Increased Hydrogel Swelling Induced by Absorption of Small Molecules

Amphibious Multifunctional Hydrogel Flexible Haptic Sensor with Self-Compensation Mechanism

In recent years, hydrogel-based wearable flexible electronic devices have attracted much attention. However, hydrogel-based sensors are affected by structural fatigue, material aging, and water absorption and swelling, making stability and accuracy a major challenge. In this study, we present a DN-SPEZ dual-network hydrogel prepared using polyvinyl alcohol (PVA), sodium alginate (SA), ethylene glycol (EG), and ZnSO4 and propose a self-calibration compensation strategy. The strategy utilizes a metal salt solution to adjust the carrier concentration of the hydrogel to mitigate the resistance drift phenomenon to improve the stability and accuracy of hydrogel sensors in amphibious scenarios, such as land and water. The ExpGrow model was used to characterize the trend of the ∆R/R0 dynamic response curves of the hydrogels in the stress tests, and the average deviation of the fitted curves ϵ¯ was calculated to quantify the stability differences of different groups. The results showed that the stability of the uncompensated group was much lower than that of the compensated group utilizing LiCl, NaCl, KCl, MgCl2, and AlCl3 solutions (ϵ¯ in the uncompensated group in air was 276.158, 1.888, 2.971, 30.586, and 13.561 times higher than that of the compensated group in LiCl, NaCl, KCl, MgCl2, and AlCl3, respectively; ϵ¯ in the uncompensated group in seawater was 10.287 times, 1.008 times, 1.161 times, 4.986 times, 1.281 times, respectively, higher than that of the compensated group in LiCl, NaCl, KCl, MgCl2 and AlCl3). In addition, for the ranking of the compensation effect of different compensation solutions, the concentration of the compensation solution and the ionic radius and charge of the cation were found to be important factors in determining the compensation effect. Detection of events in amphibious environments such as swallowing, robotic arm grasping, Morse code, and finger-wrist bending was also performed in this study. This work provides a viable method for stability and accuracy enhancement of dual-network hydrogel sensors with strain and pressure sensing capabilities and offers solutions for sensor applications in both airborne and underwater amphibious environments.

Hemostatic and Ultrasound-Controlled Bactericidal Silk Fibroin Hydrogel via Integrating a Perfluorocarbon Nanoemulsion

Excessive blood loss and infections are the prominent risks accounting for mortality and disability associated with acute wounds. Consequently, wound dressings should encompass adequate adhesive, hemostatic, and bactericidal attributes, yet their development remains challenging. This investigation presented the benefits of incorporating a perfluorocarbon nanoemulsion (PPP NE) into a silk-fibroin (SF)-based hydrogel. By stimulating the β-sheet conformation of the SF chains, PPP NEs drastically shortened the gelation time while augmenting the elasticity, mechanical stability, and viscosity of the hydrogel. Furthermore, the integration of PPP NEs improved hemostatic competence by boosting the affinity between cells and biomacromolecules. It also endowed the hydrogel with ultrasound-controlled bactericidal ability through the inducement of inner cavitation by perfluorocarbon and reactive oxygen species (ROS) generated by the sonosensitizer protoporphyrin. Ultimately, we employed a laparotomy bleeding model and a Staphylococcus aureus-infected trauma wound to demonstrate the first-aid efficacy. Thus, our research suggested an emulsion-incorporating strategy for managing emergency wounds.

Study on preservation and monitoring effect of sodium alginate-konjac glucomannan films loaded with tea polyphenols and Lycium ruthenicum anthocyanins

To investigate the efficacy of sodium alginate-konjac glucomannan (SA-KGM) films with anthocyanins (LRA) and tea polyphenols (TP) in meat, beef and grass carp were selected as representative meat products for preservation and freshness monitoring experiments at 4 °C. Concurrently, storage experiments of the films were conducted in this controlled environment. The results of the storage experiment showed that the films delayed meat spoilage by 2-4 days, nearly doubling the preservation time compared to the blank control. Additionally, the film exhibited significant capability to monitor the spoilage process of beef and grass carp. It was revealed by curve fitting analysis that there was a significant correlation between the color change of the film and the spoilage index of the meat. Throughout the storage experiment with the film, it was observed that moisture significantly influenced the microstructure and bonding situation of the films, thereby impacting their mechanical and barrier properties. However, the films were still able to maintain satisfactory physicochemical properties in general. The above findings were crucial in guiding the promotion of the film within the food preservation industry.

