Hydrogel Layer Research Articles

3D Printing of Branched Polyurethane with Tough Mechanical Properties for Stretchable Sensors

The poor mechanical properties and difficulties in manufacturing complex structures seriously limit the applications of elastomers especially in flexible electronic sensor. Herein, a series of polyether amine (PEA) grafted polyurethane acrylate oligomers (PUA‐g‐PEAs) and the corresponding low‐viscosity UV‐curable flexible 3D printing elastomers (PEA‐1/IDAs) are synthesized. The results show that a certain amount of PEA branch exactly has strengthening and toughening effect on polyurethane, resulting in 12% increase in tensile strength and 44% increase in elongation at break of PUA‐g‐PEA‐1. When mixed PUA‐g‐PEA‐1with acrylimorpholine and IDA in the ratio of 3:5:2, PEA‐1/IDA‐20 with best overall mechanical properties is obtained. Its tensile strength and elongation at break are 18.5 MPa and 297.4%, respectively. The unprecedented fatigue resistance of PEA‐1/IDA‐20 ensures that it can withstand 100 compression cycles at 80% strain without damage. Besides, piezoresistive sensors and wearable finger guard sensors are fabricated by laminating a layer of conductive hydrogel on the surface of the 3D‐printed devices. The impressive mechanical properties and 3D printing producing process of this branched PUA endow it with great potentials in advanced electronic sensors.

A Temperature‐Sensing Hydrogel Coating on The Medical Catheter

AbstractMedical surgical catheters are widely used in the medical field for drug delivery or postoperative drainage. However, infections associated with local temperature rise often occur at the catheter‐tissue interface, resulting in irreversible pathological damage, cognitive behavioral abnormalities, or even an increased risk of mortality if not monitored in time. Herein, an in situ temperature‐sensing hydrogel coating on the outer surface of medical surgical catheters for real‐time infection monitoring is developed. The hydrogel coating exhibits a record temperature coefficient of resistance of 2.90% °C−1 and maintains stable in vivo. Besides, the hydrogel layer forms a mechanically compatible catheter‐tissue interface and minimizes the risk of inflammatory responses due to its tissue‐like softness (Young's modulus of 4.24 kPa). By applying it in the early detection of infections in the brain of SD rats, the individual survival rate has increased to 90% with timely intervention.

Electromagnetic triggering with metallic microparticles for prospective biomedical applications

Biomedical devices like microfluidic chips and externally triggered drug delivery devices can activate their drug release mechanisms using external triggers such as ultrasound, electric field, alternating magnetic field and electromagnetic radiation. This work proposes an electromagnetic triggering technique based on the interaction of electromagnetic waves with metallic microparticles that are placed under a temperatures sensitive hydrogel. The heating effect of the electromagnetic interaction results in a localized rise in temperature. The change in temperature manipulates the physical structure of the hydrogel which can be used for releasing drug particles in a drug delivery device or controlling fluid flow in a microfluidic chip. The design and operation of the device is explained with the help of Multiphysics simulations in COMSOL followed by experimental verification using sub-100-μm iron powder particles placed under 2 mm thick layer of a thermosensitive hydrogel. The primary experiments for the device operating at 2.4 GHz and 145 mW show a temperature increment of 2.7 °C after 50 min.

Factors affecting diffusion of polar organic compounds in agarose hydrogel applied to control mass transfer in passive samplers.

