Graphene/PVA buckypaper for strain sensing application

AbstractStrain sensors in the form of buckypaper (BP) infiltrated with various polymers are considered a viable option for strain sensor applications such as structural health monitoring and human motion detection. Graphene has outstanding properties in terms of strength, heat and current conduction, optics, and many more. However, graphene in the form of BP has not been considered earlier for strain sensing applications. In this work, graphene-based BP infiltrated with polyvinyl alcohol (PVA) was synthesized by vacuum filtration technique and polymer intercalation. First, Graphene oxide (GO) was prepared via treatment with sulphuric acid and nitric acid. Whereas, to obtain high-quality BP, GO was sonicated in ethanol for 20 min with sonication intensity of 60%. FTIR studies confirmed the oxygenated groups on the surface of GO while the dispersion characteristics were validated using zeta potential analysis. The nanocomposite was synthesized by varying BP and PVA concentrations. Mechanical and electrical properties were measured using a computerized tensile testing machine, two probe method, and hall effect, respectively. The electrical conducting properties of the nanocomposites decreased with increasing PVA content; likewise, electron mobility also decreased while electrical resistance increased. The optimization study reports the highest mechanical properties such as tensile strength, Young’s Modulus, and elongation at break of 200.55 MPa, 6.59 GPa, and 6.79%, respectively. Finally, electrochemical testing in a strain range of ε ~ 4% also testifies superior strain sensing properties of 60 wt% graphene BP/PVA with a demonstration of repeatability, accuracy, and preciseness for five loading and unloading cycles with a gauge factor of 1.33. Thus, results prove the usefulness of the nanocomposite for commercial and industrial applications.

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Anisotropic, Wrinkled, and Crack-Bridging Structure for Ultrasensitive, Highly Selective Multidirectional Strain Sensors

Nano-Micro Letters ◽

10.1007/s40820-021-00615-5 ◽

2021 ◽

Vol 13 (1) ◽

Author(s):

Heng Zhang ◽

Dan Liu ◽

Jeng-Hun Lee ◽

Haomin Chen ◽

Eunyoung Kim ◽

...

Keyword(s):

Rational Design ◽

Full Range ◽

Human Motion ◽

Strain Sensors ◽

Gauge Factor ◽

Wearable Electronics ◽

Trade Off ◽

Human Motion Detection ◽

Sensing Applications ◽

Anisotropic Structures

AbstractFlexible multidirectional strain sensors are crucial to accurately determining the complex strain states involved in emerging sensing applications. Although considerable efforts have been made to construct anisotropic structures for improved selective sensing capabilities, existing anisotropic sensors suffer from a trade-off between high sensitivity and high stretchability with acceptable linearity. Here, an ultrasensitive, highly selective multidirectional sensor is developed by rational design of functionally different anisotropic layers. The bilayer sensor consists of an aligned carbon nanotube (CNT) array assembled on top of a periodically wrinkled and cracked CNT–graphene oxide film. The transversely aligned CNT layer bridge the underlying longitudinal microcracks to effectively discourage their propagation even when highly stretched, leading to superior sensitivity with a gauge factor of 287.6 across a broad linear working range of up to 100% strain. The wrinkles generated through a pre-straining/releasing routine in the direction transverse to CNT alignment is responsible for exceptional selectivity of 6.3, to the benefit of accurate detection of loading directions by the multidirectional sensor. This work proposes a unique approach to leveraging the inherent merits of two cross-influential anisotropic structures to resolve the trade-off among sensitivity, selectivity, and stretchability, demonstrating promising applications in full-range, multi-axis human motion detection for wearable electronics and smart robotics.

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Practical and Durable Flexible Strain Sensors Based on Conductive Carbon Black and Silicone Blends for Large Scale Motion Monitoring Applications

Sensors ◽

10.3390/s19204553 ◽

2019 ◽

Vol 19 (20) ◽

pp. 4553 ◽

Cited By ~ 2

Author(s):

Yun Xia ◽

Qi Zhang ◽

Xue E. Wu ◽

Tim V. Kirk ◽

Xiao Dong Chen

Keyword(s):

Carbon Black ◽

Large Scale ◽

Low Cost ◽

Strain Range ◽

Human Motion ◽

Flexion Angle ◽

Gauge Factor ◽

Large Strains ◽

Human Motion Detection

Presented is a flexible capacitive strain sensor, based on the low cost materials silicone (PDMS) and carbon black (CB), that was fabricated by casting and curing of successive silicone layers—a central PDMS dielectric layer bounded by PDMS/CB blend electrodes and packaged by exterior PDMS films. It was effectively characterized for large flexion-angle motion wearable applications, with strain sensing properties assessed over large strains (50%) and variations in temperature and humidity. Additionally, suitability for monitoring large tissue deformation was established by integration with an in vitro digestive model. The capacitive gauge factor was approximately constant at 0.86 over these conditions for the linear strain range (3 to 47%). Durability was established from consistent relative capacitance changes over 10,000 strain cycles, with varying strain frequency and elongation up to 50%. Wearability and high flexion angle human motion detection were demonstrated by integration with an elbow band, with clear detection of motion ranges up 90°. The device’s simple structure and fabrication method, low-cost materials and robust performance, offer promise for expanding the availability of wearable sensor systems.

