Current railway track condition monitoring relies on inefficient human inspectors and expensive inspection vehicles, where high-frequency inspection is unreachable since these methods occupy the tracks. This paper proposes a battery-less railway monitoring system based on RF energy harvesting to detect early defects on rail tracks. The key part of the system is a battery-less wireless sensor tag (BLWST) installed on railway tracks. The BLWST can harvest RF energy from a reader installed on the train, and precisely measure and wirelessly transmit vibration condition of tracks back to the reader. The proposed system eliminates the demands for cables and battery replacement, thus achieving low installation and maintenance cost. The high-frequency monitoring also provides a more reliable inspection than existing methods. The BLWST is based on the 3-stage Dickson voltage multiplier (DVM) and can be activated by a dedicated RF power source at a maximum distance of 2.3 meters. Experiments show that a maximum energy conversion efficiency of 25% and 500 working cycles per second are achieved. For demonstration, we construct a miniaturized railway system with the battery-less prototype and exhibit a reliable wireless power transfer and data communication.

Bioelectronic devices implanted within the human body are increasingly used for diagnostic and therapeutic purposes, in which their functions and lifespan could be significantly improved with wireless energy transfer technology. However, limited by electromagnetic radiation, low power output, high stiffness, short transfer distance and tissue attenuation, most wireless energy transfer systems cannot meet the requirements of implantable medical devices (IMDs). Here, inspired by natural wood structures, we present a transmuscular ultrasonic wireless power transfer system based on a flexible wood-templated piezoelectric ultrasonic energy harvester (W-PUEH) in a unidirectional 3D interconnected ceramic–polymer topology. The developed flexible W-PUEH device demonstrates an output voltage of 21 V, an output current of 2 mA, and an average output power density of 304 μW cm⁻², one order of magnitude higher than the state of the art. Further ex vivo and in vivo experiments demonstrate the sufficient power supply capacity of W-PUEH and its potential applications in implantable devices for the improvement of life quality and well-being of the recipients.

A novel self-powered wearable motion sensor for monitoring the spiking gesture of volleyball athletes has been manufactured from piezoelectric PVDF film. The PVDF film can convert body mechanical energy into electricity through the piezoelectric effect, and the flexible device can be conformably attached on the hand or arm. The sensor can work independently without power supply and actively output piezoelectric signals as the sports information. The sensor can detect the tiny and fine motion of spiking movement in playing volleyball, reflecting the skill. Additionally, the sensor can also real-time monitor the pulse changes and language during a volleyball match. The self-powered sensors can link to a wireless transmitter for uploading the sports information and building big sports data. This work can provoke a new direction for real-time sports monitoring and promote the development of big sports data.

Sensor matrices are essential in various fields including robotics, aviation, health care, and industrial machinery. However, conventional sensor matrix systems often face challenges such as limited reconfigurability, complex wiring, and poor robustness. To address these issues, we introduce a one-wire reconfigurable sensor matrix that is capable of conforming to three-dimensional curved surfaces and resistant to cross-talk and fractures. Our frequency-located technology, inspired by the auditory tonotopy, reduces the number of output wires from row × column to a single wire by superimposing the signals of all sensor units with unique frequency identities. The sensor units are connected through a shared redundant network, giving great freedom for reconfiguration and facilitating quick repairs. The one-wire frequency-located technology is demonstrated in two applications—a pressure sensor matrix and a pressure-temperature multimodal sensor matrix. In addition, we also show its potential in monitoring strain distribution in an airplane wing, emphasizing its advantages in simplified wiring and improved robustness.