Magneto-Induced Janus Adhesive-Tough Hydrogels for Wearable Human Motion Sensing and Enhanced Low-Grade Heat Harvesting

Janus hydrogels with different properties on the two surfaces have considerable potential in the field of material engineering applications. Various Janus hydrogels have been developed, but there are still some problems, such as stress mismatch caused by the double-layer structure and Janus failure caused by material diffusion in the gradient structure. Here, we report a Janus adhesive-tough hydrogel with polydopamine-decorated Fe3O4 nanoparticles (Fe3O4@PDA) at one side induced by magnetic field to avoid uncontrollable material diffusion in the cross-linking polymerization of acrylamide with alginate-calcium. The magneto-induced Janus (MIJ) hydrogel has an adhesive surface and a tough bulk without an obvious interface to avoid stress mismatch. Due to the intrinsic dissipative matrix and the abundant catechol groups on the adhesive surface, it shows strong adhesion onto various substrates. The MIJ hydrogel has high sensitivity (GF = 0.842) in detecting tiny human motion. Owing to the synergy of Fe3O4@PDA-enhanced interfacial adhesion and heat transfer, it is possible to quickly generate effective temperature differences when adhering to human skin. The MIJ hydrogel achieves a Seebeck coefficient of 13.01 mV·K-1 and an output power of 462.02 mW·m-2 at a 20 K temperature difference. This work proposes a novel strategy to construct Janus hydrogels for flexible wearable devices in human motion sensing and low-grade heat harvesting.

Controlled-release alginate-bentonite polymer gel granules of emamectin benzoate and control efficacy against Spodoptera frugiperda

BACKGROUND

The fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith), is known to cause large agricultural production losses. Emamectin benzoate is one of the most effective insecticides to control this pest; however, its effective time is not sufficiently long to control FAW. Therefore, it is important that new controlled insecticide formulations with new application methods are developed.

RESULTS

A series of emamectin benzoate polymer gel granules were prepared with sizes ranging from 0.95 to 1.5 mm. As the bentonite content increased, the release rate decreased. The cumulative release process of emamectin benzoate mainly depends on the cracks in the surface of the granules, and the release rate can be described by non-Fickian and Fickian diffusion, which are closely related to the water content. By spreading the developed polymer gel granules into maize leaf whorls, the control effect reached 83% after 21 days in field trials.

CONCLUSION

A novel polymer gel granule was developed that can effectively regulate emamectin benzoate release. By broadcasting polymer gel granules into maize leaf whorls, significant control efficacy against FAW can be obtained, and this could potentially be used for the effective control of FAW. © 2022 Society of Chemical Industry.

Analyzing the Water Confined in Hydrogel Using Near-Infrared Spectroscopy

Analysis of the confined water in hydrogels is essential for understanding the chemical and physical properties. Methods to quantify the content and study the structure of water in hydrogel using near-infrared (NIR) spectroscopy were proposed. The NIR spectra of poly-N,N-dimethylacrylamide (PDMAA) hydrogel with different water contents were measured at different temperatures. A partial least squares (PLS) model was established using the spectra of the samples with water content (w_h) from 0.9 to 387.6%. Continuous wavelet transform (CWT) was adopted to calculate the resolution enhanced spectra from which the spectral features of water species with free OH (S₀) and with one or two hydrogen bonds (S₁ and S₂) was obtained. The variation of these water species with water content suggests the existence of the water molecules bonding to NH groups by one hydrogen bond (S_1NH) and hydrating the CH groups of the polymer network and bulk-like water. Moreover, the variation of water structures with temperature shows that the release of bulk-like water occurs in the phase transition of the hydrogel, but the S_1NH and the hydration water stay unchanged. The former explains the sudden volume shrinkage for the phase transition and the latter may be the reason for the shape memory effect in the repeated swelling and deswelling of hydrogels.