Diffusive hydrogel-based passive sampler (HPS) based on diffusive gradients in thin films (DGT) is designed for monitoring polar organic contaminants in the aquatic environment. DGT technique controls the compound's overall uptake rate by adding a hydrogel layer of known thickness, which minimizes the importance of the resistive water boundary layer in the compound uptake process. In this work, we investigated several factors which may influence the diffusion of a range of aquatic contaminants in 1.5% agarose hydrogel. Diffusion in hydrogel was tested using the sheet stacking method. We demonstrated that a thin nylon netting incorporated into the diffusive hydrogel for mechanical strengthening does not significantly affect the diffusion of 11 perfluoroalkyl compounds. Further, we investigated the effect of pH in the range from 3 to 11 on the diffusion of a range of 39 aromatic amines (AAs)-36 aromatic, 2 aliphatic, and azobenzene in hydrogel. AAs were chosen as representatives of compounds with pH-dependent dissociation in water. Analysis of variance showed no significant difference in meandiffusion coefficient log D value at five pH values. The demonstration that the diffusion coefficient D and thus the sampling rate Rs are independent on pH simplifies the interpretation of data from field studies because we can neglect the influence of pH on the Rs. log D values (m2 s-1) of tested AAs ranged from to - 9.77 for 3,3'-dimethylbenzidine to - 9.19 for azobenzene. A negative correlation of log D with molar mass (log M) and molecular volume (log Vm) was observed (R = - 0.57 and - 0.56, respectively). The diffusion coefficient presents a critical parameter for the sampling rate estimation of HPS. Theoretical sampling rates Rs of AAs were calculated for a HPS using the average D values. TheoreticalRs values calculated for AAs at 22°C ranged from 29 mL day-1 for 3,3'-dimethylbenzidine to 106 mL day-1 for 2-aminopyridine. Our calculated values of Rs are in the same range as those already published for a range of low-molecular polar organic contaminants, which supports the possibility of deriving sampler performance parameters in the field from laboratory-derived diffusivity of analytes in hydrogel.

Fewer polymer chains but higher adhesion: How gradient-stiffness hydrogel layers mediate adhesion through network stretch.

The presence of gradient softer outer layers, commonly observed in biological systems (such as cartilage and ocular tissues), as well as synthetic crosslinked hydrogels, profoundly influences their interactions with opposing surfaces. Our prior research demonstrated that gradient-stiffness hydrogel layers, characterized by increasing elasticity with depth, control contact mechanics, particularly in proximity to the layer thickness. We postulate that the distribution of polymers within these gradient layers imparts extraordinary stretch and adhesion characteristics due to network adaptability and stress-induced reorganization. To investigate this phenomenon, we utilized Atomic Force Microscopy nanoindentation to assess the depth-dependent adhesion behavior of polyacrylamide hydrogels with varying gradient layer thicknesses. Two gradient layer thicknesses were achieved by employing different molding materials: glass and polyoxymethylene (POM). Glass-molded hydrogels exhibited a thinner gradient layer alongside a stiffer bulk layer compared to their POM-molded counterparts. In indentation experiments, the POM-molded hydrogel had larger adhesion compared to glass-molded hydrogel. We find that indenting within the gradient layer engenders increased load-unload hysteresis due to heightened fluid transport in the sparse outer polymer network. Consequently, this led to augmented adhesion and work of separation at shallow depths. We suggest that the prominent stretching capability of the sparse outer polymer network during probe retraction contributes to enhanced adhesion. The Maugis-Dugdale adhesive model only fits well to indentations on the thin layer or indentations which engage significantly with the bulk. These results facilitate a comprehensive characterization of adhesion mechanics in gradient-stiffness hydrogels, which could foster their application across emerging contexts in health science and environmental domains.

Development of a Novel Hierarchically Biofabricated Blood Vessel Mimic Decorated with Three Vascular Cell Populations for the Reconstruction of Small-Diameter Arteries.

The availability of grafts to replace small-diameter arteries remains an unmet clinical need. Here, the validated methodology is reported for a novel hybrid tissue-engineered vascular graft that aims to match the natural structure of small-size arteries. The blood vessel mimic (BVM) comprises an internal conduit of co-electrospun gelatin and polycaprolactone (PCL) nanofibers (corresponding to the tunica intima of an artery), reinforced by an additional layer of PCL aligned fibers (the internal elastic membrane). Endothelial cells are deposited onto the luminal surface using a rotative bioreactor. A bioprinting system extrudes two concentric cell-laden hydrogel layers containing respectively vascular smooth muscle cells and pericytes to create the tunica media and adventitia. The semi-automated cellularization process reduces the production and maturation time to 6 days. After the evaluation of mechanical properties, cellular viability, hemocompatibility, and suturability, the BVM is successfully implanted in the left pulmonary artery of swine. Here, the BVM showed good hemostatic properties, capability to withstand blood pressure, and patency at 5 weeks post-implantation. These promising data open a new avenue to developing an artery-like product for reconstructing small-diameter blood vessels.

