Non-Monotonic Sensor Behavior of Carbon Particle-Filled Textile Strain Sensors

Carbon particle-filled elastomers are a widely researched option to be used as piezoresistive strain sensors for soft robotics or human motion monitoring. Therefore, various polymers can be compounded with carbon black (CB), carbon nanotubes (CNT) or graphene. However, in many studies, the electrical resistance strain response of the carbon particle-filled elastomers is non-monotonic in dynamic evaluation scenarios. The non-monotonic material behavior is also called shoulder phenomenon or secondary peak. Until today, the underlying cause is not sufficiently well understood. In this study, several influencing test parameters on the shoulder phenomena are explored, such as strain level, strain rate and strain history. Moreover, material parameters such as CNT content and anisotropy are varied in melt-spun CNT filled thermoplastic polyurethane (TPU) filament yarns, and their non-monotonic sensor response is evaluated. Additionally, a theoretical concept for the underlying mechanism and thereupon-based model is presented. An equivalent circuit model is used, which incorporates the visco-elastic properties and the characteristic of the percolation network formed by the conductive filler material. The simulation results are in good agreement when compared to the experimental results.

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A highly stretchable and transparent silver nanowire/thermoplastic polyurethane film strain sensor for human motion monitoring

Inorganic Chemistry Frontiers ◽

10.1039/c9qi00989b ◽

2019 ◽

Vol 6 (11) ◽

pp. 3119-3124 ◽

Cited By ~ 10

Author(s):

Runfei Wang ◽

Wei Xu ◽

Wenfeng Shen ◽

Xiaoqing Shi ◽

Jian Huang ◽

...

Keyword(s):

Silver Nanowires ◽

Thermoplastic Polyurethane ◽

Human Motion ◽

Strain Sensors ◽

Silver Nanowire ◽

Transparent Film ◽

Polyurethane Film ◽

Highly Stretchable ◽

Human Motion Monitoring ◽

Human Motions

Transparent film strain sensors based on silver nanowires and thermoplastic polyurethane are promising candidates for detecting various human motions and monitoring the mass of some kinetic objects.

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Influence of filler hybridization on thermomechanical properties of hemp/silver epoxy composite

Polymers and Polymer Composites ◽

10.1177/0967391120978112 ◽

2020 ◽

pp. 096739112097811

Author(s):

Munjula Siva Kumar ◽

Santosh Kumar ◽

Krushna Gouda ◽

Sumit Bhowmik

Keyword(s):

Thermal Conductivity ◽

Silver Nanoparticles ◽

Epoxy Polymer ◽

Hybrid Composites ◽

Conductive Filler ◽

Weight Fraction ◽

Mechanical Analysis ◽

Thermomechanical Properties ◽

Material Behavior ◽

Good Crystallinity

The polymer composite material’s thermomechanical properties with fiber as reinforcement material have been widely studied in the last few decades. However, these fiber-based polymer composites exhibit problems such as fiber orientation, delamination, fiber defect along the length and bonding are the matter of serious concern in order to improve the thermomechanical properties and obtain isotropic material behavior. In the present investigation filler-based composite material is developed using natural hemp and high thermal conductive silver nanoparticles (SNP) and combination of dual fillers in neat epoxy polymer to investigate the synergetic influence. Among various organic natural fillers hemp filler depicts good crystallinity characteristics, so selected as a biocompatible filler along with SNP conductive filler. For enhancing their thermal conductivity and mechanical properties, hybridization of hemp filler along with silver nanoparticles are conducted. The composites samples are prepared with three different combinations such as sole SNP, sole hemp and hybrid (SNP and hemp) are prepared to understand their solo and hybrid combination. From results it is examined that, chemical treated hemp filler has to maximized its relative properties and showed, 40% weight % of silver nanoparticles composites have highest thermal conductivity 1.00 W/mK followed with hemp filler 0.55 W/mK and hybrid 0.76 W/mK composites at 7.5% of weight fraction and 47.5% of weight fraction respectively. The highest tensile strength is obtained for SNP composite 32.03 MPa and highest young’s modulus is obtained for hybrid composites. Dynamic mechanical analysis is conducted to find their respective storage modulus and glass transition temperature and that, the recorded maximum for SNP composites with 3.23 GPa and 90°C respectively. Scanning electron microscopy examinations clearly illustrated that formation of thermal conductivity chain is significant with nano and micro fillers incorporation.

