Micro magnetofluidics: droplet manipulation of double emulsions based on paramagnetic ionic liquids

Abstract

The ability to control and manipulate discrete fluid droplets by magnetic fields offers new opportunities in microfluidics. A surfactant-free and easy to realize technique for the continuous generation of double emulsion droplets, composed of an organic solvent and a paramagnetic ionic liquid, is applied. The inner phase of the emulsion droplet consists of imidazolium-based ionic liquids with either iron, manganese, nickel or dysprosium containing anions which provide paramagnetic behaviour. The double emulsion droplets are dispersed in a continuous phase of FC-40. All substances - the organic phase, the paramagnetic ionic liquid and the continuous phase -are immiscible. The magnetic properties of ionic liquids allow, through the influence of external magnetic fields, the manipulation of individual emulsion droplets such as capture and release, rotation and distortion. Arrays of magnets allow a coalescence of emulsion droplets and their subsequent mixing by flowing through an alternating permanent magnetic field. In addition, the double emulsion droplets can be split and reunified, or continuously separated into their original phases.

Investigation of droplet coalescence propelled by dielectrophoresis

“…In the presence of solid walls, the motion of the contact line also has an influence on coalescence besides surface tension and viscosity. Several techniques like wettability gradient, thermocapillary action, magnetic field,and so forth have been used to manipulate liquid droplets on solid surfaces including agglomeration. However, the application of an electric potential has been established as the most efficient technique for manipulation of liquid drops in lab‐on‐a‐chip and μTAS.…”

Magnetic digital microfluidics – a review

“…71 Another type of fluid used for magnetic digital microfluidics is a solution containing a relatively high concentration of iron ions. 72,73 This type of liquid, which is sometimes incorrectly referred to as a ferrofluid, is better described as ionic or ferric fluid. Due to the high concentration of iron ions, the droplet responds to an external magnetic field and can be directly manipulated without the addition of actuator magnetic particles to the droplets.…”

Ionic liquids and continuous flow processes: a good marriage to design sustainable processes

“…106,107 In this regard, a surfactant-free technique for the continuous generation of double emulsion droplets, composed of an organic solvent and a paramagnetic ionic liquid, has been recently reported. 108 The specific magnetic properties of the IL allow, through the application of external magnetic fields, for selective and controllable manipulation of the individual emulsion droplets. Such systems might provide, even in a continuous flow set-up, a quick and simple method for the separation of a catalyst immobilized in the IL phase from the reaction mixture.…”