High-performance surface-micromachined inchworm actuator

This work demonstrates a polycrystalline silicon surface-micromachined inchworm actuator that exhibits high-performance characteristics such as large force (/spl plusmn/0.5 millinewtons), large velocity range (0 to /spl plusmn/4.4 mm/sec), large displacement range (/spl plusmn/100 microns), small step size (/spl plusmn/10, /spl plusmn/40 or /spl plusmn/100 nanometers), low power consumption (nanojoules per cycle), continuous bidirectional operation and relatively small area (600 /spl times/ 200/spl mu/m/sup 2/). An in situ load spring calibrated on a logarithmic scale from micronewtons to millinewtons, optical microscopy and Michelson interferometry are used to characterize its performance. The actuator consists of a force-amplifying plate that spans two voltage-controlled clamps, and walking is achieved by appropriately sequencing signals to these three components. In the clamps, normal force is borne by equipotential rubbing counterfaces, enabling friction to be measured against load. Using different monolayer coatings, we show that the static coefficient of friction can be changed from 0.14 to 1.04, and that it is load-independent over a broad range. We further find that the static coefficient of friction does not accurately predict the force generated by the actuator and attribute this to nanometer-scale presliding tangential deflections.     

Single crystal silicon nanopillars, nanoneedles and nanoblades with precise positioning for massively parallel nanoscale device integration

Arrays of precisely positioned single crystal silicon nanopillars, nanoneedles, and nanoblades with minimum feature sizes as small as 30 nm are fabricated using entirely scalable top-down fabrication techniques. Using the same scalable technologies, devices consisting of electrically connected silicon nanopillars with multiple addressable electrodes for each nanostructure are realized. The arrays of nanopillars, nanoneedles, and nanoblades are shown to exhibit Raman signal enhancement on 1,2-benzenedithiol monolayers, opening a path to nanodevices that manipulate, position, detect and analyze molecules.     

Evaluation of the Effects of Hydrothermal Treatment on Rice Flour and Its Related Starch

The main aim of this research was to compare the effects of hydrothermal treatment on rice flour and its related rice starch. The treatment was performed at 120°C for 3 and 5 h. Scanning electron microscopy results showed that the proteins of hydrothermaled rice flour were denatured and formed clusters and the granules of hydrothermaled rice starch became aggregated and had an irregular surface. The treatment reduced water solubility and water absorption and decreased peak viscosity while increased pasting temperature. It increased the final visosity of modified rice flour while reduced the final viscosity of modified rice starch. Following hydrothermal treatment, the hardness and elasticity of the gels increased. The cohesiveness of rice flour gels decreased while that of the rice starch gels remained unchanged. This study showed how the hydrothermal treatment can have different effects on rice flour and its related rice starch. The effects of hydrothermal treatment on rice flour were stronger than rice starch. Increasing the treatment time from 3 to 5 h was more effective on rice starch.     

Nonenzymatic glucose sensing based on deposited palladium nanoparticles on epoxy-silver electrodes

A new approach for nonenzymatic glucose sensing, based on a simple modification of epoxy-silver surfaces deposited on the tip of commercial copper electric wires, is presented. Palladium was galvanically displaced on the surface of the epoxy-silver surface in order to obtain metal nanoparticles that act as catalyst for the direct oxidation of glucose. Scanning electron microscopy revealed the formation of the metal nanoparticles. X-ray photoelectron spectroscopy confirmed the metallic nature of the formed nanostructures on the surface. Electrochemical characterization and calibration of the palladium-modified epoxy-silver electrode is reported, obtaining a linear range of 1–20 mM for the detection of glucose with low interference of ascorbic acid and uric acid. A simple 3-step coulometry was used as the detection technique. The developed sensing material is believed to be a great candidate for integration in small devices for clinical essays, due to the simplicity and cost effectiveness of the presented approach, compared to the state-of-the-art devices reported recently in the literature. Simplicity in the coulometry determinations makes these Pd-modified epoxy-silver sensors a good candidate for easy glucose determinations.     

Morphological,Electrical, and Chemical Changes in Cyclically Contacting Polycrystalline Silicon Surfaces Coated with Perfluoroalkylsilane Self-Assembled Monolayer

The evolution of morphology, electrical properties, and chemical composition has been studied in cyclically contacting polycrystalline silicon (polysilicon) surfaces coated with perfluoroalkylsilane self-assembled monolayer (SAM). The microinstrument used is a MEMS cantilever that is repeatedly actuated out-of-plane to impact a landing pad and is then moved in-plane to enable nondestructive in situ inspection of the impacted area. Analyses show that a device with a monolayer coating exhibits signs of surface degradation after a much higher number of cycles than its uncoated counterpart. A sharp increase in contact resistance between the cantilever and landing pad is observed at ~10 billion cycles for a coated device, versus ~25 million cycles for an uncoated device. Likewise, the onset of grain fracture in the landing pad occurs at ~25 billion cycles for the SAM-coated device, versus ~3 billion cycles for its uncoated counterpart. The effectiveness of the monolayer coating diminishes after more than 100 billion contact cycles as the SAM layer is removed, and the polysilicon substrate becomes susceptible to adhesive wear.     

