Performance Of Strain Sensors Research Articles

Development and characterization of a coaxial strain-sensing cable integrated steel strand for wide-range stress monitoring

Abstract Monitoring the stress of steel strands, from initial tension to eventual failure, is paramount for assessing structural safety and understanding its failure mechanism. Current monitoring methods are restricted in measuring stress only until yielding because of their limited range. This study proposes a novel coaxial strain-sensing cable (CSSC) based intelligent steel strand (CSSC-ISS), which has both functions of force-bearing and self-sensing. First, the prototype design of CSSC-ISS and the sensing principle of CSSC are introduced. Then, a fabrication method of small-diameter CSSC is proposed, which is then encapsulated with glass fiber reinforced polymer (GFRP) material, forming a GFRP sensing rod (GFRP-SR). The next step involves replacing the strand’s central wire with the GFRP-SR, culminating in the creation of the CSSC-ISS. Finally, Laboratory tests show that the CSSC has excellent strain-sensing performance with a resolution of at least 100 µε and a measurement range of 150,000 µε. The GFRP-SR offers good sensing potential and comparable mechanical strength to standard GFRP rods. Notably, the CSSC-ISS could measure stress up to strand failure, retaining 87.9% tensile strength and 88.7% elastic modulus compared to standard steel strands. It is verified that the CSSC-ISS can consistently measure its stress condition throughout its life cycle without compromising its load-bearing potential.

Ultra-stretchable and anti-freezing ionic conductive hydrogels as high performance strain sensors and flexible triboelectric nanogenerator in extreme environments

Conductive hydrogels have shown promising applications in a variety of portable smart wearable electronics and flexible sensors due to their high flexibility, stretchability, adjustable mechanical properties and excellent electrical conductivity. However, most of the current hydrogel-based flexible strain sensors and portable triboelectric nanogenerator (TENG) generally suffer from low stretchability/flexibility, poor mechanical properties, weak low-temperature tolerance and low power output. Herein, a multifunctional ionic conductive hydrogel (PPAVC-BA) with ultra-stretchability (∼1750%), high transparency (85%), high electrical conductivity (13.7 mS/cm), and outstanding anti-freezing properties (below −80°C without freezing). The strain sensor assembled from the PPAVC-BA hydrogel shows high sensitivity (GF=4.43) and ultra-wide sensing detection range (0%-1100%) as well as fast response time. Based on these properties, the PPAVC-BA hydrogel strain sensor can accurately recognize different joint movements of the human body as well as weak muscle beats. In addition, the PPAVC-BA hydrogel-based TENG (PPAVC-BA-TENG) exhibits excellent electrical output performance, with an open circuit voltage (Voc) of about 420 V, a short circuit current (Isc) of 23 μA, a short-circuit transfer charge (Qsc) of 112 nC and a maximum power density of 2246.03 mW/m2, which allows it to power small electronic devices. This PPAVC-BA-TENG also shows outstanding tensile performance and can output stable electrical signals at 200% strain. Impressively, the PPAVC-BA-TENG exhibits good electrical output performance even at low temperature of −50°C and high temperature of 80°C. The flexible strain sensors and stretchable TENG for high performance and multifunctionality reported in this work provide viable references in the development of motion detection, energy harvesting and self-powered electronic devices.

Strain Monitoring of Concrete Using Carbon Black-Based Smart Coatings.

Given the challenges we face of an ageing infrastructure and insufficient maintenance, there is a critical shift towards preventive and predictive maintenance in construction. Self-sensing cement-based materials have drawn interest in this sector due to their high monitoring performance and durability compared to electronic sensors. While bulk applications have been well-discussed within this field, several challenges exist in their implementation for practical applications, such as poor workability and high manufacturing costs at larger volumes. This paper discusses the development of smart carbon-based cementitious coatings for strain monitoring of concrete substrates under flexural loading. This work presents a physical, electrical, and electromechanical investigation of sensing coatings with varying carbon black (CB) concentrations along with the geometric optimisation of the sensor design. The optimal strain-sensing performance, 55.5 ± 2.7, was obtained for coatings with 2 wt% of conductive filler, 3 mm thickness, and a gauge length of 60 mm. The results demonstrate the potential of applying smart coatings with carbon black addition for concrete strain monitoring.

