Ferroptosis is a new type of cell death that was discovered in recent years and is usually accompanied by a large amount of iron accumulation and lipid peroxidation during the cell death process; the ...occurrence of ferroptosis is iron-dependent. Ferroptosis-inducing factors can directly or indirectly affect glutathione peroxidase through different pathways, resulting in a decrease in antioxidant capacity and accumulation of lipid reactive oxygen species (ROS) in cells, ultimately leading to oxidative cell death. Recent studies have shown that ferroptosis is closely related to the pathophysiological processes of many diseases, such as tumors, nervous system diseases, ischemia-reperfusion injury, kidney injury, and blood diseases. How to intervene in the occurrence and development of related diseases by regulating cell ferroptosis has become a hotspot and focus of etiological research and treatment, but the functional changes and specific molecular mechanisms of ferroptosis still need to be further explored. This paper systematically summarizes the latest progress in ferroptosis research, with a focus on providing references for further understanding of its pathogenesis and for proposing new targets for the treatment of related diseases.
Hydrogels have promising applications in diverse areas, especially wet environments including tissue engineering, wound dressing, biomedical devices, and underwater soft robotics. Despite strong ...demands in such applications and great progress in irreversible bonding of robust hydrogels to diverse synthetic and biological surfaces, tough hydrogels with fast, strong, and reversible underwater adhesion are still not available. Herein, a strategy to develop hydrogels demonstrating such characteristics by combining macroscale surface engineering and nanoscale dynamic bonds is proposed. Based on this strategy, excellent underwater adhesion performance of tough hydrogels with dynamic ionic and hydrogen bonds, on diverse substrates, including hard glasses, soft hydrogels, and biological tissues is obtained. The proposed strategy can be generalized to develop other soft materials with underwater adhesion.
Tough hydrogels with fast, strong, and reversible underwater adhesion are developed by combining a clingfish‐inspired macroscale surface structure and nanoscale dynamic bonds. The surface structure accelerates water drainage, prevents water trapping and delays crack propagation; the dynamic bonds of the gel form reversible bridges at the interface and dissipate a significant amount of energy in bulk during detachment.
Reinforcing hydrogels with a rigid scaffold is a promising method to greatly expand the mechanical and physical properties of hydrogels. One of the challenges of creating hydrogel composites is the ...significant stress that occurs due to swelling mismatch between the water‐swollen hydrogel matrix and the rigid skeleton in aqueous media. This stress can cause physical deformation (wrinkling, buckling, or fracture), preventing the fabrication of robust composites. Here, a simple yet versatile method is introduced to create “macroscale” hydrogel composites, by utilizing a rigid reinforcing phase that can relieve stress‐induced deformation. A low‐melting‐point alloy that can transform from a load‐bearing solid state to a free‐deformable liquid state at relatively low temperature is used as a reinforcing skeleton, which enables the release of any swelling mismatch, regardless of the matrix swelling degree in liquid media. This design can generally provide hydrogels with hybridized functions, including excellent mechanical properties, shape memory, and thermal healing, which are often difficult or impossible to achieve with single‐component hydrogel systems. Furthermore, this technique enables controlled electrochemical reactions and channel‐structure templating in hydrogel matrices. This work may play an important role in the future design of soft robots, wearable electronics, and biocompatible functional materials.
“Macroscale” double‐network hydrogel composites, consisting of a mesh‐like rigid skeleton within a soft hydrogel matrix, are reported. A low‐melting‐point alloy frame is used as the functional skeleton to introduce properties activated via thermal stimulus (e.g., releasing swelling mismatch, shape memory, and thermal healing). The resulting composites exhibit excellent mechanical properties based on the macroscopic “double‐network” effect.
Ionogels have gained increasing attentions as a flexible conductive material. However, it remains a big challenge to integrate multiple functions into one gel that can be widely applied in various ...complex scenes. Herein, a kind of multifunctional ionogels with a combination of desirable properties, including transparency, high stretchability, solvent and temperature resistance, recyclability, high conductivity, underwater self‐healing ability, and underwater adhesiveness is reported. The ionogels are prepared via one‐step photoinitiated polymerization of 2,2,2‐trifluoroethyl acrylate and acrylamide in a hydrophobic ionic liquid. The abundant noncovalent interactions including hydrogen bonding and ion–dipole interactions endow the ionogels with excellent mechanical strength, resilience, and rapid self‐healing capability at room temperature, while the fluorine‐rich polymeric matrix brings in high tolerance against water and various organic solvents, as well as tough underwater adhesion on different substrates. Wearable strain sensors based on the ionogels can sensitively detect and differentiate large body motions, such as bending of limbs, walking and jumping, as well as subtle muscle movements, such as pronunciation and pulse. It is believed that the designed ionogels will show great promises in wearable devices and ionotronics.
