Polydimethysiloxane Research Articles

A highly-sensitive wearable capacitance pressure sensor based on calcium copper titanate/polydimethysiloxane/graphene oxide and polydimethysiloxane/silver nanowires sanwich strustures combination for human body monitoring

In recent years, flexible pressure sensors, with their high sensitivity, low detection limit, wide working pressure range and fast response speed, have been playing an important role in the development of wearable artificial devices, human-computer interaction and healthcare systems, and have attracted wide attention. However, the pressure sensors face challenges related to the weak tightness of bipolar materials, low charge density, and limitation in dielectric layers. In this paper, we present a novel configuration of flexible capacitive pressure sensors, utilizing a polydimethysiloxane (PDMS) thin film covered by silver nanowires (PDMS/SN, PSN) as the electrode materials and a porous material composed of calcium copper titanate (@CCTO), PDMS and graphene oxide (GO)(@CCTO/PDMS/GO, @CPG) as the positive electrode material. The sacrificial material, sugar, is employed to create dense internal pores within the substrate material, @CPG, leading to the formation of a profoundly porous substrate. The integration of the flexible capacitive pressure sensor using @CPG/PSN results in enhanced output performance. The modified sensors achieves a sensitivity of 0.22 kPa−1, which is 7 times higher than that of a pure PDMS dielectric layer sensor. Moreover, the sensors has a response time of 87 ms, a low detection pressure of 5 Pa with an extensive detection range from 0 to 150 kPa, and are capable of enduring 7200 cycles without sustaining damage. To validate the practical performance of the @CPG/PSN sensor, various human body activities are detected, including swallowing, coughing, neck bending, wrist bending, elbow bending, finger flexing, and holding objects like cups using a digitally designed glove capable of accommodating different materials. The pressure sensor based on @CPG/PSN demonstrates significant promise in detecting both low and high pressures, thus expanding the potential applications of capacitive pressure sensors.

Solar-driven, highly-efficient, and environmentally-friendly oil spill cleanup by a superelastic photothermal thermoplastic polyurethane monolith with aligned channels

Cleanup of crude oil spills is challenging due to its high viscosity. Reducing the viscosity of crude oil by elevating its temperature and thus promoting absorption is considered a promising and environmentally-friendly way to address this worldwide issue. Herein, we propose a photothermal superelastic thermoplastic polyurethane (TPU)-based monolith with aligned channels successively modified with MXene and polydimethysiloxane (PDMS) (P-MXene@TPU) for crude oil absorption and recovery. The well-oriented structures help reduce mass transfer hindrance and accelerate heat transfer, while MXene and PDMS endow the monolith with excellent photothermal conversion property and hydrophobicity, respectively. P-MXene@TPU monolith demonstrates superior oil absorption performance under solar irradiation as self-heating is realized to decrease the crude oil viscosity and promote its absorption rate. Particularly noteworthy is that P-MXene@TPU monolith can bear 300 compression cycles with a deformation of 9 % owing to the superelastic TPU skeleton and aligned channels. The stable compression performance and anti-fatigue property validate that the monolith is suitable for recovering crude oil by extrusion. Continuous crude oil recovery is achieved via a pumping device and solar irradiation (1.0 kW/m2) enhances the recovery rate by a factor of 18, as compared to the one without irradiation. Given the unique structural design and exceptional properties, this monolith provides a highly efficient approach for handing the crude oil spills.

Pysanky to Microfluidics: An Innovative Wax-Based Approach to Low Cost, Rapid Prototyping of Microfluidic Devices.

