Flexible sensors are becoming required in heath monitoring and human–machine interfaces, but it is still a challenge to develop flexible sensors with integrated high performances. Herein, high‐performance flexible sensors are fabricated that are self‐healing, reversibly adhesive, and utilizing stretchable hydrogels, which are composed of a pluronic F127 diacrylate (F127DA) cross‐linked poly(acrylic acid) (PAA) network and polydopamine (PDA), and further cross‐linked by Fe3+. The unique structure endows the resulting hydrogels (PAA‐PDA‐Fe3+ hydrogels) excellent self‐healing property, reversible adhesion property, mechanical stretchability, and electrical conductivity. On the basis of the excellent properties of PAA‐PDA‐Fe3+ hydrogels, flexible sensors with large sensing range (0–575%), high sensitivity (GF = 6.31), low response time (0.25 s), and excellent robustness (>500 cycles) are assembled and further applied in detecting both large and subtle strains induced by human motions and water ripple. Overall, this work not only provides an alternative clue to construct multi‐functional hydrogels, but also offers a new kind of high‐performance materials for flexible electronic devices, especially those for health monitoring and human–machine interface. 相似文献
Stretchable, flexible, and strain‐sensitive hydrogels have gained tremendous attention due to their potential application in health monitoring devices and artificial intelligence. Nevertheless, it is still a huge challenge to develop an integrated strain sensor with excellent mechanical properties, broad sensing range, high transparency, biocompatibility, and self‐recovery. Herein, a simple paradigm of stretchable strain sensor based on multifunctional hydrogels is prepared by constructing synergistic effects among polyacrylamide (PAM), biocompatible macromolecule sodium alginate (SA), and Ca ion in covalently and ionically crosslinked networks. Under large deformation, the dynamic SA‐Ca2+ bonds effectively dissipate energy, serving as sacrificial bonds, while the PAM chains bridge the crack and stabilize the network, endowing hydrogels with outstanding mechanical performances, for instance, high stretchability and compressibility, as well as excellent self‐recovery performance. The hydrogel is assembled to be a transparent and wearable strain sensor, which has good sensitivity and very wide sensing range (0–1700%), and can precisely detect dynamic strains, including both low and high strains (20–800% strain). It also exhibits fast response time (800 ms) and long‐time stability (200 cycles). The sensor can monitor and distinguish complicated human motions, opening up a new route for broad potential applications of eco‐friendly flexible strain‐sensing devices. 相似文献
A simple, multiple‐hydrogen‐bond approach to fabricating physically crosslinked, Amylopectin reinforced polyacrylamide/poly(vinyl alcohol) (Amy/PAAm/PVA) double‐network (DN) hydrogels with super toughness in bulk and at solid interfaces is reported. The Amy/PAAm/PVA DN hydrogels exhibit high tensile strength (854.1 kPa), high extensibility (≈eight times), high bulk toughness (4094.8 kJ m?3), good self‐recovery property (≈92% of self‐recovery at room temperature), and strong adhesion to nonporous glass surfaces (≈158 kPa). Such tough and adhesive DN hydrogels have great potential for various applications in engineering artificial soft tissues, flexible electronics, and wearable devices. 相似文献
Despite recent significant progress in fabricating tough hydrogels, it is still a challenge to realize high strength, large stretchability, high toughness, rapid recoverability, and good self‐healing simultaneously in a single hydrogel. Herein, Laponite reinforced self‐cross‐linking poly(N‐hydroxyethyl acrylamide) (PHEAA) hydrogels (i.e., PHEAA/Laponite nanocomposite [NC] gels) with dual physically cross‐linked network structures, where PHEAA chains can be self‐cross‐linked by themselves and also cross‐linked by Laponite nanoplatelets, demonstrate integrated high performances. At optimal conditions, PHEAA/Laponite NC gels exhibit high tensile strength of 1.31 MPa, ultrahigh tensile strain of 52.23 mm mm?1, high toughness of 2238 J m?2, rapid self‐recoverability (toughness recovery of 79% and stiffness recovery of 74% at room temperature for 2 min recovery without any external stimuli), and good self‐healing properties (strain healing efficiency of 42%). The work provides a promising and simple strategy for the fabrication of dual physically cross‐linked NC gels with integrated high performances, and helps to expand the fundamentals and applications of NC gels. 相似文献
