Structural Formation and Pore Control of Freeze-Cast Directional Graphene Aerogel (DGA).

Directional graphene aerogels (DGAs) are proposed as electrode materials to alleviate ionic and mass transport issues in organic redox flow batteries (ORFBs). DGAs with high pore directionality would provide low resistance channels for effective ionic charge and liquid electrolyte transport in these devices. DGAs' porous and directional characteristics can be controlled by the growth of ice crystals during freeze casting, which is influenced by the self-diffusivity of water, phase change driving forces, water-ice graphene interactions, and convection in the water-graphene media.

Enhanced Thermoelectric Conversion Efficiency of CVD Graphene with Reduced Grain Sizes.

The grain size of CVD (Chemical Vapor Deposition) graphene was controlled by changing the precursor gas flow rates, operation temperature, and chamber pressure. Graphene of average grain sizes of 4.1 µm, 2.

In-Plane Thermal Conductivity of Polycrystalline Chemical Vapor Deposition Graphene with Controlled Grain Sizes.

Manipulation of the chemical vapor deposition graphene synthesis conditions, such as operating P, T, heating/cooling time intervals, and precursor gas concentration ratios (CH/H), allowed for synthesis of polycrystalline single-layered graphene with controlled grain sizes. The graphene samples were then suspended on 8 μm diameter patterned holes on a silicon-nitride (SiN) substrate, and the in-plane thermal conductivities k(T) for 320 K < T < 510 K were measured to be 2660-1230, 1890-1020, and 680-340 W/m·K for average grain sizes of 4.1, 2.

High-efficiency electrochemical thermal energy harvester using carbon nanotube aerogel sheet electrodes.

Conversion of low-grade waste heat into electricity is an important energy harvesting strategy. However, abundant heat from these low-grade thermal streams cannot be harvested readily because of the absence of efficient, inexpensive devices that can convert the waste heat into electricity. Here we fabricate carbon nanotube aerogel-based thermo-electrochemical cells, which are potentially low-cost and relatively high-efficiency materials for this application.

Nano Sensing and Energy Conversion Using Surface Plasmon Resonance (SPR).

Nanophotonic technique has been attracting much attention in applications of nano-bio-chemical sensing and energy conversion of solar energy harvesting and enhanced energy transfer. One approach for nano-bio-chemical sensing is surface plasmon resonance (SPR) imaging, which can detect the material properties, such as density, ion concentration, temperature, and effective refractive index in high sensitivity, label-free, and real-time under ambient conditions. Recent study shows that SPR can successfully detect the concentration variation of nanofluids during evaporation-induced self-assembly process.

Femtosecond Laser Fabrication of Cavity Microball Lens (CMBL) inside a PMMA Substrate for Super-Wide Angle Imaging.

Since microlenses have to date been fabricated primarily by surface manufacturing, they are highly susceptible to surface damage, and their microscale size makes it cumbersome to handle. Thus, cavity lenses are preferred, as they alleviate these difficulties associated with the surface-manufactured microlenses. Here, it is shown that a high repetition femtosecond laser can effectively fabricate cavity microball lenses (CMBLs) inside a polymethyl methacrylate slice.

How to reliably determine the complex refractive index (RI) of graphene by using two independent measurement constraints.

Reliable determination of the complex refractive index (RI) of graphene inherently requires two independent measurement realizations for two independent unknowns of the real (nG) and imaginary (kG) components, i.e., RI = nG + i kG.

Wetting and evaporative aggregation of nanofluid droplets on CVD-synthesized hydrophobic graphene surfaces.

The wetting and evaporative aggregation of alumina nanofluids (Al2O3) are examined for CVD-synthesized graphene-coated (GC) surfaces that are known as strongly hydrophobic (θcontact ≈ 90°). Our findings are compared to those associated with a hydrophilic cover glass (CG) substrate (θcontact ≈ 45°). The nanofluidic self-assemblies on the GC substrate are elaborately characterized in terms of the droplet wetting/crack formation, the particle migration time over the evaporative time (CR), the Derjaguin-Landau-Verwey-Overbeek forces (FDLVO), and the relative thermal conductivity (KR).

Nonsteroidal anti-inflammatory drug sulindac sulfide suppresses structural protein Nesprin-2 expression in colorectal cancer cells.