A wax-based contact printing method to create microfluidic devices is demonstrated. This printing technology demonstrates a new pathway to rapid, cost-effective device prototyping, eliminating the use of expensive micromachining equipment and chemicals. Derived from the traditional Ukrainian Easter egg painting technique called "pysanky" a series of microfluidic devices were created. Pysanky is the use of a heated wax stylus, known as a "kistka", to create micro-sized, intricate designs on the surface of an egg. The proposed technique involves the modification of an x-y-z actuation translation system with a wax extruder tip in junction with Polydimethysiloxane (PDMS) device fabrication techniques. Initial system optimization was performed considering design parameters such as extruder tip size, contact angle, write speed, substrate temperature, and wax temperature. Channels created ranged from 160 to 900 μm wide and 10 to 150 μm high based upon system operating parameters set by the user. To prove the capabilities of this technology, a series of microfluidic mixers were created via the wax technique as well as through traditional photolithography: a spiral mixer, a rainbow mixer, and a linear serial dilutor. A thermo-fluidic computational fluid dynamic (CFD) model was generated as a means of enabling rational tuning, critical to the optimization of systems in both normal and extreme conditions. A comparison between the computational and experimental models yielded a wax height of 57.98 μm and 57.30 μm, respectively, and cross-sectional areas of 11,568 μm2 and 12,951 μm2, respectively, resulting in an error of 1.18% between the heights and 10.76% between the cross-sectional areas. The device's performance was then compared using both qualitative and quantitative measures, considering factors such as device performance, channel uniformity, repeatability, and resolution.

Compatibilization of immiscible polymer blends by reactive polymer grafted graphene with interfacial crosslinking

AbstractWe investigate reactive compatibilization by applying two multifunctional polymers grafted on a graphene surface, which leads to crosslinked interphase at immiscible polymer blends. Reactive compatibilizer‐grafted graphene (RCG) nanoparticles were synthesized through esterification and amidation reactions between oxidative groups of graphene oxide and reactive multifunctional groups of polymers. Polymer blends of polyisoprene (PI) and polydimethysiloxane (PDMS) with PI:PDMS ratio of 30:70 or 70:30 and RCG nanoparticle loadings from 0.1 and 1 wt% were evaluated by optical microscopy and rheometry. The results indicated that the blend with 0.1 wt% RCG showed unusual characteristics including nonspherical and bridged droplets, while those containing 1 wt% RCG showed usual droplet‐matrix morphology. The rheological results are also asymmetric: the blend with 0.1 wt% RCG displayed gel‐like behavior in the dynamic oscillatory tests, high viscosity, slow interfacial relaxation during startup shear flow, and divergence in the transient stress response due to coalesced and bridged droplets. However, the latter blend containing 1 wt% RCG reveals liquid‐like behavior, low viscosity, and convergence in the transient stress response due to stabilized droplet‐matrix morphology. Overall, it was suggested that these asymmetries are attributable to interfacial crosslinked interphase formed through an in‐situ reaction between multifunctional polymers grafted on graphene sheets.

Nanotribological interactions at the interface between polydimethylsiloxane and silane-modified silica

This research was conducted to show that long alkyl chains of silane, grafted on the surface of silica, can interact with liquid polydimethysiloxane (PDMS) matrix through a so called nanotribological interaction at the interface. Some nonlinear behavior was reported as the result of this interaction. For this purpose, composites of PDMS and silica modified by silanes with two different alkyl chain lengths of three (short) and sixteen (long) carbons were prepared. Also, small molecule silicone oil was utilized as the matrix to be compared with the rubber matrix in this type of interaction. Initially, the surface energy of modified silicas as an enthalpic driving force for polymer-filler and filler-filler interactions were made almost equal in order to reveal features of nanotribological interactions resulting from long alkyl chains of silane. Microscopic results indicated that long alkyl chains of silane are effective in better dispersion of silica particles in the rubber matrix. Also, the strain-sweep rheological behavior of the composites showed that at concentrations below the percolation threshold of silica, the long alkyl chains of silane can tribologically engage with the rubber matrix, resulting in an instability in storage modulus, even with better dispersion of particles. This observation was attributed to some engagement-disengagement of polymer at the interface rather than networking of particles, known as the Payne effect. However, silica grafted by the short chain silane did not show this behavior. This type of interaction was showed to be also effective in filler-filler interactions and networking for silica grafted with long chain silane, high above the percolation threshold of silica in PDMS. It was shown that this type of interaction is absent in silicone oil, revealing the essential role of molecular weight of matrix in nanotribological interactions with the long alkyl chains of silane.

