Two-Dimensional, Magnetic Actuation of Ferrofluid Droplet on an Open-Surface Microfluidic Platform

The role of non-contact manipulation of discrete droplets on surface microfluidic platforms has wide applications in development of low-cost biosensors and biomedical diagnostic systems. Magnetic digital microfluidic platforms utilize magnetic force to actuate ferrofluid droplets on open hydrophobic surface and offer distinctive benefits compared to other digital microfluidic actuation schemes. This allows droplets—containing different type of sample and reagents—to be actuated and controlled independently; this can be leveraged to achieve different bioanalytical protocols for point-of-care diagnosis and other different micro-total analytical systems. Here, investigate, through a physically realistic model, magnetic field-actuated transport of a spherical cap ferrofluid droplet on a surface microfluidic platform. Manipulation of a microliter volume droplet in a sequence of rectilinear paths, leading to a guided transport, is achieved through an array of double-layer, planar, square-shaped electromagnetic micro-coils embedded in the substrate. Appropriate sequence of coil energization for attaining the desired trajectory of the droplet is described. The study paves the foundation of developing more complex digital microfluidic devices for different biomicrofluidic applications.