Water-Induced Phase Separation for Anti-Swelling Hydrogel Adhesives in Underwater Soft Electronics.

The development of hydrogel-based underwater electronics has gained significant attention due to their flexibility and portability compared to conventional rigid devices. However, common hydrogels face challenges such as swelling and poor underwater adhesion, limiting their practicality in water environments. Here, a water-induced phase separation strategy to fabricate hydrogels with enhanced anti-swelling properties and underwater adhesion is presented. By leveraging the contrasting affinity of different polymer chains to water, a phase-separated structure with rich hydrophobic and dilute hydrophilic polymer phases is achieved. This dual-phase structure, meticulously characterized from the macroscopic to the nanoscale, confers the hydrogel network with augmented retractive elastic forces and facilitates efficient water drainage at the gel-substrate interface. As a result, the hydrogel exhibits remarkable swelling resistance and long-lasting adhesion to diverse substrates. Additionally, the integration of carboxylic multiwalled carbon nanotubes into the hydrogel system preserves its anti-swelling and adhesion properties while imparting superior conductivity. The conductive phase-separated hydrogel exhibited great potential in diverse underwater applications, including sensing, communication, and energy harvesting. This study elucidates a facile strategy for designing anti-swelling underwater adhesives by leveraging the ambient solvent effect, which is expected to offer some insights for the development of next-generation adhesive soft materials tailored for aqueous environments.

Analysis of COVID-19 outbreak in Hubei province based on Tencent's location big data.

Rapid urbanization has gradually strengthened the spatial links between cities, which greatly aggravates the possibility of the spread of an epidemic. Traditional methods lack the early and accurate detection of epidemics. This study took the Hubei province as the study area and used Tencent's location big data to study the spread of COVID-19. Using ArcGIS as a platform, the urban relation intensity, urban centrality, overlay analysis, and correlation analysis were used to measure and analyze the population mobility data of 17 cities in Hubei province. The results showed that there was high similarity in the spatial distribution of urban relation intensity, urban centrality, and the number of infected people, all indicating the spatial distribution characteristics of "one large and two small" distributions with Wuhan as the core and Huanggang and Xiaogan as the two wings. The urban centrality of Wuhan was four times higher than that of Huanggang and Xiaogan, and the urban relation intensity of Wuhan with Huanggang and Xiaogan was also the second highest in the Hubei province. Meanwhile, in the analysis of the number of infected persons, it was found that the number of infected persons in Wuhan was approximately two times that of these two cities. Through correlation analysis of the urban relation intensity, urban centrality, and the number of infected people, it was found that there was an extremely significant positive correlation among the urban relation intensity, urban centrality, and the number of infected people, with an R2 of 0.976 and 0.938, respectively. Based on Tencent's location big data, this study conducted the epidemic spread research for "epidemic spatial risk classification and prevention and control level selection" to make up for the shortcomings in epidemic risk analysis and judgment. This could provide a reference for city managers to effectively coordinate existing resources, formulate policy, and control the epidemic.

Are the epidemic prevention facilities effective? How cities should choose epidemic prevention facilities: Taking Wuhan as an example.

The COVID-19 pandemic highlighted the limitations of urban public health emergency response capabilities. Taking Wuhan as an example, this study used breakpoint regression, kernel density analysis, overlay analysis, and accessibility analysis from Stata and ArcGIS, and divided epidemic prevention facilities into the basic epidemic prevention facilities (hospitals), and the emergency epidemic prevention facilities (mobile cabin hospitals) for further analysis. The results showed that over 70% of the basic epidemic prevention facilities in Wuhan were located in high density population areas. On the contrary, most of the emergency epidemic prevention facilities were located in low density population areas. The local treatment effect of the implementation of the emergency epidemic prevention facility policy is about 1, indicating that there was a significant impact of emergency epidemic prevention facilities on outbreak control, which passed the bandwidth test. What's more, the analysis of the accessibility of residential points revealed that more than 67.3% of people from the residential points could arrive at the epidemic prevention facilities within 15 min, and only 0.1% of them took more than 20 min to arrive. Therefore, the epidemic prevention facilities can effectively curb the spread of the epidemic, and people from residential areas can quickly get there. This study summarized the spatial characteristics of epidemic prevention facilities in Wuhan and analyzed the importance of them, thus providing a new perspective for future research on upgrading the city's comprehensive disaster prevention system.

