Structural health monitoring (SHM) has been increasingly investigated for decades. Different physical principles have been developed for damage identification, such as electronics, mechanics, magnetics, etc., with different coverage (i.e., global, large-area, and local monitoring) and sensitivity. Mechanical acousto-ultrasonic-based methods have formed a big family in SHM technologies. Multiple wave/resonance modes have been utilized for versatile SHM tasks. The permanently integrated sensing networks play a significant role in achieving a cost-effective and reliable SHM system, with major concerns including weight increase for large-scale deployment and conformity for complex geometry structures. In this review, typical acousto-ultrasonic sensors made of different material systems are discussed, along with advantages and limitations. Moreover, advanced network installation methods have been introduced, including surface-mounting with pre-integrated networks on substrates and in situ printing, and embedding with composite layup and metal additive manufacturing. Sensor versatility and usage in multi-scale SHM techniques are then highlighted. Different wave/resonance modes are transmitted and received with corresponding elements and network designs. In conclusion, this systematic review mainly covers a collection of acousto-ultrasonic sensors, two modalities of network installation, and their employment with various SHM methods, hopefully providing a useful guide to building lightweight and conformal networks with passive or active-passive sensors, and developing complete and reliable SHM strategies by integrating different damage identification methods on multiple scales.

Biological neural systems, composed of neurons and synaptic networks, exhibit exceptional capabilities in signal transmission, processing, and integration. Inspired by the mechanisms of these systems, researchers have been dedicated to developing artificial neural systems based on flexible synaptic devices that effectively mimic the functions of biological synapses, providing hardware support for the advancement of artificial intelligence. In recent years, ionic gels, known for their high ionic conductivity and intuitive synaptic mimicry, have been utilized in the development of ionic-gel synapses (IGSs). They are considered ideal materials for the next wearable generation of neuromorphic systems. This review introduces IGS devices and summarizes the recent progress in flexible IGS-based neuromorphic systems. Additionally, key challenges and future development prospects related to flexible IGSs are outlined, and potential suggestions are provided.

Flexible sensing technologies are pivotal for achieving multidimensional spatial freedom in sensing capabilities. Within this domain, flexible acceleration sensors stand out as innovative devices capable of accurately monitoring acceleration signals, even amidst deformation scenarios such as bending, compression, or stretching. These sensors are increasingly recognized for their transformative potential across various sectors, including health monitoring, industrial machinery, soft robotics, and so on. This review delves into the recent progress in the field of flexible acceleration sensors, examining their operational mechanisms, the materials used for the sensing layers, and their performance characteristics based on different operational principles. Moreover, we explore the diverse applications of these sensors in areas such as wearable devices, infrastructure surveillance, and automotive safety, providing a comprehensive overview of their current uses. Additionally, we assess the advantages and limitations of flexible acceleration sensors and propose potential directions for their advancement. Through this review, we aim to highlight the significant role that flexible acceleration sensors play in the ongoing evolution of sensing technologies, underscoring their importance in a wide array of applications.

The emergence of perovskite semiconductors for field-effect transistor (FET) applications has received significant research attention due to their excellent electronic properties. The rapid development of perovskite FETs over the last few years has been driven by advances in understanding the thin-film morphologies of perovskite layers and their intriguing correlations with charge carrier transport, device performance, and stability. Here we summarize the progress in morphological engineering aimed at improving the electrical parameters of perovskite FETs. We first discuss the mechanisms of crystal nucleation and growth in solution-processed polycrystalline perovskite thin films, along with their morphological characteristics, including grain boundaries, defects, ionic and charge transport properties. We then elaborate on the impacts of these microstructures on the performance of perovskite FET devices. Representative optimization strategies are also presented, showcasing how fundamental understandings have been translated into state-of-the-art perovskite FETs. Finally, we provide a perspective on the remaining challenges and future directions of optimizing perovskite morphologies, toward an in-depth understanding of the relationships between film morphology, electrical property and device performance for the next advances in transistor.

The exploration of afterglow in small molecule-doped polymer composites, rooted in a nuanced understanding of structure-properties relationships, holds paramount importance for optoelectronics. However, conventional strategies face challenges in achieving high-throughput discovery of these polymers. This study introduces a novel combinatorial approach, employing photoinitiated solvent-free polymerization, to craft afterglow aromatic boronic acid-doped polymer composites. The afterglow activation results from stabilizing the triplet states of doped small molecules through a synergy of chemical and physical fixation effects. Aromatic boronic acids emerge as crucial dopants, exhibiting versatility in afterglow development across the visible spectrum. Notably, the influence of functional groups and the number of non-fused benzene rings on afterglow wavelengths is minimal, while significantly impacting afterglow lifetimes. Besides conjugation degrees, the optimal size and doping concentrations of dopants play a pivotal role in extending afterglow lifetimes. This strategy not only facilitates exploration of small molecule-based afterglow materials but also enables the feasible fabrication of intricate, multicolor afterglow polymeric objects via a step-polymerization strategy for anti-counterfeiting.

Photo-thermoelectric (PTE) conversion with soft carbon nanotube (CNT) thin-films potentially facilitates non-destructive inspections as image sensor devices through ultrabroadband optical monitoring and freely attachable 3D omni-directional views. Toward real-time and large-area measurements, printing fabrication methods are effective for multi-pixel integrations of all-solution-processable CNT film PTE sensors. However, the conventional printing method of CNT PTE sensors yields fatally low-efficient in fabricating each pixel due to insufficient diffusion of n-type liquid dopants on the pristine p-type film channels. Herein, this work demonstrates high-yield fabrications of pn-junction type PTE sensors by employing p-/n-type CNT inks. For such conceptualization, the presenting strategy first develops all-solution-processable n-type CNT inks. Specifically, this work fabricates the n-type inks by simply mixing the pristine p-type CNT source solution and chemical liquid agents (hydroxide and crown-ether) at high-yield via ultrasonic vibration. The presenting CNT solution functions stability as n-type materials on various supporting substrates by several fabrication methods in the counterpart junction with pristine p-type film channels. Available fabrication methods and formable substrates are as follows: printing (screen, air-jet dispense), coating (spin, casting), and manual application on papers, polymer sheets (parylene, polyimide, polyurethane, and polyethylene terephthalate), glass, and semiconductor wafers. Furthermore, the all-solution-processable pn-junction CNT film PTE sensor fabricated by printing of p-/n-type inks sufficiently satisfies superior inherent optical properties. Following these, the presenting uniform high-yield pn-junction fabrication, 100 % forming at an error ratio of response signal intensities within 8.54 %, potentially facilitates large-scale integrations of ultrabroadband deformable thin-film PTE sensor sheets and the associated functional non-destructive inspections.