Simultaneous Voltammetric Determination of Synthetic Colorants in Foods Using a Magnetic Core–Shell Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@SiO<Subscript>2</Subscript>/MWCNTs Nanocomposite Modified Carbon Paste Electrode

This paper reports the production of a novel magnetic nanocomposite based on multi-walled carbon nanotubes (MWCNTs) decorated with magnetic core–shell Fe₃O₄@SiO₂ nanoparticles which were used to fabricate a modified carbon paste electrode (Fe₃O₄@SiO₂/MWCNT-CPE). The Fe₃O₄@SiO₂/MWCNT-CPE was investigated for the simultaneous determination of sunset yellow (SY) and tartrazine (TT) in 0.1 mol/L phosphate buffer solution (pH 6.0) using square wave voltammetry (SWV). The synthesized nanocomposite was characterized by transmission electron microscopy, scanning electron microscopy, energy dispersive spectroscopy and Fourier transform infrared spectroscopy. The proposed electrode exhibits linear ranges of 0.5–100 μmol/L SY and TT with detection limits of 0.05 and 0.04 μmol/L for SY and TT, respectively. The novel proposed voltammetric method was successfully applied in the simultaneous determination of SY and TT in food products, with results similar to those obtained using a HPLC method at 95 % confidence level.

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Graphical Abstract A magnetic nanocomposite based on MWCNTs decorated with core–shell Fe₃O₄@SiO₂ was prepared and showed good ability to distinguish the response of SY and TT

     

Tribological Impact of SiC Encapsulation of Released Polycrystalline Silicon Microstructures

A method for coating released polysilicon microstructures with thin, uniform and conformal coatings of SiC derived from the single source precursor, 1,3-disilabutane (DSB) has been developed. This coating method has been successfully applied to micromechanical test devices which allow evaluation of friction and wear properties of the coating. Here, data on the coefficient of static friction of SiC coatings produced from DSB is presented. Also, a comparative wear study for devices which have been oxidized, treated with an anti-adhesion coating, and SiC coated is shown. Wear is examined by scanning electron microscopy (SEM) on devices which have been cycled repetitively under a nominal load. It is found that the application of a few nanometers-thin SiC coating provides exceptional wear resistance as well as significant reduction in friction on the microscale.     

Diagnosis of attention deficit hyperactivity disorder using non‐linear analysis of the EEG signal

Attention deficit hyperactivity disorder (ADHD) is a common behavioural disorder that may be found in 5%–8% of the children. Early diagnosis of ADHD is crucial for treating the disease and reducing its harmful effects on education, employment, relationships, and life quality. On the other hand, non‐linear analysis methods are widely applied in processing the electroencephalogram (EEG) signals. It has been proved that the brain neuronal activity and its related EEG signals have chaotic behaviour. Hence, chaotic indices can be employed to classify the EEG signals. In this study, a new approach is proposed based on the combination of some non‐linear features to distinguish ADHD from normal children. Lyapunov exponent, fractal dimension, correlation dimension and sample, fuzzy and approximate entropies are the non‐linear extracted features. For computing, the chaotic time series of obtained EEG in the brain frontal lobe (FP1, FP2, F3, F4, and Fz) need to be analysed. Experiments on a set of EEG signal obtained from 50 ADHD and 26 normal cases yielded a sensitivity, specificity, and accuracy of 98, 92.31, and 96.05%, respectively. The obtained accuracy provides a significant improvement in comparison to the other similar studies in identifying and classifying children with ADHD.Inspec keywords: feature extraction, time series, fractals, electroencephalography, medical disorders, neurophysiology, medical signal processing, entropy, signal classification, Lyapunov methodsOther keywords: nonlinear extracted features, chaotic time series, identifying classifying children, attention deficit hyperactivity disorder, nonlinear analysis methods, electroencephalogram signals, brain neuronal activity, chaotic behaviour, chaotic indices, EEG signals, nonlinear features, approximate entropies, common behavioural disorder, early diagnosis, life quality, ADHD     

Excitation of Cy5 in self-assembled lipid bilayers using optical microresonators

Due to their sensitivity and temporal response, optical microresonators are used extensively in the biosensor arena, particularly in the development of label-free diagnostics and measurement of protein kinetics. In the present letter, we investigate using microcavities to probe molecules within biomimetic membranes. Specifically, a method for self-assembling lipid bilayers on spherical microresonators is developed and the bilayer-nature is verified. Subsequently, the microcavity is used to excite a Cy5-conjugated lipid located within the bilayer while the optical performance of the microcavity is characterized. The emission wavelength of the dye and the optical behavior of the microcavity agree with theoretical predictions.