Numerical Investigation of the Combined Effects of Biomolecular Adsorption and Microdroplet Evaporation on the Performance of the Electrocapillary-Based Digital Microfluidic Systems

2011 ◽  
Author(s):  
Ali Ahmadi ◽  
Mina Hoorfar
Keyword(s):  
Mass Loss ◽  
Protein Concentration ◽  
Adsorption Rate ◽  
Force Balance ◽  
Combined Effects ◽  
Microfluidic Systems ◽  
Gibbs Equation ◽  
Rate Effects ◽  
Digital Microfluidic ◽  
Force Balance Equation

In this article, microdroplet motion in the electrocapillary-based digital microfluidic systems is modeled accurately, and the combined effects of the biomolecular adsorption and micro-droplet evaporation on the performance of the device are investigated. An electrohydrodynamic approach is used to model the driving and resisting forces, and Fick’s law and Gibbs equation are used to calculate the microdroplet evaporation and adsorption rate. Effects of the adsorption and evaporation rates are then implemented into the microdroplet dynamics by adding new terms into the force balance equation. It is shown that mass loss due to the evaporation tends to increase the protein concentration, and on the other hand, the increased concentration due to the mass loss increases the biomolecular adsorption rate which has a reverse effect on the concentration. The modeling results indicate that evaporation and adsorption play crucial roles in the microdroplet dynamics.

scholarly journals Split and flow: reconfigurable capillary connection for digital microfluidic devices

Lab on a Chip ◽  
2014 ◽  
Vol 14 (18) ◽  
pp. 3589-3593 ◽  
Author(s):  
Florian Lapierre ◽  
Maxime Harnois ◽  
Yannick Coffinier ◽  
Rabah Boukherroub ◽  
Vincent Thomy
Keyword(s):  
Microfluidic Devices ◽  
Microfluidic Systems ◽  
Digital Microfluidic

How to take advantage of superhydrophobic microgrids to address the problem of coupling continuous to digital microfluidic systems? A reconfigurable capillary connection for digital microfluidic devices is presented.

Numerical Multiphysics Modeling of Microdroplet Motion Dynamics in Digital Microfluidic Systems

2010 ◽  
Author(s):  
Ali Ahmadi ◽  
Jonathan F. Holzman ◽  
Homayoun Najjaran ◽  
Mina Hoorfar
Keyword(s):  
Numerical Algorithm ◽  
Moving Boundary ◽  
Microfluidic Systems ◽  
Multiphysics Modeling ◽  
Transient Motion ◽  
Proposed Model ◽  
Digital Microfluidic ◽  
Motion Dynamics

In this paper a novel numerical algorithm is proposed for modeling the transient motion of microdroplets in digital microfluidic systems. The new methodology combines the effects of the electrostatic and hydrodynamic pressures to calculate the actuating and opposing forces and the moving boundary of the microdroplet. The proposed model successfully predicts transient motion of the microdroplet in digital microfluidic systems, which is crucial in the design, control and fabrication of such devices. The results of such an analysis are in agreement with the expected trend.

Static Determinacy in the Theory of Finite Width Foil Bearings

1974 ◽  
Vol 41 (1) ◽  
pp. 51-54 ◽  
Author(s):  
W. E. Langlois
Keyword(s):  
Force Balance ◽  
Finite Width ◽  
Foil Bearings ◽  
Lubrication Equation ◽  
Foil Bearing ◽  
Edge Conditions ◽  
Single Force ◽  
Static Determinacy ◽  
Force Balance Equation ◽  
Determinate Problem

The assumption of “perfect flexibility” is shown to be self-consistent in an important class of finite-width foil bearing problems. When the membrane equations are written in the “stretched coordinates” of foil bearing theory, the usual edge conditions on the tape result in a statically determinate problem. The tape dynamics couples to the Reynolds lubrication equation through a single force-balance equation which does not entail the elastic strain.

scholarly journals Self-Cleaning: From Bio-Inspired Surface Modification to MEMS/Microfluidics System Integration

Micromachines ◽  
2019 ◽  
Vol 10 (2) ◽  
pp. 101 ◽  
Author(s):  
Di Sun ◽  
Karl Böhringer
Keyword(s):  
Surface Modification ◽  
System Integration ◽  
State Of The Art ◽  
Mechanical Systems ◽  
Surface Cleaning ◽  
Practical Application ◽  
Microfluidic Systems ◽  
Micro Electro Mechanical Systems ◽  
Self Cleaning ◽  
Digital Microfluidic

This review focuses on self-cleaning surfaces, from passive bio-inspired surface modification including superhydrophobic, superomniphobic, and superhydrophilic surfaces, to active micro-electro-mechanical systems (MEMS) and digital microfluidic systems. We describe models and designs for nature-inspired self-cleaning schemes as well as novel engineering approaches, and we discuss examples of how MEMS/microfluidic systems integrate with functional surfaces to dislodge dust or undesired liquid residues. Meanwhile, we also examine “waterless” surface cleaning systems including electrodynamic screens and gecko seta-inspired tapes. The paper summarizes the state of the art in self-cleaning surfaces, introduces available cleaning mechanisms, describes established fabrication processes and provides practical application examples.