Smart nanogels for cancer treatment from the perspective of functional groups.

Introduction: Cancer remains a significant health challenge, with chemotherapy being a critical treatment modality. However, traditional chemotherapy faces limitations due to non-specificity and toxicity. Nanogels, as advanced drug carriers, offer potential for targeted and controlled drug release, improving therapeutic efficacy and reducing side effects. Methods: This review summarizes the latest developments in nanogel-based chemotherapy drug delivery systems, focusing on the role of functional groups in drug loading and the design of smart hydrogels with controlled release mechanisms. We discuss the preparation methods of various nanogels based on different functional groups and their application in cancer treatment. Results: Nanogels composed of natural and synthetic polymers, such as chitosan, alginate, and polyacrylic acid, have been developed for chemotherapy drug delivery. Functional groups like carboxyl, disulfide, and hydroxyl groups play crucial roles in drug encapsulation and release. Smart hydrogels have been engineered to respond to tumor microenvironmental cues, such as pH, redox potential, temperature, and external stimuli like light and ultrasound, enabling targeted drug release. Discussion: The use of functional groups in nanogel preparation allows for the creation of multifunctional nanogels with high drug loading capacity, controllable release, and good targeting. These nanogels have shown promising results in preclinical studies, with enhanced antitumor effects and reduced systemic toxicity compared to traditional chemotherapy. Conclusion: The development of smart nanogels with functional group-mediated drug delivery and controlled release strategies represents a promising direction in cancer therapy. These systems offer the potential for improved patient outcomes by enhancing drug targeting and minimizing adverse effects. Further research is needed to optimize nanogel design, evaluate their safety and efficacy in clinical trials, and explore their potential for personalized medicine.

Significant Roles of Ions in Enhancing and Functionalizing Anisotropic Hydrogels.

Salt ions are multifunctional in living beings, in contrast to their limited efficiency in abiotic materials. Achieving the versatility of salt ions in synthetic materials is promising yet demanding. Here, we report that multivalent metallic ions can act multiple crucial roles in a polyacrylamide/sodium alginate (PAAm/SA) composite hydrogel system, inducing a quadruple effect that toughens and functionalizes the originally weak gel. Fixation of anisotropic structures (effect I), mechanical enhancement (effect II), conductivity improvement (effect III), as well as antifreezing and moisture retention properties (effect IV) simultaneously emerge in the gel, all of which are enabled by the ion effect. The resulting tough hydrogels exhibit excellent comprehensive properties that rival existing state-of-the-art hydrogels, promising a wide range of potential applications. As proof-of-concept demonstrations, extremely durable hydrogel-based soft electronic devices are developed, which operate stably even in harsh environments. We also prove that the ion effect can be induced by other multivalent metallic ions. This work highlights the versatility of salt ions in nonliving materials, providing a simple but enlightening idea for the development of all-around soft materials.

Regulable Mixed-Solvent-Induced Phase Separation in Hydrogels for Information Encryption.

The rapid progress of information technology is accompanied by plenty of information embezzlement and forgery, but developing advanced encryption technologies to ensure information security remains challenging. Phase separation commonly leads to a dramatic change in the transmittance of hydrophilic polymer networks, which is a potential method for information security but is often neglected. Here, taking the polyacrylamide (PAAm) hydrogel system as a typical example, facilely adjustable information encryption and decryption via its regulable phase separation process in ethanol/water mixed solvent, are reported. By controlling the osmotic pressure of the external and internal environment, it is demonstrated that the diffusion coefficient during deswelling and reswelling, as well as the corresponding change of transmittance of the gel, can be well controlled. Relatively high osmotic pressure leads to rapid phase separation of the initial gel but slow phase remixing of the phase-separated gel, opening the opportunity of applying the gel as a reversible information encryption device. As proof-of-concept demonstrations, several stable and reversible information encryption and decryption systems by making use of the phase separation process of the gels are designed, which are expected to inspire the development of next-generation soft devices for information technology.

