Optorheological Characteristics of Photosynthetic Bacterium Suspension.

Understanding the rheological behavior of materials is of great importance in science. Here, we report a microscopic foundation for optorheology by manipulating the rheological feature through light. A new phenomenon is observed in the photosynthetic bacterial suspension, that the fluid viscosity changes by light-induced electrons.

A Broadband Multiplex Living Solar Cell.

Developing renewable and sustainable energy sources is a compelling goal in materials science and engineering. In particular, natural photosynthesis with its infinite energy reservoir provides profound inspiration for energy conversion and storage systems. Here, we report a multiplex living solar cell that offers a drastic power enhancement by harnessing the broadband spectra of the visible wavelength range for photosynthesis.

Hydrodynamic Metamaterial Cloak for Drag-Free Flow.

Metamaterials engineered based on transformation optics have facilitated inaccessible manipulation of various physical phenomena. However, such metamaterials have not been introduced for flowing viscous matter. Here we propose a hydrodynamic metamaterial cloak that can conceal an object in two-dimensional creeping flow by guiding viscous forces.

Gold-Nanocluster-Assisted Nanotransfer Printing Method for Metasurface Hologram Fabrication.

Given the development of nano/microscale patterning techniques, efforts are being made to use them for fabricating metasurfaces. In particular, by using abrupt phase discontinuities, it is possible to generate holographic images from two-dimensional nanoscale-patterned metasurfaces. However, the fabrication of metasurface holograms is hindered by the high costs and long fabrication time involved, because the process requires expensive equipment such as that for electron-beam lithography.

Enhanced Plasmonic Particle Trapping Using a Hybrid Structure of Nanoparticles and Nanorods.

Plasmon-enhanced particle trapping was demonstrated using a hybrid structure of nanoparticles and nanorods. In order to intensify localized surface plasmon resonance (LSPR), gold nanoparticles (AuNPs) were deposited on zinc oxide nanorods (ZnONRs). The synergistic effect caused by the hybrid structure was identified experimentally.

Eco-friendly flame retardant nanocrystalline cellulose prepared via silylation.

Employing proper flame retardant materials is one of the most important fire safety guidelines when constructing buildings. Most flame retardants, however, contain halogen atoms that might become harmful gases to human body during combustion. We designed and fabricated an environmentally friendly flame retardant material with a superior performance for thermal insulation.

Programmable microfluidic logic device fabricated with a shape memory polymer.

Manipulation of particles in a microfluidic system is an important research subject in biomedical engineering. However, most conventional passive techniques for particle control have difficulties in integrating other functions into microfluidic channels. A unique microfluidic valve was proposed in this study for switchable particle control by employing a shape memory polymer (SMP).

Focusing manipulation of microalgae in a microfluidic device using self-produced macromolecules.

Extracellular polymeric substances (EPSs) are self-produced biosynthetic macromolecules that have a three-dimensional architecture in bacterial biofilms and are mainly composed of a mixture of polysaccharides, proteins and nucleic acids. Compared with synthetic polymers, EPSs can have a long relaxation time due to their structural complexity. We exploited the non-Newtonian rheological behavior of EPSs extracted from Chlorella vulgaris with the help of cell focusing and particle focusing in confined microchannels.

Carbon Nanotube Embedded Nanostructure for Biometrics.

Low electric energy loss is a very important problem to minimize the decay of transferred energy intensity due to impedance mismatch. This issue has been dealt with by adding an impedance matching layer at the interface between two media. A strategy was proposed to improve the charge transfer from the human body to a biometric device by using an impedance matching nanostructure.

Covalent bonding-assisted nanotransfer lithography for the fabrication of plasmonic nano-optical elements.

Many high-resolution patterning techniques have been developed to realize nano- and microscale applications of electric devices, sensors, and transistors. However, conventional patterning methods based on photo or e-beam lithography are not employed to fabricate optical elements of high aspect ratio and a sub-100 nm scale due to the limit of resolution, high costs and low throughput. In this study, covalent bonding-assisted nanotransfer lithography (CBNL) was proposed to fabricate various structures of high resolution and high aspect ratio at low cost by a robust and fast chemical reaction.

Multiple-Line Particle Focusing under Viscoelastic Flow in a Microfluidic Device.

Particles in a viscoelastic fluid are typically focused at the center and four corners of a rectangular channel because of the combination of fluid elasticity and inertia forces. In this study, we observe the transition between single-line and multiple-line particle focusing in a microfluidic device induced by the synergetic effect of inertia and viscoelasticity. The elastic and inertial forces acting on suspended particles are manipulated by controlling the concentration of dilute polymer solution and the flow rate of a fluid.