A physically crosslinked multifunctional ionogel is designed and prepared via a simple one‐step photoinitiated polymerization of a fluorinated monomer and a hydrogen bond enabling comonomer in a hydrophobic ionic liquid. The ionogels possess excellent comprehensive performance, including high transparency, robust mechanical properties, self‐healing and self‐adhesion in air/underwater, easy recyclability, solvent tolerance, and sensitive and reliable strain sensing.
Hybrid systems of hydrogels and metals with tough bonding may find widespread applications. Here, a simple and universal method to obtain strong adhesion between hydrogels and diverse metal surfaces, ...such as titanium, steel, nickel, tantalum, argentum, and aluminum, with adhesion energy up to >1000 J m−2 is reported. To achieve such, the metal surfaces are instantly modified with a linker molecule via soaking, dip‐coating, or drop‐casting. The designed linker molecule has a carboxylic acid group to bind with a metal surface, and a methacrylic group to crosslink with a hydrogel, thus bridging the interface between them. In addition, by introducing a stimulus‐responsive disulfide bond into the linker molecule, the on‐demand debonding between toughly bonded hydrogel and metal surface, which is enabled by reductive cleavage of the disulfide chemical linkage, is also demonstrated. More interestingly, after the reductive debonding, the resulting metal surface with free thiol groups can be easily rebonded with a second hydrogel without any further surface modification. The strategy may provide unique opportunities in designing hybrid devices that are suitable for complex and dynamic environments.
Strong adhesion between hydrogels and diverse metal surfaces through a linker molecule is obtained through a simple method. By introducing a stimulus‐responsive moiety into the linker molecule, on‐demand debonding between toughly bonded hydrogels and metal surfaces and facile rebonding is further achieved. This strategy provides unique opportunities in designing hybrid devices that are suitable for complex and dynamic environments.
In this work, we develop a series of novel elastomers from acrylate monomers by one-step free radical copolymerization without using organic solvents. The dynamics of the elastomers, characterized by ...the Kuhn segment relaxation time
τ
0
, is tuned over six orders of magnitude by varying the structure and composition of the acrylate monomers. Comprehensive studies on linear rheology at small deformation and tensile/fracture behaviors at large deformation of the materials are performed. A universal ductile-brittle transition of the elastomers with the criterion of
&z.egrda;τ
0
≂ 0.1 is observed for the diverse monomer pairs and stretch-strain rate
&z.egrda;
and the elastomers exhibit maximum energy dissipation around the ductile-brittle transition reaching a work of extension at fracture of ∼25 MJ m
−3
and a fracture energy of 20 kJ m
−2
. Such toughness is comparable to that of natural rubbers and is among the highest ever reported. In addition, these elastomers possess 100% self-recovery, and a relatively high self-healing efficiency (37-70%) of the cut samples at room temperature even for relatively rigid samples and strong adhesive strength on glass and polymethylmethacrylate (PMMA) substrates. The universal ductile-brittle transition of the materials means that we can use the linear rheology dynamics as fingerprints for predicting the dynamic spectra of toughness of the materials. The wide range of tunable dynamics substantially enriches the choice of elastomers for various applications, and the facile and solvent-free synthesis of these elastomers is eco-friendly, cost-effective and scalable, which greatly lowers the barrier for practical applications.
We propose a universal strategy to design novel advanced elastomers with excellent properties through dynamic linear rheology.
Forming robust associative interactions has been an effective strategy for the design of tough hydrogels. However, the role of associative interactions in the dynamics of hydrogels still remains ...elusive. Here, we report a series of poly(acrylamide-co-methacrylic acid) hydrogels with moderate water contents and excellent mechanical properties that are facilely synthesized by free-radical copolymerization. The mechanical properties of these hydrogels vary with the feeding molar fraction of acrylamide (f am). The gels with f am of 0.2–0.35 exhibit high toughness and good stability in water, which is related to the dense hydrogen bonds and relatively high segment rigidity of the matrix. Dynamic modulus spectra extended by time-temperature superposition and relaxation measurements indicate that the gels undergo glassy-to-rubbery transition with decreased frequency, and the robust hydrogen bonds, whose density is 1–3 times that of entanglements, retard chain disentanglement and contribute to the plateau modulus of the gels at low frequencies. The activation energy for the dissociation of the robust hydrogen bonds is ∼46 kJ mol–1. Furthermore, a decrease in water content results in the shift of dynamic modulus spectra to low frequencies and an increase in transition temperature due to the reduced segment relaxation. To further examine the structure of gel networks, the tensile behaviors of the gels are analyzed using a viscoelastic model. It is found that each partial chain includes 20–30 Kuhn segments, which are stretched after the fracture of intrachain hydrogen bonds to release the hidden length, dissipate energy, and thus toughen the gels. This understanding of the dynamics of the network at different timescales and the contribution of associative interactions to the mechanical properties should be informative for the design of other tough hydrogels.
