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Owing to the ability to parallel manipulate micro-objects, dynamic holographic optical tweezers (HOTs) are widely used for assembly and patterning of particles or cells. However, for simultaneous control of large-scale targets, potential collisions could lead to defects in the formed patterns. Herein we introduce the artificial potential field (APF) to develop dynamic HOTs that enable collision-avoidance micro-manipulation. By eliminating collision risks among particles, this method can maximize the degree of parallelism in multi-particle transport, and it permits the implementation of the Hungarian algorithm for matching the particles with their target sites in a minimal pathway. In proof-of-concept experiments, we employ APF-empowered dynamic HOTs to achieve direct assembly of a defect-free 8 × 8 array of microbeads, which starts from random initial positions. We further demonstrate successive flexible transformations of a 7 × 7 microbead array, by regulating its tilt angle and inter-particle spacing distances with a minimalist path. We anticipate that the proposed method will become a versatile tool to open up new possibilities for parallel optical micromanipulation tasks in a variety of fields. [ABSTRACT FROM AUTHOR]

The multi-responsive ternary poly(N-isopropyl acrylamide) (PNIPAM)/ /sodium alginate (SA)/graphene oxide (GO) composite hydrogels were prepared. The influence of GO content on the microstructure and physical properties of the composite hydrogel was researched. The ternary composite hydrogels exhibited significantly larger mechanical strength and higher water uptake compared to binary PNIPAM/SA composite hydrogels. The effects of temperature, pH, and contact time on the adsorption capacity of rhodamine B (RB) for the PNIPAM/SA/GO ternary composite hydrogels were further investigated. The adsorption kinetic and isotherm for the adsorption behavior of the ternary composite hydrogel were well fitted with the pseudo-second-order kinetic model and Langmuir model, respectively. Besides, the PNIPAM/SA/GO ternary composite hydrogel could be easily removed from the dye solutions and reused without the obvious decrease of its performance. It indicated that the ternary composite hydrogel could serve as an effective adsorbent for the removal of organic pollutants. [ABSTRACT FROM AUTHOR]

Pull-up, as an important physical fitness test event of the "National Student Physical Health Standard", is known as a difficult physical fitness test event. To improve the assessment criteria of pull-ups, this paper uses the functional near-infrared spectroscopy (fNIRS) to monitor the changes and activation of oxyhemoglobin (HbO) signals in the brain motor cortex of people with different body mass indexes (BMIs) during the pullup assessment. Then the relationship between BMIs and evaluation criteria is discussed. After collecting and analyzing experimental data of 18 recruited college students, it is found that the number of pull-ups performed by people with different BMIs is different when they reach the peak state of brain activation. The results of the study indicate that different assessment criteria should be adopted for different BMI groups. It is suggested that the BMI should be introduced as one of the test indexes in the examination of pull-ups event in "National Student Physical Health Standard". [ABSTRACT FROM AUTHOR]

Flexible films based on polypyrrole/silver (PPy/Ag) nanocomposites are fabricated through the reaction between polypyrrole nanotubes and silver ions and subsequent direct filtration. The microstructure and composition of the as-prepared nanocomposite films are investigated by x-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy, and so on. The thermoelectric performances of the nanocomposite films with different silver contents are studied. Compared with pure polypyrrole (PPy) film, as the silver content in the nanocomposite increases, the electric conductivity of the nanocomposite film increases greatly while the Seeback coefficient decreases. Therefore, the power factor of the nanocomposite film is much higher than that of polypyrrole film. Moreover, there is no obvious change of thermoelectric performance of the polypyrrole/silver nanocomposite film after bending for 500 times. The results indicate that the film of polypyrrole/silver nanocomposites is promising as one kind of high-performance and flexible thermoelectric materials. [ABSTRACT FROM AUTHOR]

The alginate/reduced graphene oxide composite hydrogels with hierarchical network structures were synthesized through the hydrothermal treatment of graphene oxide and alginate in an aqueous solution followed by ionically cross-linking of metal ions. The network of reduced graphene oxide was prepared via self-assembly of graphene nanosheets in the presence of alginate during the hydrothermal process; then, the polymer network of alginate was obtained by ionically cross-linking, forming the composite hydrogel. The effect of metal ions on the physical properties of the composite hydrogels was investigated. The prepared alginate/reduced graphene oxide composite hydrogel cross-linked by Fe3+ ions showed higher compression strength and lower swelling ratio. Moreover, due to the synergetic interaction between graphene and alginate, the composite hydrogels exhibited the improved dye adsorption performance, especially for cationic dyes. Even after ten adsorption/desorption cycles, the composite hydrogels can retain more than 90% dye adsorption capacity. The results indicated that the composite hydrogel with good stability, adsorption and regeneration ability could be a promising candidate for dye removal from waste aqueous solutions. [ABSTRACT FROM AUTHOR]