Biofabrication of Heterogeneous, Multi‐Layered, and Human‐Scale Tissue Transplants Using Eluting Mold Casting

AbstractThe creation of multi‐tissue auricular transplants for the treatment of microtia is a challenge due to the complex and layered structure of this anatomical tissue. A novel casting technique for the 3D biofabrication of heterogeneous, multi‐layered, and human‐scale tissue transplants using eluting agarose molds is presented. The molds are generated by casting agarose into custom 3D‐printed containers, termed metamolds, optimized to facilitate the hydrogel casting process based on geometric and topological constraints. Casting yields high resolution (50 µm) and allows for subsequent casting of further hydrogel layers on the transplant. Multi‐layered auricular constructs are fabricated on a cartilage core consisting of a hyaluronic acid‐alginate double network and an adjacent gelatin‐based dermal layer. Bonding between adjacent layers is achieved by orthogonal physical and enzymatic crosslinking of residual functional groups between each layer. Material composition and culture duration are optimized for each layer allowing for maturation into cartilaginous and pre‐vascularized dermal tissues. To demonstrate the scalability of this technique for the biofabrication of human‐sized transplants, bi‐layered human‐sized ears are cast. Overall, this novel casting technique offers a promising approach for the fabrication of complex tissue grafts, overcoming the limitations of other traditional biofabrication methods.

Catheter-Assisted Bioinspired Adhesive Magnetic Soft Millirobot for Drug Delivery.

Soft millirobots have evolved into various therapeutic applications in the medical field, including for vascular dredging, cell transportation, and drug delivery, owing to adaptability to their surroundings. However, most soft millirobots cannot quickly enter, retrieve, and maintain operations in their original locations after removing the external actuation field. This study introduces a soft magnetic millirobot for targeted medicine delivery that can be transported into the body through a catheter and anchored to the tissues. The millirobot has a bilayer adhesive body with a mussel-inspired hydrogel layer and an octopus-inspired magnetic structural layer. It completes entry and retrieval with the assistance of a medical catheter based on the difference between the adhesion of the hydrogel layer in air and water. The millirobot can operate in multiple modes of motion under external magnetic fields and underwater tissue adhesion after self-unfolding with the structural layer. The adaptability and recyclability of the millirobots are demonstrated using a stomach model. Combined with ultrasound (US) imaging, operational feasibility within organisms is shown in isolated small intestines. In addition, a highly efficient targeted drug delivery is confirmed using a fluorescence imaging system. Therefore, the proposed soft magnetic millirobots have significant potential for medical applications.

Droplet absorption and spreading into thin layers of polymer hydrogels

From biological tissues to microactuators and absorption of solvents into layers of paint, macroscopically non-porous materials with the capacity to swell when in contact with a solvent are ubiquitous. In these systems, owing to strong solid–fluid interactions, chemically driven flows can yield large geometric changes. We study experimentally and theoretically the canonical problem of the swelling of a thin hydrogel layer by a single water drop. Using a bespoke experimental set-up, we observe fast absorption leading to a radially spreading axisymmetric blister. We use a fully three-dimensional linear poroelastic framework with nonlinear kinematic equations to obtain governing equations, which we then reduce with thin-layer scalings to a one-dimensional nonlinear diffusion equation for the evolution of the blister geometry. In the limits of large and small deformations, the evolution of the blister characteristic height and radius are self-similar, following power laws in time. Our experimental measurements show that the evolution of the blister is broadly within the theoretical predictions in the large and small deformation regimes. In the general intermediate deformation regime, the measurements are well captured by our reduced one-dimensional diffusion model, which does not require the sophisticated and computationally expensive numerical approaches necessary for the original two-dimensional nonlinear coupled transport problem. By adapting modelling techniques from the fluid dynamics of thin porous elastic layers to a polymer swelling problem, our modelling framework extends the range of polymer swelling problems that can be treated with semi-analytical methods. Moreover, our detailed experimental data can serve as a test case for future nonlinear poroelastic frameworks of swelling polymer materials.

