Controlled Surface Roughness Research Articles

Reusable biosensors via in situ electrochemical surface regeneration in microfluidic applications

Biosensors support biological and clinical diagnostic applications, offering high accuracy, precision, and functionality. Viable reusable biosensors for enclosed microfluidics are challenging because regeneration methods must ensure precision and sensitivity after recycle. Self-Assembled Monolayers (SAMs) and electrochemical processes show promise; intermediate and long chain SAMs are commonly used, but during desorption, re-adsorption and non-specific adsorption degrades biosensors, limiting reusability. Overcoming these limits is the focus of this work. We tested a prototype and regeneration method using densely packed, short-chain SAMs. Used in conjunction with controlled surface roughness, they reduced re-adsorption and non-specific molecule adsorption. Results confirmed short-chain SAM formation in enclosed microfluidic devices, and desorption promoted “clean” surface recycling for up to 50 cycles. Sensor reusability was evaluated in situ and in real time by Surface Plasmon Resonance (SPR), with a Relative Standard Deviation (RSD) of less than 0.82%, suggesting reusable microfluidics biosensors are finally within reach.

Micro/Nanoscale Patterning of Nanostructured Metal Substrates for Plasmonic Applications

The ability to precisely control the pattern of different metals at the micro- and nanoscale, along with their topology, has been demonstrated to be essential for many applications, ranging from material science to biomedical devices, electronics, and photonics. In this work, we show a novel approach, based on a combination of lithographic techniques and galvanic displacement reactions, to fabricate micro- and nanoscale patterns of different metals, with highly controlled surface roughness, onto a number of suitable substrates. We demonstrate the possibility to exploit such metal films to achieve significant fluorescence enhancement of nearby fluorophores, while maintaining accurate spatial control of the process, from submicron resolution to centimeter-sized features. These patterns may be also exploited for a wide range of applications, including SERS, solar cells, DNA microarray technology, hydrophobic/hydrophilic substrates, and magnetic devices.

Transition Criteria for Entropy Reduction of Convective Heat Transfer from Micropatterned Surfaces

This paper develops an entropy-transition number for characterizing irreversibilities of external flow past micropatterned surfaces with controlled surface roughness. It is shown that embedded surface microchannels can reduce flow irreversibilities below a classical boundary-layer limit, due to drag reduction of slip-flow conditions within the microchannels. A surface-irreversibility ratio establishes the proportion of entropy production of slip-flow relative to no-slip conditions. Then an entropy-transition number is defined to characterize flow regimes in which the ratio decreases below unity, thereby indicating conditions in which surface micropatterning has an overall beneficial impact on energy conversion efficiency. Results are presented for various micropatterned surfaces. It is shown that slip-flow conditions within the embedded surface microchannels can overcome the additional friction irreversibility of more surface area, reducing the total entropy production up to 20% below the boundary-layer flow without microchannels. At lower Reynolds numbers, it is shown that the irreversibility ratio decreases (for example, down to 0.79) at a Reynolds number of 1200. The newly defined surface-irreversibility and entropy-transition numbers are shown to provide useful new parameters to characterize the boundary-layer irreversibilities of convective heat transfer.

Modification of single-walled carbon nanotube electrodes by layer-by-layer assembly for electrochromic devices

We have studied the morphological properties and electrochromic (EC) performance of polythiophene multilayer films on single wall carbon nanotube (SWCNT) conductive electrodes. The morphology for different numbers of layer-by-layer (LbL) bilayer on the SWCNT electrode has been characterized with atomic force microscopy and scanning electron microscope, and it was found that the LbL multilayers significantly decrease the surface roughness of the nanoporous nanotube films. The controlled surface roughness of transparent nanotube electrodes could be beneficial for their device applications. We have also fabricated EC devices with LbL films of poly[2-(3-thienyl) ethoxy-4-butylsulfonate∕poly(allylamine hydrochloride) on SWCNT electrodes, which not only have high EC contrast but also sustain higher applied voltage without showing any degradation for more than 20000cycles, which is not possible in the case of indium tin oxide electrodes. Cyclic voltammetry of the LbL films formed on SWCNT shows higher current at low potential, revealing the feasibility of SWCNT electrode as a good host for electrolyte ion insertion.

Designer Binary Nanostructures toward Water Slipping Superhydrophobic Surfaces

This report demonstrates a synthetic route for ordering a set of Au nanoparticles on the vertically aligned conducting polymer (polypyrrole) for the superhydrophobic surfaces with low water flow friction. It demonstrates how one can use polymer nanorod pillars and a variety of Au nanoparticles to generate controlled surface roughness. Synthetic strategies utilized to make such surfaces include the electrochemical polymerization of conducting polymers within the confines of anodized alumina templates and subsequent Au nanoparticle immobilization on the surface of polymer pillars. This method provides a surface that contains roughness on two independently controllable levels, say, the submicroscopic roughness from polymer pillar dimensions and the nanoscopic roughness from the appropriate size selection of Au nanoparticles. With the present results, it is clearly evident that a combination of two scale roughnesses composed of nanorods and nanoparticles could be utilized for the synthesis of superhydrophobic...

