Stimuli-responsive materials with multiple functions occupy a significant position in the research of bionic artificial intelligence materials. It is a challenge to integrate rapid shape deformation and color change synergistically by a simple method in the same system. Herein, an effective strategy to develop an anisotropic bilayer hydrogel actuator with unified complex deformation and color change is proposed via combining the near-infrared (NIR) light-responsive graphene oxide/poly(N-isopropylacrylamide) (GO-PNIPAM) active hydrogel layer and an UV light-responsive fluorescent poly(acrylic acid [4-(1,2,2-triphenylvinyl)] benzyl ester/N-isopropylacrylamide) passive hydrogel layer. The actuator can undergo light-controlled sapphire fluorescence color change and complex shape deformation simultaneously or separately under light irradiation. It can be remotely manipulated without the requirement for additional reagents, and the irradiation dosage can be accurately modulated through adjusting the irradiation parameters. This work provides new perspectives of intelligent systems with synergistic multiple functions, including smart robots, environmental sensors, and intelligent biomimetic devices. 相似文献
A poly(styrene‐butadiene‐styrene)/poly(N‐isopropylacrylamide) (SBS/PNIPAM) hydrogel elastomer with interpenetrating polymeric network structure is prepared by using solution free radical polymerization in benzene/tetrahydrofuran solvent mixture. The characterizations of hydrogel elastomers are investigated by Fourier transform infrared spectroscopy, scanning electron microscope, rheology, equilibrium swelling studies, and oscillatory swelling study. Results show that these hydrogel elastomers exhibit a temperature‐sensitivity inherited from PNIPAM component at the temperature around 30 °C. Besides, change with tetrahydrofuran to different proportion in solvent mixtures, constituent, and properties as gel content, swelling capacity, mechanical strength and volume phase transition degree are affected deeply. 相似文献
Gold nanorod (AuNR)‐embedded poly(N‐isopropylacrylamide) (PNIPAM) hydrogels offer the possibility of achieving near‐infrared (NIR) light‐triggered drug release. In addition, using nanoparticles as a crosslinker can enhance the mechanical properties of PNIPAM hydrogels, and nanoparticle‐crosslinked hydrogels provide an important approach for dual drug release. Here, NIR light‐triggered dual drug release using AuNR‐embedded thermosensitive nanogel‐crosslinked hydrogels is reported for the first time. Two kinds of drugs are encapsulated, one in the nanogel and the other in the hydrogel. The volume phase transition of the PNIPAM hydrogels is induced by NIR light by utilizing the photothermal effect of AuNRs. By changing the number of embedded AuNRs and the intensity of NIR light, the release rate and drug quantity can be adjusted for on‐demand release. Because of its NIR light‐triggering and nanoparticle‐crosslinking capabilities, AuNR‐embedded thermosensitive nanogel‐crosslinked hydrogels may expand the application scope of hydrogels and provide enhanced properties in their applications. 相似文献
Thermosensitive nanocomposite (NC) hydrogels are considered as a significant kind of intelligent material to be utilized as sensor, biomaterial, drug carrier, etc. Recently, preparation of remotely controlled NC hydrogel with high‐performance attracts more and more concern. To produce facile remote‐stimuli thermosensitive NC hydrogel, a novel near‐infrared (NIR) laser switched CuS/clay/poly(OEGMA‐co‐MEO2MA) hydrogel is demonstrated, which can be precisely remote‐stimulated by NIR irradiation based on the excellent NIR photothermal conversion property of CuS nanoparticle. The temperature change of hydrogel is related to the NIR intensity, CuS content, and crosslinking density. Moreover, the influences on dimensional variation of hydrogel on macroscale are systematically studied, and the hydrogel as smart liquid valve is further utilized which can be remotely controlled by NIR switch on/off successfully. Cyclic test illustrates that this novel CuS/clay/poly(OEGMA‐co‐MEO2MA) hydrogel exhibits stable cyclic volume transition property which has promising applications in the areas of sensors, valves, and intelligent switches. 相似文献
A novel composite thermo‐responsive membrane system for improved controlled‐release is successfully developed. The membrane is composed of a porous membrane with grafted poly(N‐isopropylacrylamide) (PNIPAM) gates acting as functional valves, and a cross‐linked PNIPAM hydrogel inside the reservoir acting as the solute carrier. The thermo‐responsive controlled‐release characteristics of the proposed system are studied when the ambient temperature is continuously increased from 20 to 45 °C (across the LCST of PNIPAM) at a constant rate of 1.5 °C/min. The experimental results show that the prepared system exhibits significantly better performance for thermo‐responsive controlled‐release than single‐functional systems currently in existence, due to the cooperative action of the gating membrane and the inner cross‐linked hydrogel. Furthermore, due to the distinctive composite architecture, the proposed system can overcome some inherent disadvantages of current systems, such as the drug security problem of the reservoir‐type systems and the mechanical strength problem of the hydrogel matrix‐type systems. The system proposed in this study provides a new mode for thermo‐responsive controlled‐release. 相似文献
A multi‐wavelength light drivable bilayer actuator is fabricated by depositing a thin layer of reduced graphene oxide (RGO) onto a flexible poly(dimethyl siloxane) (PDMS) substrate. The RGO/PDMS bilayer film shows fast and reversible bending/unbending motions upon exposure to UV light, visible light, or near‐infrared light (NIR). The photo‐thermal effect of the pump lights is studied by measuring and comparing the light induced temperature rises on RGO/PDMS film. The results demonstrate that the RGO absorbs and converts the light into heat. Thus the bilayer film undergoes thermal expansion under light irradiation. The calculated thermal expansion of the RGO thin layer is smaller than that of the PDMS layer, which results in the bilayer actuator bending towards the layer on the RGO side. Oscillational motion on the bilayer film is successfully achieved using continuous light irradiation on an offset sandwiched RGO/PDMS bilayer cantilever. Light induced motion on the RGO based film provides a new strategy for absorbing light energy and outputting photomechanical work.
