Coaxial Printing of Silicone Elastomer Composite Fibers for Stretchable and Wearable Piezoresistive Sensors

Despite the tremendous efforts dedicated to developing various wearable piezoresistive sensors with sufficient stretchability and high sensitivity, challenges remain pertaining to fabrication scalability, cost, and efficiency. In this study, a facile, scalable, and low-cost coaxial printing strategy is employed to fabricate stretchable and flexible fibers with a core–sheath structure for wearable strain sensors. The highly viscous silica-modified silicone elastomer solution is used to print the insulating sheath layer, and the silicone elastomer solutions containing multi-walled carbon nanotubes (CNTs) are used as the core inks to print the conductive inner layer. With the addition of silica powders as viscosifiers, silica-filled silicone ink (sheath ink) converts to printable ink. The dimensions of the printed coaxial fibers can be flexibly controlled via adjusting the extrusion pressure of the inks. In addition, the electro-mechanical responses of the fiber-shaped strain sensors are investigated. The printed stretchable and wearable fiber-like CNT-based strain sensor exhibits outstanding sensitivities with gauge factors (GFs) of 1.4 to 2.5 × 106, a large stretchability of 150%, and excellent waterproof performance. Furthermore, the sensor can detect a strain of 0.1% and showed stable responses for over 15,000 cycles (high durability). The printed fiber-shaped sensor demonstrated capabilities of detecting and differentiating human joint movements and monitoring balloon inflation. These results obtained demonstrate that the one-step printed fiber-like strain sensors have potential applications in wearable devices, soft robotics, and electronic skins.

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Highly sensitive and stretchable strain sensors based on chopped carbon fibers sandwiched between silicone rubber layers for human motion detections

Journal of Composite Materials ◽

10.1177/0021998319855758 ◽

2019 ◽

Vol 54 (3) ◽

pp. 423-434 ◽

Cited By ~ 4

Author(s):

MB Azizkhani ◽

Sh Rastgordani ◽

A. Pourkamali Anaraki ◽

J Kadkhodapour ◽

B Shirkavand Hadavand

Keyword(s):

Carbon Fibers ◽

Motion Detection ◽

Silicone Rubber ◽

Low Cost ◽

High Sensitivity ◽

Human Motion ◽

Strain Sensors ◽

Body Motion ◽

Gauge Factor ◽

Human Motion Detection

Tuning the electromechanical performance in piezoresistive composite strain sensors is primarily attained through appropriately employing the materials system and the fabrication process. High sensitivity along with flexibility in the strain sensing devices needs to be met according to the application (e.g. human motion detection, health and sports monitoring). In this paper, a highly stretchable and sensitive strain sensor with a low-cost fabrication is proposed which is acquired by embedding the chopped carbon fibers sandwiched in between silicone rubber layers. The electrical and mechanical features of the sensor were characterized through stretch/release loading tests where a considerably high sensitivity (the gauge factor about 100) was observed with very low hysteresis. This implies high strain reversibility (i.e. full recovery in each cycle) over 700 loading cycles. Moreover, the sensors exhibited ultra-high stretchability (up to ∼300% elongation) in addition to a low stiffness meaning minimal mechanical effects induced by the sensor for sensitive human motion monitoring applications including large and small deformations. The results suggest the promising capability of the present sensor in reflecting the human body motion detection.

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E-Skin Pressure Sensors Made by Laser Engraved PDMS Molds

Proceedings ◽

10.3390/proceedings2131039 ◽

2018 ◽

Vol 2 (13) ◽

pp. 1039 ◽

Cited By ~ 4

Author(s):

Andreia dos Santos ◽

Nuno Pinela ◽

Pedro Alves ◽

Rodrigo Santos ◽

Elvira Fortunato ◽

...

Keyword(s):

Pressure Wave ◽

Pressure Range ◽

Low Cost ◽

Pressure Sensors ◽

High Sensitivity ◽

Wave Detection ◽

Piezoresistive Sensors ◽

Electronic Skin ◽

Large Pressure ◽

Skin Pressure

This work describes the production of electronic-skin (e-skin) piezoresistive sensors, which micro-structuration is performed using laser engraved molds. With this fabrication approach, low-cost sensors are easily produced with a tailored performance. Sensors with micro-cones and a high sensitivity of −1 kPa−1 under 600 Pa are more adequate for the blood pressure wave detection, while sensors micro-structured with semi-spheres and a maximum sensitivity of −6 × 10−3 kPa−1 in a large pressure range (1.6 kPa to 100 kPa) are more suitable for robotics and functional prosthesis.

