Human fingers exhibit both high sensitivity and wide tactile range. The finger skin structures are designed to display gradient microstructures and compressibility. Inspired by the gradient ...mechanical Young's modulus distribution, an electric‐field‐induced cationic crosslinker migration strategy is demonstrated to prepare gradient ionogels. Due to the gradient of the crosslinkers, the ionogels exhibit more than four orders of magnitude difference between the anode and the cathode side, enabling gradient ionogel‐based flexible iontronic sensors having high‐sensitivity and broader‐range detection (from 3 × 102 to 2.5 × 106 Pa) simultaneously. Moreover, owing to the remarkable properties of the gradient ionogels, the flexible iontronic sensors also show good long‐time stability (even after 10 000 cycles loadings) and excellent performance over a wide temperature range (from −108 to 300 °C). The flexible iontronic sensors are further integrated on soft grips, exhibiting remarkable performance under various conditions. These attractive features demonstrate that gradient ionogels will be promising candidates for smart sensor applications in complex and extreme conditions.
Inspired by gradient modulus distribution of human fingers, gradient ionogels are prepared by an electric‐field‐induced cationic crosslinkers migration strategy. The gradient of the modulus distribution enables the gradient‐ionogel‐based flexible sensors to demonstrate high sensitivity and broader‐range detection simultaneously. Moreover, the flexible iontronic sensors also show good longtime stability and excellent performance over a wide temperature range.
Common natural and synthetic high‐strength materials (such as rubber, plastics, ceramics, and metals) undergo the occurrence of poor deformability. Achieving high strength and large deformation ...simultaneously is a huge challenge. Herein, high‐strength ionogels are developed through the synergy of force‐induced crystallization and halometallate ionic liquid created supramolecular ionic networks. The prepared poly(vinyl alcohol)/halometallate ionic liquid ionogels show excellent mechanical properties, including ultimate fracture stress (63.1 ± 2.1 MPa), strain (5248 ± 113%), and unprecedented toughness (1947 ± 52 MJ m−3), which is much higher than that of most metals and alloys. Furthermore, the ionogels can achieve reversibility by water to realize green recovery and restoration of damaged mechanical properties.
Ultrastrong and superstretchable ionogels tougher than that of metals are produced through the synergy of force‐induced crystallization and halometallate ionic liquid created supramolecular ionic networks. The prepared ionogels with environmental applicability and sustainability are expected to replace lightweight high‐strength materials, such as plastics and rubbers in the applications of aerospace, robotics, and other fields.
The mechanical properties of most hydrogels (ionogels) are considerably affected by covalently cross‐linked networks. However, the interactions between solvent/solvent molecules and solvent/polymer ...chains are usually ignored. Herein, a series of ultra‐tough ionogels were prepared via a supramolecular solvent, halometallate ionic liquid, in which cations and coordinating anions form a 3D supramolecular network. The linear polymer chains are physically cross‐linked with supramolecular solvents synergistically enhancing the strength (14.3 MPa), toughness (78 MJ m−3), and Young's modulus (55 MPa) of ionogels, effectively dispersing the stress concentration under load, and obtaining better fatigue resistance and higher fracture energy (198 kJ m−2). Furthermore, the reversible cross‐linking enables green recovery and recycling of ionogels, simply by water. This strategy shows broad applicability based on a variety of supramolecular solvents and coordinatable polymers.
Ultra‐tough and recyclable ionogels are constructed by physical cross‐linking of coordinated supramolecular solvents and linear polymer segments. The solvents in ionogels function as 3D supramolecular networks, which provide strong mechanical support for ionogels.
