Nanowire-based technological advancements thrive in various fields, including energy generation and storage, sensors, and electronics. Among the identified nanowires, silicon nanowires (SiNWs) ...attract much attention as they possess unique features, including high surface-to-volume ratio, high electron mobility, bio-compatibility, anti-reflection, and elasticity. They were tested in domains of energy generation (thermoelectric, photo-voltaic, photoelectrochemical), storage (lithium-ion battery (LIB) anodes, super capacitors), and sensing (bio-molecules, gas, light, etc). These nano-structures were found to improve the performance of the system in terms of efficiency, stability, sensitivity, selectivity, cost, rapidity, and reliability. This review article scans and summarizes the significant developments that occurred in the last decade concerning the application of SiNWs in the fields of thermoelectric, photovoltaic, and photoelectrochemical power generation, storage of energy using LIB anodes, biosensing, and disease diagnostics, gas and pH sensing, photodetection, physical sensing, and electronics. The functionalization of SiNWs with various nanomaterials and the formation of heterostructures for achieving improved characteristics are discussed. This article will be helpful to researchers in the field of nanotechnology about various possible applications and improvements that can be realized using SiNW.
In the last decade, microelectromechanical systems (MEMS) SU-8 polymeric cantilevers with piezoresistive readout combined with the advances in molecular recognition techniques have found versatile ...applications, especially in the field of chemical and biological sensing. Compared to conventional solid-state semiconductor-based piezoresistive cantilever sensors, SU-8 polymeric cantilevers have advantages in terms of better sensitivity along with reduced material and fabrication cost. In recent times, numerous researchers have investigated their potential as a sensing platform due to high performance-to-cost ratio of SU-8 polymer-based cantilever sensors. In this article, we critically review the design, fabrication, and performance aspects of surface stress-based piezoresistive SU-8 polymeric cantilever sensors. The evolution of surface stress-based piezoresistive cantilever sensors from solid-state semiconductor materials to polymers, especially SU-8 polymer, is discussed in detail. Theoretical principles of surface stress generation and their application in cantilever sensing technology are also devised. Variants of SU-8 polymeric cantilevers with different composition of materials in cantilever stacks are explained. Furthermore, the interdependence of the material selection, geometrical design parameters, and fabrication process of piezoresistive SU-8 polymeric cantilever sensors and their cumulative impact on the sensor response are also explained in detail. In addition to the design-, fabrication-, and performance-related factors, this article also describes various challenges in engineering SU-8 polymeric cantilevers as a universal sensing platform such as temperature and moisture vulnerability. This review article would serve as a guideline for researchers to understand specifics and functionality of surface stress-based piezoresistive SU-8 cantilever sensors.
Flexible and stretchable strain sensors are in great demand in advanced health care, human–machine interface, stretchable electronics, electronic skin, etc. Of the various strain sensing mechanisms, ...the piezoresistive technique has many advantages over other methods such as capacitive, piezoelectric, and optical sensing techniques. A typical flexible/stretchable resistive sensor is realized using an insulating polymer substrate with conducting filler materials. Intrinsically conducting polymers (ICPs) such as polypyrrole (PPy), polyaniline (PANI), and poly(3,4-ethylenedioxythiophene): polystyrenesulfonate (PEDOT:PSS) are used as primary or secondary filler in the polymeric or fibrous substrates to fabricate stretchable composite sensors. This review comprehensively discusses the development of flexible and stretchable strain sensors using conducting polymers. The material combinations, fabrication methods, quantitative metrics such as maximum sensitivity, stretchability, durability, and salient features of various stretchable resistive strain sensors are summarized, which would serve as a vademecum to the researchers developing ICP-based stretchable strain sensors.
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MOF derived porous carbon materials have emerged as a research hotspot in recent years due to its exceptional properties like high electrical conductivity, large specific surface area, presence of ...numerous accessible active sites, high porosity etc. which endows them with diverse applications. The unique properties associated with derived material are inherited from the precursor MOF and the provision of in situ heteroatom doping into the carbon structure further enhances its properties specific to diverse applications. In this review, we discuss the recent advancements in MOF derived carbon focusing on its properties and electrocatalytic applications. In the first part, an overview of the unique properties, methods to regulate the morphology and composition, and the structure of MOF derived carbon materials are discussed. Then, the application of MOF derived carbon as a promising electrode material for electrochemical sensing as well as electrocatalytic process focusing on OER and HER are explained in detail. Furthermore, the challenges that need to be addressed and future aspects of MOF derived carbon research are presented.
Biomedical catheters are thin hollow tubes inserted into the human body to accurately measure various physiological parameters during invasive surgical procedures and diagnostic methods. Sensors ...realized using micro-/nano-electro-mechanical systems (MEMS/NEMS) technology are integrated with catheters to measure blood pressures, flows, pH- and glucose levels, and temperature. Of these physiological parameters, pressure sensing is of significant importance in identifying and treating various biomedical conditions. Piezoresistive technique is a widely investigated and preferred sensing mechanism to realize miniature sensors for its numerous advantages. In this paper, we critically review biomedical catheters as well as miniature piezoresistive pressure sensors developed for catheters. First, the evolution of catheters and their applications in measuring physiological parameters are discussed in detail. Next, the progress of piezoresistive pressure sensors developed for integration with catheters are described under three broad categories by considering various aspects such as diaphragm shape, material & size, piezoresistor type & material, readout type, fabrication processes, salient features of the device, and packaging techniques. A detailed section is devoted to alternative recent piezoresistive materials, including silicon nanowire (SNW), carbon nanotube (CNT), and Graphene. Finally, the process of catheterization and testing of biomedical catheters with integrated pressure sensors in the clinical environment are elaborated.
