Figure 3
From: Directional Movement of Droplets in Grooves: Suspended or Immersed?
IM-to-SU and SU-to-IM resting mode transitions for the Etched SAM and Smooth SAM grooves as β changed.
(a1) The IM-to-SU transition occurs around β = 106° for the Etched SAM groove as β decreases from high-to-low. (a2) The SU-to-IM transition occurs around β = 109° as β increases. (b1) The IM-to-SU transition is not observed in the Smooth SAM groove when β is decreasing from high-to-low. (b2) The SU-to-IM transition occurs around β ~ 70° when β is increasing. The difference between b1 and b2 indicates that the droplet resting state is also affected by the contact angle hysteresis. (c1) Schematic diagram of a droplet in the stable IM mode. (c2) When β decreases slightly to β′, the upper meniscus is deformed and the local contact angle increases from θ to θu′. (c3) θu′ reaches θa, which drives the upper meniscus contact line to move upward. The driving force for the IM-to-SU transition is provided by the meniscus deformation. The scale bar denotes 1 mm.