Ultrasensitive and highly stretchable bilayer strain sensor based on bandage-assisted woven fabric with reduced graphene oxide and liquid metal

Flourishing flexible and wearable strain sensors still meet a challenge to realize ultrahigh sensitivity and wide working range simultaneously through a convenient strategy. Here, a strain sensor is designed based on natural rubber (NR) matrix and a bilayer structure composed of a highly stretchable liquid metal (LM) layer and a susceptible reduced graphene oxide (RGO)@carbonized bandage (CB) layer. By painting LM onto the surface of a graphene oxide (GO)-coated bandage template followed with a rapid flame pyrolysis, a dual conductive-layer woven fabric based on LM/RGO@CB was obtained. NR was then employed as an elastic substrate. Benefiting from the synergistic bilayer network and the high stretchability of the elastomer, the fabricated strain sensor exhibited ultrahigh sensitivity (gauge factor of up to 1.63 × 105), quite wide detection range (strain of 0 ∼ 515 %), low detection limit (0.25 %), fast response/recovery (135 ms/135 ms), and satisfactory durability (5700 cycles). The extraordinary strain-sensing performance allowed comprehensive monitoring of full-range (vigorous and subtle) human motions and physiological activities. This work provides a facile bilayer strategy for the preparation of high-performance strain sensors.

Electrical/optical dual-energy-driven MXene fabric-based heater with fast response actuating and human strain sensing

Multi-functional smart textiles are receiving a lot of attention for their tremendous application development in the fields of personal thermal management, artificial muscle, electronic skin, and human-machine interaction. For the complex use of many different smart textiles, designing a multifunctional textile that integrates personal thermal management, smart sensing, and flexible actuating is still a great challenge. Here, we decorated MXene on elastic fabrics by simple dip-coating and asymmetric Ecoflex encapsulation protocol to obtain electrical/optical dual-energy-driven wearable heaters with highly responsive actuating and strain-sensing performance. The MXene fabric-based heaters (MFHs) have high efficiency of Joule heating (Steady state temperature of 116.7 °C at 12 V) and photothermal conversion performance (180.3 °C in 60 s under the near infrared lamp irradiation, up to 57.5 °C under 600 W m–2 simulated solar irradiation). Benefiting from high electrical/optical dual-energy conversion efficiency, MFH has a fast photothermal driving effect (bending angle up to 360° in 5 s) due to the different curvature of thermal expansion on both sides of the fabric. Interestingly, MFH has the capability to monitor human strain (such as muscle and joint movements). Based on the above excellent performance, we finally believe that the MFHs have broad application prospects in the fields of all-weather body heat management, health monitoring, thermal health care, and thermal robotics.

Ultraflexible Temperature-Strain Dual-Sensor Based on Chalcogenide Glass-Polymer Film for Human-Machine Interaction.

Skin-like thermoelectric (TE) films with temperature- and strain-sensing functions are highly desirable for human-machine interaction systems and wearable devices. However, current TE films still face challenges in achieving high flexibility and excellent sensing performance simultaneously. Herein, for the first time, a facile roll-to-roll strategy is proposed to fabricate an ultraflexible chalcogenide glass-polytetrafluoroethylene composite film with superior temperature- and strain-sensing performance. The unique reticular network of the composite film endows it with efficient Seebeck effect and flexibility, leading to a high Seebeck coefficient (731 µV/K), rapid temperature response (≈0.7 s), and excellent strain sensitivity (gauge factor = 836). Based on this high-performance composite film, an intelligent robotic hand for action feedback and temperature alarm is fabricated, demonstrating its great potential in human-machine interaction. Such TE film fabrication strategy not only brings new inspiration for wearable inorganic TE devices, but also sets the stage for a wide implementation of multifunctional human-machine interaction systems.

Tailoring polypyrrole film characteristics with multi-step oxygen plasma treatment for high-performance strain sensors: Impact on bonding, microstructure, and electrical responsivity

We investigate the impact of oxygen plasma treatment (O2 PT) on the performance of polypyrrole (PPy)/polydimethylsiloxane strain sensors. Utilizing a three-step chemical oxidative polymerization method for PPy growth, we explore various durations of O2 PT (0, 30, 60, and 90 s) during intermediate growth stages. Through analyses using X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy, we elucidate the relationship between O2 PT, structural changes, and strain sensor performance. Sensor devices plasma-treated for 30 s exhibit exceptional characteristics: a gauge factor of 432 at 50% strain and a response time of 50 ms under quasi-step function strain variation from 0% to 1% in 40 ms. These results underscore the pivotal role of O2 PT in enhancing the performance of PPy-based strain sensors, providing insights for advanced sensor design and fabrication techniques.

