scholarly journals A Flexible Strain Sensor Based on Embedded Ionic Liquid

Sensors ◽  
2021 ◽  
Vol 21 (17) ◽  
pp. 5760
Author(s):  
Huiyang Zhang ◽  
Andrew Lowe ◽  
Anubha Kalra ◽  
Yang Yu
Keyword(s):  
Ionic Liquid ◽  
Low Cost ◽  
Microfluidic Channel ◽  
Strain Sensor ◽  
Gauge Factor ◽  
Peak Strain ◽  
Healthcare Monitoring ◽  
Flexible Strain Sensor ◽  
A Minor ◽  
Glycol Solution

We present a simple-structured strain sensor based on a low-cost ionic liquid. The ionic liquid was made of sodium chloride/propylene glycol solution and was embedded in a linear microfluidic channel fabricated using Ecoflex. The proposed sensor is capable of measuring strain up to 100% with excellent repeatability. The highest gauge factor is obtained as 6.19 under direct current excitation and 3.40 under alternating current excitation at 1 kHz. The sensor shows negligible hysteresis and overshoot, and survived 10,000 rapid stretch-release cycles of a 100% peak strain with a minor deviation in the response signal. The sensor can be mounted to different locations on the human body and suits a variety of applications in the field of motion detection, human–machine interface and healthcare monitoring.

scholarly journals Wearable Flexible Strain Sensor Based on Three-Dimensional Wavy Laser-Induced Graphene and Silicone Rubber

Sensors ◽  
2020 ◽  
Vol 20 (15) ◽  
pp. 4266 ◽  
Author(s):  
Lixiong Huang ◽  
Han Wang ◽  
Peixuan Wu ◽  
Weimin Huang ◽  
Wei Gao ◽  
...  
Keyword(s):  
Silicone Rubber ◽  
Mechanical Performance ◽  
Low Cost ◽  
Three Dimensional ◽  
Strain Sensor ◽  
High Sensitivity ◽  
Polyimide Film ◽  
Gauge Factor ◽  
Joint Movement ◽  
Flexible Strain Sensor

Laser-induced graphene (LIG) has the advantages of one-step fabrication, prominent mechanical performance, as well as high conductivity; it acts as the ideal material to fabricate flexible strain sensors. In this study, a wearable flexible strain sensor consisting of three-dimensional (3D) wavy LIG and silicone rubber was reported. With a laser to scan on a polyimide film, 3D wavy LIG could be synthesized on the wavy surface of a mold. The wavy-LIG strain sensor was developed by transferring LIG to silicone rubber substrate and then packaging. For stress concentration, the ultimate strain primarily took place in the troughs of wavy LIG, resulting in higher sensitivity and less damage to LIG during stretching. As a result, the wavy-LIG strain sensor achieved high sensitivity (gauge factor was 37.8 in a range from 0% to 31.8%, better than the planar-LIG sensor), low hysteresis (1.39%) and wide working range (from 0% to 47.7%). The wavy-LIG strain sensor had a stable and rapid dynamic response; its reversibility and repeatability were demonstrated. After 5000 cycles, the signal peak varied by only 2.32%, demonstrating the long-term durability. Besides, its applications in detecting facial skin expansion, muscle movement, and joint movement, were discussed. It is considered a simple, efficient, and low-cost method to fabricate a flexible strain sensor with high sensitivity and structural robustness. Furthermore, the wavy-LIG strain senor can be developed into wearable sensing devices for virtual/augmented reality or electronic skin.

Flexible Strain Sensor Using Additive Manufacturing and Conductive Liquid Metal: Design, Fabrication, and Characterization

2018 ◽  
Author(s):  
Austin Smith ◽  
Hamzeh Bardaweel
Keyword(s):  
3D Printing ◽  
Liquid Metal ◽  
Strain Sensor ◽  
Gauge Factor ◽  
Limiting Factor ◽  
Successful Implementation ◽  
Conductive Liquid ◽  
Fused Deposition ◽  
3D Printed ◽  
Flexible Strain Sensor

