Subnanometer Translation of Microelectromechanical Systems Measured by Discrete Fourier Analysis of CCD Images

Abstract—In-plane linear displacements of microelectromechanical systems are measured with subnanometer accuracy by observing the periodic micropatterns with a charge-coupled device camera attached to an optical microscope. The translation of the microstructure is retrieved from the video by phase-shift computation using discrete Fourier transform analysis. This approach is validated through measurements on silicon devices featuring steep-sided periodic microstructures. The results are consistent with the electrical readout of a bulk micromachined capacitive sensor, demonstrating the suitability of this technique for both calibration and sensing. Using a vibration isolation table, a standard deviation of σ = 0.13 nm could be achieved, enabling a measurement resolution of 0.5 nm (4σ) and a subpixel resolution better than 1/100 pixel. [2010-0170

Magnetically actuated micropumps

"Lab-On-a-Chip" (LOC) systems are intended to transpose complete laboratory instrumentations on the few square centimetres of a single microfluidic chip. With such devices the objective is to minimize the time and cost associated with routine biological analysis while improving reproducibility. At the heart of these systems, a fluid delivery unit controls and transfers tiny quantities of liquids enabling the biological assays. This explains the need for robust integrated micropumps as a precondition for the development of many LOC devices. In this context, we have developed a rapid prototyping method for the fabrication of microfluidic chips in plastic and glass materials. The microfabrication principle, which is based on the powder blasting microstructuring process, was used to build devices in either polymethylmethacrylate (PMMA) or borosilicate glass. Various types of micropumps have been developed which were all based on external magnetic actuation. The use of ferrofluids (or magnetic liquids) has been the subject of the first part of the research. A piston pump using a ferrofluid plug moved by an external magnet has been studied. The integration of a rare-earth material (NdFeB) in a flexible polydimethylsiloxane (PDMS) membrane, in the form of a powder or as a classical permanent magnet, has then been proposed. An external electromagnet was used to actuate the magnet-containing diaphragm of a reciprocating micropump. Different types of valves, which constitute the critical element in reciprocating micropumps, have also been investigated. We have studied silicone membrane valves, nozzle-diffuser elements and ball valves. While nozzle-diffuser elements present the simplest valving solution from a manufacturing point of view, ball valves have been proposed as a very promising alternative due to their high efficiency. Together with the detailed characterization of the prototypes, we have proposed analytical models that predict the hydrodynamic behaviour of the micropumps. The performances of our micropumps indicate that magnetic actuation is well adapted for LOC microsystems. While we have demonstrated that our proposed microfabrication technique is an excellent rapid prototyping method for disposable plastic devices, our glass micropumps present a competitive low-cost alternative satisfying criteria of biocompatibility and high temperature (130 °C) resistance

High-Performance Shuffle Motor Fabricated by Vertical Trench Isolation Technology

Shuffle motors are electrostatic stepper micromotors that employ a built-in mechanical leverage to produce large output forces as well as high resolution displacements. These motors can generally move only over predefined paths that served as driving electrodes. Here, we present the design, modeling and experimental characterization of a novel shuffle motor that moves over an unpatterned, electrically grounded surface. By combining the novel design with an innovative micromachining method based on vertical trench isolation, we have greatly simplified the fabrication of the shuffle motors and significantly improved their overall performance characteristics and reliability. Depending on the propulsion voltage, our motor with external dimensions of 290 μm × 410 mm displays two distinct operational modes with adjustable step sizes varying respectively from 0.6 to 7 nm and from 49 to 62 nm. The prototype was driven up to a cycling frequency of 80 kHz, showing nearly linear dependence of its velocity with frequency and a maximum velocity of 3.6 mm/s. For driving voltages of 55 V, the device had a maximum travel range of ±70 μm and exhibited an output force of 1.7 mN, resulting in the highest force and power densities reported so far for an electrostatic micromotor. After five days of operation, it had traveled a cumulative distance of more than 1.5 km in 34 billion steps without noticeable deterioration in performance.\u

Humidity Dependence of Charge Transport through DNA Revealed by Silicon-Based Nanotweezers Manipulation

