Evaporation-driven electricity generation has recently emerged as a promising strategy for harvesting ubiquitous ambient energy. Among various material platforms, wood-based evaporation-driven electricity generators have attracted growing attention owing to their aligned microchannels, intrinsic capillary transport capability, and sustainability. However, the electrical output of unmodified wood remains insufficient to meet the power requirements of practical microsystems. Here, inspired by the architecture of the lotus, we report a bioinspired wood-based evaporation-driven electricity micro-generator with enhanced performance. The hydrophobic micro-nano hierarchical structures of lotus leaves inspire the construction of a microstructured and fluorinated interface on the wood surface to enhance interfacial evaporation. Meanwhile, inspired by the vascular structure of lotus petioles, partial delignification is applied to the bottom region of the wood to enlarge pore channels and establish capillary-Laplace pressure gradients for accelerated water transport. In combination with poly(4-styrenesulfonic acid) (PSS) modification to regulate ionic transport, the resulting device exhibits an approximately 234% increase in output voltage compared with natural wood. Furthermore, assembled devices can be connected in series to charge conventional low-power electronic systems, demonstrating strong potential for autonomous Internet of Things (IoT) and off-grid micro-energy applications.

Wearable biomechanical energy harvesting devices have received a lot of attention recently, benefiting from the rapid advancement of theories and devices in the field of the micro electromechanical system (MEMS). They not only fulfil the requirements for powering wearable electronic devices but also provide an attractive prospect for powering self-powered flexible electronic devices when wearing. In this article, we provide a review of the theories and devices of biomechanical energy harvesting technology for wearable applications. Three different forms of biomechanical energy harvesting mechanisms, including the piezoelectric effect, electromagnetic effect, and electrostatic effect, are investigated in detail. The fundamental principle of converting other types of energy from the biomechanical environment into electrical energy, as well as the most commonly-used analytical theoretical models, are outlined for each process. Therefore, the features, properties, and applications of energy harvesting devices are summarized. In addition, the coupled multi-effect hybrid energy harvesting devices are listed, showing the various possibilities of biomechanical energy harvesting devices for serving as sources, sensors, and actuators. Finally, we present perspectives on the future trends of biomechanical energy harvesting devices for wearable electronics applications.

Transparent conductive films that are based on nanowire networks are essential to construct flexible, wearable, and even stretchable electronics. However, large-scale precise micropatterning, especially with regard to the controllability of the organizing orientation of nanowires, is a critical challenge. Herein, we proposed a liquid film rupture self-assembly approach for manufacturing transparent conductive films with microstructure arrays based on a highly ordered nanowire network. The large-scale microstructure conductive films were fabricated through air–liquid interface self-assembly and liquid film rupture self-assembly. Six typical micropattern morphologies, including square, hexagon, circle, serpentine, etc., were prepared to reveal the universal applicability of the proposed approach. The homogeneity and controllability of this approach were verified for multiple assemblies. With the assembly cycles increasing, the optical transmittance decreases slightly. In addition, theoretical model analysis is carried out, and the analytical formula of the speed of the film moving with the surface tension and the density of the liquid film is presented. Finally, the feasibility of this approach for piezoresistive strain sensors is verified. This fabrication approach demonstrated a cost-effective and efficient method for precisely arranging nanowires, which is useful in transparent and wearable applications.

As one of the promising human–machine interfaces, wearable sensors play an important role in modern society, which advances the development of wearable fields, especially in the promising applications of electronic skin (e-skin), robotics, prosthetics, and healthcare. In the last decades, wearable sensors tend to be capable of attractive capabilities such as miniaturization, multifunction, and smart integration, and wearable properties such as lightweight, flexibility, stretchability, and conformability for wider applications. In this work, we developed a stretchable multifunctional sensor based on porous silver nanowire/silicone rubber conductive film (P-AgNW/SR). Its unique structural configuration, i.e., an assembly of the P-AgNW/SR with good conductivity, stability, and resistance response, and the insulated silicone rubber layer, provided the feasibility for realizing multiple sensing capabilities. Specifically, porous microstructures of the P-AgNW/SR made the device to be used for pressure sensing, exhibiting outstanding dynamic and static resistive responsive behaviors and having a maximum sensitivity of 9.062 %∙N⁻¹ in a continuous compressive force range of ~ 16 N. With the merit of the good piezoresistive property of AgNW/SR networks embedded into the surface of micropores of the P-AgNW/SR, the device was verified to be a temperature sensor for detecting temperature changes in the human body and environment. The temperature sensor had good sensitivity of 0.844 %∙°C⁻¹, high linearity of 0.999 in the range of 25–125 °C, and remarkable dynamic stability. Besides, the developed sensor was demonstrated to be a single electrode-triboelectric sensor for active sensing, owing to the unique assembly of the conductive P-AgNW/SR electrode and the silicone rubber friction layer. Based on the coupling effect of the triboelectrification and electrostatic induction, the generated electrical signals could be used to sense the human motions, according to the quantitative correlation between the human motions and the features in amplitude and waveform of the output signals. Thus, the developed stretchable sensor successfully achieved the integration of two types of passive sensing capabilities, i.e., pressure and temperature sensing, and one type of active sensing capability, i.e., triboelectric sensing, demonstrating the feasibility of monitoring multiple variables of the human body and environment.