Novel nanocomposite actuator based on sulfonated poly(styrene-b-ethylene-co-butylene-b-styrene) polymer

Ionic polymer metal composite (IPMC) actuators were developed with multi-walled carbon nanotubes (MWNT) and sulfonated poly(styrene-b-ethylene-co-butylene-b-styrene) (SSEBS) ionic polymers. MWNT with the diameter of 10 approximately 15 nm and length of 10 approximately 20 microm was used to enhance the mechanical and electrical performances of IPMC actuators. Ultrasonic treatment and high speed mixing were employed to disperse MWNTs homogeneously in SSEBS solution. The electroless plating method was used to make electrodes on the both side of the composite membrane. Scanning electron microscope (SEM) and transmission electron microscope (TEM) images were taken to characterize the surface and micro-structures of the composite actuators. In this study, novel nano-composite actuators were fabricated with different weight ratio of the MWNT 0.5%, 1.5% and the bending actuation performance and electrical power consumptions were investigated.     

The highly stable air-working electro-active ionic polymer actuator based on nitrogen-doped graphene aerogel flexible electrode

Journal of Materials Science: Materials in Electronics - Three-dimensional nitrogen-doped graphene aerogels (3D N-GAs) were prepared by ultrasonic stripping, hydrothermal reduction and freeze...     

Biodegradable electrospun nanocomposite fibers based on Poly(2-hydroxy ethyl methacrylate) and bamboo cellulose

Electrospun fibers resemble extracellular matrix and are successfully being used in drug delivery and wound healing. The present study reports the extraction of cellulose from natural fiber such as bamboo which is cost effective. It was then added to Poly(2-hydroxy ethyl methacrylate) (pHEMA) solution and electrospun to obtain pHEMA-bamboo cellulose nanocomposite fibers. The characterization of the prepared bamboo cellulose, pHEMA-bamboo cellulose nanocomposite fibers were carried out using FTIR, XRD, TGA and SEM analysis. The biocompatibility of the prepared nanocomposite fiber were studied by MTT extraction method using Vero cell lines. Similarly the anticancer activity of paclitaxel incorporated nanocomposite fibers were assessed using MCF 7 cancer cell lines. The prepared nanocomposite fibers showed 96% cell viability and the paclitaxel incorporated pHEMA-bamboo cellulose nanocomposite fiber showed 7.4% cancer cell viability in 72 h. This proves the applicability of the prepared polymer matrix composite fiber as a fibrous mesh covering the affected skin area for skin cancers or wound healing.     

Highly stretchable self-sensing actuator based on conductive photothermally-responsive hydrogel

Soft robots built with active soft materials have been increasingly attractive. Despite tremendous efforts in soft sensors and actuators, it remains extremely challenging to construct intelligent soft materials that simultaneously actuate and sense their own motions, resembling living organisms’ neuromuscular behaviors. This work presents a soft robotic strategy that couples actuation and strain-sensing into a single homogeneous material, composed of an interpenetrating double-network of a nanostructured thermo-responsive hydrogel poly(N-isopropylacrylamide) (PNIPAAm) and a light-absorbing, electrically conductive polymer polypyrrole (PPy). This design grants the material both photo/thermal-responsiveness and piezoresistive-responsiveness, enabling remotely-triggered actuation and local strain-sensing. This self-sensing actuating soft material demonstrated ultra-high stretchability (210%) and large volume shrinkage (70%) rapidly upon irradiation or heating (13%/°C, 6-time faster than conventional PNIPAAm). The significant deswelling of the hydrogel network induces densification of percolation in the PPy network, leading to a drastic conductivity change upon locomotion with a gauge factor of 1.0. The material demonstrated a variety of precise and remotely-driven photo-responsive locomotion such as signal-tracking, bending, weightlifting, object grasping and transporting, while simultaneously monitoring these motions itself via real-time resistance change. The multifunctional sensory actuatable materials may lead to the next-generation soft robots of higher levels of autonomy and complexity with self-diagnostic feedback control.     

