Polyacrylamide/sodium alginate double network hydrogel with easily repairable superhydrophobic surface for strain sensor resistant to fluid interference.

Constructing an easily repairable hydrophobic layer on the hydrogel surface that confers resistance to liquid interference remains a great challenge for hydrogel strain sensors. In this paper, superhydrophobic hydrogel sensors were prepared by driving hydrophobic organically modified silica (o-SiO2) nanoparticles to the surface of polyacrylamide/sodium alginate (PAM/SA) double network hydrogels by a weak ultrasonic field in o-SiO2/cyclohexane dispersion. The hydroxyl groups present on the surface of o-SiO2 are able to form hydrogen bonds with hydrogels, which in turn form a strong surface hydrophobic layer on its surface. The sensor exhibits superhydrophobic properties for different types of liquids, such as acids, salt solutions, etc., even in the stretched state. The broken o-SiO2 layers can be repaired by immersing in the o-SiO2/cyclohexane dispersion. The SA significantly improved the mechanical properties as well as the strain response sensitivity of the hydrogels. The hydrogel sensor is characterized by low hysteresis to strain, wide detection range (0-894 %), low detection limit (1 %), high sensitivity (GF = 4.8), and good cyclic stability. The superhydrophobic surface allows the sensor to exhibit excellent anti-liquid interference. Salt solution droplets, prolonged contact with salt solution, and even short-term water immersion will not affect the sensor's response to strain. Moreover, repairing the broken hydrophobic layer enables the sensor to restore its resistance to liquid interference. The prepared hydrogel can be used for human motion monitoring in complex scenarios, including exercise sweating, rain, and short-time exposure to water.

Recyclable Bimodal Polyvinyl Alcohol/PEDOT:PSS Hydrogel Sensors for Highly Sensitive Strain and Temperature Sensing.

Multimodal flexible sensors, consisting of multiple sensing units, can sense and recognize different external stimuli by outputting different types of response signals. However, the recovery and recycling of multimodal sensors are impeded by complex structures and the use of multiple materials. Here, a bimodal flexible sensor that can sense strain by resistance change and temperature by voltage change was constructed using poly(vinyl alcohol) hydrogel as a matrix and poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT:PSS) as a sensing material due to its conductivity and thermoelectric effect. The plasticity of hydrogels, along with the simplicity of the sensor's components and structure, facilitates easy recovery and recycling. The incorporation of citric acid and ethylene glycol improved the mechanical properties, strain hysteresis, and antifreezing properties of the hydrogels. The sensor exhibits a remarkable response to strain, characterized by high sensitivity (gauge factor of 4.46), low detection limit (0.1%), fast response and recovery times, minimal hysteresis, and excellent stability. Temperature changes induced by hot air currents, hot objects, and light cause the sensor to exhibit high response sensitivity, fast response time, and good stability. Additionally, variations in ambient humidity and temperature minimally affect the sensor's strain response, and temperature response remains unaffected by humidity changes. The recycled sensors are essentially unchanged for bimodal sensing of strain and temperature. Finally, bimodal sensors are applied to monitor body motion, and robots to sense external stimuli.

Recyclable Polymer Composites with a Wrinkled Core-Shell Structure for Highly Efficient EMI Shielding and Low Reflection.

Green electromagnetic interference (EMI) shielding materials not only require high shielding effectiveness (SE) and low reflection but also need to be recyclable after damage; however, it is challenging to strike a balance in practice. Here, a polyacrylamide (PAM) composite composed of numerous chemically cross-linked PAM@carbon nanotube (cPAM@CNT) core-shell particles featuring rich wrinkled microstructures was prepared using an adsorption-drying-shrinking strategy. The wrinkled microstructures enable the incident electromagnetic waves (EMWs) to undergo attenuation within the composites, achieving an average EMI SE of 67.5 dB in the X band. Due to the hygroscopicity of hydrophobically associated PAM (hPAM, an adhesive for cPAM@CNTs core-shell particles), the average EMI SE of the composites further increased to 83.2 dB after exposure to 91% relative humidity for 24 h, with only a 2.7 dB low reflection. Additionally, the composites also demonstrated excellent Joule heating, photothermal performance, and recyclability, which exhibit substantial promise for advanced EMI shielding applications.

Study on the Performance Mechanism of Polyformaldehyde Glycol Ether Polymer for Crude Oil Recovery Enhancement.