AbstractThe study of the electrical properties of DNA has aroused increasing interest since the last decade. So far, controversial arguments have been put forward to explain the electrical charge transport through DNA. Our experiments on DNA bundles manipulated with silicon-based actuated tweezers demonstrate undoubtedly that humidity is the main factor affecting the electrical conduction in DNA. We explain the quasi-Ohmic behavior of DNA and the exponential dependence of its conductivity with relative humidity from the adsorption of water on the DNA backbone. We propose a quantitative model that is consistent with previous studies on DNA and other materials, like porous silicon, subjected to different humidity conditions

Subpixel translation of MEMS measured by discrete Fourier transform analysis of CCD images

We present a straightforward method for measuring in-plane linear displacements of microelectromechanical systems (MEMS) with a subnanometer resolution. The technique is based on Fourier transform analysis of a video recorded with a Charge-Coupled Device (CCD) camera attached to an optical microscope and can be used to characterize any device featuring periodic patterns along the direction of motion. Using a digital microscope mounted on a vibration isolation table, a subpixel resolution better than 1/100 pixel could be achieved, enabling quasi-static measurements with a resolution of 0.5 nm

Capillary-valve-based platform towards cell-on-chip mechanotransduction assays

Reliable in vitro models are required to understand the ability of cells to respond and adapt to mechanical stimuli. To mimic and interface with the microenvironment, lab-on-a-chip devices and microelectromechanical systems (MEMS) provide excellent options. However, little effort has been done in combining them. To address this shortcoming, we have developed a versatile microengineered platform which consists of two parts: an electrostatically actuated MEMS device used for mechanobiology assays, and a fluidic system for cell culture. A capillary valve allows inserting a silicon chip horizontally in the culture medium without leakage and without wetting of the electrostatic microactuators. The platform is designed for mechanotransduction assay on cells and aims specifically human mesenchymal stem cells. The proof of principle of the platform was performed by stable and long-term cultures of rat fibroblasts. We could also study the effect of periodic stress at various excitation frequencies

Modal analysis and modeling of a frictionless electrostatic rotary stepper micromotor

We present the design, modeling and characterization of a 3-phase electrostatic rotary stepper micromotor. The proposed motor is a monolithic device fabricated using silicon-on-insulator (SOI) technology. The rotor is suspended with a frictionless flexural pivot bearing and reaches an unprecedented rotational range of 30° (+/- 15°) at 65 V. We have established a mechanical model of the deformation structure and performed finite element analysis (FEA) simulations of the dynamic properties. These studies are consistent with the extensive experimental characterization performed in the quasi-static, transient, and dynamic regimes

A Monolithic Stepper Micromotor with a Flexural Pivot Bearing

La demanda agroalimentaria en el mundo presenta una tendencia dinámica, como resultado de las nuevas preferencias de consumo. Esto ofrece oportunidades para los alimentos en general y para la palta o aguacate, en particular. Las exportaciones mundiales de palta en la última década han experimentado un crecimiento del 292% en volumen, aproximadamente. Estados Unidos es el principal país demandante a nivel mundial, con una participación del 43%. En respuesta a esta creciente demanda, Perú ha venido aumentado su participación a este mercado, llegando al 3,7%. En base a este escenario, el objetivo de la investigación consistió en estudiar la dinámica de las variables intervinientes en el comportamiento de consumo de palta de EE. UU., a fin de mejorar el posicionamiento y la inserción en el mercado de EEUU. El logro del objetivo implicó el uso de metodologías descriptivas (variables de mercado y económicas), cuantitativas (modelo econométrico) y cualitativas (modelo de posicionamiento). Mediante el análisis descriptivo se encontró un crecimiento del consumo per-cápita de palta en los Estados Unidos entre 1961 – 2016, de 0,27 kg a 3,40 kg respectivamente, a una TACA del 5%. A través, del modelo econométrico se observó la importancia del ingreso per-cápita sobre el consumo que arrojó una elasticidad de 2,5. Por último, con respecto a los principales países proveedores, el modelo de posicionamiento permitió establecer que México se encuentra mejor posicionado, seguido de Perú. En conclusión, se proyecta que el crecimiento del consumo en este mercado seguirá en aumento a una tasa anual promedio del 1,3%, permitiendo inferir un aumento en el consumo. Perú se posiciona en el corredor con una relación equilibrada de precio–diferenciación percibida lo que parece adecuado de acuerdo con el precio del producto