Segmenting individual street trees from a street side-view point cloud is the first and key step of obtaining a street tree inventory. Using the classification-segmentation framework for individual ...tree segmentation makes tree detection simple and accurate, but segmenting overlapping trees is still challenging. To more accurately segment overlapping trees, a coarse-to-fine method for segmenting individual street trees from a side-view point cloud is proposed in this paper. Following the classification-segmentation framework, the tree points are first detected from the side-view street point cloud by a pointwise classifier fused from 13 local geometric features and then trained using random forest (RF). Second, the tree proposals are obtained by density-based spatial clustering of applications with noise (DBSCAN) clustering and detection error filtering. Third, the overlapping tree proposals are recognized by trunk identification, and the single tree proposals are directly output as individual trees. Fourth, the overlapping trees are roughly divided into individual tree proposals through vertical planes. Finally, individual trees with optimized contours are obtained by iteratively using DBSCAN clustering and k-nearest neighbor (k-NN) classification. The side-view point cloud of a 290 m-long urban street containing 77 street trees is captured by a hand-held mobile ZEB Horizon laser scanner. The tree detection attained an F1 score of 0.9916 with a precision of 0.9989 and a recall of 0.9864. For individual tree segmentation, the F1 score was 0.9745 with a precision of 0.9672 and a recall of 0.9819. Compared to two current classification-segmentation methods, the overlapping tree segmentation F1 scores were increased by 0.0914 and 0.0617, respectively. The proposed method can be applied to tree parameter extraction, which is an important urban forest inventory task and is crucial for urban forest management. In our experiment, the root mean squared error (RMSE) of the trunk diameter at breast height (DBH) estimation was 0.8485 cm.
The development of hydrogels and ionic gels for applications in fields such as soft electronics and wearable sensors is limited by liquid evaporation or leakage. Ionic conductors without volatile ...liquids are better choices for flexible and transparent devices. Here, a liquid polymer electrolyte (LPE) is prepared from a mixture of lithium bis(trifluoromethane)sulfonimide and polyethylene glycol (PEG) above the melting point of PEG. A three-dimensional (3D) printable solvent-free ionic elastomer (IE) is introduced by photopolymerization of ethyl acrylate and hydroxyethyl acrylate in the prepared LPE. The conductivity is significantly improved by the presence of a high content of the lithium salt. Dynamic cross-linking networks improve the stretchability and resilience of the elastomer. The pattern design capability of the IE is provided by light-curing 3D printing. These features demonstrate that the IE has broad application prospects in flexible sensors, ion skins, and soft robots.
With the continuous development of impact protection materials, lightweight, high‐impact resistance, flexibility, and controllable toughness are required. Here, tough and impact‐resistant poly(ionic ...liquid) (PIL)/poly(hydroxyethyl acrylate) (PHEA) double‐network (DN) elastomers are constructed via multiple cross‐linking of polymer networks and cation‐π interactions of PIL chains. Benefiting from the strong noncovalent cohesion achieved by the cation‐π interactions in PIL chains, the prepared PIL DN elastomers exhibit extraordinary compressive strength (95.24 ± 2.49 MPa) and toughness (55.98 ± 0.66 MJ m−3) under high‐velocity impact load (5000 s−1). The synthesized PIL DN elastomer combines strength and flexibility to protect fragile items from impact. This strategy provides a new research idea in the field of the next generation of safety and protective materials.
Tough and impact‐resistant poly(ionic liquid) (PIL) double‐network (DN) elastomers are constructed via multiple cross‐linking of polymer networks and cation‐π interactions of PIL chains. The rational structural design and the introduction of cation‐π interactions significantly enhance the strength and toughness of PIL DN elastomers, providing excellent impact resistance as impact protection materials.
