Textile-based Pressure Sensors Research Articles

Flexible Pressure Sensors for Integration into Karate Body Protector.

The increasing interest in karate has also attracted the attention of researchers, especially in combining the equipment used by practitioners with technology to prevent injuries, improve technical skills and provide appropriate scoring. Contrary to the sport of taekwondo, the development of a smart body protector in the sport of karate is still a niche field to be researched. This study focused on developing piezoresistive, textile-based pressure sensors using piezoresistive film, conductive fabric as well as different bonding materials and methods. Primarily, small-scale sensors were produced using ultrasonic welding, hot press welding and oven curing. These were characterized using a universal testing machine and specific conditioning and data-acquisition hardware combined with custom processing software. Large-scale sensors were then manufactured to be placed inside the karate body protector and characterized using cyclic testing. The conditioning circuit allows flexible gain adjustment, and it was possible to obtain a stable signal with an output of up to 0.03 V/N, an adequate signal for the tested force range. The transfer function shows some drift over the cycles, in addition to the expected hysteresis and slight nonlinearity, which can be compensated for. Finally, the configuration with the best results was tested in real practice tests; during these tests the body protector was placed on a dummy as well as on a person. The results showed that the piezoresistive textile-based pressure sensor produced is able to detect and quantify the impact of even light punches, providing an unobtrusive means for performance monitoring and score calculation for competitive practice of this sport.

Superhydrophobic Conductive Suede Fabrics Based on Carboxylated Multiwalled Carbon Nanotubes and Polydopamine for Wearable Pressure Sensors

Textile-based pressure sensors have attracted considerable attention due to their potential to detect vital signals in humans, enhance sports performance, and facilitate human–machine interactions. However, practical challenges, such as unstable assembly structures, weak interfacial bonds with functional materials, and incompatibility with current established finishing technologies in production, remain significant obstacles to their widespread applications. This research explores commercially available suede fabric as a promising substrate for pressure sensing. The conductive suede sensor was readily by integrating carboxylated multiwalled carbon nanotubes (C-MWCNTs) and polydopamine (PDA) and subsequently modifying it with hexadecyltrimethoxysilane to achieve a superhydrophobic surface. The resulting suede sensor, featuring a robust PDA-(C-MWCNTs)-HDTMS chemical configuration, exhibited satisfactory hydrophobicity, excellent stability, and repeatability, capable of detecting pulse, throat movement, and daily human motions. Furthermore, the properties of the suede sensor can be well preserved after 60 min of machine washing and ultrasonic cleaning, highlighting its potential in practical applications. This study provides an environmentally stable, lightweight, and well-structured substrate for high-performance electronic textiles suitable for large-scale production.

Graphene/SiC-coated textiles with excellent electromagnetic interference shielding, Joule heating, high-temperature resistance, and pressure-sensing performances

Multifunctional, wearable, and durable textiles integrated with smart electronics have attracted tremendous attention. However, it remains a great challenge to balance new functionalities with high temperature stability. Herein, textile-based pressure-sensors with excellent electromagnetic interference (EMI) shielding, Joule heating and high temperature resistance were fabricated by constructing graphene/SiC (G/SiC) heterostructures on carbon cloth via laser chemical vapor deposition (LCVD). The resultant textile exhibited excellent EMI efficiency of 74.2 dB with a thickness of 0.45 mm, Joule heating performance within low working voltage range of 1 to 3 V and fast response time within 20 s. These properties arose from multiple reflections, interfacial polarizations and high conductivity due to the numerous amounts of nanoscale G/SiC heterostructures. More importantly, the G/SiC/CFs demonstrated well high temperature resistance with a <em>T</em>_HRI of 380.16 ^oC owing to the protection of the coating layer on the carbon fibers upon oxidation. Meanwhile, the G/SiC/CFs presented good pressure-sensing performance with a high sensitivity of 52.93 kPa⁻¹, fast response time of 85 ms and wide pressure range up to 186 kPa. These features imply the potential of G/SiC/CFs as an efficient EMI shielding, electrical heater and piezoresistive sensor textiles.

