Conductive Hydrogel- and Organohydrogel-Based 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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High strength and conductive hydrogel with fully interpenetrated structure from alginate and acrylamide

e-Polymers ◽

10.1515/epoly-2021-0043 ◽

2021 ◽

Vol 21 (1) ◽

pp. 391-397

Author(s):

Tao Liu ◽

Ripeng Zhang ◽

Jianzhi Liu ◽

Ling Zhao ◽

Yueqin Yu

Keyword(s):

Mechanical Performance ◽

Three Dimensional ◽

High Strength ◽

Extreme Environment ◽

Natural Polymers ◽

Conductive Hydrogel ◽

Wide Range ◽

Interpenetrated Structure ◽

Conductive Hydrogels ◽

Conductive Properties

Abstract Highly stretched and conductive hydrogels, especially synthetized from natural polymers, are beneficial for highly stretched electronic equipment which is applied in extreme environment. We designed and prepared robust and tough alginate hydrogels (GMA-SA-PAM) using the ingenious strategy of fully interpenetrating cross-linking, in which the glycidyl methacrylate (GMA) was used to modify sodium alginate (SA) and then copolymerized with acrylamide (AM) and methylenebisacrylamide (BIS) as cross-linkers. The complete cross-linked structures can averagely dissipate energy and the polymer structures can maintain hydrogels that are three-dimensional to greatly improve the mechanical performance of hydrogels. The GMA-SA-PAM hydrogels display ultra-stretchable (strain up to ∼407% of tensile strain) and highly compressible (∼57% of compression strain) properties. In addition, soaking the GMA-SA-PAM hydrogel in 5 wt% NaCl solution also endows the conductivity of the hydrogel (this hydrogel was named as GSP-Na) with excellent conductive properties (5.26 S m−1). The GSP-Na hydrogel with high stability, durability, as well as wide range extent sensor is also demonstrated by researching the electrochemical signals and showing the potential for applications in wearable and quickly responded electronics.

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Stimuli-responsive conductive hydrogels: design, property and applications

Materials Chemistry Frontiers ◽

10.1039/d0qm00868k ◽

2021 ◽

Author(s):

Zexing Deng ◽

Rui Yu ◽

Baolin Guo

Keyword(s):

Conductive Polymers ◽

Research Field ◽

Stimuli Responsive ◽

Conductive Hydrogel ◽

Design Property ◽

Conductive Hydrogels

Stimuli-responsive conductive hydrogel has been emerged as a new surging concept in hydrogel research field due to its combined advantages of stimuli-responsivity and conductivity from conductive polymers (such as polyaniline,...

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Robust Conductive Hydrogels with Ultrafast Self-Recovery and Nearly Zero Response Hysteresis for Epidermal Sensors

Nanomaterials ◽

10.3390/nano11071854 ◽

2021 ◽

Vol 11 (7) ◽

pp. 1854

Author(s):

Xiuru Xu ◽

Chubin He ◽

Feng Luo ◽

Hao Wang ◽

Zhengchun Peng

Keyword(s):

Guar Gum ◽

Strain Range ◽

Sio2 Nanoparticles ◽

Fast Response ◽

Gauge Factor ◽

Practical Applications ◽

Hydroxypropyl Guar ◽

Stable Chemical ◽

Conductive Hydrogel ◽

Conductive Hydrogels

Robust conductive hydrogels are in great demand for the practical applications of smart soft robots, epidermal electronics, and human–machine interactions. We successfully prepared nanoparticles enhanced polyacrylamide/hydroxypropyl guar gum/acryloyl-grafted chitosan quaternary ammonium salt/calcium ions/SiO2 nanoparticles (PHC/Ca2+/SiO2 NPs) conductive hydrogels. Owing to the stable chemical and physical hybrid crosslinking networks and reversible non-covalent interactions, the PHC/Ca2+/SiO2 NPs conductive hydrogel showed good conductivity (~3.39 S/m), excellent toughness (6.71 MJ/m3), high stretchability (2256%), fast self-recovery (80% within 10 s, and 100% within 30 s), and good fatigue resistance. The maximum gauge factor as high as 66.99 was obtained, with a wide detectable strain range (from 0.25% to 500% strain), the fast response (25.00 ms) and recovery time (86.12 ms), excellent negligible response hysteresis, and good response stability. The applications of monitoring the human’s body movements were demonstrated, such as wrist bending and pulse tracking.