Oriented and Nanostructured Polycarbonate Substrates for the Orientation of Conjugated Molecular Materials and Gold Nanoparticles

A simple method to prepare large areas of polycarbonate (PC) alignment layers with a high degree of polymer chain orientation, a periodic and oriented nanoscale pattern, and a controlled surface roughness is presented. The method involves three steps: (i) the preparation of a film of bisphenol A polycarbonate in its glassy state, (ii) the near-surface orientation of the polymer chains by rubbing, and (iii) exposure to vapors of acetone which acts as a plasticizer removing the microgrooves formed by rubbing and promotes solvent induced crystallization of PC. The resulting surface of the PC films is oriented and nanostructured, it consists of the periodic alternation of edge-on oriented crystalline lamellae and amorphous interlamellar zones with a total periodicity of ∼20 nm. The roughness of the oriented and nanostructured PC layers can be tuned by adjusting the exposure time to the solvent. The PC films exhibit a high orienting ability for various materials grown from the vapor phase, e.g., conjugated or...

Control of Specular and Diffuse Reflection of Light Using Particle Self‐Assembly at the Polymer and Metal Interface

AbstractWe present a novel method of controlling the specular and diffuse reflection of light by the electrostatic deposition of a spherical particle monolayer followed by electroless plating. Charged polystyrene colloidal particles, ranging in size from 100 nm to 5 μm, were adsorbed from solution onto oppositely charged polyelectrolyte multilayers (PEM). The monodisperse particle monolayers were coated with nickel in a two‐step electroless plating process using palladium catalysts. These surfaces can be used as diffusive metal reflectors with a uniformly controlled surface roughness due to the uniform size of deposited particles. In addition, the self‐assembled particles at the polymer and metal interface deflected the internal stresses that build‐up at the interface while the metal was being deposited. This allowed a thicker metal film to be deposited before delamination occurred. A UV‐VIS spectrometer with movable fiber optic cables was employed to characterize the optical properties of the reflectors. The optical fibers permit versatile and precise measurements of specular and diffuse reflectance. By measuring the angular dependent reflectance, we demonstrate how to estimate the distribution of reflected light from the nickel coated surface and how to calculate the ratio of specular and diffuse reflection in the total reflected light. Optical measurements of our nickel samples showed that this approach could be used to control the portion of diffuse reflection from 8.25 to 59.97 %. Additionally, a quartz crystal microbalance was employed to study the electroless nickel plating rate on PEM. Our proposed method is simple, cost‐effective and convenient for mass production because the process consists of a series of simple immersion steps without vacuum technology or special equipment.

Pressure Controlled Surface Roughness of SiC Plasma Etching

The effects of pressure on the surface roughness of silicon carbide (SiC) film were investigated with variations in other process parameters, including radio frequency source power, bias power, O2 fraction and gap. The SiC films were etched in a C2F6 inductively coupled plasma. The surface roughness, measured by atomic force microscopy, was examined in three particular situations: generated at minimum parameter level (case 1), at high source power (case 2); and at high bias power (case 3). For all variations in the process parameters except the O2 variation, smoother surfaces were observed at lower pressures in all cases. Both surface roughness and dc bias due to the pressure variation were highly correlated in case 1. In case 3, they were inversely related. It is noticeable that in cases 1 and 2 the surface roughness was little affected by the pressure, particularly at high bias power. This feature can be used not only for tight control of surface roughness, but for optimising other etch outputs.

Nanostructured Surfaces: Scientific and Optical Device Applications

Surfactant and polymer-coated substrates may be patterned on microscopic and nanoscopic length scales by the stylus of an atomic force microscope. The resulting easy axes control the director orientation, facilitating both scientific studies and technological devices that were not possible using previous techniques. In this talk I will present a review of work from my laboratory, performed in collaboration with Milind P. Mahajan, Wen Bing, Ghanshyam P. Sinha, and Rolfe G. Petschek, along with colleagues L.V. Mirantsev (St. Petersburg, Russia) and Jong-Hyun Kim and Hiroshi Yokoyama (Tsukuba, Japan). Work includes a number of optical gratings for beam steering applications, gray scale images, anchoring strength studies, effects of controlled surface roughness on smectic order, and nanoscopic elasticity and anchoring effects on the nematic-isotropic phase transition.