High-performance elastic supercapacitors represent a promising kind of energy storage devices that can be employed in soft robotics and wearable electronics. The development of novel functional materials as supercapacitor electrode is still tremendously challenging. In the present work, the conductive polyvinyl alcohol–graphene oxide–polypyrrole (PVA–GO–PPy) composite hydrogels are fabricated through in situ polymerization of pyrrole in the presence of PVA and GO and subsequent freeze-thawing. Owing to the unique porous layered-wrinkle network and functional component of PVA–GO–PPy composite hydrogels, the as-prepared hydrogels exhibit lightweight, elasticity, compressibility, formability and softness. Furthermore, the mechanically robust and microstructured PVA–GO–PPy composite hydrogels are used to construct an elastic symmetric solid-state supercapacitor with good electrochemical performance. The device exhibits long-term compression/recovery elasticity under 50% strain, and even the volumetric capacitance retention is still about 81% when the strain is up to 80%. The excellent compression/recovery elasticity and good mechanical integrity of the high-performance supercapacitor based on PVA–GO–PPy composite hydrogel open up new opportunities for next-generation electronic devices in the practical application. [ABSTRACT FROM AUTHOR]

Three-dimensional porous sponge with good mechanical strength, high absorption capacity and recyclability is of scientific and technological interest. In this work, graphene oxide has been incorporated into poly(vinyl alcohol)–chitosan sponge during acetalization reaction of poly(vinyl alcohol) for the fabrication of macroporous and amphiphilic sponges. Mercury intrusion porosimetry and scanning electron microscopy indicate that the as-prepared sponges have interconnected open-cell structures. The incorporation of graphene oxide and the interconnected macroporous structures in the amphiphilic sponges endow them with improved absorption capacity for both water and organic liquids. Moreover, the absorbed liquids can be effectively collected through simple squeezing and the sponges can be used repeatedly while maintaining a relative high absorption capacity. The simple fabrication and improved performance of the resulting sponges suggest that they have potential industrial applications. [ABSTRACT FROM AUTHOR]

Poly(N-methylpyrrole) nanotubes were facilely fabricated by in situ chemical polymerization via a reactive template of MnO2 and were developed as electrode materials for the detection of dopamine. The microstructure, morphology, and chemical composition of the as-prepared poly(N-methylpyrrole) nanotubes have been investigated by X-ray powder diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Furthermore, a glassy carbon electrode (GCE) was modified with poly(N-methylpyrrole) nanotubes and showed sensitive catalytic activity for electrochemical detection of low concentration of dopamine even in the presence of and ascorbic acid. [ABSTRACT FROM AUTHOR]

Three-dimensional polypyrrole/chitosan nanocomposite monoliths are fabricated by polymerization of pyrrole in chitosan aqueous solution. The static polymerization of pyrrole monomer and the cross-linking of chitosan by glutaraldehyde occur simultaneously, resulting in the self-assembly of polypyrrole/chitosan nanocomposite aerogel monolith. The addition of methyl orange and glutaraldehyde and the static reaction play key roles in the formation of the self-standing aerogel monolith. The as-prepared monolith with larger specific surface area exhibits much better adsorption capability for Cr(VI) removal in comparison with that prepared without the addition of glutaraldehyde. The adsorption process and adsorption isotherms are found to well follow the pseudo-second-order and Langmuir models, respectively. Furthermore, this polypyrrole/chitosan nanocomposite monolith is stable and recyclable. About 73.5% of the initial adsorption capability is kept after eight adsorption-desorption cycles. The polypyrrole/chitosan nanocomposite monolith can be a promising candidate for the efficient removal of Cr(VI). [ABSTRACT FROM AUTHOR]

A simple procedure is employed for the growth of silver nanoparticles (Ag NPs) onto the silicon substrate modified by poly(acrylic acid) (PAA) brushes, via: (1) surface-initiated ATRP of tert-butyl acrylate on Si surface to the preparation of poly( tert-butyl acrylate) brushes, (2) acid hydrolysis of PBA to the formation of PAA, and (3) in situ synthesis of Ag NPs via chemical reduction of AgNO in the presence of PAA brushes. The polymer brushes are thoroughly characterized. Moreover, Ag nanoparticles are homogeneously immobilized into the brush layer and have been used to fabricate a sensor platform of surface-enhance Raman scattering for the detection of organic molecules and effectively catalyze the reduction of methylene blue by NaBH. [ABSTRACT FROM AUTHOR]

