prior to MS analysis. The identification of metabolites using TiO(2) NPs was compared with a conventional organic matrix 2,5-dihydroxybenzoic acid (DHB) where signals of 179 molecules were specific to TiO(2) NPs, 4 were specific to DHB, and 21 were common to both TiO(2) NPs and DHB. The use of TiO(2) NPs enabled the detection of a higher number of LMWM as compared to DHB and gold NPs as a matrix. This approach is a simple, inexpensive, washing, and separation free for imaging and identification of LMWM in mouse brain. We believe that the biochemical information from distinct regions of the brain using a Nano-PALDI-IMS will be helpful in elucidating the imbalances linked with diseases in biomedical samples.     

Nondestructive inspection of thermal barrier coating of gas turbine high temperature components

A thermal barrier coating (TBC) is applied to high‐temperature components in gas turbines, and consists of a ceramic topcoat and a metallic bondcoat. Various kinds of TBC degradation and damage occur in high‐temperature components during service, such as topcoat thinning, topcoat delamination, and formation of a thermally grown oxide (TGO) layer below the topcoat, each of which can be examined using a suitable nondestructive inspection technique. Topcoat thinning can be detected by topcoat thickness measurement using terahertz waves, which are electromagnetic waves in the frequency region between optical and radio waves. The measurement resolution is about 10 μm, which is comparable to microscopic observation of the cross section in destructive inspection. Topcoat delamination can be detected by active thermography, in which the topcoat surface is scanned by a heating laser and the surface temperature distribution is measured by a thermal infrared camera. The combination of temperature peak and residual thermal image detection is effective in eliminating false detection. The TGO layer can be detected using photoluminescence, in which the Cr³⁺ ions included as an impurity in Al₂O₃ are detected. Since delamination tends to occur at locations at which the TGO layer has grown, TGO layer detection provides an effective method to select regions where delamination has occurred or is likely to occur. An inspection flow based on these techniques is proposed, which is expected to aid the establishment of condition‐based maintenance strategies of high‐temperature components. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Preparation of polyimide-epoxy composites

The formation of a three dimensional network of crosslinked epoxy leads all unmodified epoxies to have inherent brittleness and relatively low degradation temperatures. Polyimides, on the other hand, are widely used for applications that require high degrees of flexibility and thermal resistance. Here, we have focused on the preparation of epoxy systems cured with polyamic acids instead of traditional amino-group-containing hardening agents. The cure behavior and potential reaction mechanisms of EPON 828 resin and polyamic acid mixtures were evaluated by DSC and TGA. Thermal analysis showed a complex reaction sequence taking place in the mixture and also determined the extent of reaction of the polyamic acid with itself and the competitive reaction of the polyamic acid with the epoxy. The compositions of the mixtures were varied to see the dependence of the cure behavior on component concentrations. Solutions of the two components did not phase separate and also phase separation was not apparent either optically or microscopically in the cured samples. This phase behavior was attributed to a unique in situ reaction. A novel solvent system for the polyamic acid precursor was also used.     

Ex Vivo Expanded and Activated Natural Killer Cells Prolong the Overall Survival of Mice with Glioblastoma-like Cell-Derived Tumors

Glioblastoma (GBM) is the leading malignant intracranial tumor and is associated with a poor prognosis. Highly purified, activated natural killer (NK) cells, designated as genuine induced NK cells (GiNKs), represent a promising immunotherapy for GBM. We evaluated the anti-tumor effect of GiNKs in association with the programmed death 1(PD-1)/PD-ligand 1 (PD-L1) immune checkpoint pathway. We determined the level of PD-1 expression, a receptor known to down-regulate the immune response against malignancy, on GiNKs. PD-L1 expression on glioma cell lines (GBM-like cell line U87MG, and GBM cell line T98G) was also determined. To evaluate the anti-tumor activity of GiNKs in vivo, we used a xenograft model of subcutaneously implanted U87MG cells in immunocompromised NOG mice. The GiNKs expressed very low levels of PD-1. Although PD-L1 was expressed on U87MG and T98G cells, the expression levels were highly variable. Our xenograft model revealed that the retro-orbital administration of GiNKs and interleukin-2 (IL-2) prolonged the survival of NOG mice bearing subcutaneous U87MG-derived tumors. PD-1 blocking antibodies did not have an additive effect with GiNKs for prolonging survival. GiNKs may represent a promising cell-based immunotherapy for patients with GBM and are minimally affected by the PD-1/PD-L1 immune evasion axis in GBM.     