The demand for energy continues to increase as the global economy continues to grow. The role of oilfield chemicals in the process of oil and gas exploration, development, and production is becoming more and more important, and the demand is rising year by year. The support of national policies and the formulation of environmental protection regulations have put forward higher requirements for oilfield chemical products, which has promoted the innovative research and development and market application of oilfield chemicals. Polyformaldehyde glycol ether polymer (PGEP) is simple to synthesize, easily biodegradable, green and environmentally friendly, and in line with the development trend of chemicals used in oil and gas development. The interfacial tension performance of PGEP after compounding with different surfactants can reach as low as 0.00034 mN/m, which meets the requirements of the oilfield (interfacial tension ≤ 5 × 10-3 mN/m). The best oil washing efficiency performance of PGEP compounded with different surfactants reached 78.2%, which meets the requirements of the oilfield (oil washing efficiency ≥ 40%). The fracturing fluid drainage efficiency of PGEP after compounding with different surfactants reaches 22%, which meets the requirements of the oilfield (drainage efficiency ≥ 15%). The surface interfacial tension of the system remains constant after the concentration exceeds 0.2% and decreases with lower concentrations. The drainage efficiency increases with increasing concentrations in the range below 0.6%. It was determined that PGEP can be used as a surfactant instead of fatty-alcohol ethoxylates (FAE) in oilfield development.

Flexible Sensors with a Multilayer Interlaced Tunnel Architecture for Distinguishing Different Strains.

The diversity of body joints and the complexity of joint motions cause flexible strain sensors to undergo complex strains such as stretching, compression, bending, and extrusion, which results in sensors that do not recognize different strains, facing great challenges in detecting the true motion characteristics of joints. Here, the monitoring of body joints' real motion characteristics has been realized by the sensor that can output response signals with different resistance trends for different strains. The sensor prepared by the sacrificial template method is characterized by a multilayered interlaced tunnel architecture and carbon black embedded in the inner wall of the tunnel. Stretching, compressive, and bending strains result in increasing, decreasing, and increasing resistance, followed by a decrease in resistance of the sensor, respectively. The sensor can still output distinguishable response signals, even in the presence of complex strains induced by squeezing. Low strain detection limits (0.03%) and wide detection ranges (>600%) are achieved due to the localized strain enhancement caused by the unique structure. The sensor can detect the motion characteristics of different joints in flexion-extension, abduction-adduction, and internal-external rotation, which, in turn, can be used for real-time monitoring of complex joint motions involved in limb rehabilitation. In addition, the sensor recognizes the 26 letters of the alphabet represented by sign language gestures. The above studies demonstrate the potential application of our prepared sensors in flexible, wearable devices.

Ultrathin Superhydrophobic Flexible Tactile Sensors for Normal and Shear Force Discrimination.

Flexible tactile sensors, with the ability to sense and even discriminate between different mechanical stimuli, can enable real-time and precise monitoring of dexterous and complex robotic motions. However, making them ultrathin and superhydrophobic for practical applications is still a great challenge. Here, superhydrophobic flexible tactile sensors with hierarchical micro- and nanostructures, that is, warped graphene nanosheets adhered to micron-height wrinkled surfaces, were constructed using ultrathin medical tape (40 µm) and graphene. The tactile sensor enables the discrimination of normal and shear forces and senses sliding friction and airflow. Moreover, the tactile sensor exhibits high sensitivity to normal and shear forces, extremely low detection limits (15 Pa for normal forces and 6.4 mN for shear forces), and cyclic robustness. Based on the abovementioned characteristics, the tactile sensor enables real-time and accurate monitoring of the robotic arm's motions, such as moving, gripping, and lifting, during the process of picking up objects. The superhydrophobicity even allows the sensor to monitor the motions of the robotic arm underwater in real time. Our tactile sensors have potential applications in the fields of intelligent robotics and smart prosthetics.

Use of Surface Penetration Technology to Fabricate Superhydrophobic Multifunctional Strain Sensors with an Ultrawide Sensing Range.

Flexible sensors with wide sensing ranges require responsiveness under tiny and large strains. However, the development of strain sensors with wide detection ranges is still a great challenge due to the conflict between the tiny strain requirements of sparse conductive networks and the large strain requirement of dense conductive networks. Herein, we present a facile method for fabricating a gradient conductive network composed of sparse and dense conductive networks. The surface penetration technology in which carbon black (CB) penetrated from the natural rubber latex (NRL) glove surface to the interior was used to fabricate a gradient conductive network. The prolonged immersion time from 1 to 30 min caused the penetration depth of CB to increase from 2 to 80 µm. Moreover, CB formed hierarchical rough micro- and nanoscale structures, creating a superhydrophobic surface. The gradient conductive network of sensors produced an ultrawide detection range of strain (0.05-300%) and excellent reliability and reproducibility. The sensors can detect a wide range of human motions, from tiny (wrist pulse) to large (joint movements) motion monitoring. The flexible sensors attached to a flexible basement can be used to detect pressure in a wide detection range (1.7-2900 kPa). Pressure responsiveness was used to detect the weight, sound pressure, and dripping of tiny droplets. The sensor showed an excellent response to organic solvents, and the response intensity increased with the increasing swelling degree of the solvent for NRL.

Adsorption Kinetics of Arsenic (V) on Nanoscale Zero-Valent Iron Supported by Activated Carbon.

