Manipulation of Ferrofluid‐Wrapped Drops: Translation, Coalescence, and Release

Abstract

Abstract Magnetic manipulation of droplets has emerged as a promising strategy to achieve several complex tasks ranging from targeted drug delivery and micro‐robotics to controlled chemical synthesis. Hence, proper control in creating magnetically responsive droplets is indispensable for successful implementation. Here, an impact‐based encapsulation technique is employed to create stable ferrofluid‐wrapped single‐liquid and compound droplets inside a water bath. Thereafter, a permanent magnet is used to manipulate the resulting encapsulated cargo and demonstrate its feasibility for various applications. The manipulations reported herein are underwater magnet‐assisted drop translation and coalescence of compound droplets. The release of the innermost cargo in the compound droplet is also experimentally demonstrated via magnetic actuation. Importantly, for the first time, magnetically controlled coalescence of ferrofluid encapsulated compound droplets containing water‐soluble species in a water pool is demonstrated. The non‐contact manipulation technique presented in this work promises significant implications for magnet‐assisted actuation technologies.

Keywords

• coalescence
• compound droplets
• encapsulation
• ferrofluids
• magnetic manipulation