Biomimetic electro-active polymer based on sulfonated poly (styrene-b-ethylene-co-butylene-b-styrene)

Based on the sulfonated poly (styrene-b-ethylene-co-butylene-b-styrene) ionic membrane, a novel electro-active polymer, which can be used as sensors and actuators, was developed through the electroless plating procedure. The surface and cross-sectional morphologies of the SSEBS actuator were disclosed by using scanning electron microscope and transmission electron microscopy. The electromechanical results of the SSEBS actuators show high-speed bending actuation under constant voltages and also give excellent harmonic responses under sinusoidal excitation. In the voltage-current test, the electrical current is almost synchronous with the applied voltages, while the mechanical displacement shows high phase shift from the voltage signals. The SSEBS-based ionic polymer-metal composite can be a promising smart material and may possibly be used to implement biomimetic motion.     

Hybrid nanocomposite based on cellulose and tin oxide: growth,structure, tensile and electrical characteristics

Abstract

A highly flexible nanocomposite was developed by coating a regenerated cellulose film with a thin layer of tin oxide (SnO₂) by liquid-phase deposition. Tin oxide was crystallized in solution and formed nanocrystal coatings on regenerated cellulose. The nanocrystalline layers did not exfoliate from cellulose. Transmission electron microscopy and energy dispersive x-ray spectroscopy suggest that SnO₂ was not only deposited over the cellulose surface, but also nucleated and grew inside the cellulose film. Current–voltage characteristics of the nanocomposite revealed that its electrical resistivity decreases with deposition time, with the lowest value obtained for 24 h of deposition. The cellulose–SnO₂ hybrid nanocomposite can be used for biodegradable and disposable chemical, humidity and biosensors.     

Hybrid nanocomposite based on cellulose and tin oxide: growth,structure, tensile and electrical characteristics

A highly flexible nanocomposite was developed by coating a regenerated cellulose film with a thin layer of tin oxide (SnO₂) by liquid-phase deposition. Tin oxide was crystallized in solution and formed nanocrystal coatings on regenerated cellulose. The nanocrystalline layers did not exfoliate from cellulose. Transmission electron microscopy and energy dispersive x-ray spectroscopy suggest that SnO₂ was not only deposited over the cellulose surface, but also nucleated and grew inside the cellulose film. Current–voltage characteristics of the nanocomposite revealed that its electrical resistivity decreases with deposition time, with the lowest value obtained for 24 h of deposition. The cellulose–SnO₂ hybrid nanocomposite can be used for biodegradable and disposable chemical, humidity and biosensors.     

Novel nanocomposite concept based on cross-linking of hyperbranched polymers in reactive cellulose nanopaper templates

Cellulosic fibers offer interesting possibilities for good interfacial adhesion due to the high density of hydroxyl groups at the surface. In the present study, the potential of a new nanocomposite concept is investigated, where a porous cellulose nanofiber network is impregnated with a solution of reactive hyperbranched polyester. The polymer is chemically cross-linked to form a solid matrix. The resulting nanocomposite structure is unique. The matrix surrounds a tough nanopaper structure consisting of approximately 20 nm diameter nanofibers with an average interfiber distance of only about 6 nm. The cross-linked polymer matrix shows strongly altered characteristics when it is cross-linked in the confined space within the nanofiber network, including dramatically increased T_g, and this must be due to covalent matrix-nanofiber linkages.     

聚(D,L-乳酸)基仿生聚合物材料的合成与表征

探索一种新型聚乳酸基仿生聚合物材料的制备新方法.具体实验步骤是:利用聚乳酸上叔碳原子的自由基反应活性,在过氧化二苯甲酰的催化作用下,将马来酸酐引入聚乳酸侧链上,以此提供高反应活性的酸酐键;然后利用酸酐基团与-NH2发生N-酰化反应这一特点,将脂肪族二胺引入聚乳酸侧链上,从而克服聚乳酸降解产物的体液环境呈酸性的缺陷;再用碳二亚胺作缩合剂,在二胺改性聚乳酸材料中共价引入一种细胞粘附肽段Arg-Gly-Asp-Ser(RGDS),赋予材料生物活性和生物特异性,这样就制备了一种新型聚乳酸基仿生材料.采用MALLS、FTIR和XPS对仿生材料进行结构表征;采用罗丹明比色法、茚三酮显色法和氨基酸分析仪检测法对仿生材料中的马来酸酐、二胺和粘附肽RGDS进行定量测定.结果表明,按文中所述之制备技术,在不改变聚乳酸材料主链结构的前提下,该仿生材料中粘附肽RGDS的含量是5.12μmol/g.这就形成了一种具有类似细胞外基质的新型仿生材料.     