Tough and Strain-Sensitive Organohydrogels Based on MXene and PEDOT/PSS and Their Effects on Mechanical Properties and Strain-Sensing Performance.

Conductive hydrogels have shown promising application prospects in the field of flexible sensors, but they often suffer from poor mechanical properties, low sensitivity, and lack of frost resistance. Herein, we report a tough, highly sensitive, and antifreeze strain sensor assembled from a conductive organohydrogel composed of a dual-cross-linked polyacrylamide and poly(vinyl alcohol) (PVA) network, as well as MXene nanosheets as nanofillers and poly(3,4-ethylenedioxythiophene)-doped poly(styrenesulfonate) (PEDOT/PSS) as the main conducting component (PPMP-OH organohydrogel). The tensile strength and toughness of PPMP-OH had been greatly enhanced by MXene nanosheets due to the mechanical reinforcement of MXene nanosheets, as well as various strong noncovalent interactions formed in the organohydrogels. The PPM1P-OH organohydrogels showed a tensile strength of 1.48 MPa at 772% and a toughness of 5.59 MJ/m3. Moreover, the conductivity and strain-sensing performance of PPMP-OH were significantly improved by PEDOT/PSS, which can form hydrogen bonds with PVA and electrostatic interactions with MXene. This was greatly beneficial for constructing a uniformly distributed and stable 3D conductive network and helped to obtain strain-dependent resistance of PPMP-OH. The strain sensors assembled from PPMP1-OH exhibited a high sensitivity of 5.16, a wide range of detectable strains up to 500%, and a short response time of 122 ms, which can effectively detect various physiological activities of the human body with high stability. In addition, the corresponding pressure sensor array also showed high sensitivity in identifying pressure magnitude and position.

Differential pressure sensors based on transfer-free piezoresistive layered PdSe2 thin films

Piezoresistive layered two-dimensional (2D) crystals offer intriguing promise as pressure sensors for microelectromechanical systems (MEMS) due to their remarkable strain-induced conductivity modulation. However, integration of the conventional chemical vapor deposition grown 2D thin films onto a micromachined silicon platform requires a complex transfer process, which degrades their strain-sensing performance. In this study, we present a differential pressure sensor built on a transfer-free piezoresistive PdSe2 polycrystalline film deposited on a SiN x membrane by plasma-enhanced selenization of a metal film at a temperature as low as 200 °C. Based on the resistance change and finite element strain analysis of the film under membrane deflection, we show that a 7.9 nm thick PdSe2 film has a gauge factor (GF) of −43.3, which is ten times larger than that of polycrystalline silicon. The large GF enables the development of a diaphragm pressure sensor with a high sensitivity of 3.9 × 10−4 kPa−1 within the differential pressure range of 0–60 kPa. In addition, the sensor with a Wheatstone bridge circuit achieves a high voltage sensitivity of 1.04 mV·kPa−1, a rapid response time of less than 97 ms, and small output voltage variation of 8.1 mV in the temperature range of 25 °C to 55 °C. This transfer-free and low-temperature grown PdSe2 piezoresistive thin film is promising for MEMS transducer devices.

Role of natural rubber structure in the electrical conductivity and strain sensor performance of natural rubber/carbon nanotube nanocomposites stabilized by sodium alginate

Strain-sensitive sensors utilizing nanocomposites of natural rubber (NR) were produced through latex mixing technology, employing different varieties of NR, namely, unmodified NR and epoxidized NR with 25 and 50 mol% epoxidized natural rubber (ENR25 and ENR50) respectively. A linear polysaccharide, sodium alginate (Alg), was used as an effective dispersing agent. This work revealed that the polar functional group on the rubber structure showed a positive impact on the dispersion state of carbon nanotubes (CNTs) in the nanocomposite suspensions. The incorporation of Alg as a dispersing agent in rubber nanocomposites remarkably improved the uniformity and overall performance of the nanocomposite suspensions. The results demonstrated the critical role of the polar functional group on the NR molecules in achieving an outstanding electrical conductivity of 102 S/cm. In addition, the mechanical properties were dramatically improved with the introduction of Alg into NR, ENR25, and ENR50 filled with CNTs. Alg improved the electrical conductivity and strain sensitivity of the rubber nanocomposites and the variation of R/R0, demonstrating its beneficial effect on the strain sensor.

