Fig. 2: Directional droplet transport on SEMR.
From: Spontaneous droplet transport on shape-evolving microfiber rails
a Directional transport of a water droplet (1.8 μL, dyed red) on the SEMR, displaying three stages after droplet deposition: (Ⅰ) bidirectional spreading, (Ⅱ) asymmetric retraction, and (Ⅲ) directional transport. The microfiber arrangement is perpendicular to gravity. Lf ≈ 25 mm, s0 ≈ 600 μm. b Optical (top left) and scanning electron microscopy (SEM; top right and bottom) images showing the structural characteristics, surface morphology, and cross-sections of the microfiber. The encapsulated microparticles create protrusions (bottom right SEM image), and the diatomite-alginate joints form valleys (top right SEM image) on the microfiber. c Plot showing the positions of the droplet’s leading and trailing ends over time. The difference between the two ends defines the droplet’s body length. d Schematic showing droplet-microfiber interactions during directional droplet transport. The droplet’s dimensions are characterized by its width (Wdrop) and length (Ldrop). e Plot showing the droplet’s characteristic width (Wdrop) and the SEMR’s dynamic wedge angle (α) over time.