Cross-linked nanocomposite hydrogels based on cellulose nanocrystals and PVA: Mechanical properties and creep recovery

Cellulose nanocrystal (CNC) reinforced poly(vinyl alcohol) (PVA) hydrogels with a water content of ∼92% were successfully prepared with glutaraldehyde (GA) as a cross-linker. The effects of the CNC content on the thermal stability, swelling ratio and mechanical and viscoelastic properties of the cross-linked hydrogels were investigated. The compressive strength at 60% strain for the hydrogels with 1 wt% CNCs increased by 303%, from 17.5 kPa to 53 kPa. The creep results showed that the addition of CNCs decreased the creep elasticity due to molecular chain restriction. The almost complete strain recovery (∼97%) after fixed load removal for 15 min was observed from the hydrogels with CNCs, compared with 92% strain recovery of the neat cross-linked PVA hydrogels. The incorporation of CNCs did not affect the swelling ratio and thermal stability of the hydrogels. These results suggest the cross-linked CNC-PVA hydrogels have potential for use in biomedical and tissue engineering applications.     

Highly sensitive surface enhanced Raman scattering substrates based on filter paper loaded with plasmonic nanostructures

We report a novel surface enhanced Raman scattering (SERS) substrate platform based on a common filter paper adsorbed with plasmonic nanostructures that overcomes many of the challenges associated with existing SERS substrates. The paper-based design results in a substrate that combines all of the advantages of conventional rigid and planar SERS substrates in a dynamic flexible scaffolding format. In this paper, we discuss the fabrication, physical characterization, and SERS activity of our novel substrates using nonresonant analytes. The SERS substrate was found to be highly sensitive, robust, and amiable to several different environments and target analytes. It is also cost-efficient and demonstrates high sample collection efficiency and does not require complex fabrication methodologies. The paper substrate has high sensitivity (0.5 nM trans-1,2-bis(4-pyridyl)ethene (BPE)) and excellent reproducibility (~15% relative standard deviation (RSD)). The paper substrates demonstrated here establish a novel platform for integrating SERS with already existing analytical techniques such as chromatography and microfluidics, imparting chemical specificity to these techniques.     

MGF-Ct24E改性聚乳酸的合成、表征及其对成骨细胞增殖的评价

力生长因子(MGF)是骨修复重建的一种重要生长因子。以二环己基碳二亚胺为缩合剂,将MGF羧基端E结构域24肽(MGF-Ct24E)共价接枝到丁二胺改性的聚乳酸上(DPLA),制得了新型MGF-Ct24E改性聚乳酸仿生材料(MGF-Ct24E-DPLA)。采用氨基酸分析和高效液相色谱对MGF-Ct24E含量进行了定性定量表征,静态水接触角和吸水率测定了MGF-Ct24E-DPLA材料的亲水性,MTT法评价了其对成骨细胞的增殖作用。结果表明,MGF-Ct24E成功引入到DPLA中,接枝效率为24.7%,并且和DPLA相比,MGF-Ct24E-DPLA材料具有更好的亲水性和促进成骨细胞增殖的能力。因此这种新型MGF-Ct24E改性聚乳酸仿生材料有望成为骨组织工程领域中一种卓越的生物材料。     

New nanocomposite based on poly(lactic-co-glycolic acid) copolymer and magnetite. Synthesis and characterization

