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Multifunctional ferrofluid-infused surfaces with reconfigurable multiscale topography

2018

Article

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Developing adaptive materials with geometries that change in response to external stimuli provides fundamental insights into the links between the physical forces involved and the resultant morphologies and creates a foundation for technologically relevant dynamic systems1,2. In particular, reconfigurable surface topography as a means to control interfacial properties 3 has recently been explored using responsive gels 4 , shape-memory polymers 5 , liquid crystals6-8 and hybrid composites9-14, including magnetically active slippery surfaces12-14. However, these designs exhibit a limited range of topographical changes and thus a restricted scope of function. Here we introduce a hierarchical magneto-responsive composite surface, made by infiltrating a ferrofluid into a microstructured matrix (termed ferrofluid-containing liquid-infused porous surfaces, or FLIPS). We demonstrate various topographical reconfigurations at multiple length scales and a broad range of associated emergent behaviours. An applied magnetic-field gradient induces the movement of magnetic nanoparticles suspended in the ferrofluid, which leads to microscale flow of the ferrofluid first above and then within the microstructured surface. This redistribution changes the initially smooth surface of the ferrofluid (which is immobilized by the porous matrix through capillary forces) into various multiscale hierarchical topographies shaped by the size, arrangement and orientation of the confining microstructures in the magnetic field. We analyse the spatial and temporal dynamics of these reconfigurations theoretically and experimentally as a function of the balance between capillary and magnetic pressures15-19 and of the geometric anisotropy of the FLIPS system. Several interesting functions at three different length scales are demonstrated: self-assembly of colloidal particles at the micrometre scale; regulated flow of liquid droplets at the millimetre scale; and switchable adhesion and friction, liquid pumping and removal of biofilms at the centimetre scale. We envision that FLIPS could be used as part of integrated control systems for the manipulation and transport of matter, thermal management, microfluidics and fouling-release materials.

Author(s): Wang, Wendong and Timonen, Jaakko V. I. and Carlson, Andreas and Drotlef, Dirk-Michael and Zhang, Cathy T. and Kolle, Stefan and Grinthal, Alison and Wong, Tak-Sing and Hatton, Benjamin and Kang, Sung Hoon and Kennedy, Stephen and Chi, Joshua and Blough, Robert Thomas and Sitti, Metin and Mahadevan, L. and Aizenberg, Joanna
Journal: Nature
Year: 2018
Month: June
Day: 25

Department(s): Physical Intelligence
Bibtex Type: Article (article)
Paper Type: Journal

DOI: 10.1038/s41586-018-0250-8
URL: https://rdcu.be/9xpG

BibTex

@article{Wang2018,
  title = {Multifunctional ferrofluid-infused surfaces with reconfigurable multiscale topography},
  author = {Wang, Wendong and Timonen, Jaakko V. I. and Carlson, Andreas and Drotlef, Dirk-Michael and Zhang, Cathy T. and Kolle, Stefan and Grinthal, Alison and Wong, Tak-Sing and Hatton, Benjamin and Kang, Sung Hoon and Kennedy, Stephen and Chi, Joshua and Blough, Robert Thomas and Sitti, Metin and Mahadevan, L. and Aizenberg, Joanna},
  journal = {Nature},
  month = jun,
  year = {2018},
  url = {https://rdcu.be/9xpG},
  month_numeric = {6}
}