In the present work, by using the in situ polymerization of aniline in acidic aqueous solution of PVA and freezing-thawing method, the reinforced conducting polymer hydrogel of polyaniline/polyvinyl alcohol (PANI/PVA) was prepared and directly used as the self-supported electrode for supercapacitor. The chemical structure of PANI/PVA hydrogel was characterized by UV-Vis, and the three-dimensional (3D) interconnected hierarchical nanoporous structure was observed by scanning electron microscopy. The measurement of compressive strength demonstrated the high mechanical strength of the hydrogel. The electrochemical properties of PANI/PVA hydrogel electrodes were evaluated by using cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge/discharge, which indicated their good responsiveness and rate capability, low resistance, high specific capacitance (240 F/g at current density of 1 A/g) and excellent cycling stability. The easily fabricated PANI/PVA hydrogel combined hierarchical nanoporous microstructure, self-supported feature and favorable capacitive behavior and provided a new strategy for constructing high-performance electrode for supercapacitors. [ABSTRACT FROM AUTHOR]

Unique polypyrrole (PPy) hydrogels are prepared by using orange IV as the dopant and FeCl as the oxidant. The static polymerization of pyrrole monomer in aqueous solution is accompanied with self-assembly of PPy hydrogel. PPy hydrogels not only show good electrical conductivities, but also exhibit excellent water-absorbent behaviors. The macroscopic appearance, microscopic morphology and water-absorbent behaviors of PPy hydrogels can be controlled by the choice of the reaction condition. The effects of ionic strength on the physical properties of PPy hydrogels are also studied. The results indicate that PPy hydrogels show improved water absorbencies in saline solution. Moreover, PPy hydrogel is used as an efficient adsorbent to remove Cr(VI) from aqueous solutions. PPy hydrogel exhibits much better adsorption performance than common PPy nanoparticles. This kind of PPy hydrogel is expected to be a potential candidate for water treatment. [ABSTRACT FROM AUTHOR]

The polypyrrole (PPy)/graphene oxide (GO) composite hydrogels with hierarchical porous structures were fabricated by one-step self-assembly method. The static oxidation polymerization of pyrrole monomer in GO aqueous solution resulted in the formation of three-dimensional (3D) PPy/GO composite hydrogels, which consisted of one-dimensional PPy nanofibers and two-dimensional GO nanosheets. The as-prepared composite hydrogels exhibited shrinking-swelling behavior with cycles of suction and water-supplying. The effects of GO nanosheets content on the swelling properties were investigated. Results showed that the well-dispersed GO nanosheets in the hydrogel networks resulted in a significant improvement in water absorbencies of the hydrogels. PPy/GO composite hydrogels exhibited unobvious variation in the water absorbency even in saline solutions. Such excellent properties in water absorbencies endow the conducting 3D PPy/GO composite hydrogels with great potential applications in electrochemical sensors or controlled release. [ABSTRACT FROM AUTHOR]

Multi-photon product (F-state) of bacteriorhodopsin (BR) polymeric films excited by femtosecond laser shows permanently photoinduced birefringence and dichroism. Based on this property, polarization-sensitive diffractive optical elements (PDOEs), e.g., gratings, two-dimensional optical lattice, Bessel zone plate, were firstly fabricated and investigated in BR films by femtosecond laser multi-beam interference with rotationally symmetric pyramid lenses. These fabricated PDOEs are completely stable at room temperature. The dependence of diffraction efficiency on the incident polarization state was measured. The micro-structures of PDOEs were observed under polarization microscope, and the selective readout diffraction patterns from the polarization-multiplexed PDOEs were demonstrated. [ABSTRACT FROM AUTHOR]

Polyaniline–palladium (PANi-Pd) composite microflakes were synthesized through an immiscible organic/inorganic biphasic system in the presence of poly(ethylene glycol) with molecular weight 4,000 (PEG4000). Aniline was oxidized by PdCl2 in the interface polymerization system, yielding PANi microflakes and elemental Pd nanoparticles simultaneously. Palladium nanoparticles were uniformly dispersed in the microflakes of PANi. The results of FTIR spectra suggested that the oxidation degree of PANi was affected by the initial ratio of metal ions to monomer. The PANi-Pd composites were characterized using X-ray photoelectron spectroscopy and the conductivity of the composite was measured by conventional four-probe method. Scanning and transmission electron microscopy were used to show the morphology of the composites. [ABSTRACT FROM AUTHOR]

In merits of super-resolved resolution and fast speed of three-dimensional (3D) optical sectioning capability, structured illumination microscopy (SIM) has found variety of applications in biomedical imaging. So far, most SIM systems use monochrome CCD or CMOS cameras to acquire images and discard the natural color information of the specimens. Although multicolor integration scheme are employed, multiple excitation sources and detectors are required and the spectral information is limited to a few of wavelengths. Here, we report a new method for full-color SIM with a color digital camera. A data processing algorithm based on HSV (Hue, Saturation, and Value) color space is proposed, in which the recorded color raw images are processed in the Hue, Saturation, Value color channels, and then reconstructed to a 3D image with full color. We demonstrated some 3D optical sectioning results on samples such as mixed pollen grains, insects, micro-chips and the surface of coins. The presented technique is applicable to some circumstance where color information plays crucial roles, such as in materials science and surface morphology. [ABSTRACT FROM AUTHOR]