Three crosslinkers, poly(ethylene glycol) diacrylate (PEGDA), glycerol ethoxylate triacrylate (GETA) and citric acid-(PEG acrylate)3 (CA-PEGTA) derived from poly(ethylene glycol) (PEG) were synthesized at first. The three series of poly (N-isopropylacrylamide) (PNIPAAm) hydrogels were prepared by photopolymerization with the crosslinkers and compared with a hydrogel based on commercial crosslinker, N,N′-methylene bis-acrylamide (NMBA). The influence of the crosslinker structures and contents on the swelling behaviour, mechanical properties, and drug release of the hydrogels was investigated. The results showed that the hydrogels based on PEGDA and NMBA exhibited the highest and the lowest swelling ratio, respectively. The content of crosslinker of all hydrogel series showed good thermosensitivity and thermo-reversibility. The critical gel transition temperature (CGTT) appeared at 32 °C for the hydrogel based on NMBA, but appeared at about 34 °C for other hydrogels due to higher hydrophilicity of the crosslinker. In the mechanical properties, three-arms crosslinker GETA and CA-PEGTA led to higher mechanical strength than a linear crosslinker PEGDA. A hydrogel based on GETA (NG6) showed the highest shear modulus of 656.9 kPa and Young’s modulus of 1655.0 kPa. The hydrogels containing higher content of crosslinker revealed lower swelling ratio and higher mechanical strength. In the drug release, the hydrogels with higher swelling ratios showed higher drug absorbed. The highest release percentage of caffeine and vitamin B12 for hydrogel based on PEGDA (NP6) could reach 68.3% and 75.4%, respectively. In addition, the bound water and toxicity of the hydrogels were also investigated.
Intelligent hydrogels with excellent flexibility, biocompatibility, and stimulus responsivity can mimic the functions of the skin to detect human motions. However, the low mechanical strength limits its application in the field of biomimetic materials. In this work, polyacrylamide-reduced graphene oxide (PAM-rGO) composite hydrogels were prepared by the combination of PAM and partially rGO, and their biomimetic strain sensors were studied. The rGO played the role of “2D flexible crosslinking point” in the composite hydrogel. Through the H-bonds between rGO and hydrogels, the toughness and strength of the composite hydrogel were enhanced. The maximum strain of the hydrogel changed from 751% to 1097%, and the maximum stress changed from 0.065 to 0.20 MPa. On the other hand, the interaction between the PAM backbone and the rGO provided a credible resistance response to the stimulation of strain. The better linear relationship between resistance and length was built, with R2 of 0.992. Furthermore, the composite hydrogels were assembled into wearable devices to monitor human-motion, including fingers bending, elbows bending and walking. The experimental results showed that the PAM-rGO composite hydrogel had great potential in the field of bionic skin. 相似文献
Novel injectable thermoreversible hydrogel compositions with semi-interpenetrating network structure were prepared through the addition of sodium alginate (SA) to poly(N-isopropylacrylamide) (PNIPAM) aqueous solutions. The addition of the hydrophilic alginate strongly improved the stability against syneresis of the 15 wt% PNIPAM hydrogels formed at 37°C from less than 15 min in the absence of alginate to more than 7 days in the presence of 4 wt% SA. Besides the SA concentration, the hydrogel stability depended on the molecular weight and polydispersity of PNIPAM, being lower when a high molecular weight fraction was present. The phase transition temperature (Tph) of the PNIPAM aqueous solutions decreased with alginate concentration, while the dynamic viscosity and elastic modulus of the hydrogels increased. By decreasing the PNIPAM molecular weight and polydispersity, the dynamic viscosity and elastic modulus of the PNIPAM–alginate hydrogels formed above Tph diminished, while their viscoelastic behavior changed from predominantly elastic to predominantly viscous. 相似文献
The reduced graphene oxide (rGO) decorated with Ag nanoparticles was synthesized by the chemical reduction of graphene oxide in an aqueous solution containing AgNO3, in the presence of hydrazine hydrate as a reducing agent. The reduction of graphene oxide was confirmed by FT-IR and raman spectroscopy analyses. The x-ray diffraction pattern and UV–visible investigations demonstrated the formation of Ag particles on the surface of rGO sheets. After successful decoration, the Ag/rGO nano-composite was used as the reinforcement in the copper matrix composite. Cu–Ag/rGO composites with different percentages of Ag/rGO (0.4, 0.8, 1.6 and 3.2 vol%.) were prepared by mechanical milling and spark plasma sintering (SPS). The effects of the Ag/rGO content on the consolidation