Current Issue : July - September Volume : 2012 Issue Number : 3 Articles : 6 Articles
We present a fibre-optic-based device for the automated readout of microcantilever arrays for fast microorganism growth\r\ndetection.We determined the ability of our device to track shifts in resonance frequency due to an increase in mass on the cantilever\r\nsurface or changes in mechanical stiffness. The resonance frequency response of 7 �µm thick agarose-functionalised cantilevers was\r\ntracked as humidity levels were varied revealing a mass responsivity of ~51�±1 pg/Hz. The resonance response of microcantilevers\r\ncoated with Aspergillus niger (A. niger) spores was monitored for >48 h revealing a growth detection time of >4 h. The growth\r\nof mycelium along the cantilevers surface is seen to result in an increase in resonance frequency due to the reinforcement of\r\nthe cantilever structure. The use of our fibre optic detection technique allows data to be recorded continuously and faster than\r\npreviously reported....
Hepatitis B surface antigen (HBsAg) concentrations were measured using a piezoelectric microcantilever sensor (PEMS) developed\r\nby the authors. The developed PEMS is label-free and detects the sensing signal electrically. It was designed to measure the mass of\r\nbiomolecules attached to it using an accurate mass-microbalancing technique; its probe area is confined to the end of the cantilever,\r\nand its equivalent spring constant is relatively high to minimize the effect of changes in the surface stress when the biomolecules\r\nare attached to it. The ââ?¬Å?dip- and-dryââ?¬Â technique was used to enable the probe area of the sensor to react with reagents in controlled\r\nenvironmental conditions. HBsAg was detected by an immunoreaction whereas the reaction time, antibody density, and its area\r\non the probe were kept at a constant level. The mass of the detected HBsAg was measured in the range of 0.1ââ?¬â??100 ng/mL....
The qualitative agreement between experimental measurements of the Q factors and flexural resonance frequencies in air of\r\nmicrocantilevers and calculations based on the compressible fluid model of Van Eysden and Sader (2009) is presented. The Q\r\nfactors and resonance frequencies observed on two sets of cantilever arrays were slightly lower than those predicted by the model.\r\nThis is attributed to the individual design and geometry of the microfabricated hinged end of the cantilever beams in the array....
Early detection of protein aggregation is of great importance in the field of neurodegenerative diseases. The successful detection\nof the aggregation of the protein a-synuclein in a quantitative, label-free manner by functionalising a microcantilever with a-\nsynuclein monomers and operating it in dynamic mode in the presence of a-synuclein monomers in solution is reported. A total\nmass of 6 ng of a-synuclein was detected over 9 hours on the surface of the cantilever. The result is compared to conventional\nfluorescence measurements of a-synuclein aggregation under similar conditions. It is found that the label-free cantilever detection\nmethod requires a concentration of protein 50 times smaller than that of the current method and indicated potential for\nsignificantly faster response times....
This paper presents a control design for flexible manipulators using piezoelectric actuators bonded\r\non nonprismatic links. The dynamic model of the manipulator is obtained in a closed form through\r\nthe Lagrange equations. Each link is discretized using finite element modal formulation based on\r\nEuler-Bernoulli beam theory. The control uses the motor torques and piezoelectric actuators for\r\ncontrolling vibrations. An optimization problem with genetic algorithm GA is formulated for\r\nthe location and size of the piezoelectric actuator and sensor on the links. The natural frequencies\r\nand mode shapes are computed by the finite element method, and the irregular beam geometry\r\nis approximated by piecewise prismatic elements. The State-Dependent Riccati Equation SDRE\r\ntechnique is used to derive a suboptimal controller for a robot control problem. A state-dependent\r\nequation is solved at each new point obtained for the variables from the problem, along the\r\ntrajectory to obtain a nonlinear feedback controller. Numerical tests verify the efficiency of the\r\nproposed optimization and control design....
Wave data from five 12-13MHz SeaSondes radars along the central California coast were analyzed to evaluate the utility of\r\noperational wave parameters, including significant wave height, period, and direction. Data from four in situ wave buoys served to\r\nverify SeaSonde data and independently corroborate wave variability. Hourly averaged measurements spanned distance is 150 km\r\nalongshore Ã?â?? 45 km offshore. Individual SeaSondes showed statistically insignificant variation over 27 km in range. Wave height\r\ninter-comparisons between regional buoys exhibit strong correlations, approximately 0.93, and RMS differences less than 50 cm\r\nover the region. SeaSonde-derived wave data were compared to nearby buoys over timescales from 15 to 26 months, and revealed\r\nwave height correlations R = 0.85ââ?¬â??0.91 and mean RMS difference of 53 cm. Results showed that height RMS differences are\r\na percentage of significant wave height, rather than being constant independent of sea state. Period and directions compared\r\nfavorably among radars, buoys, and the CDIP model. Results presented here suggest that SeaSondes are a reliable source of wave\r\ninformation. Supported by buoy data, they also reveal minimal spatial variation in significant wave height, period, and direction in\r\ncoastal waters from ~45 kmÃ?â?? ~150 km in this region of the central California coast. Small differences are explained by sheltering\r\nfrom coastal promontories, and cutoff boundaries in the case of the radars....
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