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

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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Ultrasensitive Strain Sensor Based on Pre-Generated Crack Networks Using Ag Nanoparticles/Single-Walled Carbon Nanotube (SWCNT) Hybrid Fillers and a Polyester Woven Elastic Band

Sensors ◽

10.3390/s21072531 ◽

2021 ◽

Vol 21 (7) ◽

pp. 2531

Author(s):

Yelin Ko ◽

Ji-seon Kim ◽

Chi Cuong Vu ◽

Jooyong Kim

Keyword(s):

High Performance ◽

Strain Sensor ◽

Strain Range ◽

Human Motion ◽

Strain Sensors ◽

Gauge Factor ◽

Elastic Band ◽

Practical Applications ◽

Single Walled Carbon ◽

Novel Strategy

Flexible strain sensors are receiving a great deal of interest owing to their prospective applications in monitoring various human activities. Among various efforts to enhance the sensitivity of strain sensors, pre-crack generation has been well explored for elastic polymers but rarely on textile substrates. Herein, a highly sensitive textile-based strain sensor was fabricated via a dip-coat-stretch approach: a polyester woven elastic band was dipped into ink containing single-walled carbon nanotubes coated with silver paste and pre-stretched to generate prebuilt cracks on the surface. Our sensor demonstrated outstanding sensitivity (a gauge factor of up to 3550 within a strain range of 1.5–5%), high stability and durability, and low hysteresis. The high performance of this sensor is attributable to the excellent elasticity and woven structure of the fabric substrate, effectively generating and propagating the prebuilt cracks. The strain sensor integrated into firefighting gloves detected detailed finger angles and cyclic finger motions, demonstrating its capability for subtle human motion monitoring. It is also noteworthy that this novel strategy is a very quick, straightforward, and scalable method of fabricating strain sensors, which is extremely beneficial for practical applications.

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High Effective Sensitivity, Wide Working Range of Melt-blown Nonwoven Conductive Substrates for Smart Wearable Strain Sensors

Journal of Physics D Applied Physics ◽

10.1088/1361-6463/ac4653 ◽

2021 ◽

Author(s):

Jingfang Liu ◽

Rangtong Liu ◽

Shuping Liu ◽

Liang Li ◽

Shujing Li

Keyword(s):

Strain Range ◽

High Sensitivity ◽

Fast Response ◽

Strain Sensors ◽

Gauge Factor ◽

High Durability ◽

Voice Changes ◽

Conductive Substrates ◽

Smart Wearable ◽

Melt Blown Nonwoven

Abstract High sensitivity, wide working range and flexible portability of strain sensors are crucial for smart wearable applications. To obtain these performances, several elastic melt-blown nonwoven substrates with excellent flexibility and high conductivity were developed by loading with polypyrrole through a double-dipping and double-rolling finishing method. The structure and conductivity are characterized by scanning electron microscope, infrared spectrometer, digital source meter and so on. The results indicate that the conductivity of prepared substrates is affected by the pyrrole concentration and polypyrrole amount deposited in nonwovens. Obviously, the conductivity and sensitivity of substrates as strain sensors are highly and positively correlated to the fiber orientation in nonwovens, and the effective working range and corresponding sensitivity of sensors are determined by the elastic deformation interval of melt-blown substrate. When the pyrrole concentration is 5.5%, the nonwoven substrate with 45.30% porosity possesses the anisotropic optimal conductivity with 23.491 S m-1 along winding direction and 15.063 S m-1 along width direction. Moreover, the as-prepared flexible conductive substrate exhibits the characteristics of wide working strain range (0-24.2%), high sensitivity with 1.94 gauge factor at the range, fast response (0.023 s), tiny hysteresis (0.011s), high durability and stability after 1000 cycles. Furthermore, the as-prepared sensor provides an effective method to prepare smart wearable strain sensors used as the monitor of finger bending in details and the precise recognition of human voice changes.

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Transparent, Conductive Hydrogels with High Mechanical Strength and Toughness

Polymers ◽

10.3390/polym13122004 ◽

2021 ◽

Vol 13 (12) ◽

pp. 2004

Author(s):

Xiuru Xu ◽

Chubin He ◽

Feng Luo ◽

Hao Wang ◽

Zhengchun Peng

Keyword(s):

