Small‐Scale Biological and Artificial Multidimensional Sensors for 3D Sensing

A vast majority of existing sub‐millimeter‐scale sensors have a planar, 2D geometry as a result of conventional top‐down lithographic procedures. However, 2D sensors often suffer from restricted sensing capability, allowing only partial measurements of 3D quantities. Here, nano/microscale sensors with different geometric (1D, 2D, and 3D) configurations are reviewed to introduce their advantages and limitations when sensing changes in quantities in 3D space. This Review categorizes sensors based on their geometric configuration and sensing capabilities. Among the sensors reviewed here, the 3D configuration sensors defined on polyhedral structures are especially advantageous when sensing spatially distributed 3D quantities. The nano‐ and microscale vertex configuration forming polyhedral structures enable full 3D spatial sensing due to orthogonally aligned sensing elements. Particularly, the cubic configuration leveraged in 3D sensors offers an array of diverse applications in the field of biosensing for micro‐organisms and proteins, optical metamaterials for invisibility cloaking, 3D imaging, and low‐power remote sensing of position and angular momentum for use in microbots. Here, various 3D sensors are compared to assess the advantages of their geometry and its impact on sensing mechanisms. 3D biosensors in nature are also explored to provide vital clues for the development of novel 3D sensors.     

面向结构健康监测的压电传感器综述

压电传感器在结构健康监测方面的应用日益广泛。大型工程结构、混凝土结构及微电子构件的损伤监测与智能传感为其提供了广阔的应用平台。压电薄膜与涂层制备工艺不断革新,使压电传感器性能逐步优化,从而开拓了更广阔的应用领域与前景。结合国内外的研究热点和现状,简述了压电传感的动态监测原理,综合概述了外贴式压电传感、埋入式压电传感及表面涂覆式压电传感在结构智能监测中的研究进展,其中针对不同制备工艺,分别阐述了不同表面涂覆式压电传感器的应用研究,归纳并总结了3种传感器的优缺点及表面涂覆式压电传感器的制备工艺,最后展望了未来的应用前景和发展方向。     

Photonic Metamaterial Absorbers: Morphology Engineering and Interdisciplinary Applications

Recent advances in nanofabrication technologies have spurred many breakthroughs in the field of photonic metamaterials that provide efficient ways of manipulating light–matter interaction at subwavelength scales. As one of the most important applications, photonic metamaterials can be used to implement novel optical absorbers. First the morphology engineering of various photonic metamaterial absorbers is discussed, which is highly associated with impendence matching conditions and resonance modes of the absorbers, thus directly determines their absorption efficiency, operational bandwidth, incident angle, and polarization dependence. Then, the recent achievements of various interdisciplinary applications based on photonic metamaterial absorbers, including structural color generation, ultrasensitive optical sensing, solar steam generation, and highly responsive photodetection, are reviewed. This report is expected to provide an overview and vision for the future development of photonic metamaterial absorbers and their applications in novel nanophotonic systems.     

Plasmonic‐Nanopore Biosensors for Superior Single‐Molecule Detection

Plasmonic and nanopore sensors have separately received much attention for achieving single‐molecule precision. A plasmonic “hotspot” confines and enhances optical excitation at the nanometer length scale sufficient to optically detect surface–analyte interactions. A nanopore biosensor actively funnels and threads analytes through a molecular‐scale aperture, wherein they are interrogated by electrical or optical means. Recently, solid‐state plasmonic and nanopore structures have been integrated within monolithic devices that address fundamental challenges in each of the individual sensing methods and offer complimentary improvements in overall single‐molecule sensitivity, detection rates, dwell time and scalability. Here, the physical phenomena and sensing principles of plasmonic and nanopore sensing are summarized to highlight the novel complementarity in dovetailing these techniques for vastly improved single‐molecule sensing. A literature review of recent plasmonic nanopore devices is then presented to delineate methods for solid‐state fabrication of a range of hybrid device formats, evaluate the progress and challenges in the detection of unlabeled and labeled analyte, and assess the impact and utility of localized plasmonic heating. Finally, future directions and applications inspired by the present state of the art are discussed.     

Tools for synthesising and characterising Bragg grating structures in optical fibres and waveguides

Optical waveguide filters based on optical fibre Bragg gratings are used for a wide range of applications in communications systems, fibre lasers and optical fibre sensors. The technical specifications for many of these grating based devices are becoming increasingly challenging. To make technological advances in this area a number of tools, such as: grating synthesis, advanced fabrication techniques, characterisation and reconstruction techniques, are required to improve grating structures. Closing the loop between design and physical realisation has the potential to achieve an unprecedented degree of accuracy in device fabrication. Grating design, fabrication and characterisation has moved from merely an inexact experimental procedure to a highly controlled engineering process. The mathematical and physical tools to achieve this are described and examples of applications are used to illustrate the potential of these capabilities to accelerate further understanding and development of photosensitivity and gratings in novel optical fibres and waveguides in the future.     

