Porous microstructure pressure sensors that are highly sensitive, reliable, low-cost, and environment-friendly have aroused wide attention in intelligent biomedical diagnostics, human–machine interactions, and soft robots. Here, an all-tissue-based piezoresistive pressure sensor with ultrahigh sensitivity and reliability based on the bottom interdigitated tissue electrode and the top bridge of a microporous tissue/carbon nanotube composite was proposed. Such pressure sensors exhibited ultrahigh sensitivity (≈1911.4 kPa−1), fast response time (<5 ms), low fatigue of over 2000 loading/unloading cycles, and robust environmental degradability. These enabled sensors can not only monitor the critical physiological signals of the human body but also realize electrothermal conversion at a specific voltage, which enhances the possibility of creating wearable thermotherapy electronics for protecting against rheumatoid arthritis and cervical spondylosis. Furthermore, the sensor successfully transmitted wireless signals to smartphones via Bluetooth, indicating its potential as reliable skin-integrated electronics. This work provides a highly feasible strategy for promoting high-performance wearable thermotherapy electronics for the next-generation artificial skin.
Improving image sticking in liquid crystal display (LCD) has attracted tremendous interest because of its potential to enhance the quality of the display image. Here, we proposed a method to evaluate the residual direct current (DC) voltage by varying liquid crystal (LC) cell capacitance under the combined action of alternating current (AC) and DC signals. This method was then used to study the improvement of image sticking by doping γ-Fe2O3 nanoparticles into LC materials and adjusting the friction torque difference of the upper and lower substrates. Detailed analysis and comparison of residual characteristics for LC materials with different doping concentrations revealed that the LC material, added with 0.02 wt% γ-Fe2O3 nanoparticles, can absorb the majority of free ions stably, thereby reducing the residual DC voltage and extending the time to reach the saturated state. The physical properties of the LC materials were enhanced by the addition of a small amount of nanoparticles and the response time of doping 0.02 wt% γ-Fe2O3 nanoparticles was about 10% faster than that of pure LC. Furthermore, the lower absolute value of the friction torque difference between the upper and lower substrates contributed to the reduction of the residual DC voltage induced by ion adsorption in the LC cell under the same conditions. To promote the image quality of different display frames in the switching process, we added small amounts of the nanoparticles to the LC materials and controlled friction technology accurately to ensure the same torque. Both approaches were proven to be highly feasible.
Fabrication of organic thin-film transistors (OTFTs) via high throughput solution process routes have attracted extensive attention. Herein, we report a simple one-step coating method for vertical phase separation of the poly(3-hexylthiophene-2,5-diyl) (P3HT) and poly(methyl methacrylate) (PMMA) blends as semiconducting and dielectric layers in OTFTs. These OTFTs can be used as phototransistors for ultraviolet (UV) light detection, where the phototransistors exhibited great photosensitivity of 597.6 mA/W and detectivity of 4.25 × 1010 Jones under 1 mW/cm2 UV light intensity. Studies of the electrical properties in these phototransistors suggested that optimized P3HT contents in the blend film can facilitate the improvement of film morphology, and therefore form optimized vertical phase separation of the PMMA and P3HT. These results indicate that the simple one-step fabrication method creates possibilities for realizing high throughput phototransistors with great photosensitivity.
11 February 2020 in Journal of Physics D: Applied Physics
Image sticking in liquid crystal display (LCD) can affect the display quality. The saturated residual direct current voltage (SRDCV) can be obtained by analyzing the change in the capacitance of LC cell under the direct current bias, through which image sticking can be evaluated. On this basis, the image sticking was evaluated in the in-plane switching (IPS) cell filled in the LC with negative dielectric anisotropy for different electrode structures, cell gaps (i.e. 3.8, 5.8, and 7.5 µ m), and doping concentrations of γ -Fe 2 O 3 nanoparticles (i.e. 0.068, 0.136, 0.204, and 0.272 wt%). The SRDCV decreases under the same conditions by adjusting the ratio of electrode width and electrode gap and it decreases with the cell gap increases. For the thickness of 3.8 µ m, the SRDCV initially decreases and then increases as the doping concentration of γ -Fe 2 O 3 nanoparticles increases; while for the thicknesses of 5.8 µ m and 7.5 µ m, the SRDCV decreases as the doping concentration of γ -Fe 2 O 3 nanoparticles increases. The results show that the structure design of the IPS-LCD and the doping of nanoparticles can effectively improve image sticking and provide useful guidance for enhancing the display quality of LCD.
Traditional target motion analysis (TMA) is normally carried out with a two-step method, where the first step is to search for the parameterized measurements (e.g., bearing, Doppler) of a target with signal processing algorithms, followed by a recursive or batched geographic tracking algorithm. In this paper, we propose a new direct TMA (DTMA) algorithm with a sensor array based on the extended Kalman filter (EKF) running within the Cartesian coordinate. In such a scenario, the sensor has to execute a maneuver to gain the observability with respect to target state. By exploiting the direction of arrival (DOA) effect of the received signal, the Jacobian matrix, which is essential for linearizing the measurement function with the EKF method, is achieved. A remarkable feature of the proposed algorithm is that it can directly estimate target state in the Cartesian coordinate from the single snapshot received signal. The effectiveness of proposed algorithm is assessed via simulation experiments.