Wax Spreading in Paper under Controlled Pressure and Temperature.

This work describes a novel rapid method to fabricate high-resolution paper-based microfluidic devices using wax-ink-based printing. This study demonstrates that both temperature and pressure are important knobs in controlling the device resolution. High-resolution lines and patterns were obtained by heating the paper asymmetrically from one side up to 110 °C while applying pressure up to 49 kPa.

Effect of roughness geometry on wetting and dewetting of rough PDMS surfaces.

Rough PDMS surfaces comprising 3 μm hemispherical bumps and cavities with pitches ranging from 4.5 to 96 μm have been fabricated by photolithographic and molding techniques. Their wetting and dewetting behavior with water was studied as model for print surfaces used in additive manufacturing and printed electronics.

Anomalous thermally induced pinning of a liquid drop on a solid substrate.

The effect of substrate temperature on the wetting and spreading behavior of a UV ink monomer has been studied as a surrogate for the ink on four different substrates: DTC (digital top coat)-coated BOPP (biaxial oriented polypropylene), Flexo-coated BOPP, DTC-coated SGE (semigloss elite) paper, and Flexo-coated SGE paper. Results show that the dynamic contact angles of the monomer decrease exponentially over time after contacting the surface, and the rate of spreading is consistently higher at 95 °C than at 22 °C. This observation indicates that spreading is controlled by the viscosity of the monomer as it decreases with temperature.

Entrapment of live microbial cells in electropolymerized polyaniline and their use as urea biosensor.

The lyophilized biomass of bacterium Brevibacterium ammoniagenes was immobilized in polystyrene sulphonate-polyaniline (PSS-PANI) conducting polymer on a Pt twin wire electrode by potentiostatic electropolymerization. The bacterial cells retained their viability as well as urease activity under entrapped state, as confirmed with bacterial live-dead fluorescent assay and enzymatic assays. The entrapped cells were visualized using scanning electron microscope.

Suppression of metallic conductivity of single-walled carbon nanotubes by cycloaddition reactions.

The high carrier mobility of films of semiconducting single-walled carbon nanotubes (SWNTs) is attractive for electronics applications, but the presence of metallic SWNTs leads to high off-currents in transistor applications. The method presented here, cycloaddition of fluorinated olefins, represents an effective approach toward converting the "as grown" commercial SWNT mats into high-mobility semiconducting tubes with high yield and without further need for carbon nanotube separation. Thin-film transistors, fabricated from percolating arrays of functionalized carbon nanotubes, exhibit mobilities >100 square centimeters per volt-second and on-off ratios of 100,000.

Functionalized carbon nanotubes for detecting viral proteins.

We investigated the biocompatibility, specificity, and activity of a ligand-receptor-protein system covalently bound to oxidized single-walled carbon nanotubes (SWNTs) as a model proof-of-concept for employing such SWNTs as biosensors. SWNTs were functionalized under ambient conditions with either the Knob protein domain from adenovirus serotype 12 (Ad 12 Knob) or its human cellular receptor, the CAR protein, via diimide-activated amidation. We confirmed the biological activity of Knob protein immobilized on the nanotube surfaces by using its labeled conjugate antibody and evaluated the activity and specificity of bound CAR on SWNTs, first, in the presence of fluorescently labeled Knob, which interacts specifically with CAR, and second, with a negative control protein, YieF, which is not recognized by biologically active CAR proteins.

Aromatic interactions are not required for amyloid fibril formation by islet amyloid polypeptide but do influence the rate of fibril formation and fibril morphology.

Amyloid formation has been implicated in a wide range of human diseases, and a diverse set of proteins is involved. There is considerable interest in elucidating the interactions which lead to amyloid formation and which contribute to amyloid fibril stability. Recent attention has been focused upon the potential role of aromatic-aromatic and aromatic-hydrophobic interactions in amyloid formation by short to midsized polypeptides.

Synthesis and growth mechanism of titanate and titania one-dimensional nanostructures self-assembled into hollow micrometer-scale spherical aggregates.

Three-dimensional, dendritic micrometer-scale spheres of alkali metal hydrogen titanate 1D nanostructures (i.e., nanowires and nanotubes) have been generated using a modified hydrothermal technique in the presence of hydrogen peroxide and an alkali metal hydroxide solution.

Diffusion of redox probes in hydrated sol-gel-derived glasses. Effect of gel structure.

The diffusion coefficients of redox probes entrapped in a silica matrix prepared by the sol-gel process were measured using a combination of cyclic voltammetry and chronoamperometry at an ultramicroelectrode. In this study, the porosities of the gels were varied to assess the importance of constrained environments vs intermolecular interactions on the translational mobility of guests entrapped in this solid host matrix. The average pore diameter of the gels was varied from 40 to 400 A by utilizing different catalysts (HCl, NH3, NaF) or different silicon precursors (tetramethoxysilane or Ludox colloidal silica).

Current-less photoreactivity catalyzed by functionalized AFM tips.

A spatially confined photocatalytic oxidation of a thin film of synthetic textile azo dye (Procion Red MX-5B) using TiO2-functionalized AFM probes is described.

Controlling diffusion in sol-gel derived monoliths.

Redox probes were trapped within a silica monolith prepared in part with organoalkoxysilanes containing a quaternary ammonium functional group. The diffusion coefficients of the entrapped molecules were measured as the gels were slowly dried using chronoamperometry and cyclic voltammetry with ultramicroelectrodes. Gel-entrapped cobalt(II) tris(bipyridine) (Co(bpy)(3)(2+)) diffuses at rates similar to that measured in the sols by incorporating a small amount of the positively charged functional group in the matrix.

Fabrication of two-dimensionally ordered macroporous silica materials with controllable dimensions.

The formation of 2-D arrays of cavities of varying size and depth on an electrode surface via colloidal templating is described.

Electrochemically deposited sol-gel-derived silicate films as a viable alternative in thin-film design.

Sol-gel-derived silicate films were electrochemically deposited on conducting surfaces from a sol consisting of tetramethoxysilane (TMOS). In this method, a sufficiently negative potential is applied to the electrode surface to reduce oxygen to hydroxyl ions, which serves as the catalyst for the hydrolysis and condensation of TMOS. The electrodeposition process was followed by the electrochemical quartz crystal microbalance and cyclic voltammetry.

Microtubule sensors and sensor array based on polyaniline synthesized in the presence of poly(styrene sulfonate).

Microtubule sensors for glucose, urea, and triglyceride were fabricated based on poly(styrene sulfonate)-polyaniline (PSS-PANI) composites synthesized within the pores of track-etched polycarbonate membranes. The synthesis of a sufficiently thick and conducting PSS-PANI film at pH 5 provided the advantage of immobilizing enzymes during polymerization. This resulted in the improvement of sensor response for urea and triglyceride by a factor of approximately 10(2) with a significant increase in the linear region of response compared to polyaniline-based sensors, where the enzymes were immobilized by physical adsorption after the polymerization.

Conductimetric immunosensor based on poly(3,4-ethylenedioxythiophene).

A conductimetric reagentless immunosensor using the biospecific binding pair of goat antirabbit IgG and rabbit IgG has been designed and fabricated using poly (3,4-ethylenedioxythiophene) as the immobilization matrix-cumtransducer.