A dual cross‐linking design principle enables access to hydrogels with high strength, toughness, fast self‐recovery, and robust fatigue resistant properties. Imidazole (IMZ) containing random poly(acrylamide‐co‐vinylimidazole) based hydrogels are synthesized in the presence of Ni2+ ions with low density of chemical cross‐linking. The IMZ‐Ni2+ metal–ligand cross‐links act as sacrificial motifs to effectively dissipate energy during mechanical loading of the hydrogel. The hydrogel mechanical properties can be tuned by varying the mol% of vinylimidazole (VIMZ) in the copolymer and by changing the VIMZ/Ni2+ ratio. The resultant metallogels under optimal conditions (15 mol% VIMZ and VIMZ/Ni2+ = 2:1) show the best mechanical properties such as high tensile strength (750 kPa) and elastic modulus (190 kPa), combined with high fracture energy (1580 J m?2) and stretchability (800–900% strain). The hydrogels are pH responsive and the extent of energy dissipation can be drastically reduced by exposure to acidic pH. These hydrogels also exhibit excellent anti‐fatigue properties (complete recovery of dissipated energy within 10 min after ten successive loading–unloading cycles at 400% strain), high compressive strength without fracture (17 MPa at 96% strain), and self‐healing capability due to the reversible dissociation and re‐association of the metal ion mediated cross‐links. 相似文献
Utilization of bionics to develop stimuli responsive polymers that can heal damage with excellent restorability is particularly attractive for a sustainable society. Herein, inspired by chameleons, a hierarchical structural design strategy is proposed and illustrated to fabricate a healable photochromic material based on a self‐healable polymeric matrix and a finely dispersed photochromic spirooxazine. The self‐healable polymeric matrix is fabricated via the integration of multiple hydrogen bonds (H bonds) and covalent cross‐links into a biomass‐derived elastomer. The dynamic nature and soft characteristics enable the as‐prepared elastomer superior extensibility as well as self‐healing ability, while the covalent cross‐links can assist the reassociation of ruptured H bonds. The representative elastomer exhibits an extensibility of 2600% and toughness of 42.76 MJ m?3. Furthermore, it shows good self‐healing ability with complete recovery of scratch as well as restoration against 1900% of elongation and 24.1 MJ m?3 of toughness after healing at 60 °C for 24 h. This combination of moderate toughness, good self‐healing ability, and smart photochromic property in biomass‐derived materials should largely improve their applicability, reliability, and sustainability in various materials and devices. 相似文献
An ideal hydrogel with excellent adhesive performance has drawn much attention in research and applications. In this paper, a photo‐crosslinked polyvinyl alcohol bearing styrylpyridinium group/cellulose nanocrystals (PVA‐SbQ/CNC) composite hydrogel is designed through photo‐crosslinking technology for preventing the physical crosslinking of polyvinyl alcohol to maintain enough hydroxy groups in the hydrogel. Thus, the hydrogel exhibits excellent adhesive behavior not only for various solid substrates (plastics, rubbers, glasses, metals, and woods) but also muscle and fat. In addition, the formation mechanism, the swelling behavior, and mechanical strength are also investigated. Also, these results show that photo‐crosslinked PVA‐SbQ/CNC hydrogel possesses high swelling rate, super stretchability, and high toughness. Moreover, adhesive, mechanical, and swelling properties of PVA‐SbQ/CNC hydrogels can be changed with the increase of total incident light intensity. It is anticipated that the photo‐crosslinked PVA‐SbQ/CNC hydrogel would play a significant role in the applications of wound dressing, medical electrodes, tissue adhesives, portable equipment, and super absorbent materials. In this sense, the simple photo‐crosslinking strategy would provide new ideas for designing soft and adhesive materials through controlling the balance of cohesion and adhesion. 相似文献
Self‐healing polymer materials have attracted extensive attention and have been explored due to their ability of crack repairing in materials. This paper aims to develop a novel polyurethane‐based material with high self‐healing efficiency and excellent mechanical properties under 80 °C on the basis of reversible Diels–Alder bonds as well as zinc–ligand structure (DA‐ZN‐PU). By integrating DA bonds and zinc–ligand structure, as‐prepared DA‐ZN‐PU samples reach the maximum tensile strength as much as 28.45 MPa. After self‐healing, the tensile strength is 25.85 MPa, leading to the high self‐healing efficiency of 90.8%. In addition, by introducing carbonyl iron powder (CIP), a new polyurethane containing carbonyl iron powder (DA‐ZN‐CIP‐PU) can be achieved, exhibiting microwave‐assisted self‐healing property. And the self‐healing efficiency can be reached to 92.6% in 3 min. Due to high self‐healing efficiency and excellent mechanical properties of the prepared novel polyurethane, it has application attributes in crack repair of functional composite materials. 相似文献
