Search

The biosafety and sustainability of inorganic perovskites or organic piezopolymers is a major concern in the field of wearable piezoelectric sensors. Naturally occurring, silk fibroin (SF), is a promising alternative for the realization of organic piezoelectric devices due to its excellent biocompatibility and tunable material properties. Nevertheless, its scope for practical sensing applications is limited by the weak innate piezoelectricity of 1 pC N−1. This research aims to improve the piezoelectricity of pristine SF by intrinsically growing non‐toxic metal‐free perovskite (MFP) to achieve organic and bendable silk fibroin‐metal free perovskite (SF‐MFP) composite films. The increase in MFP loading has an influence on the resulting morphology and crystallinity of SF‐MFP films. In comparison to pristine SF, the films with the highest perovskite loading exhibit an enhanced normal piezoelectric response of 4.6 pm V−1. The poled SF‐MFP sensors display an appreciable sensitivity of 0.61 ± 0.05 V N−1 with a fast response time and outstanding stability arising from a synergistic combination of mechanically robust SF and piezoelectric MFP. Furthermore, these sensors can detect various joint bending and muscle movements in human subjects, proving their suitability for wearable bioelectronics. This research demonstrates the potential of biomaterials and organic perovskites for the development of biocompatible and sustainable wearable piezoelectric solutions. [ABSTRACT FROM AUTHOR]

Harnessing abundant kinetic water energy in diverse forms of river flows, ocean waves, tidal currents, raindrops, and others, is highly attractive to ease the energy crisis and satisfy the demands of scattered sensor network nodes in the Internet of things. Among them, raindrops, widely and ubiquitously distributed in nature and ambient living life, have been extensively explored and regarded as significant renewable energy carriers. Extensive efforts have been made to investigate droplet‐based electricity nanogenerators in fundamental mechanism, performance, and applications for achieving sustainable energy demands of the rapidly developing society over the past decade. In this review, we introduce the remarkable progress in this field and discuss the fundamental mechanisms of droplet energy harvesting technology for achieving high‐power generation. More significantly, a systematic review of droplet energy harvesting in different two‐phase interfaces, including liquid–solid, liquid–liquid, and liquid–gas interfaces, is provided. Finally, this survey reveals that droplet‐based electricity generators present vast potential in the power supply. At the same time, several development challenges and prospective solutions are discussed to spur future technological advancements. [ABSTRACT FROM AUTHOR]

The triboelectric nanogenerator (TENG) represents a burgeoning approach for harvesting ambient mechanical energy. However, practical applications suffer from the issues of insufficient charge density and material abrasion. Here, a rotational TENG that attains exceptional output performance and durability in mechanical energy harvesting and couples an ingenious coplanar charge pump by soft contact with a suspended electrostatic induction mode is presented. Thanks to the continuous and synchronous charge injection from the central charge pumping unit, the charge density can be up to 74.62 µC m−2, resulting in an outstanding peak power density of 20.72 W m−2. Moreover, the utilization of yielding polyester fur in the charge pumping unit as a tribo‐layer for soft contact decreases the material abrasion and then enhances durability and robustness. And the experimental results show that the TENG can maintain 99.2% electrical output after 100 000 operating cycles. With the optimized design, the prototype can continuously drive four commercial lamps rated 12 W in series. Furthermore, a wireless powering system is demonstrated to power the electronics, demonstrating an extensive application of the TENG. Given the compelling characteristics, this work is expected to provide a sound strategy for improving TENGs' output and durability in the field of self‐powered sensor systems. [ABSTRACT FROM AUTHOR]

Capillary‐enabled water energy harvesters (WEHs) are capable of generating direct‐current electricity continuously. However, active‐metal electrodes can introduce metal–air batteries in these WEHs. Given the nearly identical device structures and output characteristics of these two technologies, it is essential to distinguish between them. Herein, we present a systematic study of the water‐activated metal–air battery (WMB) through theoretical analyses and experimental verifications. We conclude the general formation rules of the WMB from a material and device‐structure perspective. Furthermore, we provide a comparative summary of various WEHs and WMBs for easy identification. We aim to improve the comprehension of metal–air batteries in the field of WEHs and assist in distinguishing between these technologies. [ABSTRACT FROM AUTHOR]