Chemical sensors for portable, handheld field instruments

A review of three commonly used classes of chemical sensor technologies as applicable to implementation in portable, handheld field instruments is presented. Solid-state gas and chemical sensors have long been heralded as the solution to a wide variety of portable chemical sensing system applications. However, advances in optical sensing technology have reduced the size of supporting infrastructure to be competitive with their solid-state counterparts. Optical, solid-state, and hybrid arrays of sensors have application for portable instruments, but issues of insufficient selectivity and sensitivity continue to hamper the widespread introduction of these miniaturized sensors for solving chemical sensing problems in environments outside the laboratory. In this article, we evaluate three of the major classes of compact chemical sensors for portable applications: (solid-state) chemiresistors, (solid-state) CHEMFETs, and (optical) surface plasmon resonance sensors (SPR). These sensors are evaluated and reviewed, according to the current state of research, in terms of their ability to operate at low-power, small-size, and relatively low-cost in environments, with numerous interferents and variable ambient conditions     

光谱域光纤白光干涉测量技术

光谱域光纤白光干涉测量技术(WLI)具有精度高、动态范围大、工程实用性强等优点,在光纤传感和精密测量领域有广泛的应用价值。本文回顾了光谱域光纤白光干涉测量技术的发展历程,重点介绍了本研究组在这一领域所开拓的基于相位测量技术的光谱域光纤WLI,包括傅里叶变换WLI及其相对测量术、波长扫描WLI、相移WLI、波数扫描WLI、互相关WLI、步进相移WLI,并展示了该技术在光纤温度、压力、应变等传感器中的应用。     

Bioinspired Infrared Sensing Materials and Systems

Bioinspired engineering offers a promising alternative approach in accelerating the development of many man‐made systems. Next‐generation infrared (IR) sensing systems can also benefit from such nature‐inspired approach. The inherent compact and uncooled operation of biological IR sensing systems provides ample inspiration for the engineering of portable and high‐performance artificial IR sensing systems. This review overviews the current understanding of the biological IR sensing systems, most of which are thermal‐based IR sensors that rely on either bolometer‐like or photomechanic sensing mechanism. The existing efforts inspired by the biological IR sensing systems and possible future bioinspired approaches in the development of new IR sensing systems are also discussed in the review. Besides these biological IR sensing systems, other biological systems that do not have IR sensing capabilities but can help advance the development of engineered IR sensing systems are also discussed, and the related engineering efforts are overviewed as well. Further efforts in understanding the biological IR sensing systems, the learning from the integration of multifunction in biological systems, and the reduction of barriers to maximize the multidiscipline collaborations are needed to move this research field forward.     

Quantitative nanoscale field effect sensors

Semiconductor nanowire field effect transistors have emerged as a promising technology for development of label-free biomolecular sensors for rapid diagnostics. However, their practical application has been hindered due to the significant device-to-device variations in electrical properties and the need for individual sensor calibration. Recent advances in device fabrication and demonstrations of multiplexed sensing and quantification might make this technology more competitive with respect to the current cutting-edge techniques such as surface plasmon resonance.     

Disposable Sensors in Diagnostics,Food, and Environmental Monitoring

Disposable sensors are low‐cost and easy‐to‐use sensing devices intended for short‐term or rapid single‐point measurements. The growing demand for fast, accessible, and reliable information in a vastly connected world makes disposable sensors increasingly important. The areas of application for such devices are numerous, ranging from pharmaceutical, agricultural, environmental, forensic, and food sciences to wearables and clinical diagnostics, especially in resource‐limited settings. The capabilities of disposable sensors can extend beyond measuring traditional physical quantities (for example, temperature or pressure); they can provide critical chemical and biological information (chemo‐ and biosensors) that can be digitized and made available to users and centralized/decentralized facilities for data storage, remotely. These features could pave the way for new classes of low‐cost systems for health, food, and environmental monitoring that can democratize sensing across the globe. Here, a brief insight into the materials and basics of sensors (methods of transduction, molecular recognition, and amplification) is provided followed by a comprehensive and critical overview of the disposable sensors currently used for medical diagnostics, food, and environmental analysis. Finally, views on how the field of disposable sensing devices will continue its evolution are discussed, including the future trends, challenges, and opportunities.     

