Figure 3 | Scientific Reports

Figure 3

From: Self-propelled droplet transport on shaped-liquid surfaces

Figure 3

Self-propulsion on a textured gradient liquid surface. (a) \({5}\, \upmu {\hbox {L}}\) water droplet propelled on a textured liquid surface. The gradient of rail fraction (\(\alpha = {\mathrm {d}} f_s / {\mathrm {d}} x = {0.05}\,{\hbox {mm}}^{-1}\)) induces the wettability gradient driving the droplet. The scale bar is 1 mm. (b) Droplet speed during motion for different volumes: \({2.5}\, \upmu {\hbox {L}}\) (blue), \({5}\, \upmu {\hbox {L}}\) (yellow), \({7.5}\, \upmu {\hbox {L}}\) (green) and \({10}\, \upmu {\hbox {L}}\) (red). (Yellow) circles correspond to the droplet at three of the times presented in (a) (\(t=0.7\) s, \(t=3.8\) s and \(t=8.9\) s). After an initial transient regime due to the deposition of the droplet, the velocity decreases in 1/f along the sample (dashed lines as fits). (c) Typical speed \(v_t\) of water droplets as a function of gradient of rail fraction \(\alpha\) and droplet volumes (blue circles: \({2.5}\, \upmu {\hbox {L}}\), orange squares: \({5}\, \upmu {\hbox {L}}\), green crosses: \({7.5}\, \upmu {\hbox {L}}\) and red triangles: \({10}\, \upmu {\hbox {L}}\)).

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