Background: Nonsteroidal anti-inflammatory drugs (NSAIDs) are well known for treating inflammatory disease and have been reported to have anti-tumorigenic effects. Their mechanisms are not fully understood, but both cyclooxygenase (COX) dependent and independent pathways are involved. Our goal was to shed further light on COX-independent activity.

How to optically count graphene layers.

The total thickness of a graphene sample depends upon the number of individually stacked graphene layers. The corresponding surface plasmon resonance (SPR) reflectance alters the SPR angle, depending on the number of graphene layers. Thus, the correlation between the SPR angle shift and the number of graphene layers allows for a nonintrusive, real-time, and reliable counting of graphene layers.

Hidden cavity formations by nanocrystalline self-assembly on various substrates with different hydrophobicities.

The effect of surface hydrophobicity is examined in the formation of hidden complex cavities during evaporation-induced nanocrystalline self-assembly taking place on three different substrates bearing different levels of hydrophobicity, namely, cover glass (CG), a gold thin film (Au), and a polystyrene dish (PS). It turns out that the DLVO theory, the relative thermal conductivities between the substrate and nanofluids, and the relationship between the evaporation and the radial outflow motions of nanoparticles comprehensively explain why the number of cavity cells is proportional to nanoparticle concentration and inversely proportional to surface hydrophobicity.

A new heat propagation velocity prevails over Brownian particle velocities in determining the thermal conductivities of nanofluids.

An alternative insight is presented concerning heat propagation velocity scales in predicting the effective thermal conductivities of nanofluids. The widely applied Brownian particle velocities in published literature are often found too slow to describe the relatively higher nanofluid conductivities. In contrast, the present model proposes a faster heat transfer velocity at the same order as the speed of sound, rooted in a modified kinetic principle.

Simultaneous measurements of cytoplasmic viscosity and intracellular vesicle sizes for live human brain cancer cells.

Intracellular vesicles, comprised of protein clusters, were individually tracked inside human brain cancer cells and characterized to simultaneously determine the average vesicle size and effective cytoplasmic viscosity. The cells were transfected with a TGF-β superfamily gene, non-steroidal anti-inflammatory drug-Activated Gene-1 (NAG-1) tagged with green fluorescent proteins (GFPs). Using total internal reflection fluorescent microscopy (TIRFM) the individual movements of the vesicles were categorized into either Brownian, caged, or directional type motion.

Measuring near-field nanoparticle concentration profiles by correlating surface plasmon resonance reflectance with effective refractive index of nanofluids.

Time-dependent and near-field nanoparticle concentrations are determined by correlating the surface plasmon resonance (SPR) reflectance intensities with the effective refractive index (ERI) of the nanofluid under evaporation. A critical angle measurement for total internal reflection identifies the ERI of the nanofluid at different nanoparticle concentrations. The corresponding SPR reflectance intensities correlate the nanofluidic ERI with the nanoparticle concentrations.

Cell adhesion property affected by cyclooxygenase and lipoxygenase: Opto-electric approach.

Expression of cyclooxygenases (COX) and lipoxygenases (LOX) has been linked to many pathophysiological phenotypes, including cell adhesion. However, many current approaches to measure cellular changes are performed only in a fixed-time point. Since cells dynamically move in conjunction with the cell matrix, there is a pressing need for dynamic or time-dependent methods for the investigation of cell properties.

Multicontrast microscopy technique to dynamically fingerprint live-cell focal contacts during exposure and replacement of a cytotoxic medium.

Multicontrast microscopy techniques were used to comprehensively and dynamically map the cellular contact area adhering to a substrate. The natural fringe patterns observed with interference reflection contrast microscopy were used to map the dynamic fingerprint of a porcine pulmonary artery endothelial cell's ventral surface and to examine the focal and/or close contacts to the substrate when exposed to a toxic agent Cytochalasin D. In addition, differential interference contrast microscopy sequentially imaged the overall cellular morphological responses to the agent.

Surface elasticity and charge concentration-dependent endothelial cell attachment to copolymer polyelectrolyte hydrogel.

The surface micromechanical properties of 2-hydroxyethyl methacrylate (HEMA) and 2-methacryloxyethyl trimethyl ammonium chloride (MAETAC) copolymer hydrogels are probed using atomic force microscopy. HEMA-MAETAC polyelectrolyte hydrogels with increasing positive charge concentrations ranging from 0 to 400mM in increments of 40mM, are fabricated using different proportions of HEMA and MAETAC monomers. Increasing proportions of positively charged MAETAC monomers produce hydrogels with increasingly swollen states and correspondingly decreasing measures of stiffness, or Young's modulus.