Wood with improved hydrophobicity and thermal stability after depositing polydimethysiloxane/silica sol hybrid

Abstract To improve hydrophobicity and thermal stability, polydimethysiloxane (PDMS) emulsion and silica sol were used for depositing organic/inorganic hybrid coatings in wood. PDMS emulsion could provide the hydrophobic film to improve the hydrophobicity and dimensional stability owing to its low-surface-energy. Silica sol could significantly enhance the surface hardness and thermal stability due to its penetration in cell walls, indicating the pore-filling effect in wood. Moreover, in the hybrid system, silica incorporation in PDMS emulsion helped to form integrate coatings in wood via Si-O-Si cross-linked networks. The hydrophobicity, surface hardness and thermal stability of treated wood were related to the loadings of silica sol in the PDMS. Stiff silica could compensate the negative effect on thermal stability caused by PDMS, and synergistically improve the surface hydrophobicity and hardness of wood. This work opens a facile method to produce bio-based materials with satisfied hydrophobicity and thermal stability to be used in humid environments.

Effect of graphene on self-healing performance of hydroxyapatite/polydimethysiloxane composites

ABSTRACT Recently, polymeric self-healing materials are tremendously being exploited in the fields of biomedical and other advanced engineering applications. However, mechanism of the self-healing materials is not very clear and the healing performance is very poor for the existed materials. Therefore in our present investigation, hydroxyapatite (HA) bioceramic, graphene (Gr) and polydimethysiloxane (PDMS) were used to develop a high performance novel self-healing composite. Here, we proposed a single step accessible preparation of short-layers graphene by the exfoliation of graphite layers via acid leaching method. Further, Gr/HA embedded PDMS membranes were prepared using a vascular method. We prepared the PDMS elastomer (resin:hardener ratio = 1:1) being mixed with 2 wt% HA and varying concentrations 0.1 wt%, 0.3 wt%, 0.5 wt% of Gr. The band gap, phase structure, crystalline and chemical structure of the Gr/HA composite films were characterized using UV-Vis, XRD and FTIR studies. A series of tensile tests were conducted to measure virgin and healed tensile specimens. The highest mechanical property was achieved at 2 wt% of HA. But best self-healing performance of the 0.1 wt%Gr composite was obtained from the recovery of tensile properties. The healing efficiency was found to depend on the curing properties of PDMS varied with HA/Gr reinforcement and quantity of healing agent delivered.

Characterizing phenol mass transfer coefficients of composite extractive membranes with different PDMS thicknesses by electrochemical impedance spectroscopy

The extractive membrane is typically composed of a selective layer prepared by polydimethysiloxane (PDMS) and a highly porous substrate. A thin and defect-free PDMS selective layer is critical for the extractive membrane. The extractive membrane performance is predominantly evaluated by its organic mass transfer efficiency, which needs to conduct a time-consuming aqueous-aqueous extractive test. Herein, we proposed a novel, rapid, and sensitive method to characterize the organic mass transfer efficiency of extractive membranes. In this paper, PDMS-coated nanofibrous composite membranes with controllable thickness were prepared by electrospinning. The mass transfer efficiency of as-developed membranes was characterized by electrochemical impedance spectroscopy (EIS). A straightforward relationship between the membrane impedance, the thickness of selective layer and the mass transfer rate of phenol was obtained. A theoretical equation suggesting a linear relationship between the transfer efficiency and membrane resistance was proposed, which was confirmed by the experimental data. Moreover, aniline, as another contaminant was selected to validate the effectiveness and universality of this method. Therefore, EIS can be promisingly utilized for valid predication of the organic mass transfer performances of extractive membranes without time-consuming running of extraction experiments.

Bioinspired self-stratification fouling release silicone coating with strong adhesion to substrate

Silicone-based fouling release coatings (FRCs) are considered to be one of the promising eco-friendly antifouling technologies, while traditional silicone-based FRCs generally have poor adhesion to substrate. In this work, we developed a self-stratification silicone-based mussel-inspired bionic FRCs with strong substrate adhesion and good fouling-release ability. The coatings are silicone-based polybenzoxazine synthesized by natural phenolic derivatives (eugenol, urushiol and pyrogallic) and poly-(dimethylsiloxane)etherimide, with phenolic hydroxyl groups enriched at the bottom while hydrophobic siloxane groups at the surface. The coatings exhibit strong bonding to various substrates (stainless steel, aluminum, copper, epoxy and glass) under both dry and wet conditions. The maximum substrate adhesion strength of the coating is up to 3.6 MPa (six times greater than that of polydimethysiloxane (PDMS)) under dry condition and 3.0 MPa (five times greater than that of PDMS) under wet condition. While this silicone-based self-stratification fouling release coating addictive with a low modulus and surface energy as PDMS does, it showed an enhanced anti-bacteria and anti-algae adhesion abilities. The results indicate a great potential for the application of this concept of developing the fouling release marine coatings with high substrate adhesion.

