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.

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 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 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.

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.

scholarly journals Modelling and optimal energy-saving control of automotive air-conditioning and refrigeration systems

2016 ◽  
Vol 231 (3) ◽  
pp. 291-309 ◽  
Author(s):  
Yanjun Huang ◽  
Amir Khajepour ◽  
Farshid Bagheri ◽  
Majid Bahrami
Keyword(s):  
Energy Efficiency ◽  
Energy Saving ◽  
Air Conditioning ◽  
Moving Boundary ◽  
Parameter Method ◽  
Model Predictive Controller ◽  
Automotive Air Conditioning ◽  
Lumped Parameter ◽  
Proposed Model ◽  
Predictive Controller

Air-conditioning and refrigeration systems are extensively adopted in homes, industry and vehicles. An important step in achieving a better performance and a higher energy efficiency for air-conditioning and refrigeration systems is a control-based model and a suitable control strategy. As a result, a dynamic model based on the moving-boundary and lumped-parameter method is developed in this paper. Unlike existing models, the proposed model lumps the effects of the fins into two equivalent parameters without adding any complexity and considers the effect produced by the superheated section of the condenser, resulting in a model that is not only simpler but also more accurate than the existing models. In addition, a model predictive controller is designed on the basis of the proposed model to enhance the energy efficiency of the air-conditioning and refrigeration systems. Simulations and experimental results are presented to demonstrate the accuracy of the model. The experiments show that an energy saving of about 8% can be achieved by using the proposed model predictive controller compared with the conventional on–off controller under the examined scenario. The better performance of the proposed controller requires electrification of the automotive air-conditioning and refrigeration systems so as to eliminate the idling caused by running the air-conditioning and refrigeration systems when a vehicle stops.

Non-linear elastic ring tyre model using the absolute nodal coordinate formulation

2009 ◽  
Vol 223 (3) ◽  
pp. 211-219 ◽  
Author(s):  
H Sugiyama ◽  
Y Suda
Keyword(s):  
Moving Boundary ◽  
Absolute Nodal Coordinate Formulation ◽  
Elastic Ring ◽  
Tyre Model ◽  
Inertia Effects ◽  
Absolute Nodal Coordinate ◽  
Linear Elastic ◽  
Proposed Model ◽  
Road Surfaces ◽  
Non Linear

In this investigation, a non-linear elastic ring tyre model is developed. The elastic deformation of the tyre belt is modelled using the finite element absolute nodal coordinate formulation that allows for describing large rotational motion and the non-linear inertia effects; the curved structure of the tyre belt; and moving boundary resulting from the tread and road interaction. Using a concept of elastic ring tyre models, the sidewall flexibility of a tyre is modelled using circumferential and radial springs and dampers defined between the belt and rim, while the tangential tyre force is modelled using friction elements defined at contact nodes defined within the curved belt elements. Numerical examples are presented in order to demonstrate the use of the flexible tyre model developed in this investigation. Good agreements are demonstrated in the tyre vibration characteristics obtained using the experiments and the proposed model. It is presented that the proposed tyre model can be used for assessing dynamic characteristics of tyres in high frequency ranges resulting from the interaction to uneven road surfaces.

Gravity-driven hydrodynamic particle separation in digital microfluidic systems

RSC Advances ◽  
2015 ◽  
Vol 5 (45) ◽  
pp. 35966-35975 ◽  
Author(s):  
Hojatollah Rezaei Nejad ◽  
Ehsan Samiei ◽  
Ali Ahmadi ◽  
Mina Hoorfar
Keyword(s):  
Particle Separation ◽  
Separation Method ◽  
Electrode Configuration ◽  
Microfluidic Systems ◽  
Gravity Driven ◽  
Digital Microfluidic ◽  
Actuation Scheme

In the present study, the electrode configuration and actuation scheme are designed in a fashion to implement a gravity-based hydrodynamic particle separation method on digital microfluidic systems.

scholarly journals Expansion of the Fundamental Diagram from a Microscopic Multilane Modeling Framework of Mixed Traffic

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Mudasser Seraj ◽  
Jiangchen Li ◽  
Tony Z. Qiu
Keyword(s):  
Accurate Estimation ◽  
Flow Density ◽  
Mixed Traffic ◽  
Gap Acceptance ◽  
Fundamental Diagram ◽  
Lane Changing ◽  
Car Following ◽  
Proposed Model ◽  
Density Relationship ◽  
Motion Dynamics

Microscopic modeling of mixed traffic (i.e., automaton-driven vehicles and human-driven vehicles) dynamics, particularly car-following, lane-changing, and gap-acceptance, provides the opportunity to gain a more accurate estimation of flow-density relationships for both traditional traffic with human-driven vehicles and different mixed traffic scenarios. Our paper proposes a microscopic framework to model multilane traffic for both vehicle types on shared roadways which sets the stage to explore the capability of macroscopic car-following models in general to explain the fundamental flow-density relationship. Since prior models inadequately represent the fundamental diagram realistically, we propose a rectified macroscopic flow model that can account for the impact of both lane-changing and gap-acceptance. Differentiability, boundary conditions, and flexibility of the proposed model are tested to validate its applicability. Finally, the capability to interpret the flow-density relationship by the proposed model is verified for different mixed traffic scenarios. Although few model parameter values were obtained directly from the simulation input, the rest of the parameters have been calibrated by flow and density outputs from the simulations. The analysis results show a distinct correlation between the proposed model parameters with automation-driven vehicle shares and lane-changing rates of traffic. The findings from this study emphasize the importance of taking complete motion dynamics into account, rather than partial motion dynamics (i.e., car-following) as has been the case in the previous studies, to explain macroscopic traffic flow characteristics, irrespective of the vehicle type.

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