Abstract

Micro-dimples are a specific class of surface textures that are ubiquitous in a wide range of applications where functionalities such as wetting, hydrodynamic drag reduction, and sliding friction reduction are needed. However, fabrication of the micro-dimples through the existing manufacturing techniques involves the use of complex equipment and requires relatively long cycle times. Consequently, we report here proof-of-concept of a method that enables in fabricating micro-dimples in a facile and fast manner. The industrial sieve wire masks were employed to deform metallic sheets at discrete locations by the cold rolling process. The geometry of projections on the wire masks allowed the formation of ellipsoid shaped micro-dimples in two distinct patterns on metallic sheets. The finite element modelling of process-material interactions was accurately predicted the formation of micro-dimples under different reduction ratios. We also demonstrate that the micro-dimples can be easily replicated on polymer surfaces using textured metallic moulds, which facilitates low-cost mass production in microfluidic applications. The presence of micro-dimples on polymer surfaces has led to an increase in water contact angles and resulted in a substantial drag reduction in microchannels. From the tribological viewpoint, the obtained patterns and surface area fractions of the micro-dimples are attractive. These findings provide a promising way to create textured surfaces in an economical manner, with functionalities suitable for microfluidic and tribological devices.

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