Manufacturing of nanostructures with high aspect ratios using soft UV-nanoimprint lithography with bi- and trilayer resist systems

In this contribution we introduce new multilayer (bilayer and trilayer) resist systems for the generation of nanostructures with high aspect ratios of up to 14:1 on 4-in. full wafer scale. The bilayer stack consists of a bottom resist layer (lift off polymer LOR1A) and an UV-curable top resist layer (UV-NIL resist mr-NIL210 200 nm). The top resist is structured by UV-nanoimprint lithography with a soft polydimethysiloxane (PDMS) stamp (soft UV-NIL). After removal of the residual layer a wet chemical development is performed to achieve an isotropic undercut underneath the nanostructures in the top layer. This undercut is mandatory in order to perform a reliable and precise lift-off. The bilayer system is applicable on both silicon and fused silica. For a higher variety and combination of different resists, a trilayer system is investigated. A layer stack with new materials for bottom and top layer is presented. An intermediate layer made of silicon oxide by low temperature ICP-PECVD is added between a tailor-made top resist (mr-NIL213FC 200 nm) and an organic transfer layer (UL1). The intermediate layer serves as hard mask in order to etch the bottom layer isotropically utilizing a plasma etch process and thus replacing the wet-chemical development step. Subsequently, a thin metal layer is deposited onto the structured resist stack by electron beam evaporation. After lift-off, a nanostructured metal mask remains on the substrate providing a high selectivity during the following plasma etch step. A cryogenic ICPRIE etch process creates high aspect ratio nanostructures within the substrate. An aspect ratio of 14:1 was achieved.

Mitigation of membrane biofouling via immobilizing Ag-MOFs on composite membrane surface for extractive membrane bioreactor

The extractive membrane bioreactor (EMBR) combines an extractive membrane process and bioreactor to treat highly saline recalcitrant organic wastewater, in which the organic contaminations diffuse through a semi-permeable polydimethysiloxane (PDMS) composite membrane from the feed wastewater to the receiving biomedium. During the long-term EMBR operation, membrane biofouling is an inevitable phenomenon, which is one of the main obstacles impeding its wide applications. The excessive biofilm deposited on membrane surface could significantly reduce the organic mass transfer coefficient of composite membranes by more than 40%. Therefore, in this work, the silver (Ag)-metal organic frameworks (MOFs) were synthesized and immobilized on the PDMS surface of nanofibrous composite membranes to mitigate the membrane biofouling. The robustness of Ag-MOFs coating on membrane surface was well demonstrated by ultrasonic treatment. In addition, the silver nanoparticles (AgNPs) were coated on the PDMS surface of composite membranes for comparison. In contrast with the unmodified composite membrane #M0, the AgNPs-coated (#M1) and Ag-MOFs modified (#M2) composite membranes possessed less hydrophobic and negatively charged surfaces due to the coating layers. Although the modified membranes exhibited lower phenol mass transfer coefficients (k0’s) in the aqueous-aqueous extractive membrane process due to these additional modification layers, both #M1 and #M2 displayed better long-term performance in the 12-days continuous EMBR operations due to their excellent anti-biofouling properties. Moreover, #M2 exhibited the most stable EMBR performance among the composite membranes developed in this work and other reported membranes with a finally stabilized k0 of 33.0 × 10–7 m/s (89% of initial k0). The least amounts of proteins, polysaccharides and total suspended solids (TSS) on the surface of tested #M2 also demonstrated its outstanding biofouling resistance. This excellent anti-biofouling performance should be attributed to the stable, controlled and long-lasting Ag+release from Ag-MOFs, as well as its less hydrophobic and negative charged surface properties, which made #M2 undergo the k0’s increasing and gradual stabilization stages in the long-term EMBR operations.

