3D label free bio-transfer standards

A general equation of the interference signal of white-light scanning interferometer (WSI) and its Fourier transform are derived. Based on these equations, a new method for elimination of a dispersion effect in WSI is proposed to measure exactly a reflecting surface position. A dispersion phase caused by the two sides of unequal length in a beam splitter is detected with a spectrally resolved interferometer (SRI). A spectral distribution is obtained by using Fourier transform from an interference signal detected with a WSI. The spectral phase of the SRI is subtracted from the spectral phase of the WSI to get a dispersion-free spectral phase, which provides an improved complex-valued interference signal where a position of zero phase is almost equal to a position of maximum amplitude. An accurate measurement is achieved by using the position of zero phase.

Conventional scanning white-light interferometers (SWLIs) cannot measure the exact shape of a thick glass plate because of the large dispersion effect. In this paper, a novel dual SWLI is proposed where the thicknesses of both an object and a compensation glass plate can be measured exactly in four-step measurements by decreasing the dispersion effect in both arms of the dual SWLI. The compensation glass plate is made of the same material as the object and has a similar thickness. The peak positions of the interference signals in the SWLI can be exactly measured using a piezoelectric transducer stage and an additional interference signal which detects the time-varying optical path difference in the SWLI. Experimental results show that the measurement error is less than 60 nm for a glass plate of thickness 1 mm.

BackgroundCellulose amorphogenesis, described as the non-hydrolytic “opening up” or disruption of a cellulosic substrate, is becoming increasingly recognized as one of the key steps in the enzymatic deconstruction of cellulosic biomass when used as a feedstock for fuels and chemicals production. Although this process is thought to play a major role in facilitating hydrolysis, the lack of quantitative techniques capable of accurately describing the molecular-level changes occurring in the substrate during amorphogenesis has hindered our understanding of this process.ResultsIn this work, techniques for measuring changes in cellulose accessibility are reviewed and a new quantitative assay method is described. Carbohydrate binding modules (CBMs) with specific affinities for crystalline (CBM2a) or amorphous (CBM44) cellulose were used to track specific changes in the surface morphology of cotton fibres during amorphogenesis. The extents of phosphoric acid-induced and Swollenin-induced changes to cellulose accessibility were successfully quantified using this technique.ConclusionsThe adsorption of substructure-specific CBMs can be used to accurately quantify the extent of changes to cellulose accessibility induced by non-hydrolytic disruptive proteins. The technique provided a quick, accurate and quantitative measure of the accessibility of cellulosic substrates. Expanding the range of CBMs used for adsorption studies to include those specific for such compounds as xylan or mannan should also allow for the accurate quantitative tracking of the accessibility of these and other polymers within the lignocellulosic biomass matrix.

We have developed a compressive hyperspectral imaging system that is based on single-pixel camera architecture. We have incorporated the developed system in a scanning white-light interferometer (SWLI) and showed that replacing SWLI’s CCD-based camera by the compressive hyperspectral imaging system, we have access to high-resolution multispectral images of interferometer’s fringes. Using these multi-spectral images, the system is capable of simultaneous spectroscopy of the surface, which can be used, for example, to eliminate the effect of surface contamination and providing new spectral information for fringe signal analysis which could be used to reduce the need for vertical scan, therefore making height measurement more tolerant to object’s position.

Advanced signal processing is required to make exact measurements with nanometer order accuracy. A complex-valued interference signal of a white-light scanning interferometer (WLSI) obtained from the detected real-valued interference signal through Fourier transform provides an accurate position of an object surface with an error less than 4 nm. Moreover, the sampling points of the interference signal of the WLSI detected with a camera are corrected with the measured scanning positions which are obtained from an interference signal detected by using an optical band-pass filter. This correction method provides more accurate surface profiles with an error less than 2 nm. In experiments a surface profile with a step shape of 3 μm-width is measured accurately.

Age-related changes in the surface morphology of the central sulcus

Reaction-sintered silicon carbide (RS-SiC), which is considered as a promising mirror material for space telescope systems, requires a high surface property. An ultrasmooth surface with a Ra surface roughness of 0.480 nm was obtained after water vapor plasma oxidation for 90 min followed by ceria slurry polishing for 40 min. The oxidation process of RS-SiC by water vapor plasma was analyzed based on the Deal–Grove model, and the theoretical calculation results are consistent with the measured data obtained by scanning white light interferometer (SWLI), scanning electron microscopy/energy-dispersive x-ray, and atomic force microscope. The polishing process of oxidized RS-SiC by ceria slurry was investigated according to the Preston equation, which would theoretically forecast the evolutions of RS-SiC surfaces along with the increasing of polishing time, and it was experimentally verified by comparing the surface roughnesses obtained by SWLI and the surface morphologies obtained by SEM. The mechanism analysis on the finishing of RS-SiC would be effective for the optimization of water vapor plasma oxidation parameters and ceria slurry polishing parameters, which will promote the application of RS-SiC substrates by improving the surface property obtained by the oxidation-assisted polishing method.

Surface degradation process affected by heterogeneity in nano-titanium dioxide filled acrylic urethane coatings under accelerated UV exposure

The purpose of this study was to evaluate, using scanning electron microscopy (SEM), the morphological and structural changes of the enamel induced by three bleaching agents namely old McInnes solution, modified McInnes solution and 10% carbamide peroxide gel at different time intervals. Fifteen freshly extracted noncarious human central incisors with intact enamel surface were selected. The teeth were sectioned at the cementoenamel junction separating the crown portion from the root using a diamond separating disk. Following this, the samples were subjected to three different bleaching agents: Group 1: Old McInnes solution, group 2: modified McInnes solution and group 3: 10% carbamide peroxide for a period of 15, 30 and 60 minutes, 24 and 30 hours time interval. The sample stubs were subjected to scanning electron microscope and were photographed at 2000 and 10,000 magnifications. The present study revealed no indication of either etching or significant change in surface morphology of enamel when evaluated under scanning electron microscope after 6 weeks treatment with various bleaching agents. Morphological alterations in bleached enamel are both concentration and time dependent.