Cellulose nanocrystal/phytic acid reinforced conductive hydrogels for antifreezing and antibacterial wearable sensors.

Common hydrogels containing abundant water are insulating materials and lose stretchability easily below the freezing point of water, holding limited potential in emerging applications such as wearable soft devices. The introduction of compatible biomass-derived materials into hydrogel systems could be a potential solution that simultaneously enables anti-freezing ability, mechanical enhancement, and antibacterial properties. Based on such a hypothesis, here we report the facile development of biocompatible hydrogels that are capable of maintaining satisfying mechanical properties and electrical conductivity well below zero degrees centigrade. The strategy is to reinforce neat polyacrylamide (PAAm) hydrogels with biomass-derived cellulose nanocrystal (CNC) and phytic acid (PA), transforming the originally weak, insulating hydrogels into tough, highly conductive ones. Anti-freezing and antibacterial properties also emerge in the reinforced hydrogels, enabling them to work as efficient wearable sensors below zero degrees centigrade. Considering that numerous polymer hydrogel systems are compatible with CNC and PA, we believe that this simple biomass-based strategy can work universally to enhance and functionalize various weak and insulating hydrogels that are traditionally susceptible to frost and bacteria.

Highly Deformable, Conductive Double-Network Hydrogel Electrolytes for Durable and Flexible Supercapacitors.

Developing flexible energy storage devices with the ability to retain capacitance under extreme deformation is promising but remains challenging. Here, we report the development of a durable supercapacitor with remarkable capacitance retention under mechanical deformation by utilizing a physical double-network (DN) hydrogel as an electrolyte. The first network is hydrophobically associating polyacrylamide cross-linked by nanoparticles, and the second network is Zn2+ cross-linked alginate. Through soaking such a DN hydrogel into a high concentration of ZnSO4 solution, a highly deformable electrolyte with good conductivity is fabricated, which also shows adhesion to diverse surfaces. Directly attaching the hydrogel electrolyte to two pieces of an active carbon cloth facilely produces a flexible supercapacitor with a high specific capacitance and theoretical energy density. Remarkable capacitance retention under tension, compression, and bending is observed for the supercapacitor, which can also maintain above 87% of the initial capacitance after 4000 charge-discharge cycles. This study provides a simple way to fabricate hydrogel electrolytes for deformable yet durable supercapacitors, which is expected to inspire the development of next-generation flexible energy storage devices.

Fe3+-citric acid/sodium alginate hydrogel: A photo-responsive platform for rapid water purification.

As water pollution in human society becomes more and more serious, the demand for materials that can be used for wastewater treatment is increasing. Here, we reported a sodium alginate-based hydrogel (Fe3+-CA/SA hydrogel) that can efficiently photocatalyze the degradation of malachite green. The Fe3+-CA/SA hydrogel is composed of sodium alginate, citric acid, and Fe3+. The hydrogel has multi-leveled pore structure and photochromic ability. Benefiting from the unique microstructure and positive feedback chemical reaction process, the hydrogel has high photocatalytic efficiency. Under 365 nm UV light irradiation, the hydrogel can degrade around 95% of malachite green (20 mg/L) in about 4 min, and there is no need to add H2O2 in the degradation process. The work helps to expand the application of sodium alginate-based hydrogels in the field of water treatment. It also has exploratory significance for the principle of photocatalytic degradation of malachite green.

Shape-Stable Hydrated Salts/Polyacrylamide Phase-Change Organohydrogels for Smart Temperature Management.