The study presents the preparation of the new magnetic nanocomposite based on PLGA and magnetite. The PLGA used to obtain the magnetic nanocomposites was synthesized by the copolymerization of lactic acid with glycolic acid, in the presence of tin octanoate [Sn(Oct)₂] as catalyst, by polycondensation procedure. Magnetite was obtained by co-precipitation from aqueous salt solutions FeCl₂/FeCl₃. The particles size of magnetite was 420 nm, and the saturation magnetization 62.78 emu/g, while the PLGA/magnetite nanocomposite size was 864 nm and the saturation magnetization 39.44 emu/g. The magnetic nanocomposites were characterized by FT-IR, DLS technique, SEM, VSM and simultaneous thermal analyses (TG–FTIR–MS). The polymer matrix PLGA acts as a shell and carrier for the active component, while magnetite is the component which makes targeting possible by external magnetic field manipulation. Based on the gases resulted by thermal degradation of PLGA copolymer, using the simultaneous analysis TG–FTIR–MS, a possible degradation mechanism was proposed.     

Highly flexible and sensitive wearable strain and pressure sensor based on porous graphene paper for human motion

The demand for high-performance multifunctional wearable devices drives the rapid development of sensors with flexibility, sensitivity and easy preparation. Here, we report an efficient preparation method to fabricate a wearable strain and pressure sensor based on porous graphene paper (PGP), which is prepared by polymethylmethacrylate (PMMA) microsphere as a template. The prepared PGP-based strain and pressure sensor can detect multi-dimensional deformation and shows good flexibility even after more than 1000 s of repeated deformation cycles, while the rapid response time can be up to approximately 60 ms. Moreover, the obtained PGP-based sensor exhibits a good sensitivity that the gauge factor (GF) is up to 77 when the strain is in the range of 4–8%, much higher than other graphene materials. Importantly, the porous microstructure created by the PMMA microsphere in the PGP plays a vital role in the good comprehensive performance of the PGP-based sensor. The device shows potential applications in smart wearable devices to detect or monitor the posture and movement information of human beings.

     

Molecular relaxations in the composites of liquid crystalline cellulose derivatives with poly(acrylic acid)

The molecular relaxation phenomena of the specific polymer composites obtained by photopolymerisation of the oriented lyotropic liquid-crystalline systems composed of cellulose derivatives dissolved in photopolymerisable acrylic acid are studied. We have investigated the composites based on two cellulose derivatives, which differ by the length of their side-chains and consequently by their physical properties. In this work, the molecular relaxations of such anisotropic composites were studied by dielectric relaxation spectroscopy and by thermooptical analysis. In the dielectric relaxation spectroscopy two representations were analysed: temperature dependences of dielectric loss ɛ"(T) and of electric modulus M "(T). The electric modulus representation is especially convenient to monitor the relaxations in a high temperature range where the ionic conductivity dominates the dielectric response. Received: 9 October 2000 / Reviewed and accepted: 10 October 2000     

Organic/inorganic nanocomposite films based on poly(3-methoxythiophene) and WO3

Organic/inorganic nanocomposite films based on poly(3-methoxythiophene) (PMOT) and WO₃ were prepared by a consecutive two-step electrochemical method. The products were characterized in detail by scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDS) and Fourier-transform infrared spectroscopies (FTIR). The results show that the PMOT/WO₃ nanocomposite films consist of two layers, the substrate WO₃ with 30 nm grains and superstratum PMOT, which average grain size is 60 nm. The obtained PMOT/WO₃ nanocomposite films were also characterized by cyclic voltammetry to investigate their electrochemistry properties which display significant enhancement of electrochemical activity than that of pure PMOT and WO₃ films.     

Preparation, characterization, and luminescence of host (Y zeolite)-guest (FeS, CoS, NiS) nanocomposite materials

The host-guest nanocomposites (Y zeolite)-sulfides (FeS, CoS, NiS) were successfully prepared by a hydrothermal method and characterized by powder XRD, chemical analysis, adsorption technique, infrared spectroscopy and X-ray photoelectron spectroscopy. The Y zeolite-NiS host-guest nanocomposite material was found to exhibit luminescence. This paper suggests that the luminescence mechanism of Y-NiS resulted from the excitons in the confinement areas and from the defects in the materials. The material Y-NiS may be used as luminescent materials.