Current-induced changes of surface morphology in printed Ag thin wires were investigated by current stressing tests and numerical simulation. The samples were printed Ag thin wires on a flexible substrate with input and output pads. Different experimentalresults were obtainedthroughchangingthe current density after current supply and the mechanism of those phenomena were investigated by numerical simulations based on the method of atomic flux divergence. Good agreement between the simulations and experimental results was reached. It was found that electromigration was the main factor that caused the change of the surface morphology. The contribution of thermal migration can be ignored, and the Joule heating lead by the supplied current had a very significant accelerating effect on electromigration. Guidelines for effectively changing the Ag thin wire surface through providing predetermined current density was proposed, which were expected to be useful for improving the electrical reliability and lifetime of printed Ag thin wires in flexible electronic devices.

Surface morphology is a key factor that determines the quality of laser-based micromachining processes. However, the governing laws of surface morphology in the laser processing process are yet to be clarified, and optimization of processing parameters has to rely on trial and error. Specifically, under multiple-pulse irradiation, it has been difficult to quantify the evolution of the surface morphology because the surface morphology changes with each pulse irradiation, and the ablation process changes accordingly. In this study, we investigated the evolution of surface morphology under femtosecond laser irradiation. Copper and silicon were used as targets, whose surface morphology changes exhibited seemingly opposite behaviors with respect to fluence. Using thousands of datasets, we obtained an evolution equation for surface morphology in terms of surface area, which acts as a good probe of the residual surface energy after ablation. Our model successfully quantifies the cumulative effect of multiple-pulse irradiation on surface morphology changes.

Silicon carbide (SiC) and its composites are candidate materials for the blanket components and for the first wall in a fusion reactor. If the SiC is used without any armor materials for the first wall, it is exposed by helium (He) plasma as well as hydrogen plasma. Characteristic surface morphology changes are reported for various materials by He plasma exposure. Thus, we exposed SiC specimens to He or simultaneous deuterium (D) and He (D + He) plasma by various conditions and then observed surface morphology changes by SEM. As a result, needle-like structures and whiskers-like structures at the tip were formed in He plasma and D + He irradiation, while only needle-like structures were formed in D plasma. Therefore, it indicated that the effects of He were attributed to form whiskers-like structures. Although the structures are different among He plasma, simultaneous D + He plasma and D plasma irradiations, sputtering is considered to be a dominant process for the formation of the structure formation. However, the effects of He atoms in the structure could also be attributed to form whiskers-like structures.

A scanning white light interferometer can characterize out of plane features and motion in M(N)EMS devices. Like any other form and displacement measuring instrument, the scanning interferometer results should be linked to the metre definition to be comparable and unambig uous. Traceability is built up by careful er ror characterization and calibration of the interferometer. The main challenge in this calibration is to have a reference device producing accurate and reproducible dynamic out-of-plane displacement when submitted to standard loads. We use a flat mirror attached to a piezoelectric transducer for static and (quasi)dynamic calibration of a stroboscopic scanning light interferometer. First we calibrated the piezo-scanned flexure guided transducer stage using a symmetric differential heterodyne laser interferometer developed at the Centre for Metrology and A ccreditation (MIKES). The standa rd uncertainty of the piezo stage motion calibration was 3.0 nm. Then we used the piezo-sta ge as a transfer standard to calibrate our stroboscopic interferometer whose light source was pulsed at 200 Hz and 400 Hz with 0.5% duty cycle. We measured the static position and (quasi)dynamic motion of the attached mirror relative to a reference surface. This methodology permits calibrating the vertical scale of the stroboscopic scanning white light interferometer. Keywords: Stroboscopic, Scanning White Light Interferomety,

Current commercial height profile measuring instruments, e.g. the confocal microscope and, the white light interferometer, are widely used in both research institutes and industry. The systematic error of such instruments can be the same order of magnitude as features on the surface to be measured, if care is not taken with calibration. Instrument error in most cases depends on the surface slope. Thus, calibration of the instrument is important. The random ball test, proposed by Parks et al, is a self calibration technique for transmission sphere calibration in phase shift interferometry. The idea is, by measuring a collection of random patches on the surface of a sphere and then averaging the results, the contributions from the ball go to zero leaving only the systematic biases due to the instrument. This paper shows it can also be used to calibrate slope-dependent errors in profilometers such as the scanning white light interferometer (SWLI). This will be demonstrated with both simulation and experimental results. For example, with a commercial SWLI measurement with a 20X objective, our random ball test indicates that the height error can be as large as 250 nm at a slope value of 2.9 degrees when using the envelope peak algorithm for analysis. Similarly, with a confocal microscope measurement using a 50X objective, the height error can be as large as 800 nm at a slope value of 12.1 degrees. These slope-dependent errors can be used to compensate future sloped-surface measurements.

Recently, the industrial optical inspection has been a mainstream in measuring 2D images or 3D profiles of microstructures. For the 3D profiling, the scanning white-light interferometer has a high resolution, but due to the broadband light source, it has the low coherence length. Thus, it is very difficult to obtain the focused image with clear interfered fringes, and the traditional auto-focusing approaches usually determine the wrong focused position. This paper proposed a useful approach by the passive auto-focusing to determine the accurate focus for the scanning white-light interferometers. Some experimental results are presented to verify the feasibility of the proposed approach.