The presence of arsenic (As) in drinking water is of serious concern due to its negative impact on human health. This work reports on the kinetics of nanoscale zero-valent iron (Fe0) supported by activated carbon (NZVI/AC) for the removal of As (V) species from aqueous solutions. To better understand the factors affecting this process, we investigated the effects of various experimental parameters including initial As (V) concentration, adsorbent dosage, pH, temperature, and coexisting ions on the adsorption kinetics using a batch-adsorption method. The optimum conditions for As (V) removal by NZVI/AC were found to be: 318 K, pH 3.5, an adsorbent dosage of 1.5 g/L, and an equilibrium time of 72 h. A greater mass of NZVI/AC, lower concentration of As (V) and lower pH positively promoted adsorption kinetics. The presence of phosphate (PO43-) and silicate (SiO42-) markedly inhibited As (V) removal kinetics. However, in the presence of 4.5 g/L NZVI/AC, ≥99.9% of As (V) was removed from raw groundwater.

Retraction of "Regulating the Microstructure of Intumescent Flame-Retardant Linear Low-Density Polyethylene/Nylon Six Blends for Simultaneously Improving the Flame Retardancy, Mechanical Properties, and Water Resistance".

[This retracts the article DOI: 10.1021/acsomega.8b00488.].

Regulating the Microstructure of Intumescent Flame-Retardant Linear Low-Density Polyethylene/Nylon Six Blends for Simultaneously Improving the Flame Retardancy, Mechanical Properties, and Water Resistance.

A compatibilizer was melt-blended with intumescent flame-retardant linear low-density polyethylene/nylon six blends (LLDPE/PA6/IFR) by different methods, and the effect of microstructure on the flame retardancy, mechanical properties, and water resistance was investigated. Melt-blending compatibilizers with LLDPE/PA6/IFR above the polyamide-6 (PA6) melt temperature formed the microstructure with IFR dispersion in the LLDPE matrix and good interphase adhesion between the PA6 phase and the matrix. Compared with the blends with the lack of compatibilizers, although good interphase adhesion improved the mechanical properties and water resistance, IFR dispersion in the LLDPE matrix reduced the flame retardancy sharply. To obtain the microstructure with IFR dispersion in the PA6 phase and strong interface adhesion of the PA6 phase with a matrix, a novel method in which a compatibilizer was melt-blended with LLDPE/PA6/IFR between the melt temperatures of LLDPE and PA6 was employed. The results showed that the flame retardancy, mechanical properties, and water resistance were improved simultaneously.

Synergistic effects of polymer adsorbents on the performance of bilirubin hemoperfusion.

Neonatal hyperbilirubinemia (jaundice) is a common disease with high incidence. Currently, the clinical inefficiency of adult bilirubin hemoperfusion medical adsorbent is a major technical barrier for the application of hemoperfusion treatment to rescue the severe neonatal jaundice. Based on the well-known principle of synergistic effects, a series of customized bilirubin polymeric compounds, comprised of one or more of the following components (glycidyl methacrylate, sodium acrylate, methacrylic acid isooctyl, hexamethylene diamine, albumin), were designed and fabricated based on molecular design. Their adsorption performances upon bilirubin were investigated and compared under the same conditions, and the compound with the highest adsorption performance was then subject to preliliminary safety assessments and compared with a commercial one (BS330). The results showed that positive synergistic effects appeared on the adsorption performance to adsorb bilirubin based on this study, and the one comprised of glycidyl methacrylate+sodium acrylate+methacrylic acid isoocty+hexamethylene diamine+albumin possesses the highest adsorption performance as well as outome clinical acceptable medical safety assessments, and its adsorption efficiency was up to 46% while the commerical one's was about 26% under the same conditions. This study sheds a new light on how to design and develop hemoperfusion bilirubin adsorbents with good overall clinical performance, as well as providing a novel idea and experimental referrences for future related topics.

Electrospun PS/PAN fibers with improved mechanical property for removal of oil from water.

A mechanically robust and high-capacity oil sorbent is prepared by electrospinning a blend of polystyrene (PS) and polyacrylonitrile (PAN). The morphology, oil sorption capacity and mechanical property of the fibers formed in different compositions are investigated in detail. It is shown that the oil sorption capacity is a result of both the chemical composition and the specific surface area which related to diameter size. The addition of PAN as a component in fibrous sorbents can significantly improve the mechanical properties of PS fibers. Moreover, the oil sorption capacity increases with decreasing fiber diameter. The results also show that the maximum sorption capacities of the PS/PAN sorbent for pump oil, peanut oil, diesel, and gasoline were 194.85, 131.70, 66.75, and 43.38 g g(-1), respectively. Additionally, the sorbent exhibits quick oil sorption speed as well as high buoyancy, which make it a promising candidate for use as an oil spill cleanup sorbent.