Enhancing Tungsten Oxide Gasochromism with Noble Metal Nanoparticles: The Importance of the Interface

Crystalline tungsten trioxide (WO₃) thin films covered by noble metal (gold and platinum) nanoparticles are synthesized via wet chemistry and used as optical sensors for gaseous hydrogen. Sensing performances are strongly influenced by the catalyst used, with platinum (Pt) resulting as best. Surprisingly, it is found that gold (Au) can provide remarkable sensing activity that tuned out to be strongly dependent on the nanoparticle size: devices sensitized with smaller nanoparticles display better H₂ sensing performance. Computational insight based on density functional theory calculations suggested that this can be related to processes occurring specifically at the Au nanoparticle-WO₃ interface (whose extent is in fact dependent on the nanoparticle size), where the hydrogen dissociative adsorption turns out to be possible. While both experiments and calculations single out Pt as better than Au for sensing, the present work reveals how an exquisitely nanoscopic effect can yield unexpected sensing performance for Au on WO₃, and how these performances can be tuned by controlling the nanoscale features of the system.     

Recent Advances in Conjugated Polymer Materials for Disease Diagnosis

The extraordinary optical amplification and light‐harvesting properties of conjugated polymers impart sensing systems with higher sensitivity, which meets the primary demands of early cancer diagnosis. Recent advances in the detection of DNA methylation and mutation with polyfluorene derivatives based fluorescence resonance energy transfer (FRET) as a means to modulate fluorescent responses attest to the great promise of conjugated polymers as powerful tools for the clinical diagnosis of diseases. To facilitate the ever‐changing needs of diagnosis, the development of detection approaches and FRET signal analysis are highlighted in this review. Due to their exceptional brightness, excellent photostability, and low or absent toxicity, conjugated polymers are verified as superior materials for in‐vivo imaging, and provide feasibility for future clinical molecular‐imaging applications. The integration of conjugated polymers with clinical research has shown profound effects on diagnosis for the early detection of disease‐related biomarkers, as well as in‐vivo imaging, which leads to a multidisciplinary scientific field with perspectives in both basic research and application issues.     

Textile-Based Capacitive Sensors for Respiration Monitoring

Respiration monitoring in everyday life enables the early detection of the diseases and disorders that can suddenly manifest in a life threatening episode. Long-term monitoring can extend the capabilities of healthcare providers if reliability can be achieved economically. In this paper, the potential for using capacitive sensing to serve as an inexpensive method for long-term respiration sensing is explored. This paper proposes new designs of capacitive sensors for respiration sensing and describes the design and fabrication of a prototype textile-based capacitive-sensor respiration belt. Two capacitive sensors were designed and fabricated for detecting chest or abdominal circumference changes of up to 60 mm. These sensors gave good linearity, and the respiration measurements obtained with these new sensors show that they are capable of measuring respiration rate, and possibly lung function parameters.      

Mechano‐Based Transductive Sensing for Wearable Healthcare

Wearable healthcare presents exciting opportunities for continuous, real‐time, and noninvasive monitoring of health status. Even though electrochemical and optical sensing have already made great advances, there is still an urgent demand for alternative signal transformation in terms of miniaturization, wearability, conformability, and stretchability. Mechano‐based transductive sensing, referred to the efficient transformation of biosignals into measureable mechanical signals, is claimed to exhibit the aforementioned desirable properties, and ultrasensitivity. In this Concept, a focus on pressure, strain, deflection, and swelling transductive principles based on micro‐/nanostructures for wearable healthcare is presented. Special attention is paid to biophysical sensors based on pressure/strain, and biochemical sensors based on microfluidic pressure, microcantilever, and photonic crystals. There are still many challenges to be confronted in terms of sample collection, miniaturization, and wireless data readout. With continuing efforts toward solving those problems, it is anticipated that mechano‐based transduction will provide an accessible route for multimode wearable healthcare systems integrated with physical, electrophysiological, and biochemical sensors.     

A Multifunctional Electronic Skin Empowered with Damage Mapping and Autonomic Acceleration of Self-Healing in Designated Locations

Integrating self-healing capabilities into soft electronic devices and sensors is important for increasing their reliability, longevity, and sustainability. Although some advances in self-healing soft electronics have been made, many challenges have been hindering their integration in digital electronics and their use in real-world conditions. Herein, an electronic skin (e-skin) with high sensing performance toward temperature, pressure, and pH levels—both at ambient and/or in underwater conditions is reported. The e-skin is empowered with a novel self-repair capability that consists of an intrinsic mechanism for efficient self-healing of small-scale damages as well as an extrinsic mechanism for damage mapping and on-demand self-healing of big-scale damages in designated locations. The overall design is based on a multilayered structure that integrates a neuron-like nanostructured network for self-monitoring and damage detection and an array of electrical heaters for selective self-repair. This system has significantly enhanced self-healing capabilities; for example, it can decrease the healing time of microscratches from 24 h to 30 s. The electronic platform lays down the foundation for the development of a new subcategory of self-healing devices in which electronic circuit design is used for self-monitoring, healing, and restoring proper device function.     

