Magnetic Digital Microfluidic Manipulation with Mobile Surface Energy Traps Capable of Releasable Droplet Dispensing

Magnetic digital microfluidics (MDM) is a technology that manipulates droplets on an open surface with magnetic force for lab-on-a-chip (LOC) applications. MDM is capable of dispensing droplets of desired volume using surface energy traps (SETs); however, the daughter droplets dispensed by this approach cannot be released from the SET for subsequent microfluidic manipulation. This is a major disadvantage compared to the electrowetting-on-dielectrics (EWOD)-based digital microfluidics which is capable of releasable droplet dispensing. In this work, a polydopamine-coated thin magnet is introduced to MDM as a mobile SET for droplet manipulation, and for the first time, releasable droplet dispensing is accomplished on the MDM platform. In addition, the mobile SET is capable of all-terrain droplet transport regardless of the surface condition and rapid droplet transport via a unique droplet slingshot mechanism. The mobile SET-enabled MDM platform is able to match the functionality of the EWOD-based digital microfluidic system in terms of droplet dispensing and release, which will significantly expand the applicability and acceptability of MDM technology in biosensing, in vitro diagnostics, and many other biomedical applications.