Highly sensitive and flexible pressure sensors were developed based on dielectric membranes composed of insulating microbeads contained within polyvinylidene fluoride (PVDF) nanofibers. The membrane is fabricated using a simple electrospinning process. The presence of the microbeads enhances porosity, which in turn enhances the sensitivity (1.12 kPa −1 for the range of 0−1 kPa) of the membrane when used as a pressure sensor. The microbeads are fixed in position and uniformly distributed throughout the nanofibers, resulting in a wide dynamic range (up to 40 kPa) without any sensitivity loss. The fluffy and nonsticky PVDF nanofiber features low hysteresis and ultrafast response times (∼10 ms). The sensor has also demonstrated reliable pressure detection over 10 000 loading cycles and 250 bending cycles at a 13 mm bending radius. These pressure sensors were successfully applied to detect heart rate and respiratory signals, and an array of sensors was fabricated and used to recognize spatial pressure distribution. The sensors described herein are ultrathin and ultralight, with a total thickness of less than 100 μm, including the electrodes. All of the materials comprising the sensors are flexible, making them suitable for on-body applications such as tactile sensors, electronic skins, and wearable healthcare devices.

We report high and versatile performances of 3D macroporous dielectric layers fabricated rapidly and easily using a baking-inspired foaming process.

Effects of hydroxyl group (OH) in the gate insulator (GI) of AlO x formed by atomic layer deposition on the negative bias illumination stress (NBIS) stability of amorphous InGaZnO (a-IGZO) thin film transistors (TFTs) by changing the deposition temperature (T dep ) of the AlO x GI are studied. There are no significant differences in the electrical properties and stabilities of each device, such as field effect mobility (μ FE ), subthreshold swing (S.S.), turn on voltage (V on ), positive bias temperature stress (PBTS), and negative bias temperature stress (NBTS). Meanwhile, the NBIS stability is improved, resulting in V on shift from À4.34 V to À2.48 V as the T dep of the GI increased. This suggests that as the amount of OH increases in GI, more hole/and or ionized V o trapping sites are formed in the bulk GI. Based on the energy level in photoluminescence (PL) spectra of ALD AlO x , it is suggested OH related-bulk trapping sites in ALD AlO x as the origin of non-bridging oxygen hole center (NBOHC) in AlO x GI.

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Oxide thin film transistor (TFT) and low-resistance electrode are necessary to manufacture transparent and high resolution fingerprint sensor for application to touch panel display. We adopted ITO/Ag/ITO triple layered stack as an electrode according to that inserting thin Ag layer between both sides of ITO layers definitely helps resistance decreases. Through simulation and optimization, we have chosen each thickness of three layers for optimal transmittance and sheet resistance, and developed dry etching conditions. Top gate structured IGZO TFT with triple layered S/D electrode showed outstanding electrical performance and is expected to be applied to transparent display panel.

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The sensitivity of existing fingerprint sensors (FPSs) can decrease considerably owing to environmental factors and parasitic capacitance. In order to overcome this limitation, this paper proposes a highly-sensitive 300 dpi mutual-capacitive transparent fingerprint sensor (FPS) with uniquely designed reference lines for device security. Specifically, the reference lines of the FPS induce capacitance cancellation. Images of fingertips under dry, wet, and oily surface conditions were obtained in the presence and absence of the reference lines. The results showed that the fingerprints were significantly distorted in anomalous surface environments when the reference lines were not used. However, when the reference lines were used, the sensitivity improved irrespective of the environmental conditions. With the edge-detection processing, the proposed FPS exhibited 9.25 %, 61.49 %, and 8.60 % increase in the ridge sensing improvement (RSI) of dry, oil, and wet condition, respectively, thus significantly enhancing the sensing capability. Therefore, we believe the proposed FPS can increase device security owing to its excellent performance.