Measurement of topcoat thickness of thermal barrier coating for gas turbines using terahertz waves

The topcoat thickness of thermal barrier coating (TBC) samples was measured using terahertz (THz) waves. The index of refraction of yttria‐stabilized zirconia (YSZ), which is the topcoat material, is necessary to obtain the topcoat thickness from time domain re?ectometry. Time domain THz spectroscopy was applied to YSZ samples, and the index of refraction was measured to be 4.8 in the frequency region 0.1 to 1.2 THz. The topcoat thickness of six di?erent TBC samples, which varied from 300 to 600 µm, was measured using THz waves. The results were in agreement with microscope observation results to within measurement error. In addition, the topcoat thickness pro?le of a turbine blade sample was measured with a resolution of 2.4 µm. The pro?le showed a standard deviation of 4 µm, which re?ects the actual variation in the topcoat thickness. The results showed that THz waves are e?ective for high‐resolution measurement of the topcoat thickness. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 183(4): 1–9, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22385     

Temperature Estimation and Al Content Prediction Focusing on Microstructural Change in a Thermal Barrier Coating

A superalloy with a thermal barrier coating (TBC) simulating a gas turbine blade is exposed to a high-temperature environment to develop a method for predicting the local temperature and Al content in a bond coat (BC). The Al content decreases with an increase in the test time due to the Al transport induced by the oxidation of the BC and the interdiffusion between the BC and the substrate. This brings about Al-decreased layer (ADL) at the boundary between the BC and the top coat. The thickness of the ADL increases in proportion to the square root of the test time, and the temperature dependence of the growth rate shows an Arrhenius-type behavior. Based on this relation, the local temperature of an in-service blade can be estimated by measuring the ADL thickness when the operation time is known. The Al content decreases in proportion to the ADL thickness. The prediction method of the Al content based on the relation is also presented.     

Effect of dispersed phase viscosity on maximum droplet generation frequency in microchannel emulsification using asymmetric straight-through channels

Uniformly sized droplets of soybean oil, MCT (medium-chain fatty acid triglyceride) oil and n-tetradecane with a Sauter mean diameter of d _3,2 = 26–35 μm and a distribution span of 0.21–0.25 have been produced at high throughputs using a 24 × 24 mm silicon microchannel plate consisting of 23,348 asymmetric channels fabricated by photolithography and deep reactive ion etching. Each channel consisted of a 10-μm diameter straight-through micro-hole with a length of 70 μm and a 50 × 10 μm micro-slot with a depth of 30 μm at the outlet of each channel. The maximum dispersed phase flux for monodisperse emulsion generation increased with decreasing dispersed phase viscosity and ranged from over 120 L m⁻² h⁻¹ for soybean oil to 2,700 L m⁻² h⁻¹ for n-tetradecane. The droplet generation frequency showed significant channel to channel variations and increased with decreasing viscosity of the dispersed phase. For n-tetradecane, the maximum mean droplet generation frequency was 250 Hz per single active channel, corresponding to the overall throughput in the device of 3.2 million droplets per second. The proportion of active channels at high throughputs approached 100% for soybean oil and MCT oil, and 50% for n-tetradecane. The agreement between the experimental and CFD (Computational Fluid Dynamics) results was excellent for soybean oil and the poorest for n-tetradecane.     

A Novel In Vitro Assay Using Human iPSC-Derived Sensory Neurons to Evaluate the Effects of External Chemicals on Neuronal Morphology: Possible Implications in the Prediction of Abnormal Skin Sensation

Neuronal morphological changes in the epidermis are considered to be one of causes of abnormal skin sensations in dry skin-based skin diseases. The present study aimed to develop an in vitro model optimised for human skin to test the external factors that lead to its exacerbation. Human-induced pluripotent stem cell-derived sensory neurons (hiPSC-SNs) were used as a model of human sensory neurons. The effects of chemical substances on these neurons were evaluated by observing the elongation of nerve fibers, incidence of blebs (bead-like swellings), and the expression of nicotinamide mononucleotide adenylyl transferase 2 (NMNAT2). The nerve fiber length increased upon exposure to two common cosmetic preservatives—methylparaben and phenoxyethanol—but not to benzo[a]pyrene, an air pollutant at the estimated concentrations in the epidermis. Furthermore, the incidence of blebs increased upon exposure to benzo[a]pyrene. However, there was a decrease in the expression of NMNAT2 in nerve fibers, suggesting degenerative changes. No such degeneration was found after methylparaben or phenoxyethanol at the estimated concentrations in the epidermis. These findings suggest that methylparaben and phenoxyethanol promote nerve elongation in hiPSC-SNs, whereas benzo[a]pyrene induces nerve degeneration. Such alterations may be at least partly involved in the onset and progression of sensitive skin.