Papers by Keyword: Electrostatic Force

Abstract: An electrostatically driven multi-electrode peristaltic micropump has been developed for pumping microfluid through μ-TAS. Peristaltic-type micropumps have been reported to address many of the problems of micropumps in general and electrostatic actuation in particular. Peristaltic motion can eliminate the need for valves and for proper valve timing or for a nozzle/diffuser in designing flow control, as well as contribute to reduce the dead volume which can be a critical problem for micropump to achieve higher back pressures. In this paper, we present an electrostatically driven bidirectional peristaltic micropump that was designed, fabricated, and characterized. It was fabricated on a silicon substrate with a polyimide membrane. It was consisted of single large chamber, PI membrane operated with 4 electrodes, and 4 phase sequencing actuation. The displacement of the meniscus in the capillary tube is observed and recorded by using a video camera. The micropump was operated from 115V to 135V. The maximum moving speed of the meniscus was approximately 24 mm/min at 2.2 kHz at 115V. This pump will be applied to various microfluidic fields.

Abstract: Electrostatic chuck (ESC) is one of the key components in IC manufacturing process, which applies the principle of electrostatic adsorption to clamp the wafer on its surface. In such a system, electrostatic force is considered as one of the most important indicators. The method of modeling and simulation of electrostatic force by COMSOL software is proposed, and the accurateness is validated by comparing the results with those from reference. Then, the simulation of ESC in real manufacturing process is finished using the above method, which focuses on the effects of dielectric materials and voltage on electrostatic force. The research can offer references for the design of ESC, and it has significance to reduce experimental cost and improve the reliability of the equipment.

Abstract: For MEMS devices actuated by electrostatic force, unexpected failure modes can be hardly predicted when the electrostatic force coupled with the shock. A response model is established when a micro cantilever subjected to electrostatic force and mechanical shock. First, based on the theory of transverse forced vibration in vibration mechanics, the equation of motion under shock and electrostatic fore is presented. Then the reduced order model is gained after simplifying by mode superposition method. The computing results indicate that: the shock amplitude and duration are the key factors to affect the reliability of the device; the shock load and electrostatic forces make the threshold voltage much lower than the anticipated value. The micro cantilever may collapse to the substrate even at a voltage far lower than the pull-in voltage. This early dynamic pull-in instability may cause some failures such as short circuit, adhesion or collision damage.

Abstract: As an important part of MEMS, the micro-comb electrostatic driving structure is the main source of mechanical movement in many MEMS devices. Its reliability will directly affect the using performance of the MEMS devices. The electrostatic driving system of micro-comb capacitive micro-machined gyroscope can be equivalent to a second order system. If the applied voltage is less than the pull-in voltage, the movable micro-comb will maintain a steady state. Otherwise, the micro-combs will stick together because the applied voltage is greater than the calculated pull-in voltage. If the distance between micro-combs is too narrow, the role of these micro forces will be very significant. The pull-in phenomenon occurring in the process that the micro-machined gyroscope is applied on a phase step input voltage will lead to the very narrow comb spacing. As a result that the role of micro-forces such as the capillary force, Van der Waals force and Casimir force will become very significant, and the micro-combs will stick together permanently.

Abstract: For the deformation problem of electrostatically actuated clamped-clamped micro-beams, pull-in behaviors of the micro-beams have been analyzed by using Rayleigh-Ritz method. Approximate analytical expressions for pull-in voltage and normalized pull-in displacement of the micro-beam have been obtained. When the pull-in occurs, the pull-in voltage and normalized pull-in displacement of the micro-beam at the mid-span position are 38.6V and 0.398, respectively. The results show that the approximate analytical solution possesses high accuracy.

Abstract: Single-layered metal bond diamond wheels are useful to high efficient grinding of difficult-to-grind materials because of the high gripping force of abrasive grains and the controllable grain density. In this paper, fundamental information are obtained for an application of electrostatic force to setting of diamond grains into pasted metal bond slurry layer on wheel surface, investigating experimentally jumping phenomenon of diamond grains in an electrostatic field between a electrode plate and metal bond slurry layer. The SD grains and the SDC grains coated with Ti are selected. SDC grains jump into a metal bond layer as quick as making an electrostatic field, however SD grains jump with short time lags. The setting rate of SDC grains is larger than that of SD grains, and setting position accuracy of SDC grain array is better than SD grain array. The possibility of setting abrasive grains into single-layered metal bond diamond wheel surface using electrostatic force is obtained and SDC grains are suitable to the proposed abrasive setting method.

Abstract: A simulation based on Brownian dynamic for perikinetic flocculation of fine sediment under the ionization is presented. The Langevin equation is used as dynamical equation for tracking each particle making up a floc. Monte Carlo method was used for simulate random variation in particle movement. An initial condition and periodic boundary condition which conformed to reality well is used for calculation. In each cell 1000 particles of 10𝝁 m, 15𝝁m, 20𝝁m, 25𝝁m, 30𝝁m in diameter were served as primary particles. Floc growth is based on the thermal force and the electrostatic force. The electrostatic force on a particle in the simulation cell is considered as a sum of the electrostatic force from other particles in the original cell. The particles are supposed to be motion with uncharged and charged state in dispersion system. A comparison of the initial flocculent time and smashing time in sludge density 1010kg/m³, 1025 kg/m³, 1050 kg/m³, 1075 kg/m³, 1100 kg/m³ were present to show the effect of it on floc growth. The increase of sludge density deferred the flocculation rate. To study morphological shape of floc, the radius of gyration was revealed under different situations. On one hand the radius of gyration presented random variation with uncharged particle, On the other hand, the radius of gyration increases gradually with the increase of polar electrical charges on primal particle. Moreover, the morphological shape for the charged floc was more open than that of unchanged state. Finally, a series of experimental results are present, which is coincide with model well.

Abstract: The aim of the present work is to verify experimentally the influence of the charge level on collection efficiency during the first stages of filtration. A charge classifier was used to measure the charge level of the aerosol as a function of particle diameter. The filter was made of polypropylene with diameter of 0.047 m and a thickness of 2.6 mm. The solid particles used as test dust were a phosphate rock powder (density 2940 kg/m3 and average Stokes diameter of 3.40 m). The aerosol was dispersed by a TSI Venturi type generator. The particle charging was achieved by a corona charger. In all the tests performed, a linear relation between the particles acquired charge and their diameter was observed. A gradual increase of the charge level was observed with an increase of the tension in the corona charger (0, -3, -6 kV). The filtration results indicated that the global collection efficiency of the filter was very sensitive to the variation of the charge level of the particles. Both efficiency and pressure drop increased when the charge level increased. During the tests, the small increase in pressure drop indicated that the cake had not yet been formed.

Abstract: Nonlinear modeling method for the structural dynamic analysis of a micro cantilever beam actuated by electrostatic force is presented in this study. Static deflection is first obtained by solving nonlinear static equilibrium equation and the modal and the stability characteristics are calculated at the static equilibrium position. It is found that the amplitude and the frequency of the applied electrostatic voltage influence the stability of the structure significantly.