Abstract The integration of electronic functionalities into textiles has been under extensive research as its application is witnessed in various fields, including sensing, energy generation, ...storage, displays, and interfaces. Textiles endowed with flexibility, comfort, lightweight, and washability have been tested as reliable base materials to implement various physical sensors, of which strain and pressure sensors have shown great potential in applications such as healthcare, fitness tracking, and human-machine interaction. Piezoresistive physical sensors have considerable advantages over capacitive and piezoelectric sensors made of textiles. Apart from fibers, yarns, and threads, two-dimensional textile stripes occupy a significant share as substrates in these sensors. This review article discusses the recent progress of 2D textile-based piezoresistive strain and pressure sensors. It covers the latest works in this domain, focusing on different textile choices, conductive material combinations, fabrication methods, additional functionalities like heating, features like hydrophobic properties, and various applications, with tabulations of key performance metrics. For researchers seeking an update on the state of the field, this review would be helpful as it offers insights into trends for further research and product development aimed at meeting the demands of advanced healthcare and other applications.
Microcantilever platforms with integrated piezoresistors have found versatile applications in the field of clinical analysis and diagnostics. Even though treatise encompasses numerous design details ...of the cantilever based biochemical sensors, a majority of them focus on the generic slender rectangular cantilever platform mainly due to its evolution from the atomic force microscope (AFM). The reported designs revolve around the aspects of dimensional optimization and variations with respect to the combination of materials for the composite structure. In this paper, a triangular cantilever platform is shown to have better performance metrics than the reported generic slender rectangular and the square cantilever platforms with integrated piezoresistors for biochemical sensing applications. The selection and optimization of the triangular cantilever platform is carried out in two stages. In the first stage, the preliminary selection of the cantilever shape is performed based on the initial design obtained by analytical formulae and numerical simulations. The second stage includes the geometrical optimization of the triangular cantilever platform and the integrated piezoresistor. The triangular cantilever platform shows a better performance in terms of the figure of merit (FoM), and the measurement bandwidth. The simulation results show that the magnitude of ψ of the triangular platform is 77.21% and 65.64% higher than that of the slender rectangular and the square cantilever platforms respectively. Moreover, the triangular platform exhibits a measurement bandwidth that is 70.91% and 2.04 times higher than that of the slender rectangular and square cantilever structures respectively. For a better understanding of the 2D nature of the stress generated on the cantilever platform due to the surface stress, its spatial profile has been extracted and depicted graphically. Finally, a set of design rules are provided for optimizing the triangular cantilever platform and piezoresistor dimensions in terms of the electrical sensitivity and the mechanical stability for biochemical sensing applications.
The development of precise sensors to detect hazardous heavy metal ions (HMIs) in an aqueous medium has recently attracted much attention. Metal-Organic Frameworks (MOFs) with large specific surface ...areas, more active sites, and flexible chemical structures have received tremendous research interest in many applications. MOFs composites blended with various functional materials are well suited for the electrochemical sensing of HMIs, because of their synergetic properties, including abundant active sites, enhanced electrical conductivity, and increased chemical stability. While MOFs composites’ synthesis protocols, modification techniques, and potential applications have been addressed in the previous reports, there is an increasing awareness of electrochemical detection of HMIs using MOFs composites. This review explicitly summarizes the electrochemical sensing of HMIs using various MOFs-based composites, including MOFs-carbon, MOFs-polymer, MOFs-metal nanoparticles, and MOFs-other composites. In addition, the challenges and opportunities towards electrochemical sensing with the MOFs composite-based materials are discussed.
In the present study, a detailed experimental investigation is carried out on a constant velocity-feed drilling technique of an electrochemical discharge machining (ECDM) process to fabricate ...micro-holes on quartz substrates. First, cylindrical micro-tools of four different diameters (145 µm, 195 µm, 300 µm and 400 µm) with varying tool feed rates (TFRs) (0.3 µm s−1-1.9 µm s−1) are considered to study their influence on the precision of fabricated micro-holes while using a 30 wt% NaOH solution as an electrolyte, a machining voltage of 30 V and an initial working gap of 5 µm. Minimum micro-hole diameter and overcut were achieved at a TFR 0.8 µm s−1 for the cylindrical tools of all diameters. Considering 0.8 µm s−1 as an optimal TFR, the influence of tool shape on the quality metrics was investigated using a spherical shaped tool electrode having a ball diameter of 145 µm and a spindle diameter of 90 µm. A micro-hole realized using the spherical shaped tool shows that the entrance diameter, entrance overcut, central diameter and central overcut are reduced by 12%, 29%, 28% and 67% respectively as compared to that realized using a cylindrical tool for the same process parameters. Micro-holes with improved precision and aspect ratio are achieved without using cost intensive equipments, feedback mechanisms, coated tools and tool rotation.
Abstract Monocrystalline bulk silicon with doped impurities has been the widely preferred piezoresistive material for the last few decades to realize micro-electromechanical system (MEMS) sensors. ...However, there has been a growing interest among researchers in the recent past to explore other piezoresistive materials with varied advantages in order to realize ultra-miniature high-sensitivity sensors for area-constrained applications. Of the various alternative piezoresistive materials, silicon nanowires (SiNWs) are an attractive choice due to their benefits of nanometre range dimensions, giant piezoresistive coefficients, and compatibility with the integrated circuit fabrication processes. This review article elucidates the fundamentals of piezoresistance and its existence in various materials, including silicon. It comprehends the piezoresistance effect in SiNWs based on two different biasing techniques, viz., (i) ungated and (ii) gated SiNWs. In addition, it presents the application of piezoresistive SiNWs in MEMS-based pressure sensors, acceleration sensors, flow sensors, resonators, and strain gauges.
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