Preparation of porous PbO 2 electrodes by electrochemical deposition of composites

Porous PbO 2 electrodes have been prepared by anodic codeposition of PbO 2 particles with an electrochemically grown PbO 2 matrix, with the aim of illustrating how composite deposition may be a suitable method for obtaining electrodes of large and controlled surface roughness. By exploiting the different crystal structures of PbO 2, the composition of α-PbO 2+β-PbO 2 composites (i.e. composites with an α matrix and a β dispersed phase) has been determined by X-ray diffraction. It has been found that reliable indications on composition of deposits may be also obtained by measuring the current efficiency of the deposition process, which largely exceeds unity in the case of composites. This way, the dependence of the dispersed phase concentration in the deposits on current density and suspended particles concentration has been determined. The surface roughness of the composite electrodes has been estimated by electrochemical impedance spectroscopy. It was found to increase almost linearly with the deposition charge and reach limiting values as either the deposition current density or the suspended particles concentration are increased.

ZnO/Al 2O 3 nanolaminates fabricated by atomic layer deposition: growth and surface roughness measurements

Nanolaminates are unique nanocomposites that allow various thin film properties to be tuned by changing the composition and interfacial density. ZnO/Al 2O 3 nanolaminates allow the surface roughness to be controlled because ZnO is crystalline and Al 2O 3 is amorphous at low deposition temperatures. ZnO/Al 2O 3 nanolaminates were grown using atomic layer deposition (ALD) methods. The ZnO and Al 2O 3 films were deposited at 450 K using alternating diethyl zinc/H 2O exposures and trimethyl aluminum/H 2O exposures, respectively. The growth rate and surface topography of the pure oxide films were examined using ex situ ellipsometry, stylus profilometry and atomic force microscopy (AFM) techniques. The ZnO ALD films grew at 2.01 Å/cycle and roughened significantly versus film thickness because of the presence of ZnO nanocrystals. In contrast, the Al 2O 3 ALD films grew at 1.29 Å/cycle and remained remarkably smooth versus film thickness because of their amorphous structure. In situ quartz crystal microbalance measurements were employed to study the ZnO/Al 2O 3 nanolaminate growth. The individual ZnO and Al 2O 3 nanolayers nucleated and grew easily on each other with minimal interfacial effects. ZnO/Al 2O 3 nanolaminate films were prepared where the number of ZnO/Al 2O 3 interfaces was varied but the total thickness remained constant at ∼1250 Å. Using AFM techniques, the RMS roughness of the nanolaminates was observed to decrease substantially with increasing ZnO/Al 2O 3 interfacial density. The Al 2O 3 nanolayer interrupts the ZnO crystal growth and forces the ZnO nanolayer to renucleate on the Al 2O 3 surface. AFM measurements revealed that a single trimethyl aluminum/H 2O reaction cycle was sufficient to reduce markedly the surface roughness of the ZnO/Al 2O 3 nanolaminate films. ZnO/Al 2O 3 nanolaminates should be useful to fabricate a surface topography with a controlled surface roughness.

217 CNC カム研削機構のシミュレーション

This paper describes about the accurate camshaft grinding methods verified by the simulation analysis for the cam grinding mechanism based on both the curvature radius change of the cam shape and the peripheral velocity change at the grinding point. In the case of the grinding under constant rotation of the camshaft, the great fluctuations, it is necessary to optimize the rotation velocity of the camshaft and the horizontal travel speed of the wheel head. Then the effectiveness of three grinding technique are made clear, such as the controlled normal force grinding method, the controlled surface roughness grinding method and the constant velocity ratio grinding method.

Sliding wear prediction of ductile materials

This paper describes a comprehensive experimental and theoretical investigation of metallic sliding wear. A novel asperity test was proved to be capable of investigating the wear procedure and to interpret the behaviour of the metal in response to wear. The test enables the rapid acquisition of wear data under controlled surface roughness and lubrication conditions. A series of tests were performed with a range of asperity angles on aluminium, brass and copper. With the modification and approximation proposed, the rigid–plastic model can predict friction and wear well. This work makes possible a fundamental approach to predicting sliding wear. These results also give an estimate of the material properties needed to predict wear. It is possible to extend the single asperity test to use on real engineering surfaces.

Microstructures etched in doped TMAH solutions

Tetra-methyl ammonium hydroxide, or TMAH, is an anisotropic silicon etchant that is gaining more and more attention in the fabrication process of mechanical microstructures and device isolation, as an alternative to the more usual KOH and EDP etchants [1]: because of its high compatibility with conventional IC processes, due to the absence of metal ions in it. The possibility to passivate the aluminum metalisation in properly saturated TMAH solution has also been demonstrated by doping the solution with appropriate amounts of silicon or silicic acid [2, 3]. This increases the range of application of these etchants, simplifying both the post processing and the etch set-up configuration. In this paper we present some different technological solutions adopted for the fabrication of 3D structures using as anisotropic etchant doped TMAH solutions. The effects of the additives on etch uniformity and surface roughness are studied. Using the etching results under different doping conditions of the TMAH solutions, we obtained silicon bulk-micromachined structures with controlled surface roughness. Furthermore the aluminium passivation permits to etch devices with no protection of the metalisation layers as some applications require (i.e. bolometers).