process, micro-hardness, bending strength and also, fracture surface of the prepared samples were then investigated. The three-point bending strength of the sintered samples was increased from 285 to 472 MPa by the addition 0.8 vol%. of Ag/rGO, as compared to the pure Cu. Moreover, increasing the reinforcement content to the 3.2 vol%. Ag/rGO led to decreasing the bending strength to 433 MPa. The highest micro-hardness (81 Hv) was obtained for the composite sample containing the 1.6 vol%. Ag/rGO. By increasing Ag/r-GO as the reinforcement (3.2 vol%.), the Vickers hardness was decreased to 69 Hv. Also, investigation of the fracture surface morphology showed transformation of fracture mechanism from plastic changes to brittle ones by raising the Ag/rGO content volume from 0.8 to 1.6 vol %. 相似文献
As a first step towards preparing fouling-resistant coatings for water purification membranes, three series of copolymer hydrogel networks were synthesized using poly(ethylene glycol) diacrylate (PEGDA) as the crosslinker and acrylic acid (AA), 2-hydroxyethyl acrylate (HEA), or poly(ethylene glycol) acrylate (PEGA) as comonomers. Copolymers containing varying amounts of PEGDA with each of these comonomers were prepared. Glass transition temperatures obeyed the Fox equation. Crosslink density strongly influenced water uptake and water permeability for materials of constant chemical composition. For example, the volume fraction of water sorbed by a 100 mol% PEGDA hydrogel was 0.61. However, introducing comonomers into the network reduced hydrogel crosslink density, and in hydrogels having the same ethylene oxide content, water sorption increased as crosslink density decreased. The highest water volume fraction observed was 0.72, obtained in a copolymer containing 80 mol% PEGA and 20 mol% PEGDA. Water permeability increased systematically with increasing water sorption, and water permeability coefficients ranged from 10 to 26 L μm/(m2 h bar). NaCl partition coefficients ranged from 0.36 to 0.53 (g NaCl/cm3 hydrogel)/(g NaCl/cm3 solution). NaCl diffusion coefficients varied little with polymer composition; in this regard, diffusion coefficient values ranged from 4.3 × 10−6 to 7.4 × 10−6 cm2/s. Based on contact angle measurements using n-decane in water, oil exhibited a low affinity for the surfaces of these polymers, suggesting that coatings prepared from such materials might improve the fouling resistance of membranes towards oily wastewater. 相似文献
A thermally reversible hydrogel composed of a three-arm star copolymer with a specific host β-cyclodextrin (β-CD) center has been developed. The synthesis of this star copolymer initiates with β-CD core, from which sequential polymerization of a temperature-responsive poly(N-isopropylacrylamide) (PNIPAM) block and a hydrophilic poly(N,N-dimethylacrylamide) (PDMA) block as asymmetric arms (named β-CD-g-(PNIPAM-b-PDMA)3) is performed via RAFT protocol. Below the lower critical solution temperature (LCST) of PNIPAM segment, the polymer is of good water-solubility and exhibits a sol state. Upon thermal stimulus, free-standing hydrogels can be formed rapidly at sufficiently high concentrations. By comparing the sol–gel transition of the star polymer with that of its linear counterpart without this feature, we concluded that the special star-shape topology and the thermal-collapsed PNIPAM chains were responsible for this gelation behavior. The rheology measurements indicate the mechanical properties of the polymer hydrogels and the thermal reversibility of the sol–gel transition. Using Rhodamine B as a molecule to model a typical drug, we realize the favorable encapsulation and releasing process from the hydrogel, demonstrating that this star polymer has the potential to function as an injectable hydrogel for drug delivery and gene transport. 相似文献
The poly (ethylene glycol) diacrylate (PEGDA)-based hydrogels were prepared by UV radiation under
nitrogen, using PEGDA and 2-hydroxyethyl methacrylate (HEMA) as precursors. The PEGDA and HEMA precursors
were respectively added into distilled water at a predetermined feed ratio. 2-Hydroxy-1-[4-(hydroxyethoxy)phenyl]-2-methyl-1-propanone
(Irgacure2959) was used as a photoinitiator. The PEGDA-based hydrogels were characterized by FT-IR spectra,
interior morphology, equilibrium swelling ratio, and Dynamic contact angle (DCA). The results showed: (1)
-C=C- bonds of PEGDA and HEMA disappeared after photocrosslinking, which indicated hydrogel formation by
consuming -C=C- bonds; (2) swelling ratio of the hydrogels were greatly influenced by the additive precursor
ratios and microporous net; (3) with HEMA content increasing in PEGDA-based hydrogels, equilibrium water
content (EWC) increased and the contact angle decreased, which resulted from the strong H-bonding interactions
of HEMA between the polymer and water. 相似文献