Illustration from Scientific Research

Experimental design. a) Schematic of the experimental setup: a water drop slides down an inclined glass slide coated with a hydrophobic layer. Due to the process of slide electrification negative primary ions with varying density are left on the surface behind the drop as illustrated schematically (right) and experimentally (SectionS1, Supporting Information) by Kelvin probe measurements (left). For water drops containing charged PDI dyes we outline possible mechanisms for PDI+b) and PDIc) deposition during drop sliding. The red and orange dots represent the secondary ions PDI+and PDI. The yellow dots represent the small primary ions and their counterions (light green). The hydrophobic coating is indicated in dark green.

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