All textile-based robust pressure sensors for smart garments

Textile-based pressure sensors with good comfortness and breathability can be easily integrated into garments for smart wearables. Nevertheless, scalable construction of all textile-based pressure sensors with good mechanical robustness and desirable sensor performance still remains a great challenge. Here, a facile, low-cost, and scalable approach is proposed to fabricate a new paradigm of all textile-based and mechanically robust pressure sensors. These pressure sensors consist of a top elastic piezoresistive sensing fabric and a bottom textile-based robust interdigital electrodes. The top piezoresistive sensing fabric is fabricated by controllably depositing robust polyurethane/carbon nanotubes composites on a highly elastic Venetian fabric through electrostatic layer-by-layer assembly. The bottom interdigital electrodes are prepared by screen printing of an elastic and robust carbon ink on a polyester fabric. Notably, the conductive networks in both of the piezoresistive sensing layer and the bottom electrodes are firmly embedded in elastomer substrates rather than directly attached onto the fabric surface, endowing the pressure sensors with superior mechanical robustness. The as-fabricated all textile-based pressure sensors exhibit high sensitivity (3.42 kPa−1), fast response/recovery time (32 ms/4 ms), good cycling stability (10 000 cycles), superior robustness against mechanical bending (10 000 cycles) and chemical washing. As demonstrations, the pressure sensors are integrated into diverse garments for wireless and real-time monitoring of various human physiological activities, including joint bending, muscle activity, object grasping, etc. This proposed simple but efficient approach for fabricating all textile-based pressure sensors with superior robustness opens up new opportunities for the further development of smart garments and wearable devices.

Homogeneity Characterization of Textile-Integrated Wearable Sensors based on Impedance Spectroscopy.

One of the main challenges during the integration of a carbon/polymer-based nanocomposite sensor on textile substrates is the fabrication of a homogeneous surface of the nanocomposite-based thin films, which play a major role in the reproducibility of the sensor. Characterizations are therefore required in every fabrication step to control the quality of the material preparation, deposition, and curing. As a result, microcharacterization methods are more suitable for laboratory investigations, and electrical methods can be easily implemented for in situ characterization within the manufacturing process. In this paper, several textile-based pressure sensors are fabricated at an optimized concentration of 0.3 wt.% of multiwalledcarbon nanotubes (MWCNTs) composite material in PDMS. We propose to use impedance spectroscopy for the characterization of both of the resistive behavior and capacitive behavior of the sensor at several frequencies and under different loads from 50 g to 500 g. The impedance spectra are fitted to a model composed of a resistance in series with a parallel combination of resistance and a constant phase element (CPE). The results show that the printing parameters strongly influence the impedance behavior under different loads. The deviation of the model parameter of the CPE from the value 1 is strongly dependent on the nonhomogeneity of the sensor. Based on an impedance spectrum measurement followed by parameter extraction, the parameter can be determined to realize a novel method for homogeneity characterization and in-line quality control of textile-integrated wearable sensors during the manufacturing process.

Textile-based pressure sensor arrays: A novel scalable manufacturing technique

Soft pressure sensors have sparked a lot of interest over the last decade because of their applications in human motion recognition, object detection, and human–computer interaction. However, their mass production and availability to end users are limited due to the complex and time-consuming steps. The scalability of working range for various applications is also a critical challenge. Therefore, a laborless, rapid, and scalable manufacturing technique for capacitive-based soft pressure sensors with high sensitivity and high working range is proposed in this work. The novel manufacturing method enables manipulation of sensor properties by varying production parameters based on specific application needs. The proposed sensor's electrode is made of conductive knit fabric, and the dielectric layers are made of thermoplastic polyurethane (TPU) sheets. As a result of the novel approach, it is possible to generate scalable air gaps between electrodes and dielectric layers to capture low pressures of less than 1 kPa. The usage of multi-layer TPU sheets also increases the working range of sensors up to 1000 kPa. Here, the proposed technology is successfully applied to create several sensor mats for different purposes such as improved gesture and shape recognition, and interactive gaming mats for children. • Simple and fast manufacturing of a novel textile pressure sensor. • Scalable with desired pattern of the sensor mat. • Adjustable sensitivity and wide working range from 1 kPa to 1000 kPa. • Pressure mapping for e-textiles, interactive software and human gesture recognition.