Flexible and environmentally friendly phase-change materials (PCMs) with appropriate phase transition temperatures display great potential in the regulation of environmental temperature. Here, we synthesized a series of room-temperature-use phase-change organohydrogels (PCOHs) comprising phase-change hydrated salts (disodium phosphate dodecahydrate, DPDH) and polyacrylamide (PAM) glycerol hydrogels through a facile photoinitiated one-step in situ polymerization procedure. Incorporating the environmentally friendly cost-effective DPDH hydrated salts PCMs into antidrying three-dimensional (3D) networks of the PAM organohydrogel can overcome the solid rigidity and melting leakage to achieve flexibility for wearable temperature management devices. The microstructures and physical interactions among the components of the PCOHs were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR), and X-ray diffraction (XRD), which demonstrate that the DPDH were uniformly loaded in the networks of the PAM. Phase-change storage and thermal properties of the PCOHs were characterized by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA), and the PCOHs show high energy transition efficiency and shape stability during the long-term storage and thermal cycling. Dynamic rheology and compression tests demonstrate that PCOHs can withstand a certain stress and display flexibility performance even above the melting temperature of DPDH. We also described the smart temperature management capability and the potential application of the PCOHs. This investigation offers a facile method to construct a skin-friendly flexible phase-change glycerol hydrogel and provides an alternative to the traditional melt impregnation or microencapsulation method to prepare phase-change energy storage composites.

Preparation of silver nanoparticles by solid-state redox route from hydroxyethyl cellulose for antibacterial strain sensor hydrogel.

As a smart wearable sensor device, the mildew of the biocompatible hydrogel limits its application. In this paper, silver nanoparticles were prepared by solid-state reduction of hydroxyethyl cellulose and compounded into a chemically cross-linked hydrogel as an antibacterial, flexible strain sensor. Because the high surface energy of silver nanoparticles can quench free radicals, we designed three initiators to synthesize hydrogels: ammonium persulfate (APS), 2,2'-Azobis(2-methylpropionitrile) (AIBN) and 2,2'-azobis(2-methylpropionamidine) dihydrochloride (AIBA). Impressively, silver nanoparticles composite hydrogel could only be successfully fabricated and triggered by the AIBN. The mechanical property of the composite hydrogel (0.12 MPa at 704.33 % strain) was significantly improved because of dynamic crosslinking point by HEC. Finally, the composite hydrogels are applied to the field of antibacterial strain sensor and the highest Gauge Factor (GF) reached 4.07. This article proposes a novel, green and simple strategy for preparing silver nanoparticles and compounding them into a hydrogel system for antibacterial strain sensor.

Transparent Stretchable Dual-Network Ionogel with Temperature Tolerance for High-Performance Flexible Strain Sensors.

A stretchable transparent double network ionogel composed of physically cross-linked poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-co-HFP)) and chemically cross-linked poly(methyl methacrylate-co-butylmethacrylate) (P(MMA-co-BMA)) elastomer networks within [EMIM][TFSI] ionic liquid was fabricated through a facile one-pot thermal polymerization. The dual-network (DN) ionogel presents good mechanical performance (failure tensile stress 2.31 MPa, strain 307%) with a high loading of ionic liquid (70 wt %) for achieving required ionic conductivity (>0.1 S/m at room temperature). The transparent chemical cross-linked P(MMA-co-BMA) elastomer network endows high transparency (>93%) and high stretchability to the DN ionogel. The DN ionogel maintains good toughness, elasticity, and transparency in a wide temperature range (-40 to 80 °C) for the application in a harsh environment. In addition, the sensitivity of the DN ionogel to the change of environment temperature and deformation was detected and described. The practical potential of the DN ionogel in flexible electronic devices is further revealed by fabricating DN ionogel strain sensors to detect the movement of different human limbs including the bending of the finger, wrist, and elbow as well as the slight throat jitter during the swallowing and vocalization, showing fast response, high sensitivity, and good repeatability.

Polydopamine/polystyrene nanocomposite double-layer strain sensor hydrogel with mechanical, self-healing, adhesive and conductive properties.