In this work a flexible strain sensor is fabricated using Fused Deposition Modeling (FDM) 3D printing technique. The strain sensor is fabricated using commercially available flexible Thermoplastic Polyurethane (TPU) filaments and liquid metal Galinstan Ga 68.5% In 21% Sn 10%. The strain sensor consists of U-shape 2.34mm long and 0.2mm deep channels embedded inside a TPU 3D printed structure. The performance of the strain sensor is measured experimentally. Gauge Factor is estimated by measuring change in electric resistance when the sensor is subject to 13.2% – 38.6% strain. Upon straining and unstraining, results from characterization tests show high linearity in the range of 13.2% to 38.6% strain with very little hysteresis. However, changes due to permanent deformations are a limiting factor in the usefulness of these sensors because these changes limit the consistency of the device. FDM 3D printing shows promise as a method for fabricating flexible strain sensors. However, more investigation is needed to look at the effects of geometries and 3D printing process parameters on the yield elongation of the flexible filaments. Additionally, more investigation is needed to observe the effect of distorted dimensions of the 3D printed channels on the sensitivity of the strain sensor. It is anticipated that successful implementation of these commercially available filaments and FDM 3D printers will lead to reduction in cost and complexity of developing these flexible sensors.

Direct Printing of a Flexible Strain Sensor for Distributed Monitoring of Deformation in Inflatable Structures

2019 ◽  
Author(s):  
Mohammed Al-Rubaiai ◽  
Ryohei Tsuruta ◽  
Taewoo Nam ◽  
Umesh Gandhi ◽  
Xiaobo Tan
Keyword(s):  
3D Printing ◽  
Structural Changes ◽  
Strain Sensor ◽  
Strain Range ◽  
Gauge Factor ◽  
Distributed Monitoring ◽  
Inflatable Structures ◽  
Resistance Change ◽  
Flexible Strain Sensor ◽  
Conductive Paint

Abstract Inflatable structures provide significant volume and weight savings for future space and soft robotic applications. Structural health monitoring (SHM) of these structures is essential to ensuring safe operation, providing early warnings of damage, and measuring structural changes over time. In this paper, we propose the design of a single flexible strain sensor for distributed monitoring of an inflatable tube, in particular, the detection and localization of a kink should that occur. Several commercially available conductive materials, including 3D-printing filaments, conductive paint, and conductive fabrics are explored for their strain-sensing performance, where the resistance change under uniaxial tension is measured, and the corresponding gauge factor (GF) is characterized. Flexible strain sensors are then fabricated and integrated with an inflatable structure fabric using screen-printing or 3D-printing techniques, depending on the nature of the raw conductive material. Among the tested materials, the conductive paint shows the highest stability, with GF of 15 and working strain range of 2.28%. Finally, the geometry of the sensor is designed to enable distributed monitoring of an inflatable tube. In particular, for a given deformation magnitude, the sensor output shows a monotonic relationship with the location where the deformation is applied, thus enabling the monitoring of the entire tube with a single sensor.

scholarly journals Polymer-Based Self-Standing Flexible Strain Sensor

2010 ◽  
Vol 2010 ◽  
pp. 1-5 ◽  
Author(s):  
Fernando Martinez ◽  
Gregorio Obieta ◽  
Ion Uribe ◽  
Tomasz Sikora ◽  
Estibalitz Ochoteco
Keyword(s):  
Electrical Conductivity ◽  
Electrical Resistance ◽  
Strain Sensor ◽  
Strain Sensors ◽  
Gauge Factor ◽  
Wearable Electronics ◽  
Rehabilitation Devices ◽  
Flexible Strain Sensor

The design and characterization of polymer-based self-standing flexible strain sensors are presented in this work. Properties as lightness and flexibility make them suitable for the measurement of strain in applications related with wearable electronics such as robotics or rehabilitation devices. Several sensors have been fabricated to analyze the influence of size and electrical conductivity on their behavior. Elongation and applied charge were precisely controlled in order to measure different parameters as electrical resistance, gauge factor (GF), hysteresis, and repeatability. The results clearly show the influence of size and electrical conductivity on the gauge factor, but it is also important to point out the necessity of controlling the hysteresis and repeatability of the response for precision-demanding applications.

scholarly journals A Pressure-Insensitive Self-Attachable Flexible Strain Sensor with Bioinspired Adhesive and Active CNT Layers

Sensors ◽  
2020 ◽  
Vol 20 (23) ◽  
pp. 6965
Author(s):  
Minho Seong ◽  
Insol Hwang ◽  
Joosung Lee ◽  
Hoon Eui Jeong
Keyword(s):  
Tensile Strain ◽  
High Strain ◽  
Strain Sensor ◽  
Adhesive Layer ◽  
High Sensitivity ◽  
Gauge Factor ◽  
Tactile Sensors ◽  
Surface Attachment ◽  
Tactile Stimuli ◽  
Flexible Strain Sensor

