The flexoelectric effect refers to the electromechanical coupling between electric polarization and mechanical strain gradient. It universally exists in a variety of materials in any space group, such as liquid crystals, dielectrics, biological materials, and semiconductors. Because of its unique size effect, nanoscale flexoelectricity has shown novel phenomena and promising applications in electronics, optronics, mechatronics, and photovoltaics. In this review, we provide a succinct report on the discovery and development of the flexoelectric effect, focusing on flexoelectric materials and related applications. Finally, we discuss recent flexoelectric research progress and still-unsolved problems.

Artificial Intelligence (AI) has shown the power to enhance the functionality of sensors and enable intelligent human-machine interfaces through machine learning-based data analysis. However, the good performance of AI is always accompanied by a large amount of data and high computational complexity. Though cloud computing appears to be the right solution to this issue with the advent of the 5G era, a certain intelligence of the edge terminal is also important to make the entire integrated intelligent system more efficient. The current development of microelectronic, wearable, AI, and neuromorphic technologies pave the way to realize advanced edge computing by integrating silicon-based high-computing-power neuromorphic chips with anthropomorphic wearable sensory devices and show the potential to achieve human-like self-sustainable decentralized intelligence to enable the next-generation of AI. Hence, in this review, we systematically introduce the related progress in terms of wearable electronics that can mimic the biological features of humans' sensory systems and the development of neuromorphic/in-sensor computing technologies. Discussion on implementing the integrated human-like perception and sensation system with silicone-based computing chips and non-silicone-based wearable functional units and our perspectives are also provided.

Flexible and wearable electronics are attracting surging attention due to their potential applications in human health monitoring and precision therapies. Safety hazards including strong magnetic field and electric leakage are big risk factors for human health. It remains challenging to develop self-powered and wearable safety hazard sensors that could not only be able to monitor human motions but also have functions for detecting potential hazards. In this work, we fabricated a self-powered, shapeable, and wearable magnetic triboelectric nanogenerator (MTENG) based on ferrofluid, Ecoflex, and carbonized silk fabric that possessed effective hazard prevention and biomechanical motion sensing ability. A peak open-circuit voltage of 0.7 V and short-circuit current of 10 μA m−2 can be achieved when magnetic field is changed between 3.5 and 37.1 mT. As a component of triboelectric layer of the MTENG, ferrofluid can substantially extend the range of its sensing capabilities to many hazardous cues such as dangerous magnetic field. Furtherly, the developed multifunctional and self-powered sensor can be used to monitor human activities such as drinking water and bending finger. This effort opens up a new design opportunity for hazard avoidance wearable electronics and self-powered sensors.