Wearing masks has been a recommended protective measure due to the risks of coronavirus disease 2019 (COVID‐19) even in its coming endemic phase. Therefore, deploying a "smart mask" to monitor human physiological signals is highly beneficial for personal and public health. This work presents a smart mask integrating an ultrathin nanocomposite sponge structure‐based soundwave sensor (≈400 µm), which allows the high sensitivity in a wide‐bandwidth dynamic pressure range, i.e., capable of detecting various respiratory sounds of breathing, speaking, and coughing. Thirty‐one subjects test the smart mask in recording their respiratory activities. Machine/deep learning methods, i.e., support vector machine and convolutional neural networks, are used to recognize these activities, which show average macro‐recalls of ≈95% in both individual and generalized models. With rich high‐frequency (≈4000 Hz) information recorded, the two‐/tri‐phase coughs can be mapped while speaking words can be identified, demonstrating that the smart mask can be applicable as a daily wearable Internet of Things (IoT) device for respiratory disease identification, voice interaction tool, etc. in the future. This work bridges the technological gap between ultra‐lightweight but high‐frequency response sensor material fabrication, signal transduction and processing, and machining/deep learning to demonstrate a wearable device for potential applications in continual health monitoring in daily life. [ABSTRACT FROM AUTHOR]

Self‐assembled monolayers (SAMs) have been widely employed as an effective way to modify interfaces of electronic/optoelectronic devices. To achieve a good control of the growth and molecular functionality of SAMs, we develop a co‐assembled monolayer (co‐SAM) for obtaining efficient hole selection and suppressed recombination at the hole‐selective interface in inverted perovskite solar cells (PSCs). By engineering the position of methoxy substituents, an aligned energy level and favorable dipole moment can be obtained in our newly synthesized SAM, ((2,7‐dimethoxy‐9H‐carbazol‐9‐yl) methyl) phosphonic acid (DC‐PA). An alkyl ammonium containing SAM is co‐assembled to further optimize the surface functionalization and interaction with perovskite layer on top. A champion device with an excellent power conversion efficiency (PCE) of 23.59 % and improved device stability are achieved. This work demonstrates the advantage of using co‐SAM in improving performance and stability of PSCs. [ABSTRACT FROM AUTHOR]

Piezoceramic films are an essential class of energy‐conversion materials that have been widely used in the electronics industry. Although current methods create a great freedom for fabricating high‐quality piezoceramic films, it requires well‐controlled synthesis conditions, including special high‐cost equipment and planar substrates particularly. The limited substrate selections hinder the applications of piezoceramic films in 3D conformal structures where most objects possess complex curvilinear surfaces. To overcome such limitations, a fast, energy‐efficient, and cost‐effective approach, named flame treated spray (FTS) coating, is developed for preparing piezoceramic films on free‐form surfaces. The flame treatment significantly enhances the hydrophilicity of a substrate, assisting in forming a uniform and continuous thin film. The followed spray coating deposits hundreds of nanometers to several micrometers thick films on 3D free‐form surfaces. Given the size controllability and arbitrary surface compatibility of the FTS method, a highly conformal piezoelectric tactile sensor array (4 × 4) is assembled on a spherical surface for mimicking robot fingers and an on‐site thin‐film sensor on the wing of an aircraft model to monitor the vibration in real‐time during flight. The FTS film deposition offers a highly promising methodology for the application of functional thin‐film from micro‐ to marcoscale devices, regardless of conformal problems. [ABSTRACT FROM AUTHOR]

Softening of piezoelectric materials facilitates the development of flexible wearables and energy harvesting devices. However, as one of the most competitive candidates, piezoelectric ceramic-polymer composites inevitably exhibit reduced power-generation capability and weak mechanical strength due to the mismatch of strength and permittivity between the two phases inside. Herein a flexible, air-permeable, and high-performance piezoceramic textile composite with a mechanically reinforced hierarchical porous structure is introduced. Based on a template-assisted sol-gel method, a three-order hierarchical ceramic textile is constructed by intertwining submillimeter-scale multi-ply ceramic fibers that are further formed by twisting micrometer-scale one-ply ceramic fibrils. Theoretical analysis indicates that large mechanical stress can be easily induced in the multi-order hierarchical structure, which greatly benefits the electrical output. Fabricated samples generate an opencircuit voltage of 128 V, a short-circuit current of 120 μA, and an instantaneous power density of 0.75 mW cm-2, much higher than the previously reported works. The developed multi-order and 3D-interconnected piezoceramic textile shows satisfactory piezoelectricity (d33 of 190 pm V-1), air permeability (45.1 mm s-1), flexibility (Young's modulus of 0.35 GPa), and toughness (0.125 MJ m-3), collectively. The design strategy of obtaining balanced properties promotes the practicality of smart/functional materials in wearables and flexible electronics. [ABSTRACT FROM AUTHOR]