Comparative Study of Stability against Moisture for Solid Garnet Electrolytes with Different Dopants

The cubic garnet Li7La3Zr2O12 (c-LLZO) is one of the most promising solid electrolytes due to its high ionic conductivity and large electrochemical window. However, the critical issue of Li2CO3 formation on the c-LLZO surface when exposed to air is problematic, which is detrimental to the ionic conductivity and storage. Herein, comparative studies were carried out on the air stability of Al-doped Li7La3Zr2O12 (Al-LLZO), Al-Ta-doped Li7La3Zr2O12 (Al-LLZTO), and Al-Nb-doped Li7La3Zr2O12 (Al-LLZNO). It was found that Al-LLZTO and Al-LLZNO are less reactive with air than Al-LLZO. The morphology of Li2CO3 on Al-LLZTO micro-sized powders after air exposure was island-like with ~1.5 μm in thickness. The interfacial resistance of Li/Al-LLZTO was also a factor of ~3 smaller than that of Li/Al-LLZO, leading to the improved cycle stability of Li/Al-LLZTO/Li symmetric cells. The first-principles calculations based on density functional theory (DFT) verified that the decomposition energy of Al-LLZTO was larger than that of Al-LLZO, inhibiting the reaction product of Li2O and, thus, the next step product of Li2CO3 following the reactions of Li2O + H2O → LiOH and LiOH + CO2 → Li2CO3.

Tough and self-healing hydrogels based on transient crosslinking by nanoparticles

In this investigation, transient crosslinking was constructed to obtain a hydrogel with excellent mechanical and self-healing properties. Firstly, core-shell particles with hydrophilic amino groups were prepared by emulsion polymerization and subsequently dispersed into hydrophobic association polyacrylamide hydrogels. Transient crosslinking was constructed through hydrogen bonding between core-shell particles and polyacrylamide. As a result, the hydrogels exhibited a tensile strength of 1.4 MPa and self-healing efficiency of 98% at 24 h. Furthermore, reconstruction of the transient crosslinking was confirmed from rheological measurements. Therefore, the essential reinforcement principle based on transient crosslinking would open a novel strategy to obtain hydrogels with superior toughness and self-healing properties.

Highly efficient and recyclable polyolefin-based magnetic sorbent for oils and organic solvents spill cleanup

The oil dispersants have been applied in a broad oil pollution area, but the dispersed oil caused environmental problems during sedimentation. Unlike oil dispersants, flake type polyolefin-based oil absorbent (PA) is not emulsified and shows excellent swelling characteristic for oil removal. However, the sprayed PA flakes cannot be fully collected due to its tiny architectures, the uncollected flakes can cause unintentional secondary pollution. In this study, we develop a kind of flake type polyolefin-based magnetic absorbent (PMA) hybridized with magnetic nanoparticle, to facilitate the collection process. The magnetic nanoparticle is uniformly dispersed in PMA due to the hydrophobic functionalization of iron oxide nanoparticle. This enables the convenient collection of isolated sorbent flakes even when they were placed in the marine system and show a desirable oil recovery performance up to about 37 times for organic solvent. Moreover, oil-soaked PMA flakes can be fully converted into refined oil via a pyrolysis process. After pyrolysis, the thermally undecomposed compounds, which comprise of carbon residue and magnetic nanoparticle, can be also separated by a magnet. The as-prepared flake type PMA possesses good oil recovery performance, fast magnetic response, and efficient oil recycling, thus representing an environmentally promising method for oil spill cleanup.