A novel self-healing poly(vinyl alcohol) (PVA)-based hydrogel is developed by cross-linking PVA chains through multi dynamic covalent bonds by use of a small cross-linker composed by 4-formylphenylboric acid (FPBA) and lysine (Lys). The dynamic borate-imine-imine-borate bond structure between PVA chains endows the hydrogel excellent stretchability and ultra-fast self-healing ability without external stimulation. The self-healing efficiency can attain 94% and the elongation at break can reach up to near 1000% after only 3 min healing. Moreover, the self-healing of the hydrogel through the contact of two faces from both the same cut position and different cut positions has similar excellent efficiency. The hydrogel with the unusual self-healing performance and stretchability is used as an ideal material in strain sensors monitoring human movement and tiny vibrations caused by human voice. Interestingly, the sensor can continue to function normally after self-healing for only ≈3 s. It is expected that this simple strategy of fabricating self-healing hydrogels with multi dynamic bonds will provide new opportunities in the design and preparation of PVA-based hydrogels to expand their potential applications in sensors and other various fields. 相似文献
Development of artificial soft materials that have good mechanical performances and autonomous healing ability is a longstanding pursuit but remains challenging. This work reports a kind of highly flexible, tough, and self‐healable poly(acrylic acid)/Fe(III) (PAA/Fe(III)) hydrogels. The hydrogels are dually cross‐linked by triblock copolymer micelles and ionic interaction between Fe(III) and carboxyl groups. Due to the coexistence of these two cross‐linking points, the resulting PAA/Fe(III) hydrogels are tough and can be flexibly stretched, bent, knotted, and twisted. The hydrogels can withstand a deformation of 600% and an ultimate stress as high as 250 kPa. Moreover, the dynamic ionic interaction also endows the hydrogels self‐healing properties. By varying the ratio of Fe(III)/AA, a compromised healing efficiency of 73% and an ultimate stress of 200 kPa are obtained.
Self‐healable hydrogels are promising soft materials with great potential in biomedical applications due to their autonomous self‐repairing capability. Although many attempts are made to develop new hydrogels with good self‐healing performance, to integrate this characteristic along with other responsive multifunctions into one hydrogel still remains difficult. Here, a self‐healable hybrid supramolecular hydrogel (HSH) with tunable bioadhesive and stimuli‐responsive properties is reported. The strategy is imparting graphene oxide (GO) nanosheets and quadruple hydrogen bonding ureido‐pyrimidinone (UPy) moieties into a thermoresponsive poly(N‐isopropylacrylamide) (PNIPAM) polymer matrix. The obtained GO–HSH hydrogel shows rapid self‐healing behavior and good adhesion to various surfaces from synthetic materials to biological tissue. In addition, doxorubicin hydrochloride (DOX) release profiles reveal the dual thermo‐ and pH‐responsiveness of the GO–HSH hydrogel. The DOX‐loaded hydrogel can further directly adhere to titanium substrate, and the released DOX from this thin hydrogel coating remains biologically active and has high capability to kill tumor cells. 相似文献
Double network (DN) hydrogels with high strength and toughness are considered as promising soft materials. Herein, a dual physically cross‐linked hydrophobic association polyacrylamide (HPAAm)/alginate‐Ca2+ DN hydrogel is reported, consisting of a HPAAm network and a Ca2+ cross‐linked alginate network. The HPAAm/alginate‐Ca2+ DN hydrogel exhibits excellent mechanical properties with the fracture stress of 1.16 MPa (3.0 and 1.7 times higher than that of HPAAm hydrogel and HPAAm/alginate hydrogel, respectively), fracture strain of 2604%, elastic modulus of 71.79 kPa, and toughness of 14.20 MJ m?3. HPAAm/alginate‐Ca2+ DN hydrogels also demonstrate self‐recovery, notch‐insensitivity, and fatigue resistance properties without any external stimuli at room temperature through reversible physical bonds consisting of hydrophobic association and ionic crosslinking. As a result, the dual physical crosslinking would offer an avenue to design DN hydrogels with desirable properties for broadening current applications of soft materials. 相似文献
Creating load‐bearing hydrogels with superior mechanical strength and toughness is of vital importance for promoting the development of polymer hydrogels toward practical applications. Herein, a type of composite hydrogel is facilely fabricated employing simple and effective UV irradiation one‐pot method by introducing cheap and available nanosilica sol into hydrophobic association poly(acrylamide–lauryl methacrylate) (HAPAM gels). Composite hydrogels exhibit enhanced mechanical strength (compression stress reaching 4.4 MPa) and toughness (compression hysteresis energy achieved is 151.15 kJ m?3) compared to HAPAM gels. Composite hydrogels also demonstrate rapid self‐recovery behavior (95.91% stress recovery and 92.19% hysteresis energy recovery after restoration for 15 min, respectively) and favorable fatigue‐resistant ability without the help of external stimuli at room temperature based on the cyclic loading–unloading compression measurements. The simple and effective design strategy may help the development of hydrogel materials toward practical applications for soft sensors, tissue engineering, and actuators. 相似文献