Improved performance of strain sensors constructed from highly crystalline graphene with nanospacer

Graphene shows promise as an alternative material for strain sensors due to its excellent properties and could overcome the limitations of conventional metal sensors. However, current graphene-based strain sensors are fabricated from chemically reduced graphene oxide (rGO) and suffer from low linearity and large hysteresis in the sensor response as well as high initial resistance. These issues are caused by functional groups and defects remaining on the rGO. Herein, highly crystalline rGO is employed for the fabrication of the strain sensor. Porous rGO sponge with low defect density is prepared in bulk scale via the ethanol-associated thermal process at ultra-high temperature. The obtained rGO sensor exhibits improved linearity, low initial resistance, and very small hysteresis owing to the high crystallinity of the rGO. The composite of rGO with nano-diamond, which has the role of a nanospacer to separate the rGO layers, is found to be highly effective in enhancing the sensitivity.

Non-covalent crosslinked hydrogels to realize renewable and re-moldable strain sensors with excellent sensing behavior

Ion hydrogels have garnered significant attention owing to outstanding softness and tissue similarity. However, disposable mechanically available hydrogels result in low resource utilization and environmental pollution. Although self-healing hydrogels are serviceable when slightly damaged, they fail to recover after experiencing extreme conditions. Therefore, exploring renewable hydrogels effectively recycles the materials and contributes to preparing functional materials. Herein, a hydrogen-bond crosslinked polyvinyl alcohol/gelatin/tannic acid hydrogel (PGTH) was fabricated, allowing complete remolding without any additives. After the Fe3+ ions were introduced into PGTH hydrogels, the strain sensors with adhesion, freezing-resistance, biocompatibility and antibacterial properties were produced. The strain sensors based on the PGTFH showed excellent strain-sensing performance, including considerable sensitivity (GF = 1.93), exceptional linearity (R2 = 0.996), fast response (102 ms) and signal repeatability (>250 cycles). Minor and major motions (the action “saying”, “drinking” and joint bending) were detected and distinguished, which demonstrated their promising application prospects in next-generation green flexible devices for health care, motion monitoring and speech recognition.

Structural Design and Optimization of the Milling Force Measurement Tool System Embedded with Thin-Film Strain Sensors.

A milling force measurement tool system is designed with an elastic beam structure, which is divided into a two-end ring hoop compression sensor mode and a two-end square hoop compression sensor mode to improve the strain sensitivity. A simplified mechanical model of the elastic beam is established, and the relationship between the strain and force of the elastic beam under the action of three cutting force components is investigated, which can act a guide for subsequent milling force measurement tool system calibration tests. Thin-film strain sensors occupy a central position in the milling force measurement tool system, which consists of a substrate, transition layer, insulating layer and resistance grid layer. The resistance grid layer has a particularly significant effect on the thin-film strain sensor's performance. In order to further improve the sensitivity of thin-film strain sensors, the shapes of the substrate, the transition layer, the insulating layer and the resistance grid layer are optimized and studied. A new thin-film strain sensor is designed with a resistance grid beam constructed from an insulating layer and a resistive grid layer double-end-supported on the transition layer. The flow of the wet-etching process of thin-film strain sensors is studied and samples are obtained. The surface microforms of the sensor samples are observed by extended depth-of-field microscopy, confocal microscopy and atomic force microscopy. It can be seen that the boundary of the resistance grid layer pattern is tidy and has high dimensional accuracy, thus enabling the basic achievement of the expected effect of the design. The electrical performance of the samples is tested on an experimental platform that we built, and the results show that the resistive sensitivity coefficient of the samples is increased by about 20%, to 51.2%, compared with that of the flat thin-film strain sensor, which fulfils the design's requirements.

