Open AccessFerrofluid Microdroplet Splitting for Population‐Based Microfluidics and Interfacial Tensiometry
Author(s) -
Latikka Mika,
Backholm Matilda,
Baidya Avijit,
Ballesio Alberto,
Serve Amandine,
Beaune Grégory,
Timonen Jaakko V. I.,
Pradeep Thalappil,
Ras Robin H. A.
Publication year - 2020
Publication title -
advanced science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.388
H-Index - 100
ISSN - 2198-3844
DOI - 10.1002/advs.202000359
Subject(s) - ferrofluid , surface tension , instability , microfluidics , materials science , magnetic field , population , chemical physics , nanotechnology , rayleigh–taylor instability , magnetic nanoparticles , nanoparticle , mechanics , chemistry , physics , thermodynamics , demography , quantum mechanics , sociology
Ferrofluids exhibit a unique combination of liquid properties and strong magnetic response, which leads to a rich variety of interesting functional properties. Here, the magnetic‐field‐induced splitting of ferrofluid droplets immersed in an immiscible liquid is presented, and related fascinating dynamics and applications are discussed. A magnetic field created by a permanent magnet induces instability on a mother droplet, which divides into two daughter droplets in less than 0.1 s. During the splitting process, the droplet undergoes a Plateau–Rayleigh‐like instability, which is investigated using high‐speed imaging. The dynamics of the resulting satellite droplet formation is shown to depend on the roughness of the supporting surface. Further increasing the field results in additional splitting events and self‐assembly of microdroplet populations, which can be magnetically actuated. The effects of magnetization and interfacial tension are systematically investigated by varying magnetic nanoparticles and surfactant concentrations, and a variety of outcomes from labyrinthine patterns to discrete droplets are observed. As the splitting process depends on interfacial tension, the droplet splitting can be used as a measure for interfacial tension as low as 0.1 mN m −1 . Finally, a population‐based digital microfluidics concept based on the self‐assembled microdroplets is presented.