Hydrophobic and oleophobic re-entrant steel microstructures fabricated using micro electrical discharge machining

Patricia B. Weisensee, Eduardo J. Torrealba, Mark Raleigh, Anthony M. Jacobi, William P. King

Research output: Contribution to journalArticlepeer-review

Abstract

This paper presents the fabrication of metallic micro-mushroom re-entrant structures and the characterization of their hydrophobicity and oleophobicity. Five different microstructure geometries are introduced, with typical feature sizes in the range of 10-100 μm. These microstructures are realized in steel, and are fabricated over the cm-scale using micro electrical discharge machining (mEDM). The liquid repellency of these surfaces is characterized using droplets of either water (surface energy γlg= 72.4 mN m-1), RL-68H oil (γlg= 28.6 mN m-1), or Isopropanol (IPA) (γlg= 21.7 mN m-1). The water droplets form nearly perfect spheres, with contact angles in the range 146-162°, and contact angle hysteresis of 19-35°. The oil droplet contact angles are in the range 106-152° and the IPA contact angles are in the range 75-123°. Strong re-entrant features and close spacing are necessary to support a fully non-wetting state for use with oil and IPA. Water forms the highest contact angles with narrow, post-like, and widely spaced micro-mushroom geometries.

Original languageEnglish (US)
Article number095020
JournalJournal of Micromechanics and Microengineering
Volume24
Issue number9
DOIs
StatePublished - Sep 1 2014

Keywords

  • IPA
  • RL-68H
  • hydrophobicity
  • micro electrical discharge machining
  • oleophobicity
  • re-entrant structures

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Mechanics of Materials
  • Mechanical Engineering
  • Electrical and Electronic Engineering

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