In-situ gelation based on rapid crosslinking: A versatile bionic water-based lubrication strategy

Hydrogel is emerging as a new water-based lubricant due to its enhanced load-bearing capacity and lubrication effect in industrial process and biological application. But the loss and degradation issues in long-term usage become a bottleneck for its further development. Hence how to realize the continuous supplement of hydrogel lubricant in the friction process with an instant response to shear stress becomes a highly expected goal. In this study, inspired by the regeneration of cartilage, a surface engineering strategy is first put forward based on chemically active interface and cross-linking gelation, in which Borax as cross-linking agent is released in-situ with the grinding debris in friction process from polyimide/Borax composite coating into the polyvinyl alcohol (PVA) solution, followed with instant gelation to form effective lubrication mediate layer between contact interface. The combined experimental and molecular dynamics simulation studies suggest that the enhanced intermolecular interaction in hydrogel layer which highly depends on cross-linking degree, together with hydrodynamic effect is responsible for the excellent lubrication and high adaptability to various working condition even under the high contact stress of 175.90 MPa. The similar tribological performances in other chemically active interface-fluid combination systems demonstrate the versatility of this facile strategy.

Electrochemically Controlled Release from a Thin Hydrogel Layer.

In this study, we present a thermoresponsive thin hydrogel layer based on poly(N-isopropylacrylamide), functionalized with β-cyclodextrin groups (p(NIPA-βCD)), as a novel electrochemically controlled release system. This thin hydrogel layer was synthesized and simultaneously attached to the surface of a Au quartz crystal microbalance (QCM) electrode using electrochemically induced free radical polymerization. The process was induced and monitored using cyclic voltammetry and a quartz crystal microbalance with dissipation monitoring (QCM-D), respectively. The properties of the thin layer were investigated by using QCM-D and scanning electron microscopy (SEM). The incorporation of β-cyclodextrin moieties within the polymer network allowed rhodamine B dye modified with ferrocene (RdFc), serving as a model metallodrug, to accumulate in the p(NIPA-βCD) layer through host-guest inclusion complex formation. The redox properties of the electroactive p(NIPA-βCD/RdFc) layer and the dissociation of the host-guest complex triggered by changes in the oxidation state of the ferrocene groups were investigated. It was found that oxidation of the ferrocene moieties led to the release of RdFc. It was crucial to achieve precise control over the release of RdFc by applying the appropriate electrochemical signal, specifically, by applying the appropriate potential to the electrode. Importantly, the electrochemically controlled RdFc release process was performed at a temperature similar to that of the human body and monitored using a spectrofluorimetric technique. The presented system appears to be particularly suitable for transdermal delivery and delivery from intrabody implants.

Depth profiling via nanoindentation for characterisation of the elastic modulus and hydraulic properties of thin hydrogel layers

The accurate determination of the mechanical properties of hydrogels is of fundamental importance for a range of applications, including in assessing the effect of stiffness on cell behaviour. This is a particular issue when using thin hydrogel layers adherent to stiff substrate supports, as the apparent stiffness can be significantly influenced by the constraint of the underlying impermeable substrate, leading to inaccurate measurements of the elastic modulus and permeability of thin hydrogel layers. This study used depth profiling nanoindentation and a poroelastic model for spherical indentation to identify the elastic moduli and hydraulic conductivity of thin polyacrylamide (PAAm) hydrogel layers (∼27 μm–782 μm thick) on impermeable substrates. The apparent stiffness of thin PAAm layers increased with indentation depth and was significantly greater than those of thicker hydrogels, which showed no influence of indentation depth. The hydraulic conductivity decreased as the geometrical confinement of hydrogels increased, indicating that the fluid became more constrained within the confinement areas. The impact of geometrical confinement on the apparent modulus and hydraulic conductivity of thin PAAm hydrogel layers was then established, and their elastic moduli and intrinsic permeability were determined in relation to this effect. This study offers valuable insights into the mechanical characterisation of thin PAAm hydrogel layers used for the fundamental study of cell mechanobiology.