Flexible strain sensors with high sensitivity and large monitoring range prepared by biaxially stretching conductive polymer composites with a bilayer structure

AbstractIn order to prepare a flexible strain sensor with a large monitoring range, high sensitivity and excellent stability, a polyolefin elastomer (POE)/carbon nanotubes (CNTs) conductive polymer composite with a bilayer structure was prepared by biaxially stretching in this work. The results showed that the bilayer structured nanocomposites had better processability and better stability than monolayer CNT/POE nanocomposites during biaxial stretching. The biaxial stretching process could promote the dispersion and planar orientation of CNTs within the polymer, improving the crystallinity of nanocomposites and the sensing performance of strain sensors. The optimal stretching ratios (SRs) of bilayer structured nanocomposites were studied. The 8 wt% CNT/POE‐POE strain sensor with an SR of 2.5 exhibited a high sensitivity (gauge factor/GF = 72604.7 at 900% strain), wide strain range (0%–900%), and stable cycling performance (1000 cycles at 30% strain), showing a broad application prospect in wearable electronic devices. This study provides a valuable method for efficiently manufacturing high performance and low‐cost flexible strain sensors.

High performance strain sensor based on leather activated by micro-cracking conductive layer

Flexible strain sensors are capable to detect external force induced strain change owing to their unique ability to convert deformation into electrical signals. Generally, micro/nano patterning of conductive layer in strain sensor is an effective method to improve its sensitivity, however the sophisticated manipulation process is limited only in laboratory scale. In this report, a simple and scalable fabrication strategy was used to create micro-cracking conductive layer as an alternative patterning method to achieve high performance of strain sensor. In details, the sensor was fabricated using leather as the substrate to filtrated acidified multi-walled carbon nanotubes (a-MWCNTs)/layered double hydroxides (LDHs) suspension. During stretching process, micro-cracking structure emerged on the percolated a-MWCNTs/LDHs layer, causing a rise up of resistance according to increasing strain and generated a detectable electrical signal. The prepared sensor had a large detecting range (60%), high sensitivity (GF of 7238.92 at strain 30–60%), fast response (tensile response time of 270 ms), good stability and repeatability. The sensor also inherited the advantages of leather, such as biodegradability and good air permeability, and the introduction of a-MWCNTs/LDHs further enhanced its fire retardancy properties. These features ensured the sensor as an eco-friendly, comfortable and safe electronic device for human motion detection.Graphical abstract

Self-Healable PEDOT:PSS-PVA Nanocomposite Hydrogel Strain Sensor for Human Motion Monitoring.

Strain sensors based on conducting polymer hydrogels are considered highly promising candidates for wearable electronic devices. However, existing conducting polymer hydrogels are susceptible to aging, damage, and failure, which can greatly deteriorate the sensing performance of strain sensors based on these substances and the accuracy of data collection under large deformation. Developing conductive polymer hydrogels with concurrent high sensing performance and self-healing capability is a critical yet challenging task to improve the stability and lifetime of strain sensors. Herein, we design a self-healable conducting polymer hydrogel by compositing poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) nanofibers and poly(vinyl alcohol) (PVA) via both physical and chemical crosslinking. This PEDOT:PSS-PVA nanocomposite hydrogel strain sensor displays an excellent strain monitoring range (>200%), low hysteresis (<1.6%), a high gauge factor (GF = 3.18), and outstanding self-healing efficiency (>83.5%). Electronic skins based on such hydrogel strain sensors can perform the accurate monitoring of various physiological signals, including swallowing, finger bending, and knee bending. This work presents a novel conducting polymer hydrogel strain sensor demonstrating both high sensing performance and self-healability, which can satisfy broad application scenarios, such as wearable electronics, health monitoring, etc.

Conductive Viologen Hydrogel Based on Hyperbranched Polyamidoamine for Multiple Stimulus-Responsive Drug Delivery.

The emergence of precision medicine and personalized pharmacotherapy has led to the development of advanced drug delivery systems that can respond to multiple stimuli. Conductive hydrogels have excellent electrical signal responsiveness and drug storage capabilities; however, current conductive hydrogels suffer from poor mechanical properties, low ionic conductivity, and high voltage. Herein, a covalently crosslinked viologen hydrogel was prepared using electroactive hyperbranched polyamidoamine (EHP) as the crosslinking center in a polymeric network. Attributed to its unique molecular architecture, this hydrogel exhibits improved mechanical properties (high tensile strength and desirable stretchability up to 1280%). Approvable ionic conductivity, biocompatibility, antibacterial properties, and wearable strain-sensing performance were also disclosed, ascribed to the participation of versatile viologen groups in the hydrogel structure. This hydrogel exhibited high efficiency in drug release (81.6%) at a lower voltage of -1.2 V. Moreover, fascinating pH-stimulus drug release behavior was also demonstrated in both acidic and alkalescent environments owing to the dramatic conformational transition of EHP. This work provides a new design strategy for conductive hydrogels for multiple stimulus-responsive drug delivery systems.