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Gold/Polyimide-Based Resistive Strain Sensors

Electronics ◽

10.3390/electronics8050565 ◽

2019 ◽

Vol 8 (5) ◽

pp. 565 ◽

Cited By ~ 5

Author(s):

Tao Han ◽

Anindya Nag ◽

Nasrin Afsarimanesh ◽

Fowzia Akhter ◽

Hangrui Liu ◽

...

Keyword(s):

Thin Film ◽

Industrial Applications ◽

Gold Layer ◽

Gauge Factor ◽

Strain Sensing ◽

Thin Film Sensors ◽

Pressure Mapping ◽

Sensing Applications ◽

The Cost ◽

Two Sides

This paper presents the fabrication and implementation of novel resistive sensors that were implemented for strain-sensing applications. Some of the critical factors for the development of resistive sensors are addressed in this paper, such as the cost of fabrication, the steps of the fabrication process which make it time-consuming to complete each prototype, and the inability to achieve optimised electrical and mechanical characteristics. The sensors were fabricated via magnetron sputtering of thin-film chromium and gold layer on the thin-film substrates at defined thicknesses. Sticky copper tapes were attached on the two sides of the sensor patches to form the electrodes. The operating principle of the fabricated sensors was based on the change in their responses with respect to the corresponding changes in their relative resistance as a function of the applied strain. The strain-induced characteristics of the patches were studied with different kinds of experiments, such as consecutive bending and pressure application. The sensors with 400 nm thickness of gold layer obtained a sensitivity of 0.0086 Ω/ppm for the pressure ranging between 0 and 400 kPa. The gauge factor of these sensors was between 4.9–6.6 for temperatures ranging between 25 °C and 55 °C. They were also used for tactile sensing to determine their potential as thin-film sensors for industrial applications, like in robotic and pressure-mapping applications. The results were promising in regards to the sensors’ controllable film thickness, easy operation, purity of the films and mechanically sound nature. These sensors can provide a podium to enhance the usage of resistive sensors on a higher scale to develop thin-film sensors for industrial applications.

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Graphene as a Piezoresistive Material in Strain Sensing Applications

Micromachines ◽

10.3390/mi13010119 ◽

2022 ◽

Vol 13 (1) ◽

pp. 119

Author(s):

Farid Sayar Irani ◽

Ali Hosseinpour Shafaghi ◽

Melih Can Tasdelen ◽

Tugce Delipinar ◽

Ceyda Elcin Kaya ◽

...

Keyword(s):

Mechanical Strain ◽

Evolutionary Process ◽

Strain Range ◽

Device Fabrication ◽

Strain Sensors ◽

Gauge Factor ◽

Strain Sensing ◽

Characterization Methods ◽

Accuracy Measurement ◽

Sensing Applications

High accuracy measurement of mechanical strain is critical and broadly practiced in several application areas including structural health monitoring, industrial process control, manufacturing, avionics and the automotive industry, to name a few. Strain sensors, otherwise known as strain gauges, are fueled by various nanomaterials, among which graphene has attracted great interest in recent years, due to its unique electro-mechanical characteristics. Graphene shows not only exceptional physical properties but also has remarkable mechanical properties, such as piezoresistivity, which makes it a perfect candidate for strain sensing applications. In the present review, we provide an in-depth overview of the latest studies focusing on graphene and its strain sensing mechanism along with various applications. We start by providing a description of the fundamental properties, synthesis techniques and characterization methods of graphene, and then build forward to the discussion of numerous types of graphene-based strain sensors with side-by-side tabular comparison in terms of figures-of-merit, including strain range and sensitivity, otherwise referred to as the gauge factor. We demonstrate the material synthesis, device fabrication and integration challenges for researchers to achieve both wide strain range and high sensitivity in graphene-based strain sensors. Last of all, several applications of graphene-based strain sensors for different purposes are described. All in all, the evolutionary process of graphene-based strain sensors in recent years, as well as the upcoming challenges and future directions for emerging studies are highlighted.