Effect of Fabric Structure on the Performance of 3D Woven Pressure Sensor

The textile-based pressure sensors are an integral part of the wearable electronic textiles, that helps to measure the pressure/load applied to the sensor. These sensors are used predominantly for health and sports application, especially to monitor the blood pressure, heart rate or performance of muscles during exercise. The work done in this research is about the investigation of the response of a 3D woven fabric-based pressure sensor by varying the yarn interlacement pattern in 3 layered fabric. Four samples were produced using a 3D weaving technique, with two types of yarns i.e. polyester/cotton (59 tex) and multifilament steel (55.5 tex). The weave design of face and back layer of the three-layered structure was kept 1/1 plain (P), while the weave design of middle layer was changed to plain (P), matt (M), twill (T) or satin (S), resulting in structures PPP, PMP, PTP, and PSP respectively. Working of pressure sensor was evaluated in terms of resistance offered by structure, both under static and dynamic loading. The dynamic load was applied by the compression and subsequent relaxation, i.e. under incremental loading followed by decremental unloading. All the structures showed variation in resistance in response to applied load showing potential being used as a pressure sensor. The structures PPP, PMP, and PSP behaved as a pressure sensor up to 500 grams while the efficient sensor was PTP (plain/twill/plain) with activity up to a load of 5500 grams. A statistical model was developed for the structure PTP, correlating the resistance with the applied load. The developed sensors can also be produced inside the fabrics or can be embedded inside garments.

Highly Sensitive Textile-Based Capacitive Pressure Sensors Using PVDF-HFP/Ionic Liquid Composite Films.

Textile-based pressure sensors have garnered considerable interest in electronic textiles due to their diverse applications, including human–machine interface and healthcare monitoring systems. We studied a textile-based capacitive pressure sensor array using a poly(vinylidene fluoride)-co-hexafluoropropylene (PVDF-HFP)/ionic liquid (IL) composite film. By constructing a capacitor structure with Ag-plated conductive fiber electrodes that are embedded in fabrics, a capacitive pressure sensor showing high sensitivity, good operation stability, and a wide sensing range could be created. By optimizing the PVDF-HFP:IL ratio (6.5:3.5), the fabricated textile pressure sensors showed sensitivity of 9.51 kPa−1 and 0.69 kPa−1 in the pressure ranges of 0–20 kPa and 20–100 kPa, respectively. The pressure-dependent capacitance variation in our device was explained based on the change in the contact-area formed between the multi-filament fiber electrodes and the PVDF-HFP/IL film. To demonstrate the applicability and scalability of the sensor device, a 3 × 3 pressure sensor array was fabricated. Due to its matrix-type array structure and capacitive sensing mechanism, multi-point detection was possible, and the different positions and the weights of the objects could be identified.

Fully-integrated wearable pressure sensor array enabled by highly sensitive textile-based capacitive ionotronic devices

Recently, textile-based pressure sensors have gained considerable interest in the field of wearable electronics due to their wide range of applicability and good scalability. Despite recent progress, however, urgent challenges remain to develop a fully integrated textile sensor array with highly sensitive multi-sensing capability and low-power consumption. Here, we demonstrate a highly-sensitive capacitive ionotronic (CIT) pressure sensor array using high- k ion-gel (IG) film for implementation of textile-based electronic systems. With a composition and thickness optimized IG film, CIT pressure sensors with high sensitivity up to 308 nF kPa −1 and relatively good stability was successfully obtained. In addition, based on mechanical simulations using finite element method, it was found that the pressure-dependent contact-area variation between multifilament fiber electrodes and the IG film played the dominant role in capacitance change rather than the thickness change of the IG film. Furthermore, a 3 × 3 CIT pressure sensor system is implemented on a large-area textile substance with multi-point detection capability, demonstrating a textile-based pressure monitoring system integrated with a pressure variable multi-color light emitting diode array. A textile-integrated highly-sensitive capacitive ionotronic pressure sensor using high- k ion-gel film is demonstrated. The synergetic combination of multifilament fiber electrodes and ion-gel enabled a large pressure-dependent contact-area variation for high pressure sensitivity. A 3 × 3 pressure sensor array and a textile pressure monitoring circuit were demonstrated using the ionotronic pressure sensors. • A fully textile-integrated capacitive ionotronic pressure sensor array using high- k ion-gel film is demonstrated. • The multifilament fiber electrode structure allowed a large pressure-dependent contact-area variation for high sensitivity. • A 3 × 3 CIT pressure sensor array and a textile-based pressure monitoring circuit are demonstrated.