Effect of Body Lateral Extension Upon the Elastic Contact

2009 ◽  
Author(s):  
Marilena Glovnea ◽  
Emanuel Diaconescu
Keyword(s):  
Half Space ◽  
Outer Radius ◽  
Force Balance ◽  
Contact Theory ◽  
Contact Radius ◽  
Elastic Contact ◽  
Space Theory ◽  
Lateral Extension ◽  
Load Direction ◽  
Force Balance Equation

Half-space contact theory cannot be applied when either contacting bodies are thin or they possess small transversal dimensions. The former situation is often dealt with, but the latter seems to be neglected. This paper investigates the effect of outer radius of cylindrical bodies upon the contact stress field. The method consists in adding supplementary displacements and stresses to the half-space solution in order to fulfill the boundary conditions and the force balance equation on load direction. It is found that the half-space theory is applicable if transversal radius exceeds contact radius.

Truck Performance on Argentinean Highways

1996 ◽  
Vol 1555 (1) ◽  
pp. 114-123 ◽  
Author(s):  
Adrián Ricardo Archilla ◽  
Arístides Osvaldo Fernández de Cieza
Keyword(s):  
Field Data ◽  
The United States ◽  
Force Balance ◽  
Power Ratio ◽  
Ratio Distribution ◽  
Performance Curves ◽  
National Highway ◽  
Acceleration And Deceleration ◽  
Speed Prediction ◽  
Force Balance Equation

Truck performance observed on grades on National Highway 7 in Argentina is described. The observed weight-to-power ratio distribution in Argentina is shown to be considerably higher than that in North America. Also, a speed prediction model based on the simple force balance equation is fitted to the field data. The model explains about 80 percent of the observed variation, and for steep upgrades the predictions are similar to values observed in the United States. Acceleration and deceleration performance curves are also given. Finally, a validation of the model is presented by comparing the predicted and the observed speed profiles along two upgrades for trucks of known weight-to-power ratios. The shapes of the speed profiles predicted by the model closely replicate the observed speed profiles.

Debris Effects on EHL Contact

2000 ◽  
Vol 122 (4) ◽  
pp. 711-720 ◽  
Author(s):  
Young S. Kang ◽  
Farshid Sadeghi ◽  
Xiaolan Ai
Keyword(s):  
Film Thickness ◽  
Reynolds Equation ◽  
Elastohydrodynamic Lubrication ◽  
Force Balance ◽  
Time Dependent ◽  
Elasticity Equations ◽  
Minimum Film Thickness ◽  
Bounding Surfaces ◽  
Force Balance Equation ◽  
Ehl Contact

A model was developed to study the effects of a rigid debris on elastohydrodynamic lubrication of rolling/sliding contacts. In order to achieve the objectives the time dependent Reynolds equation was modified to include the effects of an ellipsoidal shaped debris. The modified time dependent Reynolds and elasticity equations were simultaneously solved to determine the pressure and film thickness in EHL contacts. The debris force balance equation was solved to determine the debris velocity. The model was then used to obtain results for a variety of loads, speeds, and debris sizes. The results indicate that the debris has a significant effect on the pressure distribution and causes a dent on the rolling/sliding bounding surfaces. Depending on the size and location of the debris the pressure generated within the contact can be high enough to plastically deform the bounding surfaces. Debris smaller than the minimum film thickness do not enter the contact and only large and more spherical debris move toward the contact. [S0742-4787(11)00501-7]

Experimental Technique for Sensing Droplet Position in Digital Microfluidic Systems Using Capacitance Measurement

2010 ◽  
Author(s):  
Heather Martin ◽  
Miguel Murran ◽  
Rachael L’Orsa ◽  
Homayoun Najjaran
Keyword(s):  
Capacitance Measurement ◽  
Experimental Setup ◽  
Accurate Approximation ◽  
Microfluidic Systems ◽  
Effective Technique ◽  
Position Sensing ◽  
Capacitance Measurements ◽  
Manufacturing Procedure ◽  
Acquisition Device ◽  
Digital Microfluidic

Capacitance measurement has been identified as an effective technique for droplet position sensing in digital microfluidic systems mainly due to its non-intrusive nature. In essence, this technique relies on the correlation between the capacitance of two top-bottom electrodes with the amount of droplet overlap on the electrode. This paper describes an experimental setup used to gather capacitance data from a set of electrodes with varying droplet overlap to determine the droplet position. A prototype closed digital microfluidic (DMF) system consisting of an array of electrodes in the form of a 2 × 2 matrix was fabricated. A circular droplet was positioned on the DMF system, and capacitance measurements for each of the four electrodes were taken using a fast data acquisition device. A sufficiently accurate approximation of the droplet position was made using the four capacitance measurements. The paper presents the experimental results and also discusses the sources of error, viability of the experimental setup and manufacturing procedure for use in the development of capacitance measurement droplet position sensing techniques.

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