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Tunable seesaw-like 3D capacitive sensor for force and acceleration sensing

npj Flexible Electronics ◽

10.1038/s41528-021-00125-9 ◽

2021 ◽

Vol 5 (1) ◽

Author(s):

Jilong Ye ◽

Fan Zhang ◽

Zhangming Shen ◽

Shunze Cao ◽

Tianqi Jin ◽

...

Keyword(s):

High Performance ◽

Low Cost ◽

High Sensitivity ◽

Capacitive Sensor ◽

Mechanical Tests ◽

Structure Design ◽

Capacitive Sensors ◽

Wearable Electronics ◽

Potential Applications ◽

The Stability

AbstractTo address the resource-competing issue between high sensitivity and wide working range for a stand-alone sensor, development of capacitive sensors with an adjustable gap between two electrodes has been of growing interest. While several approaches have been developed to fabricate tunable capacitive sensors, it remains challenging to achieve, simultaneously, a broad range of tunable sensitivity and working range in a single device. In this work, a 3D capacitive sensor with a seesaw-like shape is designed and fabricated by the controlled compressive buckling assembly, which leverages the mechanically tunable configuration to achieve high-precision force sensing (resolution ~5.22 nN) and unprecedented adjustment range (by ~33 times) of sensitivity. The mechanical tests under different loading conditions demonstrate the stability and reliability of capacitive sensors. Incorporation of an asymmetric seesaw-like structure design in the capacitive sensor allows the acceleration measurement with a tunable sensitivity. These results suggest simple and low-cost routes to high-performance, tunable 3D capacitive sensors, with diverse potential applications in wearable electronics and biomedical devices.

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Ti3C2Tx MXene/polyvinyl alcohol decorated polyester warp knitting fabric for flexible wearable strain sensors

Textile Research Journal ◽

10.1177/00405175211044163 ◽

2021 ◽

pp. 004051752110441

Author(s):

Qinghua Yu ◽

Jinhua Jiang ◽

Chuanli Su ◽

Yaoli Huang ◽

Nanliang Chen ◽

...

Keyword(s):

Polyvinyl Alcohol ◽

Self Assembly ◽

Low Cost ◽

Strain Sensor ◽

High Sensitivity ◽

Fast Response ◽

Disease Diagnosis ◽

Strain Sensors ◽

Layer By Layer ◽

Sensing Range

Flexible wearable strain sensors with excellent sensing performance have received widespread interest due to their superior application capability in the field of human-computer interaction, sports rehabilitation, and disease diagnosis. But at present, it is still a considerable challenge to exploit a flexible strain sensor with high sensitivity and wide sensing range that is easily manufactured, low-cost, and easily integrable into clothing. MXene is a promising material sensitive enough for flexible sensors due to its superior conductivity and hydrophilicity. The warp knitting weft insertion textile structure gives the fabric excellent elasticity, making it suitable as a flexible, stretchable substrate. Therefore, utilizing a polyester elastic fabric with a warp knitting weft insertion structure, a fabric strain sensor with high sensitivity and wide sensing range prepared by layer-by-layer self-assembly of polyvinyl alcohol layers and MXene layers is reported in this study. The strain sensor exhibits high sensitivity (up to 288.43), a wide sensing range (up to 50%), fast response time (50 ms), ultra-low detection limit (a strain of 0.067%), excellent cycle stability (1000 cycles), and good washability. Besides, affixing the MXene/polyvinyl alcohol/polyester elastic fabric strain sensor on the joints can detect the movement of limbs. Therefore, the MXene/polyvinyl alcohol/polyester elastic fabric strain sensor demonstrates potential application opportunities in smart wearable electronic devices, and the researcher can also apply this method in the production of other flexible, intelligent wearable devices.

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Highly Sensitive Humidity Sensors Based on Polyethylene Oxide/CuO/Multi Walled Carbon Nanotubes Composite Nanofibers

Materials ◽

10.3390/ma14041037 ◽

2021 ◽

Vol 14 (4) ◽

pp. 1037

Author(s):

Waqas Ahmad ◽

Bushra Jabbar ◽

Imtiaz Ahmad ◽

Badrul Mohamed Jan ◽

Minas M. Stylianakis ◽

...