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Embedded 3D Printing of Highly Flexible Nanocomposites With Piezoresistive Sensing Capabilities

Volume 4: Advances in Aerospace Technology ◽

10.1115/imece2020-23173 ◽

2020 ◽

Author(s):

Blake Herren ◽

Mrinal C. Saha ◽

M. Cengiz Altan ◽

Yingtao Liu

Keyword(s):

3D Printing ◽

Human Skin ◽

Strain Sensor ◽

Strain Range ◽

High Sensitivity ◽

Curing Temperature ◽

Gauge Factor ◽

Strain Sensing ◽

Sensing Applications ◽

Human Joints

Abstract In recent years, highly flexible nanocomposite sensors have been developed for the detection of a variety of human body movements. To precisely detect the bending motions of human joints, the sensors must be able to conform well with the human skin and produce signals that effectively describe the amount of deformation applied to the material during bending. In this paper, a carbon nanotube-based piezoresistive strain sensor is developed via the direct ink writing based embedded 3D printing method. The optimum weight concentration range of carbon nanotubes in the nanocomposite inks, appropriate for embedded 3D printing, is identified. Samples with complex 2D and 3D geometries are printed to demonstrate the manufacturing capabilities of the embedded printing process. The sensitivity of the piezoresistive strain sensor is optimized by determining the ideal nanofiller concentration, curing temperature, and nozzle size to produce the highest gauge factor in a wide strain range. The piezoresistive and mechanical properties of the optimized sensors are fully characterized to verify the suitability for skin-attachable strain sensing applications. The developed sensors have a wide sensing range, high sensitivity, and minimal strain rate dependence. In addition, their low elasticity and high biocompatibility allow them to be comfortably bonded on the human skin.

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Flexible, Sensitive, Multifunctional Rubber-based Sensor with Multiple Responses to Infrared, Temperature, Humidity and Strain

10.21203/rs.3.rs-1158489/v1 ◽

2021 ◽

Author(s):

Zhongjie Zheng ◽

Li Yang ◽

Yunpeng Yang ◽

Baofeng Lin ◽

Lihua Fu ◽

...

Keyword(s):

Body Temperature ◽

Near Infrared ◽

Human Motion ◽

Strain Sensing ◽

Human Motion Detection ◽

Sensing Applications ◽

Body Temperature Change ◽

Healthcare Monitoring ◽

Wearable Electronic ◽

Electronic Sensors

Abstract Flexible wearable electronic sensors have attracted immense interest in human motion detection, body temperature monitoring and personal healthcare monitoring. However, most of reported sensors cannot integrate multifunctional applications at the same time though they own excellent single achievement of strain sensing or humidity sensing. Herein, we fabricate a multifunctional rubber-based flexible sensor (MRFS) with responses to infrared, temperature, humidity and strain. The sensor owns a superior strength (5.66 MPa), high stretchability (367%), high temperature coefficient of resistance (2.046%/℃) and high photothermal conversion efficiency (78.6%). For the sensing applications, it shows a rapid sensing of only 0.5 s for the temperature and humidity changes as well as a sensitive response to low-powered near infrared of 0.14 W/cm2, body temperature change from 33.6 to 35.6 ℃, and small amount of moisture on human skin. Moreover, the MRFS shows a considerable strain sensing for human joint motion and an antibacterial property.

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Flexible and wearable strain sensor based on electrospun carbon sponge/polydimethylsiloxane composite for human motion detection

RSC Advances ◽

10.1039/d0ra09070k ◽

2021 ◽

Vol 11 (7) ◽

pp. 4186-4193

Author(s):

He Gong ◽

Chuan Cai ◽

Hongjun Gu ◽

Qiushi Jiang ◽

Daming Zhang ◽

...

Keyword(s):

Motion Detection ◽

Strain Sensor ◽

Human Motion ◽

Gauge Factor ◽

Human Motion Detection ◽

Tensile Strains

Electrospun carbon sponge was used to measure tensile strains with a high gauge factor.

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Near-Linear Responsive and Wide-Range Pressure and Stretch Sensor Based on Hierarchical Graphene-Based Structures via Solvent-Free Preparation

Polymers ◽

10.3390/polym12081814 ◽

2020 ◽

Vol 12 (8) ◽

pp. 1814 ◽

Cited By ~ 1

Author(s):

Jian Wang ◽

Ryuki Suzuki ◽

Kentaro Ogata ◽

Takuto Nakamura ◽

Aixue Dong ◽

...