Flexible Textile-Based Pressure Sensing System Applied in the Operating Room for Pressure Injury Monitoring of Cardiac Operation Patients.

Pressure injury is the most important issue facing paralysis patients and the elderly, especially in long-term care or nursing. A new interfacial pressure sensing system combined with a flexible textile-based pressure sensor array and a real-time readout system improved by the Kalman filter is proposed to monitor interfacial pressure progress in the cardiac operation. With the design of the Kalman filter and parameter optimization, noise immunity can be improved by approximately 72%. Additionally, cardiac operation patients were selected to test this developed system for the direct correlation between pressure injury and interfacial pressure for the first time. The pressure progress of the operation time was recorded and presented with the visible data by time- and 2-dimension-dependent characteristics. In the data for 47 cardiac operation patients, an extreme body mass index (BMI) and significantly increased pressure after 2 h are the top 2 factors associated with the occurrence of pressure injury. This methodology can be used to prevent high interfacial pressure in high-risk patients before and during operation. It can be suggested that this system, integrated with air mattresses, can improve the quality of care and reduce the burden of the workforce and medical cost, especially for pressure injury.

A Wearable and Highly Sensitive Textile-based Pressure Sensor with Ti3C2Tx Nanosheets

Development of low-cost, efficient, flexible and highly sensitive pressure sensors that can perceive and respond to environmental stimuli have become indispensable for wearable electronics. Herein, the Ti3C2Tx-textile based pressure sensor was successfully fabricated with the help of common fabric substrates by using simple and effective dipping-drying method. The Ti3C2Tx Nanosheets prepared by wet-chemical solution display excellent hydrophilicity, high specific surface area, metallic conductivity and controllable surface groups properties, which are extremely suitable in construction of low-cost and high-performance textile-based pressure sensors. And the Ti3C2Tx-textile based pressure sensor achieves high sensitivity (19.78 kPa−1), low detection limit (219 mN), fast response (∼149 ms) and well stability (more than 7000). With these merits, the Ti3C2Tx-textile based sensor is demonstrated to be able to recognize the human physiological signals, such as finger bending, tapping, hand movements and so on. Furthermore, the textile sensor also can be capable to measure pressure distribution and distinguish the subtle strain, which demonstrates great potential in both industrial and biomedical applications.

Foldable and washable fully textile-based pressure sensor

Smart textiles have wide applications in various sensing systems since they have the advantage of maintaining the inherent properties of textile such as light weight, flexibility, comfort, and breathability. Therefore, textile-based pressure sensors, one of the smart textiles, have attracted considerable interest in wearable electronics and homecare systems. In this study, to construct a textile-based pressure sensor, a poly(3,4-ethylenedioxythiophene) (PEDOT) thin film was fabricated on a polyethylene terephthalate microfiber fabric by vapor phase polymerization with various concentrations of the oxidant, FeCl3. The PEDOT conductive textile showed a change in conductivity depending on the applied pressure. We confirmed the excellent washing and physical durability of the sensor from the stable electrical properties of the PEDOT conductive textile after washing and repeated folding tests. Furthermore, a fully textile-based pressure sensor was successfully fabricated using the highly durable PEDOT, which could simultaneously measure both static and dynamic pressures even during physical deformation, thus suggesting great potential in smart textiles, especially textile-based homecare systems.

A Comparative Characterization of Smart Textile Pressure Sensors.

