Triboactive surfaces in multi-asperity nanotribology

In this work, n-octadecyltrichlorosilane (OTS) have been grafted on various micro-pillars created by Deep Reactive-Ion Etching (DRIE) of silicon wafers. This multi-architectured surfaces have then been tested with a ball-on-disc nanotribometer CSM Instruments (Fn: 3 mN, ball: Si3N4  1,5 mm) working in linear reciprocating mode, under various environmental conditions. Whereas the pillar's height is always fixed at 10 μm, their shapes and pitches are changed in order to test various wettability models – as Cassie-Baxter or Wenzel ones [4]. The Cassie-Baxter model can be applied in the densest pillars' area while the Wenzel one matches with weakest pillar's area. Since the frictional behavior of OTS monolayers is known to be thermally sensitive, the temperature of the structure is imposed during the tribological test by using a Peltier module.