Selected Phase Separation Renders High Strength and Toughness to Polyacrylamide/Alginate Hydrogels with Large-Scale Cross-Linking Zones

High water content usually contradicts the mechanics for hydrogels, and achieving both characteristics is extremely challenging. Herein, a novel confined-chain-aggregation (CCA) strategy is developed to fabricate ultrastrong and tough hydrogels without sacrificing their inherent water capacity. Based on the popular polyacrylamide/alginate (PAAm/Alg) system with a double network (DN), a poor solvent exchange is induced once PAAm is fully cross-linked but prior to ionic cross-linking of alginate. In this case, the alginate chains are restricted by the chemical PAAm network and undergo a confined-chain aggregation, which guarantees an interpenetrating network of both polymers and simultaneously generates micron-scale aggregates. In addition, after the subsequent water uptake, the accompanying formation of hydrogen bonds and metal-ligand coordination stabilizes the newly formed alginate aggregates, serving as large-scale cross-linking zones. However, the PAAm chains are anchored by the preformed cross-linking points and convert back to the uniformly distributed, high-water-content state, achieving a selected phase separation in a DN system. The combined CCA and hybrid cation cross-linking method gives mechanical strength and toughness to the PAAm/Alg hydrogels to reach approximately 30 and 5 times the traditional methods, respectively. This investigation provides a general strategy for the development of a new generation of double-network hydrogels, which will expand their application as structural materials for cartilage and soft robotics.

EGFR-conjugated hydrogel accelerates wound healing on ulcer-induced burn wounds by targeting collagen and inflammatory cells using photoimmunomodulatory inhibition

In the present study, we fabricated an epidermal growth factor receptor (EGFR)-conjugated hydrogel to promote wound healing in cold restraint-induced gastric ulceration on burn wounds targeting collagen and inflammatory cells for the treatment of burns and gastric ulcers. Cytotoxicity and cell proliferation assays demonstrated good biocompatibility of hydrogel as a suitable extracellular matrix for targeted cells and support for regenerative cell growth. These findings were confirmed by staining methods. In vitro wound healing was confirmed cell migration in the targeted cells. The effect of the EGFR-H was investigated in cold restraint-induced gastric ulcers in rats, where the treatment was started immediately after ulcer induction. In the in vivo experiment, the EGFR-H demonstrated enhanced ulcer healing ability and less scarring compared to the hydrogel alone and controls. Thus, EGFR-H promotes healing of cold restraint-induced gastric ulcer via EGFR conjugated with a hydrogel. The present study demonstrates a novel pathway to fabricate hydrogels as suitable wound dressing biomaterials to improve deep partial thickness burn wound healing and prevent scar formation when aided by laser therapy.

Effects of fixed charge group physicochemistry on anion exchange membrane permselectivity and ion transport

Understanding the effects of polymer chemistry on membrane ion transport properties is critical for enabling efforts to design advanced highly permselective ion exchange membranes for water purification and energy applications. Here, the effects of fixed charge group type on anion exchange membrane (AEM) apparent permselectivity and ion transport properties were investigated using two crosslinked AEMs. The two AEMs, containing a similar acrylonitrile, styrene and divinyl benzene-based polymer backbone, had either trimethyl ammonium or 1,4-dimethyl imidazolium fixed charge groups. Membrane deswelling, apparent permselectivity and ion transport properties of the two AEMs were characterized using aqueous solutions of lithium chloride, sodium chloride, ammonium chloride, sodium bromide and sodium nitrate. Apparent permselectivity measurements revealed a minor influence of the fixed charge group type on apparent permselectivity. Further analysis of membrane swelling and ion sorption, however, suggests that less hydrophilic fixed charge groups more effectively exclude co-ions compared to more hydrophilic fixed charge groups. Analysis of ion diffusion properties suggest that ion and fixed charge group enthalpy of hydration properties influence ion transport, likely through a counter-ion condensation, ion pairing or binding mechanism. Interactions between fixed charge groups and counter-ions may be stronger if the enthalpy of hydration properties of the ion and fixed charge group are similar, and suppressed counter-ion diffusion was observed in this situation. In general, the hydration properties of the fixed charge group may be important for understanding how fixed charge group chemistry influences ion transport properties in anion exchange membranes.