Flexible tactile sensors are required to maintain conformal contact with target objects and to differentiate different tactile stimuli such as strain and pressure to achieve high sensing performance. However, many existing tactile sensors do not have the ability to distinguish strain from pressure. Moreover, because they lack intrinsic adhesion capability, they require additional adhesive tapes for surface attachment. Herein, we present a self-attachable, pressure-insensitive strain sensor that can firmly adhere to target objects and selectively perceive tensile strain with high sensitivity. The proposed strain sensor is mainly composed of a bioinspired micropillar adhesive layer and a selectively coated active carbon nanotube (CNT) layer. We show that the bioinspired adhesive layer enables strong self-attachment of the sensor to diverse planar and nonplanar surfaces with a maximum adhesion strength of 257 kPa, while the thin film configuration of the patterned CNT layer enables high strain sensitivity (gauge factor (GF) of 2.26) and pressure insensitivity.

scholarly journals Direct Patterning of Carbon Nanotube via Stamp Contact Printing Process for Stretchable and Sensitive Sensing Devices

2019 ◽  
Vol 11 (1) ◽  
Author(s):  
Binghao Liang ◽  
Zian Zhang ◽  
Wenjun Chen ◽  
Dongwei Lu ◽  
Leilei Yang ◽  
...  
Keyword(s):  
Carbon Nanotube ◽  
Low Cost ◽  
Flexible Substrate ◽  
Strain Sensor ◽  
High Sensitivity ◽  
Gauge Factor ◽  
Contact Printing ◽  
Target Pattern ◽  
Wearable Electronic Devices ◽  
Application Prospects

Abstract Flexible and wearable sensing devices have broad application prospects in bio-monitoring such as pulse measurement, motion detection and voice recognition. In recent years, many significant improvements had been made to enhance the sensor’s performance including sensitivity, flexibility and repeatability. However, it is still extremely complicated and difficult to prepare a patterned sensor directly on a flexible substrate. Herein, inspired by typography, a low-cost, environmentally friendly stamping method for the mass production of transparent conductive carbon nanotube (CNT) film is proposed. In this dry transfer strategy, a porous CNT block was used as both the seal and the ink; and Ecoflex film was served as an object substrate. Well-designed CNT patterns can be easily fabricated on the polymer substrate by engraving the target pattern on the CNT seal before the stamping process. Moreover, the CNT film can be directly used to fabricate ultrathin (300 μm) strain sensor. This strain sensor possesses high sensitivity with a gauge factor (GF) up to 9960 at 85% strain, high stretchability (> 200%) and repeatability (> 5000 cycles). It has been used to measure pulse signals and detect joint motion, suggesting promising application prospects in flexible and wearable electronic devices.

scholarly journals Piezotronic effect in AlGaN/AlN/GaN heterojunction nanowires used as a flexible strain sensor

2020 ◽  
Vol 11 ◽  
pp. 1847-1853
Author(s):  
Jianqi Dong ◽  
Liang Chen ◽  
Yuqing Yang ◽  
Xingfu Wang
Keyword(s):  
Integrated Circuits ◽  
Indium Tin Oxide ◽  
Quantum Confinement Effect ◽  
Strain Sensor ◽  
Volume Ratio ◽  
High Sensitivity ◽  
Gauge Factor ◽  
Oxide Electrodes ◽  
Poly Ethylene ◽  
Flexible Strain Sensor

1D semiconductor nanowires (NWs) have been extensively studied in recent years due to the predominant mechanical flexibility caused by a large surface-to-volume ratio and unique electrical and optical properties induced by the 1D quantum confinement effect. Herein, we use a top-down two-step preparation method to synthesize AlGaN/AlN/GaN heterojunction NWs with controllable size. A single NW is transferred to a flexible poly(ethylene terephthalate) substrate and fixed by indium tin oxide electrodes to form an ohmic contact for the strain sensor. An external mechanical stress is introduced to study the performance of the fabricated piezotronic strain sensor. The gauge factor is as high as 30 under compressive or tensile stress, which indicates a high sensitivity of the strain sensor. Periodic strain tests show the high stability and repeatability of the sensor. The working mechanism of the strain sensor is investigated and systematically analyzed under compressive and tensile strain. Here, we describe a strain sensor that shows a great application potential in wearable integrated circuits, in health-monitoring devices, and in artificial intelligence.

scholarly journals Flexible Strain Sensor Based on Carbon Black/Silver Nanoparticles Composite for Human Motion Detection

Materials ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 1836 ◽  
Author(s):  
Weiyi Zhang ◽  
Qiang Liu ◽  
Peng Chen
Keyword(s):  
Silver Nanoparticles ◽  
Carbon Black ◽  
Motion Detection ◽  
Thermoplastic Polyurethane ◽  
Strain Sensor ◽  
Human Motion ◽  
Tunneling Effect ◽  
Gauge Factor ◽  
Human Motion Detection ◽  
Flexible Strain Sensor

