Spontaneous Motion of a Droplet on Wetting Gradients

Manipulation of a droplet on a solid surface is of growing interest because it is a key technology to construct lab-on-a-chip systems. The imbalance of surface tensions is known to cause spontaneous motion of a droplet on the surface, as mentioned above. The wetting gradient causing liquid motion has been prepared by chemical [32], thermal [37], electrochemical [3] and photochemical [38-40] methods. 

Abott et al. demonstrated that the flow in a microfluidic channel can be controlled by using the wetting gradient generated by electrochemical reactions ofthe surfactant 

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Figure 16.4 Spontaneous motion of a droplet on wetting gradients.

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