A Multi-Resistance Coupled Electromechanical Model for Enhanced Droplet Transport Dynamics Precision in...

To overcome the poor accuracy of classical electrowetting theory in predicting contact-angle saturation and droplet dynamics at high driving voltages in optoelectrowetting (OEW) digital microfluidics, we propose a novel electromechanical model that couples multiple resistance mechanisms. Within a conventional electrodynamic framework, the model embeds electric force, wall-shear resistance, viscous drag from the surrounding medium, and dynamic contact-line friction simultaneously into the source terms of the Navier-Stokes equations, and solves them in concert with an electric-current, phase-field, and laminar-flow multiphysics scheme. Experiments on a self-fabricated OEW chip, carried out over 160-600 V, validate the model against measured contact angles and droplet trajectories. In the high-voltage regime, the improved model limits the contact-angle deviation to ≤2° and the velocity deviation to only 0.05 mm/s-far outperforming both the Lippmann-Young equation and conventional electromechanical formulations. Parametric analyses further show that raising the dielectric constant or reducing the thickness of the dielectric layer markedly enhances the local electric field, thereby increasing droplet speed and displacement, while employing a highly photoconductive a-Si:H layer minimizes voltage drop and optimizes actuation performance. The work provides a solid theoretical and experimental foundation for OEW chip design and material selection, offering a pathway toward high-precision parallel droplet manipulation and fully integrated microfluidic systems.