Open AccessPermanent encoding of nano‐ to macro‐scale hierarchies of order from evaporative magnetic fluids
Author(s) -
Zhong Tianyu,
Andrews Mark,
Fournier Patrick,
Dion Maxime
Publication year - 2021
Publication title -
nano select
Language(s) - English
Resource type - Journals
ISSN - 2688-4011
DOI - 10.1002/nano.202000149
Subject(s) - ferrofluid , materials science , chemical physics , magnetic field , magnetization , magnetic nanoparticles , complex fluid , nanocomposite , metastability , nanotechnology , nanoparticle , condensed matter physics , chemistry , physics , thermodynamics , organic chemistry , quantum mechanics
Magnetic field‐directed assemblies of magnetic nanoparticles (MNPs) in ferrofluids exhibit complex interconvertible metastable patterns and structures. Formally, ferrofluid patterns are unstable – they disappear when the magnetic field is removed. The present study shows that ferrofluid patterns can be “trapped” as kinetically stable structures that encode a surprising degree of morphological detail over nanometer to millimeter length scales. An external magnetic field is used to direct assembly of oleic acid‐decorated magnetite (Fe 3 O 4 ) nanoparticles to make spike and labyrinthine patterns in volatile host solvents of heptane, octane and nonane. Solvent evaporation coupled with increases in sample magnetization drive pattern formation and its permanent recording. Use of a crosslinking siloxane polymer host yields remarkably different material responses. From the trapped states in both fluid systems, previously unreported hierarchies of order emerge in nanocomposite spike structures that also exhibit orientational and magnetic anisotropy. The possibility of designing hierarchical matter from initially uncorrelated MNPs is demonstrated by a directed solid‐state transformation of the magnetic nanocomposite; the spikes template memory of their origin onto the transformation products.