Wind energy as a renewable energy source is easily available and widely distributed in cities. However, current wind-energy harvesters are inadequate at capturing energy from low-speed winds in urban areas, thereby limiting their application in distributed self-powered sensor networks. A triboelectric–electromagnetic hybrid harvester with a low startup wind speed (LSWS-TEH) is proposed that also provides output power within a wide range of wind speeds. An engineering-implementable propeller design method is developed to reduce the startup wind speed of the harvester. A mechanical analysis of the aerodynamics of the rotating propeller is performed, and optimal propeller parameter settings are found that greatly improved its aerodynamic torque. By combining the high-voltage output of the triboelectric nanogenerator under low-speed winds with the high-power output of the electromagnetic generator under high-speed winds, the harvester can maintain direct current output over a wide wind-speed range after rectification. Experiments show that the harvester activates at wind speeds as low as 1.2 m/s, powers a sensor with multiple integrated components in 1.7 m/s wind speeds, and drives a Bluetooth temperature and humidity sensor in 2.7 m/s wind speeds. The proposed small, effective, inexpensive hybrid energy harvester provides a promising way for self-powered requirements in smart city settings.

Microrobotic contact manipulation enables automated and precise cell capture, positioning and screening and has potential in biomedical engineering and disease detection. However, when using an optical microscope for visual positioning of targets, the poor clarity, limited cell-background contrast and lack of global 3D information of the cells in the field of view hinder global strategy making and automation, thereby affecting the accuracy and efficiency of manipulation. Here, we propose the 3D locating of multiple biological targets based on digital holography. Global–local combined visual feedback is developed for overall spatial locating and partial locating in a liquid-phase bright-field environment. By applying a filtering-based planar locating algorithm and maximum-area-based depth detection algorithm, the 3D global distribution of micro-targets in the field of view is periodically updated with a high detection rate. By applying a planar locating algorithm based on a convolutional neural network and a depth detection algorithm based on a gradient descent, the 3D fast locating of targets is performed precisely. Experiments show that the detection rate of the global positioning is 95.1%, the mean average precision of the local planar positioning is 90.53%, and the deviation of the local depth positioning is 1.22 $\mu$ m. When capturing cells, this method reaches an average speed of 7.4 cells/min and a collection rate of 90.5%. We anticipate that our method will support the research in cell-based bioengineering including cell screening and early disease diagnosis. Note to Practitioners —Automated cell manipulation is one of the most significant techniques in cell-based biomedical applications. This paper introduces a three-dimensional multi-target visual positioning method for automated cell manipulation. Combining with holographic imaging technique, the global information for the cells in the limited field of view is provided with improved imaging clarity and extended depth of field. The visual recognition algorithm can screen and extract the rare cells in the cell population, which will support the research in the field of early disease diagnosis and biomedicine. The research outcome provides an effective and precise solution to achieve biological targets positioning, capture, and screening within 3D liquid-phase bright-field environment.

With the increase of the urbanization in modern society, road safety has become a pivotal issue of smart cities. The development of road safety monitoring is concentrated on the innovation and progress of sensors. Here, an all-in-one customizable pressure-velocity sensor (PVS) is developed for simultaneous monitoring of road traffic flow and vehicle velocity. The inclined dielectric-electrode middle layer with gradient structure and grid electrode is designed to eliminate errors caused by data fluctuations, and improve sensor sensitivity and monitoring reliability simultaneously. Under a pressure of 13N, the sensitivity of the PVS to measure velocity is 375.39 mV/mm/s. By designing the geometry of the intermediate layer as an inclined sandwich "return" structure, it is possible to improve the sensitivity of pressure measurement without changing the volume of the PVS. By using a grid structure and an inclined "return" structure, the measurement pressure error range of the PVS can be reduced to 1N. The design of inclined sandwich "return" structure also reflects the customizability of the PVS. The PVS can still output signals normally after 10,800 working cycles. With the advantages of easy installation, low cost, simple structure, easy maintenance, high integration and self-powered, the PVS is a promising sensor for road safety monitoring in the development of smart cities.