Keyword(s):

Organic Solvents ◽

Large Strain ◽

Rapid Development ◽

Wearable Sensors ◽

Human Motion ◽

Solvent Free ◽

Gauge Factor ◽

Wearable Electronics ◽

Human Motion Detection ◽

Wide Range

Flexible and wearable electronics have huge potential applications in human motion detection, human–computer interaction, and context identification, which have promoted the rapid development of flexible sensors. So far the sensor manufacturing techniques are complex and require a large number of organic solvents, which are harmful not only to human health but also to the environment. Here, we propose a facile solvent-free preparation toward a flexible pressure and stretch sensor based on a hierarchical layer of graphene nanoplates. The resulting sensor exhibits many merits, including near-linear response, low strain detection limits to 0.1%, large strain gauge factor up to 36.2, and excellent cyclic stability withstanding more than 1000 cycles. Besides, the sensor has an extraordinary pressure range as large as 700 kPa. Compared to most of the reported graphene-based sensors, this work uses a completely environmental-friendly method that does not contain any organic solvents. Moreover, the sensor can practically realize the delicate detection of human body activity, speech recognition, and handwriting recognition, demonstrating a huge potential for wearable sensors.

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Optimization of 3D Printed Elastomeric Nanocomposites for Flexible Strain Sensing Applications

Volume 1: Advances in Aerospace Technology ◽

10.1115/imece2019-11467 ◽

2019 ◽

Author(s):

Mohammad Abshirini ◽

Mohammad Charara ◽

Mrinal C. Saha ◽

M. Cengiz Altan ◽

Yingtao Liu

Keyword(s):

3D Printing ◽

Strain Sensor ◽

Sensitive Strain ◽

Curing Temperature ◽

Gauge Factor ◽

Strain Sensing ◽

Sensing Applications ◽

Wide Range ◽

Load Rate ◽

3D Printed

Abstract Flexible and sensitive strain sensors can be utilized as wearable sensors and electronic devices in a wide range of applications, such as personal health monitoring, sports performance, and electronic skin. This paper presents the fabrication of a highly flexible and sensitive strain sensor by 3D printing an electrically conductive polydimethylsiloxane (PDMS)/multi-wall carbon nanotube (MWNT) nanocomposite on a PDMS substrate. To maximize the sensor’s gauge factor, the effects of MWNT concentration on the strain sensing function in nanocomposites are evaluated. Critical 3D printing and curing parameters, such as 3D printing nozzle diameter and nanocomposites curing temperature, are explored to achieve the highest piezoresistive response, showing that utilizing a smaller deposition nozzle size and higher curing temperature can result in a higher gauge factor. The optimized 3D printed nanocomposite sensor’s sensitivity is characterized under cyclic tensile loads at different maximum strains and loading rates. A linear piezoresistive response is observed up to 70% strain with an average gauge factor of 12, pointing to the sensor’s potential as a flexible strain sensor. In addition, the sensing function is almost independent of the applied load rate. The fabricated sensors are attached to a glove and used as a wearable sensor by detecting human finger and wrist motion. The results indicate that this 3D printed functional nanocomposite shows promise in a broad range of applications, including wearable and skin mounted sensors.

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Rapid Microwave Polymerization of Porous Nanocomposites with Piezoresistive Sensing Function

Nanomaterials ◽

10.3390/nano10020233 ◽

2020 ◽

Vol 10 (2) ◽

pp. 233 ◽

Cited By ~ 1

Author(s):

Blake Herren ◽

Mohammad Charara ◽

Mrinal C. Saha ◽

M. Cengiz Altan ◽

Yingtao Liu

Keyword(s):

Human Motion ◽

Gauge Factor ◽

Microwave Curing ◽

Mechanical And Electrical Properties ◽

Human Motion Detection ◽

Closed Cell ◽

Multi Walled Carbon Nanotube ◽

Microwave Polymerization ◽

Compressive Loads ◽

Viscoelastic Stress Relaxation

In this paper, polydimethylsiloxane (PDMS) and multi-walled carbon nanotube (MWCNT) nanocomposites with piezoresistive sensing function were fabricated using microwave irradiation. The effects of precuring time on the mechanical and electrical properties of nanocomposites were investigated. The increased viscosity and possible nanofiller re-agglomeration during the precuring process caused decreased microwave absorption, resulting in extended curing times, and decreased porosity and electrical conductivity in the cured nanocomposites. The porosity generated during the microwave-curing process was investigated with a scanning electron microscope (SEM) and density measurements. Increased loadings of MWCNTs resulted in shortened curing times and an increased number of small well-dispersed closed-cell pores. The mechanical properties of the synthesized nanocomposites including stress–strain behaviors and Young’s Modulus were examined. Experimental results demonstrated that the synthesized nanocomposites with 2.5 wt. % MWCNTs achieved the highest piezoresistive sensitivity with an average gauge factor of 7.9 at 10% applied strain. The piezoresistive responses of these nanocomposites were characterized under compressive loads at various maximum strains, loading rates, and under viscoelastic stress relaxation conditions. The 2.5 wt. % nanocomposite was successfully used in an application as a skin-attachable compression sensor for human motion detection including squeezing a golf ball.

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