Kinetics of fluoride-catalysed synthesis of organosilica colloids in aqueous solutions of amphiphiles

Reactions involving hydrophobic reactants in water can be much accelerated in organic solvent-free solutions containing amphiphiles at neutral pH and room temperature. Previously, we demonstrated that organosilica colloidal particles could be conveniently synthesized by a versatile salt-catalysis method in solutions modified with various amphiphilic molecules. The method precludes the use of any solvent, any added form of energy (thermal or mechanical), and any strong (or hazardous) acids/bases. Herein, the kinetic properties of the reaction were systematically investigated for fluoride-catalysed synthesis of colloidal organosilica from a thiol-functionalized organosilane precursor, (3-mercaptopropyl)trimethoxysilane. Continuous, real-time ATR-FTIR measurements allowed probing the time evolution of organosilica condensation in different reaction systems, containing one of the following: non-ionic surfactants (Tween 20, Tween 40, Tween 60, Tween 80, Triton X-100), anionic surfactant (sodium dodecyl sulphate; SDS), cationic surfactant (cetyltrimethylammonium bromide; CTAB), and amphiphilic polymers (polyvinyl alcohol and polyvinylpyrrolidone). Overall, while some amphiphile-specific properties were revealed, fluoride-catalysed synthesis was ultrafast with a universal two-phase kinetic scheme (e.g. transition within 5–10 min) for all amphiphiles studied.

Systematic real-time ATR-FTIR studies reveal ultrafast two-phase kinetics of sodium fluoride-catalysed synthesis of organosilica colloids in purely aqueous, amphiphile-assisted systems.

A simple one-pot fabrication of silver loaded semi-interpenetrating polymer network (IPN) hydrogels with self-healing and bactericidal abilities

In the last decade, there has been a significant increase in the development of self-healing hydrogels. However, in most cases, the synthesized self-healing hydrogels possess no antibacterial properties. Further, the preparation of self-healing hydrogels usually requires sophisticated processes and also involves multiple steps. Herein, we proposed a simple one-pot synthesis of silver loaded semi-IPN hydrogels with self-healing and antibacterial properties. The hydrogels were prepared by physical cross-linking between polyacrylic acid (PAA) and ferric ions (Fe³⁺) and further modified by the interpenetration of gelatin-silver in the networks. In addition, the effect by varying the gelatin concentration was also studied. The mechanical properties of the as-prepared hydrogels reached 0.79 MPa in stress and 920% in strain with the self-healing efficiency of 87.5% (healed at 70 °C for 2 h). As displayed by the SEM images, the incorporated silver chloride nanoparticles (AgCl NPs) in gelatin-free hydrogels were agglomerated. Meanwhile, well-distributed AgCl NPs in the hydrogels were obtained in the presence of gelatin which acts as a stabilizer. Moreover, due to Fe³⁺ and AgCl NPs, the hydrogels were able to inhibit the growth of bacteria indicated by an inhibition zone (9–9.6 mm) which was examined toward Escherichia coli via the disk-diffusion method.

The semi-interpenetrating polymer network hydrogel possesses self-healing ability due to the dynamic ionic interactions between polyacrylic acid and Fe³⁺. The antibacterial properties are due to embedded silver chloride nanoparticles well-distributed in the hydrogel.

Water and Oil Insoluble PEGDA-Based Microcapsule: Biocompatible and Multicomponent Encapsulation

Despite the recent development in various materials capable of encapsulating biomolecules, there exist limited reports on multicomponent encapsulation in biocompatible microcapsules. In this letter, we utilize the molecular weight dependent solubility of poly(ethylene glycol) diacrylate (PEGDA) and droplet microfluidics to achieve direct encapsulation of both hydrophilic and hydrophobic cargoes in PEG microcapsules. By using PEGDA 250 as the middle phase, we demonstrate that these PEGDA-based microcapsules allow simultaneous encapsulation of both hydrophilic and hydrophobic cargoes. We further confirm the validity of this approach by demonstrating that complex biomolecule such as protein can be effectively encapsulated within these PEGDA-based microcapsules.