Design of an anti-scald photothermal hydrogel for rapid bacteria removal and hemostasis

Applying hydrogels as medical dressing in treating wounds has become a research hotspot in recent years. Photothermal hydrogels with antibacterial properties and favorable biocompatibility offer great potential for treating infected wounds. However, the risks associated with photosensitizer leakage and excessive heat cause edema and vascular damage, cutting off the nutrients and oxygen supply and slowing the wound healing rate. Herein, a bilayer hydrogel (AuDG2) containing the photothermal and heat-absorbing hydrogel layers is developed to generate adequate heat for quick bacteria removal and tissue protection. In this system, Au nanoparticles are firmly fixed to the nano-hydroxyapatite and coated in the photothermal hydrogel layer, effectively avoiding the leakage of the photosensitizer. Near-infrared imaging shows AuDG2 hydrogel maintains 48–50 °C at the wound by heat exchange between the two layers of it. This property enables AuDG2 to have an 89.68 % clearance rate against Staphylococcusaureus (S. aureus) and a 73.03 % removal efficiency of Escherichia coli (E. coli) within 5 min, increasing the healing area of infected wounds by 26.45 % compared to the normal saline treatment group, without adverse effects from burns, and evaporate water from the blood to stop blooding in a very short time. This anti-scald photothermal hydrogel structure is simple in preparation, offering the possibility to mitigate the side effects of photothermal therapy.

Metal ion reinforced hydrogel/Ti6Al4V bionic composite joint bearing interface with extraordinary mechanical and biotribological properties

Artificial joints are facing challenges of high friction and severe wear, which limits their application in the high stress-loading conditions of joint bearing interfaces. Inspired by the soft/hard structure of articular cartilage/subchondral bone in a natural joint and the presence of lubricating proteoglycan/lubricin on cartilage surface, a polyanionic hydrogel coating rich in carboxylates/sulfonates was constructed on a porous Ti6Al4V substrate through ultraviolet radiation combined with metal ion bridging method. In addition, metal ions were adopted to form ionic coordination bonds with the polyanionic hydrogel layer to enhance its mechanical properties. Characterization results showed that the hydrogel layer was firmly adhered to the porous Ti6Al4V surface, and the as-obtained metal ion reinforced hydrogel/Ti6Al4V joint bearing interfaces displayed improved hydrophilicity and mechanical properties. Notably, compared with Al3+ and Fe3+, Ca2+ reinforced PVA-PAA-PSPMK/DT-Ti6Al4V joint bearing interface in deionized water exhibited a lower friction coefficient (∼0.068), which was similar to that of fresh porcine cartilage, and only slight scratches on the worn surface. Moreover, after 4 h of lubrication in phosphate buffer (PBS) or calf serum, its stable and low friction coefficient further revealed its great application potential in physiological environments. The lubrication mechanisms were also discussed in detail. This work presents a simple and effective method to develop hydrogel/Ti6Al4V bionic composite joint bearing interfaces with advanced performance.

Fabrication of flexible accelerated-wound-healing chitosan/dopamine-based bilayer hydrogels for strain sensors

Flexible conductive hydrogels have great potential for healthcare and human motion sensing. However, it is difficult to simultaneously achieve conductive hydrogel epidermal sensors with reliable adhesion capabilities and excellent sensing properties, as well as accelerated wound healing performance in wearable hydrogels. Here, an epidermal sensor with excellent adhesion (0.6 kPa) and tensile strain (218.0 %) properties was assembled from an easy-to-prepare bilayer antimicrobial hydrogel, which effectively accelerates wound healing, as well as for human motion sensing. The upper hydrogel layer was composed of PVA, which could effectively enhance the mechanical properties of the bilayer hydrogel. The lower hydrogel layer consisted of polyacrylamide (PAm) and chitosan-dopamine (CC-DA). PAm with good adhesion properties adhered effectively to the skin surface. CC-DA not only had adhesion properties, but also has good antibacterial effects. It inhibited the growth of bacteria, which assisted in wound healing and infection prevention. Therefore, the design of the bilayer hydrogel combined the mechanical enhancement of PVA with the adhesion properties and antimicrobial effect of PAm and CC-DA to provide better wound repair. In addition, the double-layer hydrogel with good electrical conductivity (1.65 S·m−1) could sensitively monitor the tiny electrophysiological signals emitted by the human body during exercise rehabilitation training.

