Among kinds of flexible tactile sensors, piezoelectric tactile sensor has the advantage of fast response for dynamic force detection. However, it suffers from low sensitivity at high-frequency dynamic stimuli. Here, inspired by finger structure—rigid skeleton embedded in muscle, we report a piezoelectric tactile sensor using a rigid-soft hybrid force-transmission-layer in combination with a soft bottom substrate, which not only greatly enhances the force transmission, but also triggers a significantly magnified effect in d₃₁ working mode of the piezoelectric sensory layer, instead of conventional d₃₃ mode. Experiments show that this sensor exhibits a super-high sensitivity of 346.5 pC N⁻¹ (@ 30 Hz), wide bandwidth of 5–600 Hz and a linear force detection range of 0.009–4.3 N, which is ~17 times the theoretical sensitivity of d₃₃ mode. Furthermore, the sensor is able to detect multiple force directions with high reliability, and shows great potential in robotic dynamic tactile sensing.

Flexible pressure sensors are indispensable components in various applications such as intelligent robots and wearable devices, whereas developing flexible pressure sensors with both high sensitivity and wide linear range remains a great challenge. Here, we present an elegant strategy to address this challenge by taking advantage of a pyramidal carbon foam array as the sensing layer and an elastomer spacer as the stiffness regulator, realizing an unprecedentedly high sensitivity of 24.6 kPa⁻¹ and an ultra-wide linear range of 1.4 MPa together. Such a wide range of linearity is attributed to the synergy between the nonlinear piezoresistivity of the sensing layer and the nonlinear elasticity of the stiffness regulator. The great application potential of our sensor in robotic manipulation, healthcare monitoring, and human-machine interface is demonstrated. Our design strategy can be extended to the other types of flexible sensors calling for both high sensitivity and wide-range linearity, facilitating the development of high-performance flexible pressure sensors for intelligent robotics and wearable devices.

A highly oriented BaTiO₃ film was assembled using an interfacial method, and a piezoelectric generator was fabricated to harvest wind energy.

Herein, a piezoelectric vibration energy harvester (PVEH) using liquid as an energy-capturing medium is proposed to simultaneously achieve ultralow frequency, low intensity, and multidirectional vibration energy harvesting in a horizontal plane, which is difficult to realize using traditional PVEHs. The proposed harvester comprises a cylindrical container with a certain liquid, a piezoelectric cantilever beam, ropes, and floater-lever arrays. The experimental results indicate that the proposed harvester with a single floater-lever can generate 9.8 μW under an ultralow frequency (2.6 Hz) and a low intensity vibration excitation (0.03 g), and the normalized power density is 8.89 μW/(cm³ g² Hz). Under a multidirectional vibration excitation (360° in the horizontal plane) with frequencies below 3 Hz and an acceleration of 0.03 g, the two proposed harvesters with three and four floater-levers indicate a maximum output power (P_max) deviation of 24.92% and 28.31%, respectively, and an angle bandwidth of 360° (using $\sqrt{2}$ /2P_max as the standard). All the experimental results indicate that the proposed PVEH is highly promising as an energy supply of wireless sensor networks distributed in ultralow frequency, low intensity, and multidirectional applications.

This paper presents a novel piezoelectric vibration energy harvester (PVEH) in which a high-frequency generating beam (HFGB) is driven by an array of low-frequency driving beams (LFDBs) using ropes. Two mechanisms based on frequency upconversion and multimodal harvesting work together to broaden the frequency bandwidth of the proposed vibration energy harvester (VEH). The experimental results show that the output power of generating beam (GB) remains unchanged with the increasing number of driving beams (DBs), compared with the traditional arrays of beams vibration energy harvester (AB-VEH), and the output power and bandwidth behavior can be adjusted by parameters such as acceleration, rope margin, and stiffness of LFDBs, which shows the potential to achieve unlimited wideband vibration energy-harvesting for a variable environment.

Though numerous piezoelectric vibration energy harvesters (PVEHs) have been designed and investigated to provide power supply for wireless sensors or wearable devices, it remains a challenge for traditional PVEHs to work effectively in an environment of low frequency, low acceleration and multidirectional vibrations. This work presents a PVEH using a low-frequency energy-capturing resonant system formed by a rolling ball in a hemispherical shell and driven by a rope. Due to the symmetry of the sphere, the ball can be excited at multiple directions in 3D space, and the piezoelectric beam can be pulled by the ball through a rope in multiple directions. Thus, the efficient multidirectional energy harvesting under low frequency (<10 Hz) and ultralow intensity (<0.1 g ) vibrations could be realized. A mass-spring-damper equivalent model was built to understand the operation mechanism of the proposed PVEH. The results show that the proposed PVEH has a potential to collect energy in any direction in 3D space, and could achieve a good angle bandwidth with 360° for ϕ and 240° for β under the excitation of a = 0.04 g, f = 6.8 Hz with the acceleration a ⃗ a , β , φ defined in the spherical coordinate system. The developed PVEH can generate 6.5 μ W under a low-intensity excitation (0.03 g ), and the normalized power density can reach 22.63 μ W/(cm ³ g ² Hz). Moreover, the minimum start-up acceleration analysis of the proposed PVEH indicates that the PVEH can capture multidirectional energy from vibrations as low as 0.01 g . In addition, both simulation and experimental study on rope redundancy and ball mass show that they can be used to adjust the device performance easily without structure re-fabrication. Overall, this study demonstrates a new mechanism that could effectively harvest low frequency, ultralow intensity and multidirectional vibration energy.