Soft fiber‐reinforced polymers (FRPs), consisting of rubbery matrices and rigid fabrics, are widely utilized in industry because they possess high specific strength in tension while allowing flexural ...deformation under bending or twisting. Nevertheless, existing soft FRPs are relatively weak against crack propagation due to interfacial delamination, which substantially increases their risk of failure during use. In this work, a class of soft FRPs that possess high specific strength while simultaneously showing extraordinary crack resistance are developed. The strategy is to synthesize tough viscoelastic matrices from acrylate monomers in the presence of woven fabrics, which generates soft composites with a strong interface and interlocking structure. Such composites exhibit fracture energy, Γ, of up to 2500 kJ m−2, exceeding the toughest existing materials. Experimental elucidation shows that the fracture energy obeys a simple relation, Γ = W · lT, where W is the volume‐weighted average of work of extension at fracture of the two components and lT is the force transfer length that scales with the square root of fiber/matrix modulus ratio. Superior Γ is achieved through a combination of extraordinarily large lT (10–100 mm), resulting from the extremely high fiber/matrix modulus ratios (104–105), and the maximized energy dissipation density, W. The elucidated quantitative relationship provides guidance toward the design of extremely tough soft composites.
Novel soft fiber‐reinforced polymers (FRPs) are developed by using viscoelastic polymers that are adhesive, soft, and tough as matrices. The unique combination of these properties in the matrices ensures a strong component interface, which consequently maximizes the energy dissipation density and gives rise to a large force transfer length enabled by the extremely high fiber/matrix modulus ratio. As a result, the soft FRPs can achieve toughness of up to 2500 kJ m−2, exceeding any existing best‐in‐class materials.
In recent years, the development of highly active and selective electrocatalysts for the electrochemical reduction of CO2 to produce CO and formic acid has aroused great interest, and can reduce ...environmental pollution and greenhouse gas emissions. Due to the high utilization of atoms, atom-dispersed catalysts are widely used in CO2 reduction reactions (CO2RRs). Compared with single-atom catalysts (SACs), multi-atom catalysts have more flexible active sites, unique electronic structures and synergistic interatomic interactions, which have great potential in improving the catalytic performance. In this study, we established a single-layer nitrogen–graphene-supported transition metal catalyst (TM-C2N1) based on density functional theory, facilitating the reduction of CO2 to CO or HCOOH with single-atom and multi-atomic catalysts. For the first time, the TM-C2N1 monolayer was systematically screened for its catalytic activity with ab initio molecular dynamics, density of states, and charge density, confirming the stability of the TM-C2N1 catalyst structure. Furthermore, the Gibbs free energy and electronic structure analysis of 3TM-C2N1 revealed excellent catalytic performance for CO and HCOOH in the CO2RR with a lower limiting potential. Importantly, this work highlights the moderate adsorption energy of the intermediate on 3TM-C2N1. It is particularly noteworthy that 3Mo-C2N1 exhibited the best catalytic performance for CO, with a limiting potential (UL) of −0.62 V, while 3Ti-C2N1 showed the best performance for HCOOH, with a corresponding UL of −0.18 V. Additionally, 3TM-C2N1 significantly inhibited competitive hydrogen evolution reactions. We emphasize the crucial role of the d-band center in determining products, as well as the activity and selectivity of triple-atom catalysts in the CO2RR. This theoretical research not only advances our understanding of multi-atomic catalysts, but also offers new avenues for promoting sustainable CO2 conversion.
Real-time kinematic (RTK) technique is widely used in modern society because of its high accuracy and real-time positioning. The appearance of Android P and the application of BCM47755 chipset make ...it possible to use single-frequency RTK and dual-frequency RTK on smartphones. The Xiaomi Mi 8 is the first dual-frequency Global Navigation Satellite System (GNSS) smartphone equipped with BCM47755 chipset. However, the performance of RTK in urban areas is much poorer compared with its performance under the open sky because the satellite signals can be blocked by the buildings and trees. RTK can't provide the positioning results in some specific areas such as the urban canyons and the crossings under an overpass. This paper combines RTK with an IMU-based pedestrian navigation algorithm. We utilize attitude and heading reference system (AHRS) algorithm and zero velocity update (ZUPT) algorithm based on micro electro mechanical systems (MEMS) inertial measurement unit (IMU) in smartphones to assist RTK for the sake of improving positioning performance in urban areas. Some tests are carried out to verify the performance of RTK on the Xiaomi Mi 8 and we respectively assess the performances of RTK with and without the assistance of an IMU-based pedestrian navigation algorithm in urban areas. Results on actual tests show RTK with the assistance of an IMU-based pedestrian navigation algorithm is more robust and adaptable to complex environments than that without it.
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