Triple-defense design of multifunctional superhydrophilic surface with outstanding underwater superoleophobicity, anti-oil-fouling properties, and high transparency

Superhydrophilic surfaces with underwater superoleophobicity have attracted widely attention in various fields, especially in the frequent ocean oil-spill accidents and increasing industrial oil leakage environments. However, controlling the oil fouling properties on these superhydrophilic surfaces is challenging since the potential solutions to prevent oil fouling tend to interfere with optical transparency. To reconcile the conflict between anti-oil-fouling properties and transparency, a triple-defense designed strategy by integrating mussel-inspired polycation coating, colorless hydrogel, and mineralized amorphous inorganic materials is introduced to a surface guaranteed superhydrophilicity/underwater superoleophobicity, superior active anti-oil-fouling properties, and high transparency. Thanks to the triple-defense design strategy, a synergistic effect originating from the cooperation of third defense layer of polycation coating, second defense layer of hydrogel, and first defense layer of amorphous inorganic materials gives rise to the superior active anti-oil-fouling properties to this superhydrophilic surface, regardless of oils. Independent of the environment, the surface enables to be aggressively infused by water, thus active de-wetting of diverse oils from the surfaces upon water action. The colorless organic coating and amorphous inorganic materials gives rise to the high underwater transparency. This substrate-independent multifunctional coating can be decorated on diverse substrates, allowing it used in various fields, such as oily wastewater treatment, anti-fogging, and underwater optical devices.

Bioinspired 3D-printed scaffold embedding DDAB-nano ZnO/nanofibrous microspheres for regenerative diabetic wound healing

There is a constant demand for novel materials/biomedical devices to accelerate the healing of hard-to-heal wounds. Herein, an innovative 3D-printed bioinspired construct was developed as an antibacterial/regenerative scaffold for diabetic wound healing. Hyaluronic/chitosan (HA/CS) ink was used to fabricate a bilayer scaffold comprising a dense plain hydrogel layer topping an antibacterial/regenerative nanofibrous layer obtained by incorporating the hydrogel with polylactic acid nanofibrous microspheres (MS). These were embedded with nano ZnO (ZNP) or didecyldimethylammonium bromide (DDAB)-treated ZNP (D-ZNP) to generate the antibacterial/healing nano/micro hybrid biomaterials, Z-MS@scaffold and DZ-MS@scaffold. Plain and composite scaffolds incorporating blank MS (blank MS@scaffold) or MS-free ZNP@scaffold and D-ZNP@scaffold were used for comparison. 3D printed bilayer constructs with customizable porosity were obtained as verified by SEM. The DZ-MS@scaffold exhibited the largest total pore area as well as the highest water-uptake capacity and in vitro antibacterial activity. Treatment of Staphylococcus aureus-infected full thickness diabetic wounds in rats indicated superiority of DZ-MS@scaffold as evidenced by multiple assessments. The scaffold afforded 95% wound-closure, infection suppression, effective regulation of healing-associated biomarkers as well as regeneration of skin structure in 14 d. On the other hand, healing of non-diabetic acute wounds was effectively accelerated by the simpler less porous Z-MS@scaffold. Information is provided for the first-time on the 3D printing of nanofibrous scaffolds using non-electrospun injectable bioactive nano/micro particulate constructs, an innovative ZNP-functionalized 3D-printed formulation and the distinct bioactivity of D-ZNP as a powerful antibacterial/wound healing promotor. In addition, findings underscored the crucial role of nanofibrous-MS carrier in enhancing the physicochemical, antibacterial, and wound regenerative properties of DDAB-nano ZnO. In conclusion, innovative 3D-printed DZ-MS@scaffold merging the MS-boosted multiple functionalities of ZNP and DDAB, the structural characteristics of nanofibrous MS in addition to those of the 3D-printed bilayer scaffold, provide a versatile bioactive material platform for diabetic wound healing and other biomedical applications.

Nanocomposite Hydrogel Engineered Janus Membrane for Membrane Distillation with Robust Fouling, Wetting, and Scaling Resistance.

