Lilik Hasanah, Fasya Nur Afifah, Roer Eka Pawinanto, Muhammad Iqbal, Gilang Gumilar, Muhammad Yusuf, Widyaningrum Indrasari, Ida Hamidah, Jumril Yunas, Budi Mulyanti
Passive micromixers are essential components in microfluidic systems, enabling efficient fluid mixing under laminar flow conditions without external energy input. This study numerically investigates the mixing performance and flow mechanisms of passive micromixers incorporating Koch fractal obstacle arrays. Four fractal geometries—Secondary Snowflakes Fractal (SSF), Tertiary Snowflakes Fractal (TSF), Rounded Secondary Snowflakes Fractal (RSSF), and Rounded Tertiary Snowflakes Fractal (RTSF) are analyzed in both same-side and different-side configurations using COMSOL Multiphysics over a wide Reynolds number range (Re = 0.1–100). Model validation against benchmark obstacle-based micromixers from the literature shows good agreement in mixing efficiency and pressure drop, confirming the reliability of the numerical framework. The results demonstrate that Koch fractal obstacles enhance mixing through flow splitting, stretching, and chaotic advection. Among all configurations, the different-side rounded tertiary snowflake fractal (DSRTSF) exhibits the most stable and consistently high mixing performance, achieving a maximum mixing efficiency of 97.70% at a Reynolds number (Re) of 0.1. Performance index analysis further reveals that rounded fractal geometries provide a favorable balance between mixing efficiency and pressure drop. These findings offer practical design guidelines for high-performance fractal obstacle-based passive micromixers in lab-on-a-chip and microfluidic applications. © 2026
Study Program of Physics, Universitas Pendidikan Indonesia, Jl. Dr. Setiabudhi No.229 Bandung, West Java, 40154, Indonesia; Study Program of Industrial Automation Engineering Education and Robotics, Universitas Pendidikan Indonesia, Jl. Dr. Setiabudhi No. 229 Bandung, West Java, 40154, Indonesia; Faculty of Industrial Technology, Institut Teknologi Bandung, Ganesa 10, West Java, Bandung, 40132, Indonesia; Research Center for Electronics, National Research and Innovation Agency (BRIN), Bandung, 40135, Indonesia; Department of Chemistry, Faculty of Mathematics and Natural Sciences, Universitas Padjadjaran, Sumedang, 45363, Indonesia; Physics Study Program, Faculty of Mathematics and Natural Science, Universitas Negeri Jakarta, Jl. Rawamangun Muka, Rawamangun, Jakarta Timur, 13220, Indonesia; Study Program of Automotive Engineering Education, Universitas Pendidikan Indonesia, Jl. Dr. Setiabudhi No. 229 Bandung, West Java, 40154, Indonesia; Institute of Microengineering and Nanoelectronics, Universiti Kebangsaan Malaysia, Level 4, Research Complex, Bangi, 43000, Malaysia; Study Program of Electrical Engineering, Universitas Pendidikan Indonesia, Jl. Dr. Setiabudhi No. 229 Bandung, West Java, 40154, Indonesia; Advanced Devices and Materials in Engineering Education (ADMEE), Universitas Pendidikan Indonesia, Jl. Dr. Setiabudhi No.229 Bandung, West Java, 40154, Indonesia
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