A local symmetric pattern-based actuation algorithm (L-SPAA) for contact charge electrophoresis-based digital microfluidic systems

To address the challenges of traditional electrode polarity control algorithms and to propose a standardized framework for droplet manipulation in contact charge electrophoresis-based digital microfluidic systems that has not been previously established, to the best of our knowledge, we developed a local symmetric pattern-based electrode polarity control algorithm founded on a generalized, streamlined, and efficient control framework. This algorithm employs an initial electrode polarity arrangement in which positive and negative polarities alternate across the array. A simple modification of this initial state generates a unique configuration that consistently maintains a centrally focused and symmetrically aligned polarity arrangement, enabling direction- and path-independent manipulation of droplets. By generalizing this unique configuration, the developed algorithm significantly improves the efficiency and reliability of droplet manipulation by reducing the complexity associated with the numerous polarity assignment cases inherent to traditional algorithms. In addition, to achieve generalized manipulation of multiple droplets, an actuation strategy based on assigning priorities to individual droplets was introduced. Furthermore, we successfully demonstrated multi-droplet coalescence using the developed algorithm, and performed quantitative performance comparisons with existing algorithms to verify its usefulness and practical applicability. Finally, the generalization of droplet manipulation enabled by the developed algorithm is expected to expand the applicability of contact charge electrophoresis technology across a wide range of research fields.