Mechanical Strength ◽

Body Surface ◽

High Sensitivity ◽

Fast Response ◽

Light Transmittance ◽

Gauge Factor ◽

Strain Sensing ◽

Breaking Strain ◽

Conductive Hydrogels ◽

Strength And Toughness

Transparent, conductive hydrogels with good mechanical strength and toughness are in great demand of the fields of biomedical and future wearable smart electronics. We reported a carboxymethyl chitosan (CMCS)–calcium chloride (CaCl2)/polyacrylamide (PAAm)/poly(N-methylol acrylamide (PNMA) transparent, tough and conductive hydrogel containing a bi-physical crosslinking network through in situ free radical polymerization. It showed excellent light transmittance (>90%), excellent toughness (10.72 MJ/m3), good tensile strength (at break, 2.65 MPa), breaking strain (707%), and high elastic modulus (0.30 MPa). The strain sensing performance is found with high sensitivity (maximum gauge factor 9.18, 0.5% detection limit), wide strain response range, fast response and recovery time, nearly zero hysteresis and good repeatability. This study extends the transparent, tough, conductive hydrogels to provide body-surface wearable devices that can accurately and repeatedly monitor the movement of body joints, including the movements of wrists, elbows and knee joints. This study provided a broad development potential for tough, transparent and conductive hydrogels as body-surface intelligent health monitoring systems and implantable soft electronics.

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Design of facile technology for the efficient removal of hydroxypropyl guar gum from fracturing fluid

PLoS ONE ◽

10.1371/journal.pone.0247948 ◽

2021 ◽

Vol 16 (3) ◽

pp. e0247948

Author(s):

Shiliang Xu ◽

Mengke Cui ◽

Renjie Chen ◽

Qiaoqing Qiu ◽

Jiacai Xie ◽

...

Keyword(s):

Guar Gum ◽

Low Cost ◽

High Viscosity ◽

Fracturing Fluid ◽

X Ray ◽

Practical Applications ◽

Hydroxypropyl Guar ◽

Fracturing Fluids ◽

Removal Technologies ◽

Hydroxypropyl Guar Gum

With the increasing demand for energy, fracturing technology is widely used in oilfield operations over the last decades. Typically, fracturing fluids contain various additives such as cross linkers, thickeners and proppants, and so forth, which makes it possess the properties of considerably complicated components and difficult processing procedure. There are still some difficult points needing to be explored and resolved in the hydroxypropyl guar gum (HPG) removal process, e.g., high viscosity and removal of macromolecular organic compounds. Our works provided a facile and economical HPG removal technology for fracturing fluids by designing a series of processes including gel-breaking, coagulation and precipitation according to the diffusion double layer theory. After this treatment process, the fracturing fluid can meet the requirements of reinjection, and the whole process was environment friendly without secondary pollution characteristics. In this work, the fracturing fluid were characterized by scanning electron microscopy (SEM), Energy dispersive X-ray (EDX), X-ray diffraction (XRD) and Fourier transformed infrared (FTIR) spectroscopy technologies, etc. Further, the micro-stabilization and destabilization mechanisms of HPG in fracturing fluid were carefully investigated. This study maybe opens up new perspective for HPG removal technologies, exhibiting a low cost and strong applicability in both fundamental research and practical applications.

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CNT-Br/PEDOT:PSS/PAAS three-network composite conductive hydrogel for human motion monitoring

New Journal of Chemistry ◽

10.1039/d0nj04867d ◽

2021 ◽

Vol 45 (1) ◽

pp. 208-216

Author(s):

Zhonghua Zhao ◽

Xiang Yuan ◽

Yicheng Huang ◽

Jikui Wang

Keyword(s):

Human Motion ◽

Conductive Hydrogel ◽

Conductive Hydrogels ◽

Human Motion Monitoring

Conductive hydrogels are promising flexible conductors for human motion monitoring.

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Alcohol-based highly conductive polymer for conformal nanocoatings on hydrophobic surfaces toward a highly sensitive and stable pressure sensor

NPG Asia Materials ◽

10.1038/s41427-020-00238-z ◽

2020 ◽

Vol 12 (1) ◽

Cited By ~ 1

Author(s):

Jung Joon Lee ◽

Srinivas Gandla ◽

Byeongjae Lim ◽

Sunju Kang ◽

Sunyoung Kim ◽

...

Keyword(s):

