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Self‐Propelling and Positioning of Droplets Using Continuous Topography Gradient Surface
Author(s) -
Li Juan,
Tian Xuelin,
Perros Alexander Pyymaki,
Franssila Sami,
Jokinen Ville
Publication year - 2014
Publication title -
advanced materials interfaces
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.671
H-Index - 65
ISSN - 2196-7350
DOI - 10.1002/admi.201400001
Subject(s) - wetting , materials science , classification of discontinuities , contact angle , enhanced data rates for gsm evolution , surface (topology) , mechanics , optics , nanotechnology , geometry , composite material , physics , mathematical analysis , telecommunications , mathematics , computer science
A radial pattern with continuous topography gradient is presented, which induces a continuous inward wettability gradient and enables self‐propelling and accurate positioning of droplets to the pattern center. The effect of droplet size and wettability gradient of the pattern on the self‐mobility of droplets is investigated. The wettability gradient is found to increase towards the pattern center, enhancing the self‐motion of droplets at the inner area of the pattern. Moreover, larger droplets give rise to a larger solid‐liquid contact diameter, which helps to satisfy the self‐motion criteria that the advancing contact angle at front edge is smaller than the receding contact angle at rear edge. Consequently, a larger droplet size favors self‐motion initiated from the outer area of the pattern. The continuous topography gradient employed here allows the flexible dispensing of droplets at any place within a certain range, and avoids potential pinning defects to droplets at geometrical discontinuities. An average self‐motion velocity up to 4.0 cm/s for microliter‐sized droplets is achieved on the resultant patterned surface.