This research study investigates the impact of various insulating textile materials on the performance of smart textile pressure sensors made of conductive threads and piezo resistive material. We designed four sets of identical textile-based pressure sensors each of them integrating a different insulating textile substrate material. Each of these sensors underwent a series of tests that linearly increased and decreased a uniform pressure perpendicular to the surface of the sensors. The controlled change of the integration layer altered the characteristics of the pressure sensors including both the sensitivity and pressure ranges. Our experiments highlighted that the manufacturing design technique of textile material has a significant impact on the sensor; with evidence of reproducibility values directly relating to fabric dimensional stability and elasticity.

Development of Textile-based Pressure Sensor and Its Application

Smart textile industries have been rapidly developed and are being studied for home care system. Particularly, the healthcare field has been highlighted in the smart device industries due to an increasingly ageing society, and pressure sensors can be utilized in various elderly healthcare products such as flooring and mattress because they can obtain a variety of pressure information in a large-area at indoor without infringing privacy. In this study, the novel type of conductive textile was fabricated using vapor phase polymerization (VPP) of poly(3,4-ethylenedioxythiophene) (PEDOT) to apply a textile to the pressure sensing device. The morphology of the PEDOT-coated conductive textile was observed through the field emission scanning electron microscope (FE-SEM). Moreover, the resistance was confirmed to be adjustable to various resistance ranges depending on the concentration of the oxidant solution and polymerization conditions and measured using 4-probe system. The 3-layered 81-points textile-based pressure sensor was fabricated using the PEDOT-coated conductive textile prepared herein. The visualized system by Matlab was developed to evaluate the sensitivity, multi-pressure recognition, and position tracking. In addition, the developed system can record the data so as to track the moving pressure and detect the event considered to be an emergency. Finally, we confirmed the possibility that PEDOT-coated conductive textiles could be utilized by pressure sensors.

Textile-based pressure sensors for step detection: a preliminary assessment

This paper presents the development and performance assessment of textile-based sensor based on a three layer architecture for the step detection. Two different transducing elements (EeonTex™ LG-SLPA and velostat) and electrodes (Satatex Techniktex P-130 and Elitex yarns) were selected for the construction of the sensors. The performance of the resulting sensors was assessed based on a dynamometer cyclic compression/decompression test with different compressions loads and at different speeds. Additionally, a real-life experiment was conducted to evaluate the sensor response during walking. The results show that all sensors configurations have a non-linear resistance-force relation. The best sensor configuration for the step detection was the combination of EeonTex™ LG-SLPA as a transducing element and the Elitex yarns for the electrodes. In this configuration, the resistance magnitude varies in an order of hundreds of kohms between the stance and the swing phases.

Highly stretchable fiber-shaped e-textiles for strain/pressure sensing, full-range human motions detection, health monitoring, and 2D force mapping

Textile-based electronics (e-textiles) have attracted huge attention in wearable sensors recently. Even though highly sensitive textile-based pressure sensors and highly stretchable textile-based strain sensors are widely researched and reported in recent years, it is still full of challenges to develop high stretchable textile-based sensors simultaneously and satisfy strain and pressure sensing, which is necessary for full-range detection of human motions. On the other hand, compared to traditional planar e-textiles, fiber-shaped e-textiles have plenty of advantages due to their fibrous architecture with lightweight, portable, skin compliant, and easily weave properties. In this work, a fiber-shaped textile, knitted with hierarchical polyurethane (PU) fibers, is used to fabricate a multifunctional e-textile by coating of silver nanowires (AgNWs) and styrene–butadiene–styrene. Due to the AgNWs conductive networks, the inherent stretchability of PU fibers, and the hierarchical structure, the as-prepared e-textile exhibits high conductivity, high stretchability, high sensitivity, and multi-detection of strain and pressure. What is more, the fabricated multifunctional e-textiles are also successfully weaved into electronic fabric for 2D force mapping. The simple, scalable strategy endows the multifunctional e-textiles great potentials in full-range detection and health care areas.

