Soft, capacitive tactile (pressure) sensors are important for applications including human–machine interfaces, soft robots, and electronic skins. Such capacitors consist of two electrodes separated by a soft dielectric. Pressing the capacitor brings the electrodes closer together and thereby increases capacitance. Thus, sensitivity to a given force is maximized by using dielectric materials that are soft and have a high dielectric constant, yet such properties are often in conflict with each other. Here, a liquid metal elastomer foam (LMEF) is introduced that is extremely soft (elastic modulus 7.8 kPa), highly compressible (70% strain), and has a high permittivity. Compressing the LMEF displaces the air in the foam structure, increasing the permittivity over a large range (5.6–11.7). This is called “positive piezopermittivity.” Interestingly, it is discovered that the permittivity of such materials decreases (“negative piezopermittivity”) when compressed to large strain due to the geometric deformation of the liquid metal droplets. This mechanism is theoretically confirmed via electromagnetic theory, and finite element simulation. Using these materials, a soft tactile sensor with high sensitivity, high initial capacitance, and large capacitance change is demonstrated. In addition, a tactile sensor powered wirelessly (from 3 m away) with high power conversion efficiency (84%) is demonstrated.

In this work, a water splitting photoanode composed of a BiVO 4 thin film surface modified by the deposition of a rhodium (Rh)-doped SrTiO 3 perovskite is fabricated, and the Rh-doped SrTiO 3 outer layer exhibits special photoelectrochemical (PEC) oxygen evolution co-catalytic activity. Controlled intensity modulated photo-current spectroscopy, electrochemical impedance spectroscopy, and other electrochemical results indicate that the Rh on the perovskite provide an oxidation active site during the PEC water oxidation process by reducing the reaction energy barrier for water oxidation. Theoretical calculations indicate that the water oxidation reaction is more likely to occur on the (110) crystal plane of Rh-SrTiO 3 because the oxygen evolution reaction overpotential on the (110) crystal plane is reduced significantly. Therefore, the obtained BiVO 4 /Rh5%-SrTiO 3 photoanode exhibits an optimized PEC performance. In particular, it facilitates the saturation of the photocurrent density. Thus, the presence of doped Rh in SrTiO 3 can reduce the amount of noble metals required while achieving excellent and stable oxygen evolution properties.

No abstract

No abstract

In this paper, a novel concurrent design of integrated PIN-diode based limiter and low noise amplifier (LNA) is presented for Ka-band MMICs fabricated using a combined PIN/0.15-µm-pHEMT technology. To improve the small-signal performance and the power-handling capability of the limiter-LNA, the improvement of the PIN-limiter circuit structure and the survivability of the LNA network are proposed. In addition, the total chip area is 2.5 mm × 1.2 mm with an equalizer integrated on chip behind the limiter-LNA to improve the bandwidth with a minimum impact on overall NF. The measurements show that the proposed limiter-LNA with only two-stage limiter structure tolerates up to 38 dBm continuous wave (CW) input power without failure, and the average gain and the noise figure for the limiter-LNA are 17 dB and 2.2-2.6 dB, respectively, on the 30-38 GHz frequency bandwidth. INDEX TERMS GaAs pHEMT, integrated limiter low noise amplifier (LNA), MMIC, noise figure (NF), PIN diode.