The demand for flexible and wearable electronic devices with excellent stretchability and sensitivity is increasing, especially for human motion detection. In this work, a simple, low-cost and convenient strategy has been employed to fabricate flexible strain sensor with a composite of carbon black and silver nanoparticles as sensing materials and thermoplastic polyurethane as matrix. The strain sensors thus prepared possesses high stretchability and good sensitivity (gauge factor of 21.12 at 100% tensile strain), excellent static (almost constant resistance variation under 50% strain for 600 s) and dynamic (100 cycles) stability. Compared with bare carbon black-based strain sensor, carbon black/silver nanoparticles composite-based strain sensor shows ~18 times improvement in sensitivity at 100% strain. In addition, we discuss the sensing mechanisms using the disconnection mechanism and tunneling effect which results in high sensitivity of the strain sensor. Due to its good strain-sensing performance, the developed strain sensor is promising in detecting various degrees of human motions such as finger bending, wrist rotation and elbow flexion.

Low-Cost Flexible Strain Sensor Based on Thick CVD Graphene

NANO ◽  
2018 ◽  
Vol 13 (11) ◽  
pp. 1850126 ◽  
Author(s):  
Bailiang Chen ◽  
Ying Liu ◽  
Guishan Wang ◽  
Xianzhe Cheng ◽  
Guanjun Liu ◽  
...  
Keyword(s):  
Large Strain ◽  
Low Cost ◽  
Flexible Substrate ◽  
Graphene Film ◽  
Strain Sensor ◽  
Strain Range ◽  
Tensile Tests ◽  
Adhesive Tape ◽  
Cvd Graphene ◽  
Flexible Strain Sensor

Flexible strain sensors, as the core member of the family of smart electronic devices, along with reasonable sensing range and sensitivity plus low cost, have rose a huge consumer market and also immense interests in fundamental studies and technological applications, especially in the field of biomimetic robots movement detection and human health condition monitoring. In this paper, we propose a new flexible strain sensor based on thick CVD graphene film and its low-cost fabrication strategy by using the commercial adhesive tape as flexible substrate. The tensile tests in a strain range of [Formula: see text]30% were implemented, and a gage factor of 30 was achieved under high strain condition. The optical microscopic observation with different strains showed the evolution of cracks in graphene film. Together with commonly used platelet overlap theory and percolation network theory for sensor resistance modeling, we established an overlap destructive resistance model to analyze the sensing mechanism of our devices, which fitted the experimental data very well. The finding of difference of fitting parameters in small and large strain ranges revealed the multiple stage feature of graphene crack evolution. The resistance fallback phenomenon due to the viscoelasticity of flexible substrate was analyzed. Our flexible strain sensor with low cost and simple fabrication process exhibits great potential for commercial applications.

scholarly journals A Sprayed Graphene Pattern-Based Flexible Strain Sensor with High Sensitivity and Fast Response

Sensors ◽  
2019 ◽  
Vol 19 (5) ◽  
pp. 1077 ◽  
Author(s):  
Wei Xu ◽  
Tingting Yang ◽  
Feng Qin ◽  
Dongdong Gong ◽  
Yijia Du ◽  
...  
Keyword(s):  
Strain Sensor ◽  
High Sensitivity ◽  
Fast Response ◽  
Strain Sensors ◽  
Biomedical Science ◽  
Gauge Factor ◽  
Experimental Conditions ◽  
Simple Method ◽  
Wide Range ◽  
Flexible Strain Sensor

Flexible strain sensors have a wide range of applications in biomedical science, aerospace industry, portable devices, precise manufacturing, etc. However, the manufacturing processes of most flexible strain sensors previously reported have usually required high manufacturing costs and harsh experimental conditions. Besides, research interests are often focused on improving a single attribute parameter while ignoring others. This work aims to propose a simple method of manufacturing flexible graphene-based strain sensors with high sensitivity and fast response. Firstly, oxygen plasma treats the substrate to improve the interfacial interaction between graphene and the substrate, thereby improving device performance. The graphene solution is then sprayed using a soft PET mask to define a pattern for making the sensitive layer. This flexible strain sensor exhibits high sensitivity (gauge factor ~100 at 1% strain), fast response (response time: 400–700 μs), good stability (1000 cycles), and low overshoot (<5%) as well. Those processes used are compatible with a variety of complexly curved substrates and is expected to broaden the application of flexible strain sensors.

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