Novel highly sensitive and wearable pressure sensors from conductive three-dimensional fabric structures

Pressure sensors based on three-dimensional fabrics have all the excellent properties of the textile substrate: excellent compressibility, good air permeability and moisture transmission ability, which will find applications ranging from the healthcare industry to daily usage. In this paper, novel pressure sensors based on 3D spacer fabrics have been developed by a proposed multi-coating method. By this coating method, carbon black can be coated uniformly on the silicon elastomer which is attached and slightly cured on the 3D fabric surface beforehand. The as-made pressure sensors have good conductivity and can measure external pressure up to 283 kPa with an electrical conductivity range of 9.8 kΩ. The sensitivity of 3D fabric pressure sensors can be as high as 50.31×10−3 kPa−1, which is better than other textile based pressure sensors. When the as-made sensors are pressed, their electrical resistance will decrease because of more conductive connections and bending of fibers in the spacer layer. The sensing mechanism related to fiber bending has been explored by using an equivalent resistance model. The newly developed 3D sensor devices can be designed to exhibit different sensing performances by simply changing the structures of fabric substrate, which endows this kind of device more flexibility in related applications.

Conductive fiber-based ultrasensitive textile pressure sensor for wearable electronics.

A flexible and sensitive textile-based pressure sensor is developed using highly conductive fibers coated with dielectric rubber materials. The pressure sensor exhibits superior sensitivity, very fast response time, and high stability, compared with previous textile-based pressure sensors. By using a weaving method, the pressure sensor can be applied to make smart gloves and clothes that can control machines wirelessly as human-machine interfaces.

Flexible and Pixelated Textile Pressure Sensor Fabricated with Weaving Techniques

Recently, electronic textiles (E-textiles) that integrate sensors, actuators and computers into fabrics have attracted considerable attention and several types of textile-based devices have been widely studied. E-textiles have been applied to effectively provide a wide range of information to the people like elderly and patients since they can be worn or embedded in clothing. Among several applications of E-textiles, pressure sensors have significant role to detect a person’s information such as locations, vital signals. In previous studies, textile-based pressure sensors have generally developed by weaving metal wires due to their simple structure and fabrication process, however, it is challenging to apply these pressure sensors on sophisticated devices due to their poor sensing ability.This research proposes a novel method of fabricating highly sensitive textile-based pressure sensor that can be pixelated through weaving method. We first obtained highly flexible and conductive Kevlar fiber by coating a composite material of Ag nanoparticles and elastomeric polymer. Consequently poly(dimethylsiloxane) (PDMS) was coated on the surface of conductive fiber as a dielectric layer. Through weaving method, the PDMS-coated conductive fibers were woven into fabric to form highly sensitive capacitive pressure sensors located at crossed points of the fibers. The highly sensitive pressure sensor was pixelated in the form of arrays via weaving method. Finally, pressure sensors were applied to monitor detection of small vibration forces from music and impact of a bouncing water droplet on a superhydrophobic surface.

Sheath-core 구조 전도사 섬유센서의 Home-Textile 적용을 위한 전기·물리학적 특성연구

The usage of textile-based sensors has increased due to their many advantages (compared to IT sensors) when applied to body assessment and comfort. Textile-based sensors have different detecting factors such as pressure, voltage, current and capacitance to investigate the characteristics. In this study, textile-based sensor fabrics with sheath-core type conductive yarns were produced and the relationship between capacitance changes and applied load was investigated. The physical and electric properties of textile-based sensor fabrics were also investigated under various laminating conditions. A textile based pressure sensor that uses a sheath-core conductive yarn to ensure the stability of the pressure sensor in the textile-based sensor (the physical structure of the reaction characteristic of the capacitance) is important for the stability of the initial value of the initial capacitance value outside the characteristic of the textile structural environment. In addition, a textile based sensor is displaced relative to the initial value of the capacitance change according to pressure changes in the capacitance value of the sensor due to the fineness of the high risk of noise generation. Changing the physical structure of the fabric through the sensor characteristic of the pressure sensor via the noise generating element of laminating (temperature, humidity, and static electricity) to cut off the voltage output element to improve the data reliability could be secured.