In this study, a 0-3 piezoelectric composite based on lead zirconate-titanate (PZT)/polyvinyl-butyral (PVB) was fabricated and characterized for its potential application in tactile sensing. The 0-3 composite was developed to incorporate the advantages of both ceramic and polymer. The paste of 0-3 PZT–PVB composite was printed using a conventional screen-printing technique on alumina and mylar substrates. The thickness of the prepared composite was approximately 80 μm. After printing the top electrode of the silver paste, 10 kV/mm of DC field was applied at 25 °C, 120 °C, and 150 °C for 10 min to align the electric dipoles in the composite. The piezoelectric charge coefficient of $d_{33}$ and the piezoelectric voltage coefficient of $g_{33}$ were improved by increasing the temperature of the poling process. The maximum values of $d_{33}$ and $g_{33}$ were 14.3 pC/N and 44.2 mV·m/N, respectively, at 150 °C. The sensor’s sensitivity to the impact force was measured by a ball drop test. The sensors showed a linear behavior in the output voltage with increasing impact force. The sensitivity of the sensor on the alumina and mylar substrates was 1.368 V/N and 0.815 V/N, respectively. The rising time of the sensor to the finger touch was 43 ms on the alumina substrate and 35 ms on the mylar substrate. Consequently, the high sensitivity and fast response time of the sensor make the 0-3 PZT–PVB composite a good candidate for tactile sensors.

This study proposes an approach to enhance frequency characteristics for AlGaN/gallium nitride (GaN) high-electron-mobility transistors (HEMTs) by employing an air-bridged source-connected field plate to an asymmetric passivation structure. To overcome simulation limitations, we performed the device simulation by matching simulated results with measured data, applying various simulation models, and performing comparative analysis of frequency characteristics between simulated and calculated values using a small-signal equivalent circuit. Thus, the simulation results were well matched with the measured data, achieving an error rate of 1.4%, confirming the device simulation reliability. Asymmetric passivation HEMT for conventional source-connected field plate structures exhibited reduced parasitic capacitances, with notable increased cutoff and maximum oscillation frequencies by 21.7% and 7.8%, respectively. We applied an additional air-bridged source-connected field plate structure to the asymmetric passivation HEMT to further enhance RF performance, significantly increasing cutoff frequency by 31.6% compared with asymmetric passivation with source-connected field plate structure. These results represent outstanding RF performance without any degradation of dc characteristics.

The rapid advancement of wearable devices has increased interest in electronic skin (e-skin) equipped multifunctional sensors. Consequently, research is underway to develop stretchable sensors capable of detecting multiple external stimuli. These sensors often employ various one-dimensional nanomaterials to enhance their sensing performance. This paper introduces a novel structure and batch fabrication process for a stretchable bifunctional sensor. This sensor is composed of polyaniline nanofibers (PANI NFs) and zinc oxide nanorods (ZnO NRs), arranged in polydimethylsiloxane (PDMS). We used three Au electrodes to help measure the electrical properties of the detectors. The substrate of the stretchable bifunctional sensor was crafted from a single substrate, which comprises two types of PDMS. This design aims to achieve a Young modulus similar to human skin while protecting the Au electrodes and ZnO NRs from deformation. We also introduce a novel batch fabrication process that sequentially synthesizes PANI NFs and ZnO NRs. Unlike previous studies that used stacked structures or nanorod composites, our approach allows these nanomaterials to retain their individual sensor properties, thereby ensuring enhanced conductivity and sensitivity. As a result, the PANI NFs showed clear and repeatable sensing properties and high strain sensitivity with gauge factors exceeding 63 under 30% strain. In addition, the external quantum efficiency of ZnO NRs reached 79.6% at 340 nm wavelength with an on-off current ratio of 25.3. Overall, the proposed stretchable bifunctional sensor demonstrates the potential for various applications, including e-skin, wearable devices, healthcare, and robotics.