With the development of society and the advancement of technology, the emergence of the Internet of Things (IoT) has changed people’s lifestyles and raised the demand for energy to a new level. However, there are some drawbacks in terms of energy supply for IoT sensors, such as limited battery capacity and limitations in replacement and maintenance. Therefore, it has become urgent to develop a sustainable green energy source (wind energy) using the surrounding environment. Meanwhile, triboelectric nanogenerators (TENGs) with advantages such as flexible structure, low manufacturing cost, and environmental friendliness provide enormous potential for constructing self-powered sensing systems. In this work, we present a novel coaxial rolling charge pump TENG (CR-TENG) based on wind energy to enhance the output performance and durability. The rolling friction charge pump TENG directly injects positive and negative charges into the main TENG, which is more wear-resistant compared to sliding friction, and greatly increases the charge density and output power. In addition, the charge pumping part and the main TENG adopt the coaxial design, reducing the complexity of the structural design. On comparing the output performance of the CR-TENG under the initial state, rectifier bridge supplemental charge strategy, and charge pump supplemental charge strategy, results shown that the output voltage performance of the CR-TENG can be improved by 5800% under the charge pump supplemental charge strategy. Moreover, the output performance of the CR-TENG remains stable after 72,000 cycles. The output power of the CR-TENG can reach 1.21 mW with a load resistance of 3 × 10⁷ Ω. And the CR-TENG can charge a 0.1 μF capacitor to 5 V in just 1.6 s. This work provides new insights for the rotary durable high output charge pump compensating a triboelectric nanogenerator and demonstrates the important potential of harvesting environmental energy to supply intelligent IoT nodes.

Due to the excellent directivity, strong penetrability, and no electromagnetic shielding effect, ultrasonic waves have good potential for wireless energy transmission and information transfer inside and outside of sealed metal devices. However, traditional ultrasonic based energy transmission methods usually result in considerable energy consumption because of the impedance mismatch during the impedance modulation of the communication. This paper presents an optimal design method for efficient energy transfer during ultrasonic communication. The channel equivalent circuit model is established by only using the acoustic-electric channel scattering parameters. According to the equivalent circuit model, the channel impedance matches with a weak mismatch state is performed during the communication. In this way, the impedance modulation effect is ensured with a lower decrease in the energy transmission efficiency. Finally, the simultaneous energy transmission and impedance modulation are carried out through the 11 mm thick 304 stainless steel plate. The transmission power is 37.86 W with a transmission efficiency of 45.75%, and the modulation rate is 10 Kbps. Compared with the traditional methods, our proposed energy transmission efficiency is increased by 17.62%. The results verify the proposed method’s effectiveness and the high accuracy of the model. The proposed method has great engineering applications and broad prospects in condition monitoring of metallic environments.

The hybrid energy harvester installed on mechanical equipment can convert vibration energy into electrical energy to power sensors, microcontrollers, wireless communication, etc., effectively avoiding cumbersome battery maintenance and line failures. With the high sensitivity to vibration changes, the hybrid energy harvester can also be used to monitor the state of the mechanisms while collecting vibration energy, avoiding accidents and economic losses caused by malfunction. In this work, we designed a highly integrated device that combines energy harvesting and sensing detection functions. The main structure uses magnetic permeable materials to form a unique electromagnetic generator (EMG) with magnetic circuit switching. Piezoelectric generator (PEG) and triboelectric nanogenerator (TENG) are distributed on both sides of the cantilever beam, and the three structures are integrated together through the cantilever beam, which not only makes full use of the structural space of the device, but also improves the power generation efficiency. Under the excitation of a vibration frequency of 8 Hz and an acceleration of 2 g, the peak power of the EMG, PEG, and TENG modules were 22 mW, 1.9 mW, and 48 μW, respectively. TENG unit was selected for identifying the gear state, achieving an accuracy rate of 93% in tests. Ultimately, the hybrid generator was applied to a car engine, successfully powering a thermometer or sensing detection systems, realizing timely signal transmission. Through the performance testing of the device, it demonstrates a broad application prospect in transportation, industrial production.