Fabrication of Ag/PDMS Substrate of High-Density Hot Spots and Its Application in in situ Detection

Through a replacement reaction approach, Ag nanostructure was easily prepared on economical digital video disc (DVD) and polydimethysiloxane (PDMS) with surface structure duplicating from the former. Distinct nanoscale morphology was observed, featuring intersecting Ag nanoplates with abundant hot spots on the DVD and spherical Ag nanoparticles on the PDMS. Surface-enhanced Raman scattering (SERS) spectra, using crystal violet as a probe, revealed a superior enhancement effect in Ag/DVD versus that in Ag/PDMS. Considering the desirable flexibility and transparency of PDMS for in situ detection, we further developed a protocol to introduce intersecting Ag nanoplates onto the PDMS surface. The resulting Ag/PDMS substrate was endowed with remarkable sensitivity, excellent uniformity and good stability under mechanical bending. Furthermore, effective in situ detection of malachite green on fish was demonstrated, highlighting the great potential of our approach for the in situ detection of target molecules on a curved surface.

Fabrication of Polydimethysiloxane (PDMS) Dense Layer on Polyetherimide (PEI) Hollow Fiber Support for the Efficient CO2/N2 Separation Membranes.

The development of thin layer on hollow-fiber substrate has drawn great attention in the gas-separation process. In this work, polydimethysiloxane (PDMS)/polyetherimide (PEI) hollow-fiber membranes were prepared by using the dip-coating method. The prepared membranes were characterized by Scanning Electron Microscope (SEM), energy-dispersive X-ray spectroscopy (EDX), and gas permeance measurements. The concentration of PDMS solution and coating time revealed an important influence on the gas permeance and the thickness of the PDMS layer. It was confirmed from the SEM and EDX results that the PDMS layer’s thickness and the atomic content of silicon in the selective layer increased with the growth in coating time and the concentration of PDMS solution. The composite hollow-fiber membrane prepared from 15 wt% PDMS solution at 10 min coating time showed the best gas-separation performance with CO2 permeance of 51 GPU and CO2/N2 ideal selectivity of 21.

Designing the shape of supraparticles by controlling the apparent contact angle and contact line friction of droplets

Surface-templated evaporation-driven supraparticle synthesis is a versatile method for supraparticle fabrication. A supraparticle is formed by drying droplet of a colloidal dispersion on liquid repellent surfaces, allowing precise control of the size and mean composition of the supraparticles. The crucial factor determining the morphology is the motion of the contact line of the dispersion droplet on the liquid repellent surface. Here, we study effects of (i) the apparent contact angle and (ii) the contact line friction of a droplet on the shape of the supraparticle. In order to change the initial apparent contact angle of the dispersion droplet a surfactant was added to decrease surface tension. In addition, two different liquid repellent surfaces were used: a polydimethysiloxane (PDMS) grafted surface and a lubricated surface. Both surfaces exhibited distinctly different contact line friction during evaporation. As the initial contact angle of a droplet decreases and friction of a contact line increases, flatter supraparticles are fabricated. By using this simple manipulation principle, eventually, various shapes of supraparticles can be obtained, such as mushroom, hemispherical, convex lens, and disk shapes. This study presents fundamental and critical information that allow us to manipulate the shape of a supraparticle via surface-templated evaporation-driven synthesis that increases the scalability of supraparticles for use in a wide range of applications.

Transparent PDMS Bioreactors for the Fabrication and Analysis of Multi-Layer Pre-vascularized Hydrogels Under Continuous Perfusion.