Ocean contain abundant clean energies including tidal and wave, but such energies are known for low frequency and large excitation amplitude, posing considerable challenges for high‐efficiency energy conversion. As an emerging technology, triboelectric nanogenerators (TENGs) have been widely used in energy harvesting and novel sensor design due to their high sensitivity and flexible structure. Meanwhile, they show great advantages in the low‐frequency environment (<5 Hz), and display great potential for deployment in remote ocean waters, and construction of large‐scale TENG networks. In this review, firstly, the working principle of TENGs and various configurations developed for the marine environment are introduced, which mainly include solid–solid and solid–liquid interfaces. Then, from the viewpoint of power improvement, authors are most concerned about the modification methods of materials such as surface modification, electron injection, and chemical doping. Meanwhile, improved technologies for energy harvesters in marine environment are discussed in detail, such as improving the hydrophobicity and degradation of materials, studying the self‐healing ability of materials, and designing power management circuits. Finally, the current challenges are summarized, and research trends are given from both short‐term and long‐term perspectives. [ABSTRACT FROM AUTHOR]

Real‐time detection and differentiation of diverse external stimuli with one tactile senor remains a huge challenge and largely restricts the development of electronic skins. Although different sensors have been described based on piezoresistivity, capacitance, and triboelectricity, and these devices are promising for tactile systems, there are few, if any, piezoelectric sensors to be able to distinguish diverse stimuli in real time. Here, a human skin‐inspired piezoelectric tactile sensor array constructed with a multilayer structure and row+column electrodes is reported. Integrated with a signal processor and a logical algorithm, the tactile sensor array achieves to sense and distinguish the magnitude, positions, and modes of diverse external stimuli, including gentle slipping, touching, and bending, in real time. Besides, the unique design overcomes the crosstalk issues existing in other sensors. Pressure sensing and bending sensing tests show that the proposed tactile sensor array possesses the characteristics of high sensitivity (7.7 mV kPa−1), long‐term durability (80 000 cycles), and rapid response time (10 ms) (less than human skin). The tactile sensor array also shows a superior scalability and ease of massive fabrication. Its ability of real‐time detection and differentiation of diverse stimuli for health monitoring, detection of animal movements, and robots is demonstrated. [ABSTRACT FROM AUTHOR]

The soft millirobot is a promising candidate for emerging applications in various in‐vivo/vitro biomedical settings. Despite recent success in its design and actuation, the absence of sensing ability makes it still far from being a reality. Here, a radio frequency identification (RFID) based battery‐less soft millirobot that can move, sense, and communicate remotely by coupling the magnetic and piezoelectric effects is reported. This design integrates the robot actuation and power generation units within a thin multilayer film (<0.5 mm), i.e., a lower magnetic composite limb decorated with multiple feet imparts locomotion and a flexible piezoceramic composite film recovers energy simultaneously. Under a trigger of external magnetic guidance, the millirobot can achieve remote locomotion, environment monitoring, and wireless communication with no requirement of any on‐board battery or external wired power supply. Furthermore, this robot demonstrates the sensing capability in measuring environment temperature and contact interface by two different sensing models, i.e., carried‐on and build‐in sensing mode, respectively. This research represents a remarkable advance in the emerging area of untethered soft robotics, benefiting a broad spectrum of promising applications, such as in‐body monitoring, diagnosis, and drug delivery. [ABSTRACT FROM AUTHOR]

The utilization of hydrogels in soft electronics has led to significant progress in the field of wearable and implantable devices. However, challenges persist in hydrogel electronics, including the delicate equilibrium between stretchability and electrical conductivity, intricacies in miniaturization, and susceptibility to dehydration. Here, a lignin‐polyacrylamide (Ag‐LPA) hydrogel composite endowed with anti‐freeze, self‐adhesive, exceptional water retention properties, and high stretchability (1072%) is presented. Notably, this composite demonstrated impressive electrical conductivity at room temperature (47.924 S cm−1) and extremely cold temperatures (42.507 S cm−1). It is further proposed for microfluidic‐assisted hydrogel patches (MAHPs) to facilitate customizable designs of the Ag‐LPA hydrogel composite. This approach enhances water retention and offers versatility in packaging materials, making it a promising choice for enduring soft electronics applications. As a proof‐of‐concept, soft electronics across diverse applications and dimensions, encompassing healthcare monitoring, environmental temperature sensing, and 3D‐spring pressure monitoring electronics are successfully developed. The scenery of an extremely cold environment is further extended. The conductivity of the embedded Ag‐LPA hydrogel composite unveils the potential of MAHPs in polar rescue missions. It is envisioned that MAHPs will impact the development of sophisticated and tailored soft electronics, thereby forging new frontiers in engineering applications. [ABSTRACT FROM AUTHOR]