Membrane distillation (MD) is considered to be rather promising for high-salinity wastewater reclamation. However, its practical viability is seriously challenged by membrane wetting, fouling, and scaling issues arising from the complex components of hypersaline wastewater. It remains extremely difficult to overcome all three challenges at the same time. Herein, a nanocomposite hydrogel engineered Janus membrane has been facilely constructed for desired wetting/fouling/scaling-free properties, where a cellulose nanocrystal (CNC) composite hydrogel layer is formed in situ atop a microporous hydrophobic polytetrafluoroethylene (PTFE) substrate intermediated by an adhesive layer. By the synergies of the elevated membrane liquid entry pressure, inhibited surfactant diffusion, and highly hydratable surface imparted by the hydrogel/CNC (HC) layer, the resultant HC-PTFE membrane exhibits robust resistance to surfactant-induced wetting and oil fouling during 120 h of MD operation. Meanwhile, owing to the dense and hydroxyl-abundant surface, it is capable of mitigating gypsum scaling and scaling-induced wetting, resulting in a high normalized flux and low distillate conductivity at a concentration factor of 5.2. Importantly, the HC-PTFE membrane enables direct desalination of real hypersaline wastewater containing broad-spectrum foulants with stable vapor flux and robust salt rejection (99.90%) during long-term operation, demonstrating its great potential for wastewater management in industrial scenarios.

Fabrication, Characterization, and In Vitro Cytotoxicity Assessment of Tri-Layered Multifunctional Scaffold for Effective Chronic Wound Healing.

Chronic wounds have been a global health risk that demands intensive exploration. A tri-layered biomaterial scaffold has been developed for skin wounds. The top layer of the scaffold is superhydrophobic, and the bottom layer is hydrophilic, both of which were electrospun using recycled expanded polystyrene (EPS) and monofilament fishing line (MFL), respectively. The intermediate layer of the scaffold comprised hydrogel by cross-linking chitosan (CS) with polyethylene glycol. The surface morphology, surface chemistry, thermal degradation, and wettability characteristics of each layer of the scaffold were examined. Also, the antibacterial activity and in vitro cytotoxicity study on the combined tri-layered scaffold were assessed against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Data revealed exceptional water repellency of the heat-treated electrospun top superhydrophobic layer (TSL) with a high-water contact angle (WCA) of 172.44°. A TSL with 15 wt% of micro-/nano-inclusions had the best thermal stability above 400 °C. The bottom hydrophilic layer (BHL) displayed a WCA of 9.91°. Therapeutically, the synergistic effect of the combined tri-layered scaffold significantly inhibited bacteria growth by 70.5% for E. coli and 68.6% for S. aureus. Furthermore, cell viability is enhanced when PEG is included as part of the intermediate CS hydrogel layer (ICHL) composition.

Thermoresponsive double-network hydrogel/elastomer hybrid bilayer laminates with high interfacial toughness and controllable shape deformations

Thermoresponsive hydrogel-based actuators have shown great potential in tissue engineering, biosensors and soft robots, while the preparation of temperature-driven bilayer hydrogel actuators with rapid responseness and recovery properties remains a challenge. Inspired by the layered heterostructure of human skin, we developed a Janus bilayer structure actuator consisting of thermoresponsive double network (TDN) hydrogel and polydimethylsiloxane (PDMS) elastomer with tough interface adhesion. Specifically, PNaAMPS/P(NIPAM-co-AAm) TDN hydrogel via photocopolymerization of N-isopropyl acrylamide (NIPAM) and acrylamide (AAm) and reinforced by microgel poly(2-acrylamide-2-methylpropane sulfonate sodium salt) (PNaAMPS) was in situ grafted onto benzophenone-activated PDMS surface, exhibiting strong interface adhesion (628 Jm-2 adhesion energy). The thermoresponsive shape deformations of the double-layer structure actuator were controllable by adjusting hydrogel/elastomer thickness ratio and introduction of metal ions, taking advantage of the different swelling and shrinkage characteristics of the hydrogel layer and the elastomer layer. The TDN/PDMS bilayer structure actuator, which integrates the "Janus" structure, thermal responsiveness and photothermal conversion, provides new ideas for the application and remote control of soft robots and soft actuators.