Unveiling hidden complex cavities formed during nanocrystalline self-assembly.

The existence of hidden complex cavities formed inside a self-assembled nanocrystalline structure is discovered in real-time by using surface plasmon resonance near-field refractive index fingerprinting. Furthermore, computer analysis of the naturally occurring R-G-B interference fringes allowed us to reconstruct the 3D cavity formation and crystallization processes quantitatively. For the case of an aqueous droplet containing 10% by volume of 47 nm Al2O3 nanoparticles, the submicrometer-scale inner cavity peak grows up to 0.

Opto-Electric Cellular Biosensor Using Optically Transparent Indium Tin Oxide (ITO) Electrodes.

Indium tin oxide (ITO) biosensors are used to perform simultaneous optical and electrical measurements in order to examine the dynamic cellular attachment, spreading, and proliferation of endothelial cells (ECs) as well as cytotoxic effects when exposed to cytochalasin D. A detailed description of the fabrication of these sensors is provided and their superior optical characteristics are qualitatively shown using four different microscopic images. Differential interference contrast microscopy (DICM) images were acquired simultaneously with micro-impedance measurements as a function of frequency and time.

Simultaneous dynamic optical and electrical properties of endothelial cell attachment on indium tin oxide bioelectrodes.

This study quantifies the dynamic attachment and spreading of porcine pulmonary artery endothelial cells (PPAECs) on optically thin, indium tin oxide (ITO) biosensors using simultaneous differential interference contrast microscopy (DICM) and electrical microimpedance spectroscopy. A lock-in amplifier circuit monitored the impedance of PPAECs cultivated on the transparent ITO bioelectrodes as a function of frequency between 10 Hz and 100 kHz and as a function of time, while DICM images were simultaneously acquired. A digital image processing algorithm quantified the cell-covered electrode area as a function of time.

Full-field and real-time surface plasmon resonance imaging thermometry.

The feasibility of surface plasmon resonance (SPR) imaging thermometry is tested as a potential tool for full-field and real-time temperature field mapping for thermally transient liquid mediums. Using the well-known Kretschmann's analysis [Physik 241, 313 (1971)]. parametric examinations are performed to delineate the effects of important optical properties, including seven different prism materials with different refractive index values and seven different measured dielectric constants for thin gold (Au) films (approximately 47.

Near-Field Thermometry Sensor Based on the Thermal Resonance of a Microcantilever in Aqueous Medium.

A new concept using a near-field thermometry sensor is presented, employing atipless microcantilever experimentally validated for an aqueous medium within approximatelyone cantilever width from the solid interface. By correlating the thermal Brownian vibratingmotion of the microcantilever with the surrounding liquid temperature, the near-fieldmicroscale temperature distributions at the probing site are determined at separation distancesof z = 5, 10, 20, and 40 μm while the microheater temperature is maintained at 50°C, 70°C, or90°C. In addition, the near-field correction of the correlation is discussed to account for thequenched cantilever vibration frequencies, which are quenched due to the no-slip solid-wallinterference.

Real-time and full-field detection of near-wall salinity using surface plasmon resonance reflectance.

An idea of real-time and full-field detection of near-wall salinity is presented to use the surface plasmon resonance (SPR) reflectance that changes with refractive index variations of the tested saline fluid. The laboratory-designed SPR system, based on the Kretschmann's configuration, uses a 47.5 nm thick gold layer as the SPR resonator, coated on a BK7 prism (n=1.

Optoelectric biosensor using indium-tin-oxide electrodes.

The use of an optically thin indium-tin-oxide (ITO) electrode is presented for an optoelectric biosensor simultaneously recording optical images and microimpedance to examine time-dependent cellular growth. The transmittance of a 100 nm thick ITO electrode layer is approximately the same as the transmittance of a clean glass substrate, whereas the industry-standard Au(47.5 nm)/Ti(2.

Effect of nanoparticle sizes and number densities on the evaporation and dryout characteristics for strongly pinned nanofluid droplets.

A microfabricated linear heater array operating in a constant voltage mode has been used to study the effect of nanoparticle size on the evaporation and dryout characteristics of strongly pinned nanofluid droplets. Four different nanofluids have been tested, containing 2-nm Au, 30-nm CuO, 11-nm Al2O3, and 47-nm Al2O3 nanoparticles, each of 5-muL droplets with 0.5 vol % in water.