Keyword(s):

Carbon Nanotubes ◽

Polyethylene Oxide ◽

Composite Nanofibers ◽

Low Cost ◽

High Sensitivity ◽

Humidity Sensing ◽

Sensing Applications ◽

Multi Walled Carbon Nanotubes ◽

Lcr Meter ◽

Walled Carbon Nanotubes

Polymer composites are favorite materials for sensing applications due to their low cost and easy fabrication. In the current study, composite nanofibers consisting of polyethylene oxide (PEO), oxidized multi-walled carbon nanotubes (MWCNT) and copper oxide (CuO) nanoparticles with 1% and 3% of fillers (i.e., PEO–CuO–MWCNT: 1%, and PEO–CuO–MWCNT: 3%) were successfully developed through electrospinning for humidity sensing applications. The composite nanofibers were characterized by FTIR, XRD, SEM and EDX analysis. Firstly, they were loaded on an interdigitated electrode (IDE), and then the humidity sensing efficiency was investigated through a digital LCR meter (E4980) at different frequencies (100 Hz–1 MHz), as well as the percentage of relative humidity (RH). The results indicated that the composite nanofibers containing 1% and 3% MWCNT, combined with CuO in PEO polymer matrix, showed potent resistive and capacitive response along with high sensitivity to humidity at room temperature in an RH range of 30–90%. More specifically, the PEO–CuO–MWCNT: 1% nanocomposite displayed a resistive rapid response time within 3 s and a long recovery time of 22 s, while the PEO–CuO–MWCNT: 3% one exhibited 20 s and 11 s between the same RH range, respectively.

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Hydrogel-based piezoresistive sensor for the detection of ethanol

Journal of Sensors and Sensor Systems ◽

10.5194/jsss-7-219-2018 ◽

2018 ◽

Vol 7 (1) ◽

pp. 219-226 ◽

Cited By ~ 11

Author(s):

Jan Erfkamp ◽

Margarita Guenther ◽

Gerald Gerlach

Keyword(s):

Response Time ◽

Low Cost ◽

High Sensitivity ◽

Alcoholic Beverages ◽

Swelling Kinetics ◽

Short Response Time ◽

Piezoresistive Sensors ◽

Piezoresistive Sensor ◽

Crosslinker Content ◽

Kinetics Of

Abstract. This article describes a low-cost sensor for the detection of ethanol in alcoholic beverages, which combines alcohol-sensitive hydrogels based on acrylamide and bisacrylamide and piezoresistive sensors. For reproducible measurements, the reversible swelling and deswelling of the hydrogel were shown via microscopy. The response time of the sensor depends on the swelling kinetics of the hydrogel. The selectivity of the hydrogel was tested in different alcohols. In order to understand the influence of monomer and crosslinker content on the swelling degree and on the sensitivity of the hydrogels, gels with variable concentrations of acrylamide and bisacrylamide were synthesized and characterized in different aqueous solutions with alcohol contents. The first measurements of such hydrogel-based piezoresistive ethanol sensors demonstrated a high sensitivity and a short response time over several measuring cycles.

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Piezoresistive Multi-Walled Carbon Nanotube/Epoxy Strain Sensor with Pattern Design

Materials ◽

10.3390/ma12233962 ◽

2019 ◽

Vol 12 (23) ◽

pp. 3962 ◽

Cited By ~ 1

Author(s):

Mun-Young Hwang ◽

Dae-Hyun Han ◽

Lae-Hyong Kang

Keyword(s):

Carbon Nanotube ◽

Strain Gauge ◽

Low Cost ◽

Strain Sensor ◽

High Sensitivity ◽

Strain Sensors ◽

Gauge Factor ◽

Patch Type ◽

Multi Walled Carbon Nanotube ◽

Free Vibration Frequency

Carbon nanotube/polymer-based composites have led to studies that enable the realization of low-cost, high-sensitivity piezoresistive strain sensors. This study investigated the characteristics of piezoresistive multi-walled carbon nanotube (MWCNT)/epoxy composite strain sensors subjected to tensile and compressive loads in one direction at relatively small amounts of strain. A patterned sensor was designed to overcome the disadvantage of the load direction sensitivity differences in the existing sensors. The dispersion state of the MWCNTs in the epoxy polymer matrix with the proposed dispersion process was verified by scanning electron microscopy. An MWCNT/epoxy patterned strain sensor and a patch-type strain sensor were directly attached to an acrylic cantilever beam on the opposite side of a commercial metallic strain gauge. The proposed patterned sensor had gauge factors of 2.52 in the tension direction and 2.47 in the compression direction. The measured gauge factor difference for the patterned sensor was less than that for the conventional patch-type sensor. Moreover, the free-vibration frequency response characteristics were compared with those of metal strain gauges to verify the proposed patch-type sensor. The designed drive circuit compensated for the disadvantages due to the high drive voltage, and it was confirmed that the proposed sensor had higher sensitivity than the metallic strain gauge. In addition, the hysteresis of the temperature characteristics of the proposed sensor is presented to show its temperature range. It was verified that the patterned sensor developed through various studies could be applied as a strain sensor for structural health monitoring.