Tissue engineering in combination with stem cell technology has the potential to revolutionize human healthcare. It aims at the generation of artificial tissues that can mimic the original with complex functions for medical applications. However, even the best current designs are limited in size, if the transport of nutrients and oxygen to the cells and the removal of cellular metabolites waste is mainly dependent on passive diffusion. Incorporation of functional biomimetic vasculature within tissue engineered constructs can overcome this shortcoming. Here, we developed a novel strategy using 3D printing and injection molding technology to customize multilayer hydrogel constructs with pre-vascularized structures in transparent Polydimethysiloxane (PDMS) bioreactors. These bioreactors can be directly connected to continuous perfusion systems without complicated construct assembling. Mimicking natural layer-structures of vascular walls, multilayer vessel constructs were fabricated with cell-laden fibrin and collagen gels, respectively. The multilayer design allows functional organization of multiple cell types, i.e., mesenchymal stem cells (MSCs) in outer layer, human umbilical vein endothelial cells (HUVECs) the inner layer and smooth muscle cells in between MSCs and HUVECs layers. Multiplex layers with different cell types showed clear boundaries and growth along the hydrogel layers. This work demonstrates a rapid, cost-effective, and practical method to fabricate customized 3D-multilayer vascular models. It allows precise design of parameters like length, thickness, diameter of lumens and the whole vessel constructs resembling the natural tissue in detail without the need of sophisticated skills or equipment. The ready-to-use bioreactor with hydrogel constructs could be used for biomedical applications including pre-vascularization for transplantable engineered tissue or studies of vascular biology.

Facile Fabrication of 3D Porous Sponges Coated with Synergistic Carbon Black/Multiwalled Carbon Nanotubes for Tactile Sensing Applications.

Recently, flexible tactile sensors based on three-dimensional (3D) porous conductive composites, endowed with high sensitivity, a wide sensing range, fast response, and the capability to detect low pressures, have aroused considerable attention. These sensors have been employed in different practical domain areas such as artificial skin, healthcare systems, and human–machine interaction. In this study, a facile, cost-efficient method is proposed for fabricating a highly sensitive piezoresistive tactile sensor based on a 3D porous dielectric layer. The proposed sensor is designed with a simple dip-coating homogeneous synergetic conductive network of carbon black (CB) and multi-walled carbon nanotube (MWCNTs) composite on polydimethysiloxane (PDMS) sponge skeletons. The unique combination of a 3D porous structure, with hybrid conductive networks of CB/MWCNTs displayed a superior elasticity, with outstanding electrical characterization under external compression. The piezoresistive tactile sensor exhibited a high sensitivity of (15 kPa−1), with a rapid response time (100 ms), the capability of detecting both large and small compressive strains, as well as excellent mechanical deformability and stability over 1000 cycles. Benefiting from a long-term stability, fast response, and low-detection limit, the piezoresistive sensor was successfully utilized in monitoring human physiological signals, including finger heart rate, pulses, knee bending, respiration, and finger grabbing motions during the process of picking up an object. Furthermore, a comprehensive performance of the sensor was carried out, and the sensor’s design fulfilled vital evaluation metrics, such as low-cost and simplicity in the fabrication process. Thus, 3D porous-based piezoresistive tactile sensors could rapidly promote the development of high-performance flexible sensors, and make them very attractive for an enormous range of potential applications in healthcare devices, wearable electronics, and intelligent robotic systems.

Finite element simulation of friction and adhesion attributed contact of bio-inspired gecko-mimetic PDMS micro-flaps with SiO2 spherical surface

The remarkable tribological attributes of the gecko feet have grown much interest in the field of biomimetic tribology over the past two decades. It has been shown that the complexity of friction and adhesion phenomena made it difficult to transfer these exceptional properties into fully functional smart, dry, micro patterned adhesives. The latter, combined with the relative lack of literature on computational oriented studies on these phenomena, is the motive of the current work. Here, a 2D time-dependent finite element model of friction and adhesion attributed contact of polydimethysiloxane (PDMS) micro flaps with a smooth SiO2 spherical surface is presented. The model is tested through simulations concerning changes in the disc curvature, the flap density, as well as different disc mounting heights, representing the effect of preload. Furthermore, the effect of tribological parameters of adhesion and friction coefficient is discussed. Finally, the effect of the use of two hyperelastic material models was examined.

Inhibition of Efflorescence in Na-Based Geopolymer Inorganic Coating.