Advances in the Application of Magnetic Nanoparticles for Sensing

Magnetic nanoparticles (MNPs) are of high significance in sensing as they provide viable solutions to the enduring challenges related to lower detection limits and nonspecific effects. The rapid expansion in the applications of MNPs creates a need to overview the current state of the field of MNPs for sensing applications. In this review, the trends and concepts in the literature are critically appraised in terms of the opportunities and limitations of MNPs used for the most advanced sensing applications. The latest progress in MNP sensor technologies is overviewed with a focus on MNP structures and properties, as well as the strategies of incorporating these MNPs into devices. By looking at recent synthetic advancements, and the key challenges that face nanoparticle‐based sensors, this review aims to outline how to design, synthesize, and use MNPs to make the most effective and sensitive sensors.     

Nanostructured Materials for Room‐Temperature Gas Sensors

Sensor technology has an important effect on many aspects in our society, and has gained much progress, propelled by the development of nanoscience and nanotechnology. Current research efforts are directed toward developing high‐performance gas sensors with low operating temperature at low fabrication costs. A gas sensor working at room temperature is very appealing as it provides very low power consumption and does not require a heater for high‐temperature operation, and hence simplifies the fabrication of sensor devices and reduces the operating cost. Nanostructured materials are at the core of the development of any room‐temperature sensing platform. The most important advances with regard to fundamental research, sensing mechanisms, and application of nanostructured materials for room‐temperature conductometric sensor devices are reviewed here. Particular emphasis is given to the relation between the nanostructure and sensor properties in an attempt to address structure–property correlations. Finally, some future research perspectives and new challenges that the field of room‐temperature sensors will have to address are also discussed.     

PVDF压电薄膜的应变传感特性研究

PVDF压电薄膜是一种重要的智能材料。本文理论分析了智能材料——PVDF压电薄膜的应变传感机理；研究了PVDF应变传感器的制作与布设工艺；试验研究了PVDF传感元件在准静态和动态响应下的传感特性．得到了PVDF传感元件的电压灵敏度，并分析了PVDF压电薄膜的尺寸对灵敏度的影响。研究结果表明：PVDF传感器具有灵敏度高、线性度好、制作与布置工艺简单、面监测等优点．适用于土木工程结构的健康监测。     

Inter-sheet-effect-inspired graphene sensors: design, fabrication and characterization

With their sub-nanometer inter-sheet spacing, few-layer graphenes (FLGs) are alignment-free building blocks for nanosensors based on the inter-sheet effects. In this paper, we have tackled the challenges towards batch fabrication of inter-sheet graphene sensors through controlled layer engineering, edge tailoring and selective electrode fabrication on different atomic layers. An oxygen plasma etching (OPE) technique is developed to remove graphene layer by layer, enabling the batch fabrication of FLGs in a controllable fashion because of the faster speed and readiness of patterning of this process as compared to the conventional mechanical exfoliation. Vapor sensing experiments have shown that 'inter-sheet' sensors possess a higher sensitivity than conventional 'intra-sheet' ones. Vapor sensitivity is improved more than two times in normalized resistance changes by taking the 'inter-sheet' design upon exposure to 0.5% ethanol-nitrogen mixture and 500 Pa water vapor environments, respectively. These remarkable improvements can mainly be attributed to the inter-sheet effects such as electron tunneling, chemical doping, physical insertion and enhanced edge effects. Such effects may result from molecule adsorption/desorption, force/displacement, pressure, surface tension or thermal energy, and can potentially remarkably enrich the applicable transduction mechanisms.     

Planar waveguide photonic crystals as an alternative for refractive index optical sensors design: theoretical evaluation

In this paper, the possibilities of designing refraction index optical sensors in planar waveguide photonic crystals are demonstrated for the first time. Photonic crystals obtained by connecting in cascade planar optical waveguides with high index contrast are analyzed. Photonic band gaps (PBGs) and photonic windows (PWs) were obtained. If a local defect is introduced in the PBG structure, the optical path length is modified and on states can be created in the gap. Besides, the on states wavelengths can be tuned if the optical path of the defect is modified: changing the physical length and/or the refraction index of the defect. In this way, planar waveguide photonic crystals could be used for sensing applications when a specimen modifies the refraction index lattice site. Sensing properties of planar waveguide photonic crystals, with one, two and three sensing channels, are demonstrated.