Topology Optimization of 2D Microfluidic Channel for Passive Micro-Particles Separation. Cho Ahmed College of Engineering Gwangju Institute of Science and Technology

Abstract

This thesis presents a Genetic Algorithm-based topology optimization framework for the design of a passive two-dimensional microfluidic separator for size-based micro particle separation. The proposed device targets the separation of two spherical particles with radii of 16 μm and 8 μm by optimizing the internal geometry of a dual-outlet microchannel. The fluid flow is modeled using a Marker-and-Cell projection method combined with Brinkman penalization to represent solid obstacles on a fixed Cartesian grid. Particle transport is simulated through Lagrangian tracking with bilinear velocity interpolation, and a simplified size-dependent inertial lift model. A Genetic Algorithm is employed to optimize the pillar configuration using a composite objective function that accounts for outlet purity, separation efficiency, cross-contamination, and particle loss. The optimized design demonstrates a substantial improvement over the initial geometry. The outlet purity increases from 36.0% to 98.01% for the large-particle outlet and from 41.3% to 98.9% for the small-particle outlet. In the final optimized configuration, 147 out of 150 particles of each species are correctly routed to their target outlets, with zero missed particles. The optimized pillar arrangement also reduces the pressure drop by approximately 16% compared with the initial design, indicating improved hydraulic performance alongside enhanced separation efficiency. These results demonstrate that geometry-driven optimization can significantly improve passive microfluidic particle separation. The proposed framework provides a computationally efficient and physically interpretable design strategy for lab-on-a-chip systems requiring high-purity, continuous, and label-free micro particle sorting. MS/ME 20241235 Cho Ahmed. Topology Optimization of 2D Microfluidic Channel for Passive Micro-Particle Separation （위상 최적화 기반 2차원 마이크로유체 채널 설 계를 통한 수동 입자 분리）, Department of Mechanical and Robotic Engineering, College of Engineering 2026. 34p. Advisor: Prof. Sung Yang