3-D manipulation of millimeter- and micro-sized objects using an acoustically excited oscillating bubble

This communication describes novel 3-D manipulations of objects using an acoustically excited oscillating bubble deposited on a hydrophobic rod tip. The oscillating bubble captures various millimeter- and micron-sized neighboring objects including glass and polystyrene beads (~100 μm), fish egg, and live water flea (~1 mm). The captured objects are carried in a 3-D space by traversing the bubble tip, and released at desired positions by simply turning off the oscillation. Carrying performance is characterized along with high-speed imaging of oscillating bubbles by varying the frequency and amplitude of the acoustic excitation and the carrying speed. The higher the oscillation amplitude, the higher the carrying efficiency. The maximum carrying speed is measured at over 3 mm/s. This method is effective with a low-level acoustic excitation (bubble oscillation amplitude relative to the diameter ≤5%), possibly providing a cost-effective, soft-contact manipulating tool for handling biological objects.     

Applications, techniques, and microfluidic interfacing for nanoscale biosensing

Biosensors based on nanotechnology are rapidly developing and are becoming widespread in the biomedical field and analytical chemistry. For these nanobiosensors to reach their potential, they must be integrated with appropriate packaging techniques, which are usually based on nano/microfluidics. In this review we provide a summary of the latest developments in nanobiosensors with a focus on label-based (fluorescence and nanoparticle) and label-free methods (surface plasmon resonance, micro/nanocantilever, nanowires, and nanopores). An overview on how these sensors interface with nano/microfluidics is then presented and the latest papers in the area summarized.     

Conical microlens arrays that flatten optical-irradiance profiles of nonuniform sources

One can create conical microlens arrays on a glass plate by simply spin coating spin-on-glass film on the glass, patterning the photoresist, and then etching the glass in a HF solution. These arrays can be used to obtain more-uniform irradiance profiles from nonuniform incoherent sources.     

Chiral Se Nanobrooms with Wavelength and Polarization Sensitive Scattering

High-index dielectric nanostructures offer strong magnetic and electric resonances in the visible range and low optical losses, stimulating research interest in their use for light manipulation technologies. Lithographic fabrication of dielectric nanostructures, while providing precise control over the pattern dimensions, limits the scalability of this approach for practical applications due to an inefficient fabrication process and limited production quantity. Here, the colloidal synthesis of high-index chiral dielectric nanostructures with a broom-like geometry made from trigonal Se is demonstrated. The anisotropic morphology and crystal structure of Se nanobrooms enable both linearly and circularly polarized scattering, as well as spectrum variation along the particle axis, which is, to the authors’ knowledge, the first observation of such behavior from dielectric colloidal nanostructures. To show the versatility of the highly scattering Se NB suspensions, 2D and 3D printing of Se NB inks are demonstrated as a proof of concept. This approach provides a way to manipulate light using aqueous dispersions of high-index dielectric nanostructures, unlocking their potential to fit in various morphologies and dimensions in 2D and 3D for broad applications.     

Synthesis of Co/SiO2 hybrid nanocatalyst via twisted Co3Si2O5(OH)4 nanosheets for high-temperature Fischer-Tropsch reaction

A cobalt-silica hybrid nanocatalyst bearing small cobalt particles of diameter ～5 nm was prepared through a hydrothermal reaction and hydrogen reduction.The resulting material showed very high CO conversion (＞82％) and high hydrocarbon productivity (～1.0 gHc·g-1cat,·h-11) with high activity (～8.5 x 10-5 molco·g-1Co·S-1) in the Fischer-Tropsch synthesis reaction.     

Improvement in mechanical properties of recycled GF prepreg with CNT reinforced composites using a spray coating method

Dispersion and shape of nanoparticles, as well as interfacial conditions, add significantly to difficulties in composite manufacture. In the work reported here, an innovative method of recycling composites using out-of-date prepreg was investigated in which the carbon nanotube (CNT) on the prepreg was optimally coated. Nanocomposites utilizing the out-of-date prepreg were coated with CNT and fabricated by a sheet molding method. CNT nanofillers were observed to be uniformly dispersed on epoxy prepreg by spray coating. The mechanical and interfacial properties of these CNT coated nanocomposites were improved over those of more conventionally manufactured carbon fiber/epoxy composites. The CNT nanofillers were embedded at the epoxy and fiber interface, as a result of etching of the epoxy prepreg surface by a CNT dispersion solution which enhanced interfacial reactivity.     

Mechanical and electrical properties of electrospun CNT/PVDF nanofiber for micro-actuator applications

Electrospun polyvinylidene fluoride (PVDF)-containing carbon nanotubes (CNT) were prepared for use in fabricating actuator materials. Actuating displacement was measured in an electrochemical environment. The electrospun nanofibers were arranged using a drum-type collector, and morphology was investigated using a field emission-scanning electron microscope. The uniformity of dispersion of CNT in the PVDF nanofibers was monitored by electron probe X-ray micro-analysis. Tensile strength and electrical resistivity results were used as an indication of the state of alignment. The electrospun CNT/PVDF nanofiber sheets exhibited better mechanical and electrical properties in the arranged direction. The efficiency and electrical capacities of electrospun CNT/PVDF nanofiber sheet were compared with those of cast PVDF sheets for use in actuator applications in electrochemical environments. The electrospun CNT/PVDF nanofiber sheets exhibited much better actuator performance than PVDF sheets, which are attributed to their superior electrical properties.

Highlights

(1) The interfacial durability of CNT/PVDF nanofibers was enhanced to increase contact area by reinforcing CNT.

(2) The efficiency of CNT/PVDF actuators was improved due to interfacial properties.

(3) Thin thickness drum-type collector was made to enhance nanofiber alignment.

(4) The arranged CNT/PVDF nanofibers exhibited better mechanical and actuating displacements.     

Gas formation and biological effects of biodegradable magnesium in a preclinical and clinical observation

Magnesium alloys are biodegradable metals receiving increasing attention, but the clinical applications of these materials are delayed by concerns over the rapid corrosion rate and gas formation. Unlike corrosion, which weakens mechanical properties, the gas formation issue has received little attention. Therefore, we evaluated the gas formation and biological effects for Mg implants through preclinical (immersed in Earle’s balanced salt solution and in vivo) and clinical studies. The immersion test examined the gas volume and composition. The in vivo study also examined gas volume and histological analysis. The clinical study examined the gas volume and safety after Mg screw metatarsal fixation. Gas was mainly composed of H₂, CO and CO₂. Maximum volumes of gas formed after 5 days for in vivo and 7 days in clinical study. Within the clinical examination, two superficial wound complications healed with local wound care. Osteolytic lesions in the surrounding metaphysis of the Mg screw insertion developed in all cases and union occurred at 3 months. Mg implants released gas with variable volumes and composition (H₂, CO, and CO₂), with no long-term toxic effects on the surrounding tissue. The implants enabled bone healing, although complications of wound breakdown and osteolytic lesions developed.