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Updated: Jun 30, 2026
Electrowetting-based Digital Microfluidics Platform for Automated Enzyme-linked Immunosorbent Assay
Published on: February 23, 2020
Computational analysis on design and optimization of low-frequency dielectrophoretic microfluidic lab on a chip for
Saeed Saedy1, Navid Alaei-Sheini1, Shahrzad Ajabi1
1Faculty of Engineering, Shahid Chamran University of Ahvaz, Ahvaz, Iran.
Introduction:
Bloodstream infections (BSIs) caused by Staphylococcus aureus, particularly methicillin-resistant (MRSA) and methicillin-sensitive (MSSA) strains, remain a critical clinical concern due to high mortality rates and delays in diagnosis. Traditional approaches, such as blood culture, are time consuming, whereas molecular methods are limited by their inability to assess bacterial viability. Dielectrophoresis (DEP)-based lab-on-a-chip (LOC) technology offers a label-free, rapid, and viability preserving alternative for pathogen isolation by exploiting differences in dielectric properties.
Methods:
A dual-channel microfluidic separation device was developed with independently operated pathways. The primary channel (2000×198 μm) integrated ten crown-shaped microelectrodes, while the secondary channel (1540×80 μm) incorporated eight microelectrodes. The primary channel isolated both target strains directly from whole blood; the secondary channel enabled further separation between standard Gram-positive MRSA and MSSA. Finite element modeling was performed using COMSOL Multiphysics, which integrated the Electric Currents, Creeping Flow, and Particle Tracing modules. Separation efficiency was evaluated across varying voltages, electrode geometries, and sample-to-buffer flow rate ratios at 1 Hz. Dielectric properties from published data were used to calculate the Clausius-Mossotti (CM) factor for predicting DEP behavior.
Results:
In the primary channel, nearly 100% separation efficiency and purity were achieved for isolating MRSA and MSSA from red blood cells (RBCs), white blood cells (WBCs), and platelets (PLTs) at 24-28 Vpp and a sample-to-buffer flow rate ratio of 1:2. The secondary channel successfully differentiated MSSA from MRSA at 42-46 Vpp and a 1:5 flow rate ratio, exploiting their distinct membrane characteristics. Crown-shaped electrodes outperformed rectangular designs by generating higher electric field gradients, thereby enhancing separation performance.
Conclusion:
The dual-channel LOC system enables high-efficiency, label-free separation and identification of MRSA and MSSA directly from whole blood using low-frequency negative DEP (nDEP). The optimized configuration supports rapid pathogen detection, offering substantial advantages over conventional diagnostic platforms.
