Bio-Medical Sciences and Engineering MS Thesis Defense by Ayşenur Eser

KOÇ UNIVERSITY

GRADUATE SCHOOL OF SCIENCES & ENGINEERING

BIO-MEDICAL SCIENCES AND ENGINEERING

MS THESIS DEFENSE BY AYŞENUR ESER

Title: Modeling and Simulation of PDMS Micropillars for Microfluidic Viscometer Applications

Speaker: Ayşenur Eser

Time: 17.08.2018 – 10:00 AM

Place: ENG 208

Koç University

Rumeli Feneri Yolu

Sariyer, Istanbul

Thesis Committee Members:

Doç. Dr. Özlem YALÇIN (Advisor, Koç University)

Prof. Dr. Alper KİRAZ (Koç University)

Dr. Öğr. Üyesi Ahmet Can ERTEN (Istanbul Technical University)

Abstract:

Microfluidics technology has started to be used in a tremendous diversity of applications in various research areas. In the recent years, as one of the user-friendly microfluidic application, micropillar arrays have become very important. Reversible dry adhesives, superoleophobic surface, tunable wetting, micromechanical sensors, and actuators are examples of technological applications where micropillar arrays have been used.

Computational Fluid Dynamics (CFD) simulations are remarkably helpful at design and optimization steps of microfluidic devices. They provide an understanding of the behavior of the fluid and the initial design studies for the optimization of parameters for geometry and methods, hence, reducing the cost, and workload for the microfluidic chip development.

In the present study, we investigate fluid flow characteristics and the micropillar behavior through micropillar based microfluidic channels via conducting a set of case studies that include the change in micropillar shapes, and numbers, and the inter-pillar spacing. As the verification of the simulations, we have produced the PDMS square and cylindric micropillars using double layer SU-8 master molds fabricated by using standard photolithography method and proceeded with a set of experiments. Experiments were performed with micropillar based microfluidic channels over a range of flow rates from 30 to 150 ml/hr for 1cP, 5 cP viscosity fluids, and blood as the same with the computational fluid dynamics conditions. According to the results, we could predict the micropillar behaviors and the flow profiles under a specific flow rate and for certain viscosity of fluids. We also observed that pressure, wall shear stress, strain rate inside the microfluidic channel, and the force applied to micropillars varies linearly with increasing flow rates for different micropillar shapes and inter-pillar spacing.

The main contribution of this thesis is reducing the time spent, cost and effort in the fabrication process for the development of a micropillars based microfluidic chips. Overall this work demonstrates the simulated and fabricated micropillar based channels with a variety of parameters applied, for finding the optimum micropillar based devices that can be used for viscometer applications.