In this study, we developed a superstrong and reversible adhesive, which can possess a high bonding strength in the “adhesive” state and detach with the application of heating. An ionic crystal (IC) ...gel, in which an IC was immobilized within a soft‐polymer matrix, were synthesized via in situ photo‐crosslinking of a precursor solution composed of N, N‐dimethyl acrylamide (DMAA) and a melted IC. The obtained IC gel is homogenous and transparent at melt point. When cooled to the phase transition temperature of the IC, the gel turns into the adhesive with the adhesion strength of 5.82 MPa (on glasses), due to the excellent wetting of melted gel and a thin layer of crystalline IC with high cohesive strength formed on the substrates. The synergistic effects between IC, polymer networks and substrates were investigated by solid state 1H NMR and molecular dynamics simulation. Such an adhesive layer is reversable and can be detached by heating and subsequent re‐adhesion via cooling. This study proposed the new design of removable adhesives, which can be used in dynamic and complex environments.
Inspired by reversible ice adhesion, a reversible ionic crystal (IC) based gel adhesive was prepared, which showed superstrong and reversible adhesion due to the phase transition of ICs. In addition, the reversible adhesion can be adjusted by heating and light, and be effectively monitored by resistance and capacitance.
A one-step sol-gel synthesis of porous carbon micro/nanospheres (PCMNSs) through cationic surfactant with two long hydrophobic chains was reported to realize the tunable synthesis of carbon ...nanospheres with interconnected structures between the shell and shell. The unique pore structure of PCMNSs endows the material with efficient electrochemical energy storage performance. The abundant macropores and mesopores of PCMNSs can promote the transport of electrolyte by reducing diffusion distances and provide sufficient active sites for effective charge storage and the charge transfer can be greatly increased by the interconnected channel structure among the carbon spherical shells. By adjusting the amount of surfactant and the consumption of ethanol, the controllable synthesis of individual carbon spheres to three-dimensional carbon frameworks were successfully realized. The results showed that the representative sample A-PCMNSs-0.6-35 had excellent supercapacitive performance, excellent electrochemical specific capacitance (242 F g−1 at 1 A g−1), great capacitance retention (170 F g−1 at 100 A g−1) and superior cycle stability (93% at 10 A g−1 after 5000 cycles).
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•a three-dimensional carbon framework with interconnected pore in the shell.•high specific surface area (up to 1,746.53 m2 g−1) and large pore volume (up to 1.94 cm3 g−1).•high level doping of heteroatoms N (up to 7.07 at.%) and O (up to 4.99 at.%).•cationic surfactant with two long hydrophobic chains and a hydrophilic head group were used to regulate the structure.•excellent specific capacitance (242 F g−1 at 1 A g−1) and great capacitance retention (170 F g−1 at 100 A g−1).
The resistance of gels and elastomers increases significantly with tensile strain, which reduces conductive stability and restricts their use in stable and reliable electronics. Here, highly ...conductive tough hydrogels composed of silver nanowires (AgNWs), liquid metal (LM), and poly(vinyl alcohol) (PVA) are fabricated. The stretch‐induced orientations of AgNWs, deformable LM, and PVA nanocrystalline create conductive pathways, enhancing the mechanical properties of the hydrogels, including increased ultimate fracture stress (13‐33 MPa), strain (3000–5300%), and toughness (390.9–765.1 MJ m−3). Notably, the electrical conductivity of the hydrogels is significantly improved from 4.05 × 10−3 to 24 S m−1 when stretched to 4200% strain, representing a 6000‐fold enhancement. The incorporation of PVA nanocrystalline, deformable LM, and AgNWs effectively mitigates stress concentration at the crack tip, thereby conferring crack propagation insensitivity and fatigue resistance to the hydrogels. Moreover, the hydrogels are designed with a reversible crosslinking network, allowing for water‐induced recycling.
Highly conductive and tough hydrogels composed of liquid metal (LM), silver nanowires (AgNWs), and poly(vinyl alcohol) (PVA) are constructed. The stretch‐induced orientations of AgNWs, deformable LM, and PVA nanocrystalline form conductive pathways and enhance the mechanical properties of hydrogels, including ultimate fracture stress, strain, toughness, and dramatically enhance the electrical conductivity (from 4.05 × 10−3 to 24 S m−1 at 4200% strain).
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