Ferrofluidic aqueous two-phase system with ultralow interfacial tension and micro-pattern formation

Carlo Rigoni*, Grégory Beaune, Bent Harnist, Fereshteh Sohrabi, Jaakko V.I. Timonen

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

8 Citations (Scopus)
50 Downloads (Pure)


Ferrofluids are magnetic liquids known for the patterns they form in external magnetic fields. Typically, the patterns form at the interface between a ferrofluid and another immiscible non-magnetic fluid with a large interfacial tension γ ∼ 10−2 N m−1, leading to large pattern periodicities. Here we show that it is possible to reduce the interfacial tension several orders of magnitude down to ca. γ ∼ 10−6 N m−1 by using two immiscible aqueous phases based on spontaneous phase separation of dextran and polyethylene glycol and the asymmetric partitioning of superparamagnetic maghemite nanoparticles into the dextran-rich phase. The system exhibits classic Rosensweig instability in a uniform magnetic field with a periodicity of ∼200 μm, significantly lower than in traditional systems (∼10 mm). This system paves the way towards the science of pattern formation at the limit of vanishing interfacial tension and ferrofluid applications driven by small external magnetic fields.

Original languageEnglish
Article number26
Pages (from-to)1-11
Number of pages11
JournalCommunications Materials
Issue number1
Publication statusPublished - 3 May 2022
MoE publication typeA1 Journal article-refereed


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