Pressure Sensor ◽

Mechanical Stability ◽

Exchange Process ◽

Conductive Polymer ◽

High Sensitivity ◽

Fast Response ◽

Pdms Surface ◽

Practical Applications ◽

Sensor Applications ◽

Water Based

Abstract Conformal and ultrathin coating of highly conductive PEDOT:PSS on hydrophobic uneven surfaces is essential for resistive-based pressure sensor applications. For this purpose, a water-based poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) solution was successfully exchanged to an organic solvent-based PEDOT:PSS solution without any aggregation or reduction in conductivity using the ultrafiltration method. Among various solvents, the ethanol (EtOH) solvent-exchanged PEDOT:PSS solution exhibited a contact angle of 34.67°, which is much lower than the value of 96.94° for the water-based PEDOT:PSS solution. The optimized EtOH-based PEDOT:PSS solution exhibited conformal and uniform coating, with ultrathin nanocoated films obtained on a hydrophobic pyramid polydimethylsiloxane (PDMS) surface. The fabricated pressure sensor showed high performances, such as high sensitivity (−21 kPa−1 in the low pressure regime up to 100 Pa), mechanical stability (over 10,000 cycles without any failure or cracks) and a fast response time (90 ms). Finally, the proposed pressure sensor was successfully demonstrated as a human blood pulse rate sensor and a spatial pressure sensor array for practical applications. The solvent exchange process using ultrafiltration for these applications can be utilized as a universal technique for improving the coating property (wettability) of conducting polymers as well as various other materials.

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Degradation of hydroxypropyl guar gum at wide pH range by a heterogeneous Fenton-like process using bentonite-supported Cu(0)

Water Science & Technology ◽

10.2166/wst.2020.436 ◽

2020 ◽

Vol 82 (8) ◽

pp. 1635-1642

Author(s):

Ling Zhou ◽

Zhongying Xu ◽

Jie Zhang ◽

Zhifang Zhang ◽

Ying Tang

Keyword(s):

Active Sites ◽

Guar Gum ◽

Heterogeneous Reaction ◽

Removal Rate ◽

Catalytic Performance ◽

High Dispersion ◽

Application Process ◽

Experimental Conditions ◽

Hydroxypropyl Guar ◽

Hydroxypropyl Guar Gum

Abstract To seek for efficient Fenton-like oxidation processing for treatment of waste fracturing fluid containing hydroxypropyl guar gum (HPGG), in heterogeneous reaction, five bentonite-supported zero-valent metal catalysts were prepared by liquid-phase reduction. The results showed that the bentonite-supported zero-valent copper exhibited best catalytic performance, attributed to the high dispersion of active sites of zero-valent copper. The effects of the most relevant operating factors (H2O2 concentration, catalyst dosage, temperature and pH) were evaluated in detail. Moreover, the chemical oxygen demand removal rate of HPGG can achieve 76% when the reaction time was selected at 45 min under optimal experimental conditions. The stability evaluation showed that the catalytic performance was almost unaffected after the catalyst was recycled and used once more showing the good stability of the bentonite-supported zero-valent copper in the application process.

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Combined treatment of hydroxypropyl guar gum in oilfield fracturing wastewater by coagulation and the UV/H2O2/ferrioxalate complexes process

Water Science & Technology ◽

10.2166/wst.2017.552 ◽

2017 ◽

Vol 77 (3) ◽

pp. 565-575 ◽

Cited By ~ 3

Author(s):

Zhenchao Zhang

Keyword(s):

Removal Efficiency ◽

Guar Gum ◽

Combined Treatment ◽

Cod Removal ◽

Treated Wastewater ◽

Spectra Analysis ◽

Hydroxypropyl Guar ◽

Coagulation Process ◽

Cod Removal Efficiency ◽

Hydroxypropyl Guar Gum

Abstract Hydroxypropyl guar gum is considered to be a main component of oilfield fracturing wastewater (OFW). This work is intended to optimize the experimental conditions for the maximum oxidative degradation of hydroxypropyl guar gum by the coagulation and UV/H2O2/ferrioxalate complexes process. Optimal reaction conditions were proposed based on the chemical oxygen demand (COD) removal efficiency and UV_vis spectra analysis. The overall removal efficiency of COD reached 83.8% for a dilution ratio of raw wastewater of 1:2, pH of 4 and FeCl3 loading of 1,000 mg/L in the coagulation process; the dosage of H2O2 (30%,v/v) was 0.6% (v/v) and added in three steps, the n(H2O2)/n(Fe2+) was 2:1, n(Fe2+)/n(C2O42−) was 3:1 and pH was 4 in the UV/H2O2/ferrioxalate complexes process; pH was adjusted to 8.5–9 by NaOH and then cationic polyacrylamide (CPAM) of 2 mg/L was added in the neutralization and flocculation process. The decrease in COD during the coagulation process reduced the required H2O2 dosage and improved efficiency in the subsequent UV/H2O2/ferrioxalate complexes process. Furthermore, COD removal efficiency significantly increased by more than 13.4% with the introduction of oxalate compared with UV/Fenton. The UV_vis spectra analysis results indicated that the coagulation and UV/H2O2/ferrioxalate complexes process could efficiently remove the hydroxypropyl guar gum dissolved in OFW. An optimal combination of these parameters produced treated wastewater that met the GB8978-1996 Integrated Wastewater Discharge Standard level III emission standard.

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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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