Inspired by the adhesion mechanism of natural mussels, polydopamine (PDA) has been widely studied and applied in hydrogels due to its good adhesion to various materials. In this work, a double-layer hydrogel constituted of an adhesive layer and a tough layer was successfully prepared via in-situ polymerization. Adding polystyrene particles into the tough layer could improve the mechanical properties, and the adhesion of various substrates could be achieved with PDA nanoparticles in the adhesive layer. Furthermore, lithium chloride was introduced into the tough layer to endow the bilayer hydrogels with electrical conductivity. Due to the hydrophobic association in the tough layer and hydrogen bond in the adhesive layer, the double-layer hydrogel exhibits self-healing properties. In addition, the NIR light response property of PDA was beneficial to self-healing properties. As a result, it has proved that the prepared bilayer hydrogel has excellent conductivity, toughness (0.18 MPa), adhesion and self-healing properties, which is an ideal flexible wearable strain sensor with high sensitivity and good repeatability, suitable for human motion signal detection.

Healing, flexible, high thermal sensitive dual-network ionic conductive hydrogels for 3D linear temperature sensor.

A temperature sensor based on muti-wall carbon nanotubes (MWCNTs) composite polyacrylamide/Fe3+-polyacrylic acid (PAM/Fe3+-PAA) double network (DN) hydrogels that combines flexibility, thermal sensitivity and self-healing ability is fabricated through in situ polymerization and maceration. Due to the excellent thermal conductivity of carbon nanotubes, the temperature sensitivity of the DN hydrogels are improved and therefore can be exploited as a novel channel material for a temperature sensor. This temperature sensor can be stretched from 0 to 750% strain with the sensitivity as high as 9.4%/°Cat extreme 200% strain. Importantly, the DN hydrogels have excellent self-healing properties that it can still be stretched after cutting and healing. Similarly, the electrical and thermal sensing properties of the DN hydrogels can be self-healed analogous to the self-healing capability of human skin. In addition, DN hydrogels have high stability for bending and torsion, which can avoid errors caused by deformation in the temperature measurement. In order to attaching on nonplanar curvilinear surfaces for practical temperature detection, we designed a linear-shaped hydrogels temperature sensor, which can improve the accuracy by wrapping the surface of the measured object completely in a way that eliminates the influence of air in the holes, enabling it to be potentially integrated in soft robots to grasp real-world information for guiding their actions.

High-Strength, Self-Healable, Temperature-Sensitive, MXene-Containing Composite Hydrogel as a Smart Compression Sensor.

As a new two-dimensional material similar to graphene, MXene has attracted extensive attention in the field of electrochemical materials such as supercapacitors because of its excellent mechanical properties, electrical conductivity, and thermal conductivity. What is better than graphene is that the few-layer MXene material obtained by proper treatment has good water dispersibility and can be used as an ideal nanomaterial to enhance the conductivity of hydrogels. However, the articles about the few-layer MXene material used in the preparation of composite hydrogels are rare. In this paper, MXene was synthesized by Yury mild method. Poly(N-isopropyl acrylamide) (PNIPAM) hydrogel and physical cross-linking hydrogel were used as the matrix to prepare composite hydrogels with temperature sensitivity and stress-sensing properties. The composite hydrogels exhibited excellent mechanical properties: it could be stretched to over 14 times the original length and achieved a 0.4 MPa tensile strength while showing good self-healing ability, which was of great significance for the practical application of hydrogels. The conductivity of the composite hydrogel was 1.092 S/m, which was about 15 times that of the control hydrogel without MXene. The potential of the composite hydrogel as a smart compression sensor was also verified by the conductivity tests.

miR-194 inhibits liver cancer stem cell expansion by regulating RAC1 pathway.