Coating is one of the most important high-value-added application cases in geopolymer materials. However, efflorescence can easily cause discoloration and reduce the esthetic impression of the coating surface, thus limiting its application; hence, inhibition of efflorescence is one of the most important techniques in the application of geopolymer coatings. Efflorescence is a spontaneous behavior in a Na-based geopolymer, involving the migration of soluble alkalis. Alkalis are dissolved by water and diffuse to the material surface through nocuous pores, and then react with CO2 to produce white carbonate products. To inhibit efflorescence in geopolymer coating, this article reports a structure modification method using polydimethy siloxane (PS) and mica. To explore the inhibition mechanism, the effects of PS and mica on the pore structure, water absorption, alkali leaching, and efflorescence product were investigated. The experimental results showed that a harmful pore structure and instinctive water absorption of the geopolymer strongly contributed to efflorescence. PS and mica could reduce the pore size distribution and porosity and are helpful to establish a waterproof structure, leading to water absorption and the alkali leaching rate being significantly suppressed. Both high water glass and water content play a critical role in the increase of efflorescence, but even under a high content of water glass and water used in geopolymer coating, this method shows an 80–90% efflorescence reduction, which is much higher than that of other studies. In practical engineering, when the geopolymer coating is applied after modification, even if it is exposed to the field environment for a long time, there is no efflorescence deposit on the coating surface. It is feasible to limit water ingression in a geopolymer, which effectively blocks the efflorescence reaction process. This method is simple and practical and can be applied in practical engineering applications of geopolymer coatings conveniently.

Anti‐liquid‐Interfering and Bacterially Antiadhesive Strategy for Highly Stretchable and Ultrasensitive Strain Sensors Based on Cassie‐Baxter Wetting State

AbstractAs a large number of strain sensors are put into practical use, their stability should be considered, especially in harsh environments containing water or microorganisms, which could affect strain sensing. Herein, a novel strategy to overcome liquid interference is proposed. The strain sensor is constructed with a sandwich architecture through layer‐by‐layer (LBL) spray‐coating of a 3‐(aminopropyl)triethoxysilane (APTES) bonding layer and multi‐walled carbon nanotubes/graphene (MWCNT/G) conductive layers on an elastomeric polydimethysiloxane (PDMS) substrate, and is further decorated with silver (Ag) nanoparticles and the (heptadecafluoro‐1,1,2,2‐tetradecyl) trimethoxysilane (FAS, F in short) to obtain a F/Ag/MWCNG/G‐PDMS (FAMG) strain sensor. The superhydrophobicity and underwater oleophobicity of the outer cover layer causes this FAMG strain sensor surface to exhibit stable strain sensing resistant to liquid interference upon stretching in the Cassie−Baxter wetting state, and resistance to bacterial adhesion (Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli)). The sensor attains ultrasensitivity (with a maximum gauge factor of 1989 in the condition of liquid interference), broad strain range (0.1–170%), fast response time (150 ms), and stable response after 1000 stretching–releasing cycles. The ultrasensitivity is provided by propagation of cracks in MWCNT/G conductive layers and terminal fracture of the intermediate separating layers (APTES/MWCNT/G). The microbridge effect of MWCNTs and slippage of APTES/MWCNT/G provide a large strain range. The FAMG strain sensor is successfully used to monitor a series of human activities and an electronic bird under artificial rain and bacterial droplets, indicating the potential use of this sensor in complex environments.

Separation of BTX Fraction from Reservoir Brines by Sorption onto Hydrophobized Biomass in a Fixed-Bed-Column System

Oily brine from the gas and oil industries remains the most difficult wastewater to treat due to its complex chemical composition, which includes aromatic hydrocarbons. Even at low concentrations, the presence of BTX (benzene, toluene, xylenes) can be extremely harmful to aquatic ecosystems. Fixed-bed adsorption columns are recommended for oily water treatment due to their flexibility and easy operation. In this research, pine sawdust modified with polydimethysiloxane (PDMS) and hydrophobic nanosilica was applied as a sorbent in a filtration system. The surface modification of raw fiber allowed to change its morphology and increase the roughness of it. The Yoon–Nelson, Bohart–Adams, Clark, and Belter models were applied to simulate continuous biosorption. The Bohart–Adams model strongly correlated with the experimental data and described the whole dynamic behavior of the column. The effect of feed flow rate (10–50 mL/min) on breakthrough characteristics was determined. Both the breakthrough and saturation time decreased as the flow rate increased. This study indicated that hydrophobized pine sawdust is an effective low-cost potential biosorbent for the removal of BTX fraction from produced water in continuous column mode.