Monolithic porous glasses with controlled mesopore size

Mesoporous sol-gel glasses may play the role of host materials to study the effect of confinement on fluid properties. A method based on a peculiar drying procedure of silica gels, followed by their partial densification by a heat treatment is described. Monolithic mesoporous glasses with a porosity exceeding 50%, a well defined pore size and a controlled surface roughness are obtained. N 2 adsorption-desorption and Small Angle X-ray Scattering techniques are used to study the porous and solid texture, and the inner surface roughness of these materials. Various samples of narrow pore size distribution with half width at half height under 2nm, and mean pore size below 25nm are obtained.

Non-uniform sputtering and degradation of depth resolution during GDOES depth profiling analysis of thin anodic alumina films grown over rough substrates

Degradation of depth resolution during glow discharge optical emission spectroscopy (GDOES) depth profiling analysis of thin films, formed on relatively rough substrates, has been investigated using preconditioned aluminium substrates of controlled surface roughness. The anodic alumina films, -120 nm thick, were depth profiled partially and examined carefully by atomic force microscopy and by transmission electron microscopy of ultramicrotomed sections. It is revealed clearly that depth profiling sputters ridges, associated with the rough surface, more rapidly than valleys, thereby degrading depth resolution. Further, such observations show that film sputtering proceeds very smoothly, with relatively little damage to the remaining film material. The excellent depth resolution realized during GDOES depth profiling analysis of films grown on mirror-finished, microscopically flat substrates is clearly associated with the highly uniform sputtering of amorphous anodic alumina.

The effect of surface roughness on infrared external reflection spectroscopy

The effect of surface roughness of the back-side of a film-supporting material on Fourier transform infrared (FTIR) external reflection (ER) spectra was studied by using 9-monolayer cadmium stearate Langmuir–Blodgett (LB) films. The LB films are prepared on two infrared-transparent ZnSe substrates whose top surfaces are optically polished and bottom surfaces have controlled surface roughness with 1.2 and 0.1 μm of protrusions. Although the roughness of 0.1 μm is smaller than the wave-length of the infrared ray, both LB films show typical ER spectra qualitatively. On closer inspection, however, the LB film on the substrate with 0.1 μm protrusions is irregular and the LB film on 1.2 μm protrusions is better. These results indicate that the surface roughness of the backside of substrate is necessary for ER analyses.

Polysilicon surface-modification technique to reduce sticking of microstructures

A new and simple surface-modification technique is proposed to reduce sticking of microstructures fabricated by surface micromachining. This technique realizes a very rugged surface at the polysilicon substrate, resulting in reduced sticking through a decrease of real contact area. The surface, which consists of honeycomb-shaped grain holes at the polysilicon substrate layer, is defined by a two-step dry etch without an additional masking step for photolithography or deposition of thin films. By varying the time for etching the grain holes of the polysilicon substrate, controlled surface roughness can be obtained. Test structures, including polysilicon cantilever beams of various lengths, fabricated by surface micromachining with the proposed surface modification show a doubled detachment length without sticking to the substrate.

Experimental studies on the phase distribution of two copolarized signals scattered from two-dimensional rough surfaces

The experiment results of the phase distribution of millimeter-waves scattered from two-dimensional rough surfaces of controlled surface roughness statistics are presented. The statistics of /spl phi//sub vv/-/spl phi//sub hh/ were obtained for different surfaces, including very rough surfaces which are known to create backscattering enhancement. It is shown that the distribution of /spl phi//sub vv/-/spl phi//sub hh/ is strongly related to the surface roughness. In addition, the authors found that the standard deviation decreases as the incidence angle increases. This phenomena is contradictory to the reported data of radar scattering from soil.

Magnetic performance and tribology of sputter-textured thin film disks

A novel method for fabricating thin film disk media with controlled surface roughness via sputter deposition is described. This technique uses the deposition of a metal nitride such as AlN on a polished substrate to create discrete spherical features. The Cr or Cr alloy interlayer, the magnetic layer and the carbon overcoat are then deposited onto the AlN. The magnetic and mechanical performance of thin film disks fabricated with this technique Is presented and compared to that of a disk made with conventional mechanical texture. It is shown that the disks fabricated with this technique have no texture-induced noise, excellent magnetic performance, and tribological characteristics which make them suitable for high density recording applications.