Liver cancer stem cells (CSCs) contribute to tumorigenesis, progression, drug resistance and recurrence of hepatocellular carcinoma (HCC). However, the underlying mechanism for the propagation of liver CSCs remains unclear. Herein, we observed low expression of miR-194 in chemoresistant HCC cells. A remarkable decrease of miR-194 was detected in EpCAM or CD133-positive liver CSCs and CSC-enriched hepatoma spheres. Interference miR-194 facilitated liver CSCs expansion by enhancing the self-renewal of liver CSCs. While up-regulating miR-194 inhibited liver CSCs expansion by suppressing the self-renewal of liver CSCs. Furthermore, hepatoma cells with miR-194 overexpression performed more sensitivity to sorafenib treatment. Mechanistically, functional studies found that Ras-related C3 botulinum toxin substrate 1 (RAC1) was a direct target of miR-194. Overexpression of miR-194 inhibited the expression of RAC1 in liver CSCs. Special RAC1 siRNA diminished the discrepancy in liver CSC proportion and the self-renewal capacity between miR-194 overexpression hepatoma cells and control cells, which further confirmed that RAC1 was required in miR-194-inhibited liver CSCs expansion. More importantly, downregulated expression of miR-194 was a predictor of poor prognosis of HCC patients.

Tough hydrophobic association hydrogels with self-healing and reforming capabilities achieved by polymeric core-shell nanoparticles.

The application range of hydrogels can be greatly widened by improving their mechanical properties. It is still a great challenge to develop hydrogels with good mechanical properties, reliable self-healing properties and remolding ability at the same time. Inspired by biological soft tissue with excellent mechanical properties and self-healing properties, here, a facile method to fabricate poly (styrene-acrylic acid) (P(S-AA)) core-shell nanoparticles with plenty of carboxyl groups on their surface, and their enhancement to hydrophobic association hydrogels was reported. Under stress, the dynamic physical bonds including hydrogen bonding between polymer chains and P(S-AA) core-shell nanoparticles (NPs), and entanglement of hydrophobic chains were destroyed to effectively dissipate energy, and uniform hydrogel network leads to smooth stress-transfer, which makes the core-shell nanoparticles composite hydrophobic association hydrogels (MHA gels) excellent mechanical properties, such as excellent mechanical properties, toughness and ductility, and good self-healing properties as well. These features make the MHA gels have great potential in biomedical applications such as tissue engineering, articular cartilage and artificial skin.

Self-assembling GO/modified HEC hybrid stabilized pickering emulsions and template polymerization for biomedical hydrogels.

Graphene oxide(GO), as an amphiphilic and biocompatible material, is often used to prepare Pickering emulsion. However, the preparation of stable Pickering emulsion by a low concentration of GO is very challenging. In this research, we prepared the hydrophobic modified hydroxyethyl cellulose (mHEC) which contained quaternary ammonium group and GO which the water contact angle was 84°-86°. A stable, low cost, and biocompatible Pickering emulsion was fabricated by a low concentration of GO and different contents of mHEC. The effects of mHEC concentration, electrolyte concentration, pH, and oil/water ratio on the stability of Pickering emulsion were investigated. What's more, we prepared the biomedical macroporous polyacrylamide hydrogel by the GO/mHEC composite stabilized emulsion template for drug controlled-release. The composite hydrogel by Pickering emulsion template is a potential drug controlled-release delivery platforms. Furthermore, our strategy is extremely versatile, as Pickering particles, polymer and the monomer of hydrogel can all be varied.

Side chain effects on the solid-state emission behaviours and mechano-fluorochromic activities of 10H-phenothiazinylbenzo[d]imidazoles.

A family of 4-cyanophenyl-substituted 10H-phenothiazinylbenzo[d]imidazoles with different side chains at the 10-position are prepared and their physical properties are studied. The detailed structure-property research demonstrates that the cold crystallization temperature of ground samples and the emission wavelengths of pristine samples are in good accordance with the packing density, conformation distortion and intermolecular interactions, but emission wavelengths of ground samples are slightly chain-dependent. For benzimidazoles with alkyl chains, longer and more branched chains can produce looser packings, which cause pristine samples to display red-shifted emission and reduced MFC activity. For benzimidazoles with a phenyl chain, the emission wavelengths of both the pristine and the ground samples are remarkably red-shifted. Moreover, the degree of conformation distortion is larger, and the cold crystallization temperature is higher. Interestingly, the homologue with the n-hexyl chain displays an intense ML effect that is mainly attributed to the heavy discharge quantity on largely enhanced discharge areas under force stimuli due to the great fragility of this crystal.