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Low-Cost and Highly Sensitive Pressure Sensor with Mold-Printed Multi-Walled Carbon Nanotubes Dispersed in Polydimethylsiloxane

Sensors ◽

10.3390/s21155069 ◽

2021 ◽

Vol 21 (15) ◽

pp. 5069

Author(s):

Tim Mike de Rijk ◽

Walter Lang

Keyword(s):

Carbon Nanotubes ◽

Pressure Sensor ◽

Low Cost ◽

Conductive Polymer ◽

Pressure Sensors ◽

High Sensitivity ◽

Multi Walled Carbon Nanotubes ◽

Pressure Changes ◽

Flexible Pressure Sensors ◽

Walled Carbon Nanotubes

Flexible pressure sensors with piezoresistive polymer composites can be integrated into elastomers to measure pressure changes in sealings, preemptively indicating a replacement is needed before any damage or leakage occurs. Integrating small percentages of high aspect ratio multi-walled carbon nanotubes (MWCNTs) into polymers does not significantly change its mechanical properties but highly affects its electrical properties. This research shows a pressure sensor based on homogeneous dispersed MWCNTs in polydimethylsiloxane with a high sensitivity region (0.13% kPa−1, 0–200 kPa) and sensitive up to 500 kPa. A new 3D-printed mold is developed to directly deposit the conductive polymer on the electrode structures, enabling sensor thicknesses as small as 100 μm.

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Self-Imaging Effect in Liquid-Filled Hollow-Core Capillary Waveguide for Sensing Applications

Sensors ◽

10.3390/s20010135 ◽

2019 ◽

Vol 20 (1) ◽

pp. 135 ◽

Cited By ~ 3

Author(s):

Yijian Huang ◽

Shuhui Liu ◽

Lichao Zhang ◽

Yiping Wang ◽

Ying Wang

Keyword(s):

Simple Structure ◽

Low Cost ◽

High Sensitivity ◽

Single Mode ◽

Fiber Optic Sensor ◽

Hollow Core ◽

Sensing Applications ◽

Index Matching ◽

Potential Applications ◽

Physical And Chemical

A high sensitivity fiber-optic sensor based on self-imaging effect in a hollow-core capillary waveguide (HCCW) is presented for sensing applications. The sensor is composed of a section of HCCW fusion spliced between single mode fibers (SMFs). The self-imaging effect in the HCCW is investigated with different fiber lengths and arc-fusion parameters. By infiltrating the hollow core with index matching liquids, the peak wavelength of the proposed device shifts towards longer wavelengths. The temperature and refractive index (RI) responses of the sensor are studied systematically. When temperature is increased from 25 °C to 75 °C, the temperature sensitivity of the device can be improved significantly with the infiltrated structure, and reaches −0.49 nm/°C, compared with that of the un-filled device, which is 9.8 pm/°C. For the RI response, the liquid-filled structure achieves sensitivity of 12,005 nm/RIU in the range between 1.448 and 1.450, slightly higher than the 11,920 nm/RIU achieved by the un-filled one. The proposed sensor exhibits the advantages of simple structure, high sensitivity and low cost, which may find potential applications in physical and chemical sensing.

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VIBRATION-BASED ENERGY HARVESTER FOR SUSTAINABLE STRUCTURAL HEALTH MONITORING SYSTEM: A CASE STUDY ON A PRESTRESSED CONCRETE GIRDER

JOURNAL OF TECHNOLOGY & INNOVATION ◽

10.26480/jtin.01.2021.16.19 ◽

2020 ◽

Vol 1 (1) ◽

pp. 16-19

Author(s):

Tuan Minh Ha ◽

Saiji Fukada ◽

Toshiyuki Ueno ◽

Duc-Duy Ho

Keyword(s):

Prestressed Concrete ◽

Energy Harvester ◽

Low Cost ◽

High Sensitivity ◽

Electrical Energy ◽

Open Circuit ◽

High Durability ◽

Parametric Studies ◽

Self Powered ◽

Concrete Girder

Energy harvesting technology generating electrical energy from structural responses has been in the spotlight recently because of the development of self-powered autonomous wireless sensor systems. This study proposed and tested a high-sensitivity, high-durability, low-cost vibration power-generating device using a magnetostrictive element (Fe-Ga alloy) on a real-scale prestressed concrete girder to investigate its practical performance. The device comprises a unimorph layer having a magnetostrictive element attached to a U-shaped frame with a permanent magnet for magnetic bias wound about by a coil. An evaluation of a prototype device using a Fe-Ga element of 4 × 0.5 × 16 mm was performed. With a weight of 1221 g attached, an open-circuit voltage of ~1 V at an oscillation of 9.058 Hz and 3.8 m/s2 was generated by free damped vibrations applied via a person jumping vertically from a chair to the girder. In addition, parametric studies were carried out by changing impact locations, weights, and device locations in order to examine their possible effects on the performance of the proposed energy harvester.

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