Integration of advanced nanogenerator technology with conventional textile processes fosters the emergence of textile-based nanogenerators (NGs), which will inevitably promote the rapid development and widespread applications of next-generation wearable electronics and multifaceted artificial intelligence systems. NGs endow smart textiles with mechanical energy harvesting and multifunctional self-powered sensing capabilities, while textiles provide a versatile flexible design carrier and extensive wearable application platform for their development. However, due to the lack of an effective interactive platform and communication channel between researchers specializing in NGs and those good at textiles, it is rather difficult to achieve fiber/fabric-based NGs with both excellent electrical output properties and outstanding textile-related performances. To this end, a critical review is presented on the current state of the arts of wearable fiber/fabric-based piezoelectric nanogenerators and triboelectric nanogenerators with respect to basic classifications, material selections, fabrication techniques, structural designs, and working principles, as well as potential applications. Furthermore, the potential difficulties and tough challenges that can impede their large-scale commercial applications are summarized and discussed. It is hoped that this review will not only deepen the ties between smart textiles and wearable NGs, but also push forward further research and applications of future wearable fiber/fabric-based NGs.

Fiber/Fabric-Based Piezoelectric and Triboelectric Nanogenerators for Flexible/Stretchable and Wearable Electronics and Artificial Intelligence.

Department of Electrical and Computer Engineering, National University of Singapore, Singapore, 117576, Singapore Center for Intelligent Sensors and MEMS, National University of Singapore, Singapore, 117608, Singapore Hybrid-Integrated Flexible (Stretchable) Electronic Systems Program, National University of Singapore, Singapore, 117608, Singapore NUS Suzhou Research Institute (NUSRI), Suzhou, 215123, China NUS Graduate School for Integrative Science and Engineering, National University of Singapore, Singapore, 117456, Singapore

Progress in wearable electronics/photonics—Moving toward the era of artificial intelligence and internet of things

Electronic skin (e-skin) has been under the spotlight due to great potential for applications in robotics, human–machine interfaces, and healthcare. Meanwhile, triboelectric nanogenerators (TENGs) have been emerging as an effective approach to realize self-powered e-skin sensors. In this work, bioinspired TENGs as self-powered e-skin sensors are developed and their applications for robotic tactile sensing are also demonstrated. Through the facile replication of the surface morphology of natural plants, the interlocking microstructures are generated on tribo-layers to enhance triboelectric effects. Along with the adoption of polytetrafluoroethylene (PTFE) tinny burrs on the microstructured tribo-surface, the sensitivity for pressure measurement is boosted with a 14-fold increase. The tactile sensing capability of the TENG e-skin sensors are demonstrated through the characterizations of handshaking pressure and bending angles of each finger of a bionic hand during handshaking with human. The TENG e-skin sensors can also be utilized for tactile object recognition to measure surface roughness and discern hardness. The facile fabrication scheme of the self-powered TENG e-skin sensors enables their great potential for applications in robotic dexterous manipulation, prosthetics, human–machine interfaces, etc.

Bioinspired Triboelectric Nanogenerators as Self-Powered Electronic Skin for Robotic Tactile Sensing

Nanogenerators for smart cities in the era of 5G and Internet of Things

Wearable triboelectric nanogenerators for biomechanical energy harvesting

A stretchable dual-mode sensor array for multifunctional robotic electronic skin

Triboelectric nanogenerators enabled sensing and actuation for robotics

A self-powered smart safety belt enabled by triboelectric nanogenerators for driving status monitoring

Electronic‐skin (E‐skin) has been investigated extensively for robotic tactile sensing. However, E‐skin sensors based on flexible metamaterials are still challenging to achieve. Moreover, the implementation of E‐skin sensor arrays in the actual monitoring of robotic grasping and manipulation conditions are rather limited due to the difficulty in data processing. Herein, high‐performance E‐skin strain sensors based on flexible auxetic metamaterials are reported, which endow the sensors with the capability of measuring both compressive (40%) and tensile (>80%) strain in a wide range and superior sensitivity, as compared with sensors without the structure. With perception data collected by the sensors, a generic method for real‐time detection of unstable robotic grasping is established. Through this method, the complicated problem of processing large‐scale arrayed sensor signals is simplified into the calculation of two indices, which extract both time and frequency domain characteristics of the signals. The total detection time (including sensor measurement response and data processing) can be as short as 100 ms, in line with human skin response in slippage perception. Accurate detections in real‐time during various grasping and manipulation tasks are presented, demonstrating the great value of the sensors and the detection approach in robotic perception and dexterous manipulation.

Yangyang Li

Papers

Bioinspired Triboelectric Nanogenerators as Self-Powered Electronic Skin for Robotic Tactile Sensing

A stretchable dual-mode sensor array for multifunctional robotic electronic skin

Triboelectric nanogenerators enabled sensing and actuation for robotics

A self-powered smart safety belt enabled by triboelectric nanogenerators for driving status monitoring

Flexible Mechanical Metamaterials Enabled Electronic Skin for Real‐Time Detection of Unstable Grasping in Robotic Manipulation