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Facile Synthesis of Sprayed CNTs Layer-Embedded Stretchable Sensors with Controllable Sensitivity

Polymers ◽

10.3390/polym13020311 ◽

2021 ◽

Vol 13 (2) ◽

pp. 311 ◽

Cited By ~ 1

Author(s):

Hammad R. Khalid ◽

Iqra Choudhry ◽

Daeik Jang ◽

Nadir Abbas ◽

M. Salman Haider ◽

...

Keyword(s):

Electrical Resistance ◽

Electronic Devices ◽

Polymer Layer ◽

Facile Synthesis ◽

Optical Images ◽

Significant Interest ◽

Potential Applications ◽

Facile Fabrication ◽

Stretchable Sensors ◽

Solution Volume

Flexible electronic devices have gained significant interest due to their different potential applications. Herein, we report highly flexible, stretchable, and sensitive sensors made of sprayed CNT layer, sandwiched between two polymer layers. A facile fabrication process was employed in which the CNT solution was directly sprayed onto a patterned bottom polymer layer, above which a second polymer layer was casted to get a sandwiched composite structure. Varying amounts of CNT solution (i.e., 10, 25, 40, 70, and 100 mL) were sprayed to get conductive CNT layers of different thicknesses/densities. The physical characteristics of the conductive CNT layers were studied through SEM and optical images. The starting electrical resistance values (without strain) as well as the changes in electrical resistance against human body motions were monitored. The synthesized samples exhibited good response against finger and wrist bending. The conductivity of the samples increased with increase of CNT solution volume while the sensitivity followed the inverse relation, suggesting that the sensors with controlled sensitivity could be fabricated for targeted strain ranges using the proposed method.

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An Invisible Bionic Dragonfly Based on Fully-Transparent Conductive Hydrogel and Dielectric Elastomer

2021 21st International Conference on Solid-State Sensors, Actuators and Microsystems (Transducers) ◽

10.1109/transducers50396.2021.9495487 ◽

2021 ◽

Author(s):

Ronggang He ◽

Kai Tao ◽

Zhensheng Chen ◽

Bowen Ji ◽

Qiang Shen ◽

...

Keyword(s):

Dielectric Elastomer ◽

Conductive Hydrogel

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Preparation of Carbon Fiber-Polyacrylamide Composite Hydrogel Based on Surface Electric-Initiated Polymerization

Journal of Nanoelectronics and Optoelectronics ◽

10.1166/jno.2021.3028 ◽

2021 ◽

Vol 16 (6) ◽

pp. 861-868

Author(s):

Mengge Lv ◽

Xinfang Wei ◽

Liwen Peng

Keyword(s):

Composite Material ◽

Carbon Fiber ◽

Electrochemical Polymerization ◽

Crosslinking Agent ◽

Monomer Concentration ◽

Conductive Filler ◽

Composite Effect ◽

Conductive Hydrogel ◽

Graft Modification ◽

Conductive Hydrogels

Conductive hydrogels have shown excellent application prospects in the fields of bioelectronics, tissue engineering, wearable devices, etc. However, its poor compatibility at the organic-inorganic interface affects its mechanical strength and limits its wide application. We prepared carbon fiber-polyacrylamide organic-inorganic composite material by electrochemical polymerization using N,N-methylenebisacrylamide as the crosslinking agent, acrylamide as the monomer, and carbon fiber as the conductive filler. It forms a conductive hydrogel after absorbing water. The effects of monomer concentration, reaction time, and current on the composite material were investigated in this article. The experimental results show that a large number of irregular bumps are produced on the surface of carbon fiber, and various characterization tests show that it is polyacrylamide (PAM) that successfully attached to carbon fiber. Under the same electrochemical polymerization time, the current density and monomer concentration have little effect on the molecular weight which mainly concentrated around 6.2 × 105. The graft modification of PAM reduces the defects on the surface of the carbon fiber, and the composite effect is good.

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High Toughness Multifunctional Organic Hydrogels for Flexible Strain and Temperature Sensor

Journal of Materials Chemistry A ◽

10.1039/d1ta07127k ◽

2021 ◽

Author(s):

Hongjie Chen ◽

Jianren Huang ◽

Jiaontao Liu ◽

Jianfeng Gu ◽

Jundong Zhu ◽

...

Keyword(s):

Temperature Sensor ◽

High Toughness ◽

Conductive Hydrogel ◽

Conductive Hydrogels

Conductive hydrogel has shown extensive application in multifunctional sensors. However, the intrinsic characteristics of conductive hydrogels, such as lacking anti-freezing, mechanical strengthen, and being easily dehydrated have hindered their application...

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