Flexible and Stretchable Poly(styrene-butadiene-styrene)/MXene Nanosheet Composite and Coaxial Fibers for Wearable Strain Sensors

Fiber-based strain sensors have become a vital part for wearable electronics owing to their lightweight, flexibility, and easy processing. A poly(styrene-butadiene-styrene) (SBS)/MXene composite and coaxial fiber-based strain sensors were produced through a continuous, facile, and scalable wet-spinning approach, which exhibited both high stretchability and sensitivity. Electromechanical properties displayed that SBS/MXene composite fibers showed extremely high sensitivity (1.63 × 104), low strain detection (0.5%), and outstanding durability and reliability, which laid a foundation for detecting human motion including subtle activities, such as breathing and wrist pulse, and large-scale activities, such as bending of limb joints. The strain-sensing performance was further investigated by SBS/MXene coaxial fibers with SBS/MXene as sheath and SBS as core, presenting high sensitivity (4.69 × 103) and repeatability. SBS/MXene composite and coaxial fiber sensors demonstrated the potential application in wearable electronics with human motion detection.

A two-step homogenization micromechanical model for strain-sensing of graphene reinforced porous cement composites

The incorporation of graphene and its derivatives into cement for electrically conductive composites is currently under extensive investigations due to their potential applications as smart materials for large-scale self-sensing structures. It is of great importance to develop theoretical models to predict the response of the electrical conductivity of the cement composites when subjected to mechanical deformation. Experimental studies have demonstrated that pores and rippled graphene fillers exist in the cement composites. However, currently there are limited theoretical models to predict the electrical conductivity and piezoresistive properties of the cement composites with incorporating the effects of pores and graphene ripples. To address the research gap, this paper develops a two-step micromechanical modelling to predict the effective electrical conductivity and the response of conductivity to compression strain of graphene nanoplatelet (GNP) reinforced cement composites (GNPRCCs) with considering the effects of pores and graphene ripple for the first time. The effective medium theory and Mori-Tanaka model are employed to homogenize the GNP and pores as inclusions with considering several influencing mechanisms. Parametric study is carried out to identify the effects of the attributes of GNPs, pores and electron tunnelling on the electrical and piezoresistive properties of the GNPRCCs. It is found that the piezoresistive response is proportional to porosity when the conductive behavior of GNPRCC is dominated by the tunnelling effect. Increasing porosity has a negative impact on the strain-sensing performance of the GNPRCCs once the conductive network is formed.

Facile and Controllable Ultrasonic Nebulization Method for Fabricating Ti3C2Tx‐Based Strain Sensor and Monitoring of Human Motion and Sound Wave

AbstractFlexible and wearable electronic devices hold great potential in electronic skins, health monitoring systems and soft robotics. Among them, flexible strain sensors with high performance are key components for wearable health monitoring devices. However, the facile and controllable preparation of highly sensitive sensors still faces significant challenges. By virtue of excellent conductivity of 2D transition metal carbids (MXenes), this work reports a facile and low‐cost fabrication strategy for large‐scale production of strain sensors. The sensitive layer is deposited on flexible interdigital electrodes by ultrasonic nebulization of Ti3C2Tx nanosheets. By controlling the nebulization time, different thicknesses of Ti3C2Tx films has a great influence on the performance of strain sensors. The Ti3C2Tx‐based strain sensor exhibits good sensing performances such as high GF (19.1) in the low strain range (≈0.25%–1.14%), short response time (0.7 s), and stable durability (over 1000 cycles). In practice, the potential applications of the strain sensor in sound frequency detection, human physiological signal monitoring and facial expression recognition are demonstrated. Finally, this work integrates the strain sensor with a miniaturized analyzer to assemble a wearable motion monitoring device for mobile healthcare. This study provides a facile strategy for fabricating flexible strain sensors in the field of wearable electronics.