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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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Effects of 3D Printing-Line Directions for Stretchable Sensor Performances

Materials ◽

10.3390/ma14071791 ◽

2021 ◽

Vol 14 (7) ◽

pp. 1791

Author(s):

Chi Cuong Vu ◽

Thanh Tai Nguyen ◽

Sangun Kim ◽

Jooyong Kim

Keyword(s):

3D Printing ◽

Thermoplastic Polyurethane ◽

Three Dimensional ◽

Optimal Solution ◽

Human Motion ◽

Repeated Measurements ◽

Fused Filament Fabrication ◽

And Performance ◽

The Times ◽

Stretchable Sensors

Health monitoring sensors that are attached to clothing are a new trend of the times, especially stretchable sensors for human motion measurements or biological markers. However, price, durability, and performance always are major problems to be addressed and three-dimensional (3D) printing combined with conductive flexible materials (thermoplastic polyurethane) can be an optimal solution. Herein, we evaluate the effects of 3D printing-line directions (45°, 90°, 180°) on the sensor performances. Using fused filament fabrication (FDM) technology, the sensors are created with different print styles for specific purposes. We also discuss some main issues of the stretch sensors from Carbon Nanotube/Thermoplastic Polyurethane (CNT/TPU) and FDM. Our sensor achieves outstanding stability (10,000 cycles) and reliability, which are verified through repeated measurements. Its capability is demonstrated in a real application when detecting finger motion by a sensor-integrated into gloves. This paper is expected to bring contribution to the development of flexible conductive materials—based on 3D printing.

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An Equivalent Circuit Approach to Evaluating Conductivity of Polymer-Filler Composites

MRS Proceedings ◽

10.1557/proc-734-b9.19 ◽

2002 ◽

Vol 734 ◽

Author(s):

Vladislav Skorokhod

Keyword(s):

Equivalent Circuit ◽

Equivalent Circuit Model ◽

Conductive Filler ◽

Size Ratio ◽

Particulate Composites ◽

Mathematical Representation ◽

Matrix Size ◽

Linear System Of Equations ◽

Polymer Filler

ABSTRACTAn equivalent circuit model of electrical conduction in polymer-filler particulate composites was developed in this study. The equivalent circuit was constructed for an individual composite particle with a sub-monolayer of conductive filler, where the filler particles play the role of circuit nodes, and inter-particle contacts are represented by resistors between the nodes. The mathematical representation of the equivalent circuit in the form of a linear system of equations for nodal potentials was solved numerically with Matlab software to calculate conductance of the composite as a function of the amount of conductive filler, filled fraction of the monolayer, filler-to-matrix size ratio and the degree of structuredness (non-randomness) of the filler material. Additionally, percolation concentrations and statistical distributions of composite conductance were calculated as functions of the filler-to-matrix size ratio.

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Recent Advances of Flexible Strain Sensors Based on Conductive Fillers and Thermoplastic Polyurethane Matrixes

ACS Applied Polymer Materials ◽

10.1021/acsapm.1c00840 ◽

2021 ◽

Author(s):

Tianjiao Chen ◽

Yuntao Xie ◽

Zhiyu Wang ◽

Jingxian Lou ◽

Danyu Liu ◽

...

Keyword(s):

Thermoplastic Polyurethane ◽

Strain Sensors ◽

Recent Advances ◽

Conductive Fillers

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Characterization of the Aniline.DBSA/Thermoplastic Polyurethane Blends for the Thermo-Mechanical and Electro-Mechanical Properties

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.875.96 ◽

2021 ◽

Vol 875 ◽

pp. 96-103

Author(s):

Ayesha Afzal ◽

Iqra Abdul Rashid ◽

H.M. Faizan Shakir ◽

Asra Tariq

Keyword(s):

Mechanical Properties ◽

Thermoplastic Polyurethane ◽

Strain Sensors ◽

Sem Images ◽

Dynamic Mechanical Thermal Analyzer ◽

Thermal Analyzer ◽

Uniform Dispersion ◽

Polymerization Method

Conducting polymer blends Polyaniline-Dodecylbenzene sulfonic acid (Pani.DBSA) and thermoplastic polyurethane (TPU) were prepared using in-situ emulsion polymerization method by dissolving both components in DMF. Ani.DBSA/TPU blends were prepared with different compositions 20/80, 30/70, 40/60 and 50/50 wt%. Theses blends have good conducting and mechanical properties. Blends were characterized by Potentiostate, Thermogravimetric analysis (TGA), Infrared spectroscopy (FTIR) and Dynamic mechanical thermal analyzer (DMTA). The electrical conductivity increases up to 30 wt% loading of aniline.DBSA after that it decreases gradually. The uniform dispersion of aniline.DBSA showed in SEM images which is the indication of a strong connection between aniline.DBSA and TPU which increase the conductivity. These blends can be used as strain sensors.

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