Hydrodynamic fabrication of structurally gradient ZnO nanorods.

We studied a new approach where structurally gradient nanostructures were fabricated by means of hydrodynamics. Zinc oxide (ZnO) nanorods were synthesized in a drag-driven rotational flow in a controlled manner. The structural characteristics of nanorods such as orientation and diameter were determined by momentum and mass transfer at the substrate surface.

Ultra-high dispersion of graphene in polymer composite via solvent free fabrication and functionalization.

The drying process of graphene-polymer composites fabricated by solution-processing for excellent dispersion is time consuming and suffers from a restacking problem. Here, we have developed an innovative method to fabricate polymer composites with well dispersed graphene particles in the matrix resin by using solvent free powder mixing and in-situ polymerization of a low viscosity oligomer resin. We also prepared composites filled with up to 20 wt% of graphene particles by the solvent free process while maintaining a high degree of dispersion.

Vacuum nanohole array embedded phosphorescent organic light emitting diodes.

Light extraction from organic light-emitting diodes that utilize phosphorescent materials has an internal efficiency of 100% but is limited by an external quantum efficiency (EQE) of 30%. In this study, extremely high-efficiency organic light emitting diodes (OLEDs) with an EQE of greater than 50% and low roll-off were produced by inserting a vacuum nanohole array (VNHA) into phosphorescent OLEDs (PhOLEDs). The resultant extraction enhancement was quantified in terms of EQE by comparing experimentally measured results with those produced from optical modeling analysis, which assumes the near-perfect electric characteristics of the device.

Vacuum nano-hole array embedded organic light emitting diodes.

We demonstrated a nano-hole array (NHA) embedded structure that was fabricated for organic light emitting diodes (OLEDs) using a robust reverse transfer process. The NHA structure is proposed in this study as a strategy for maximizing the diffraction strength of two dimensional photonic crystals (PCs) by engineering vacuum nano-holes inside a dielectric slab. The electroluminescence (EL) intensity of the OLED was improved by more than twice.

Fullerene embedded shape memory nanolens array.

Securing fragile nanostructures against external impact is indispensable for offering sufficiently long lifetime in service to nanoengineering products, especially when coming in contact with other substances. Indeed, this problem still remains a challenging task, which may be resolved with the help of smart materials such as shape memory and self-healing materials. Here, we demonstrate a shape memory nanostructure that can recover its shape by absorbing electromagnetic energy.

Multiplex particle focusing via hydrodynamic force in viscoelastic fluids.

We introduce a multiplex particle focusing phenomenon that arises from the hydrodynamic interaction between the viscoelastic force and the Dean drag force in a microfluidic device. In a confined microchannel, the first normal stress difference of viscoelastic fluids results in a lateral migration of suspended particles. Such a viscoelastic force was harnessed to focus different sized particles in the middle of a microchannel, and spiral channel geometry was also considered in order to take advantage of the counteracting force, Dean drag force that induces particle migration in the outward direction.

Interaction analysis between binder and particles in multiphase slurries.

A multiphase slurry for rechargeable lithium-ion batteries is prepared using an active material, a carbon conductive, a polymeric binder and a solvent, and its physicochemical characteristics is evaluated in this study. The polymer binder interacting with particles in the slurry plays a crucial role in constructing the internal configuration of slurry components. The internal structure and dispersion states of the slurry components, which affect battery fabrication processes such as coating and even determine the final performance of battery cells, are changed over time.

Water droplet bouncing and superhydrophobicity induced by multiscale hierarchical nanostructures.

Superhydrophobicity of multiscale hierarchical structures and bouncing phenomenon of a water droplet on the superhydrophobic surface were studied. The multiscale hierarchical structures of carbon nanotube/ZnO and ZnO/carbon nanofiber were produced by the hydrothermal method. The multiscale hierarchical structure showed superhydrophobicity with a static contact angle (CA) larger than 160° due to increased air pockets in the Cassie-Baxter state.

Liquid slip on a nanostructured surface.

We explored a liquid slip, referred to as the Navier slip, at liquid-solid interface. Such a slip is provoked by the physicochemical features of the liquid-solid system. The goal of this study was to investigate the effect of a nanoengineered surface structure on liquid slip by fabricating the self-assembly structure of nano Zinc oxide (n-ZnO).

Sustainable fabrication of micro-structured lab-on-a-chip.

We have demonstrated a robust platform that can not only sustainably fabricate a lab-on-a-chip (LOC) device using microinjection molding but also elucidate the filling process of microstructures based on the multiscale analysis. In addition, a novel dimensionless number, i.e.