Polyolefin-based interpenetrating polymer network absorbent for crude oil entrapment and recovery in aqueous system

In this research, a series of different two polyolefin-based interlaced polymer network material was prepared with a semi-crystalline linear low density polyethylene (LLDPE, thermoplastic) and a crosslinked 1-decene/divinylbenzene (1-D/DVB, elastomer) having high crude oil absorption capacity. The prepared absorbents, LLDPE/D/DVB, were characterized by NMR, TEM, contact angle measurement and TGA analysis. It was observed that the mixing ratio of two interlaced polymer network played a crucial role in determining its crude oil absorption capacity. The swelling capacity of absorbent prepared from a 1:1 mixing of LLDPE and D/DVB (0.2 ml) exhibit high removal efficiency in crude oil absorption over 40 g/g at both 25 °C and 0 °C. The removal of the absorbed crude oil from the water surface is effective. As the absorbent made of polyolefin materials have pure hydrocarbon content, offer significant advantages such as high absorption capacity, simple recovery, and recyclability.

A recyclable hydroxyl functionalized polyindole hydrogel for sodium hydroxide extraction via the synergistic effect of cation–π interactions and hydrogen bonding

We have successfully constructed a new type of recyclable indole-based hydrogel, which exhibited highly effective extraction behavior for hydroxide via the synergistic effect of cation–π interactions and hydrogen bonds.

Improved ATR-FTIR detection of hydrocarbons in water with semi-crystalline polyolefin coatings on ATR elements

In situ detection of hydrocarbons in water using ATR-FTIR with LLDPE film.

High-Strength, Tough, and Self-Healing Nanocomposite Physical Hydrogels Based on the Synergistic Effects of Dynamic Hydrogen Bond and Dual Coordination Bonds

Dynamic noncovalent interactions with reversible nature are critical for the integral synthesis of self-healing biological materials. In this work, we developed a simple one-pot strategy to prepare a fully physically cross-linked nanocomposite hydrogel through the formation of the hydrogen bonds and dual metal-carboxylate coordination bonds within supramolecular networks, in which iron ions (Fe³⁺) and TEMPO oxidized cellulose nanofibrils (CNFs) acted as cross-linkers and led to the improved mechanical strength, toughness, time-dependent self-recovery capability and self-healing property. The spectroscopic analysis and rheological measurements corroborated the existence of hydrogen bonds and dual coordination bonds. The mechanical tests and microscopic morphology were explored to elucidate the recovery properties and toughening mechanisms. The hydrogen bonds tend to preferentially break prior to the coordination bonds associated complexes that act as skeleton to maintain primary structure integrity, and the survived coordination bonds with dynamic feature also serve as sacrificial bonds to dissipate another amount of energy after the rupture of hydrogen bonds, which collectively maximize the contribution of sacrificial bonds to energy dissipation while affording elasticity. Additionally, the multiple noncovalent interactions in diverse types synergistically serve as dynamic but highly stable associations, leading to the effective self-healing efficiency over 90% after damage. We expect that this facile strategy of incorporating the biocompatible and biodegradable CNFs as building blocks may enrich the avenue in exploration of dynamic and tunable cellulosic hydrogels to expand their potential applications in the biomedical field.

Durability and Self-healing Effects of Hydrogel Coatings with respect to Contact Condition

The self-healing property of a hydrogel applied to a glass substrate as a thin polymer coating was assessed. The motivation was to develop a durable hydrogel coating that may be used to protect the surface of precision components from surface damage and scratches. The intrinsic swelling behavior of hydrogel fibers when they are exposed to moisture was exploited to attain the self-healing effect. The mechanical and self-healing properties of the dehydrated hydrogel coating by the freeze-drying process and the hydrated hydrogel coating that was reconstituted by the addition of water were analyzed. After conducting sliding tests with different loads and sliding distances, the wear area was hydrated with water to successfully induce self-healing of the hydrogel coating. It was also found that both the dehydrated hydrogel coating and the hydrated hydrogel coating had improved friction characteristics. In particular, the hydrated hydrogel coating had a much higher durability than the dehydrated coating.

A pH, glucose, and dopamine triple-responsive, self-healable adhesive hydrogel formed by phenylborate–catechol complexation

A pH, glucose, and dopamine triple-responsive, self-healable and adhesive polyethylene glycol hydrogel was developed via the formation of phenylborate–catechol complexation.