Rapid Fabrication of T-Shaped Micropillars on Polypropylene Surfaces with Robust Cassie–Baxter State for Quantitative Droplet Collection

Abstract

Applying microinjection compression molding technology, a fast and flexible method is first proposed for the successive and mass replication of polypropylene surfaces with T-shaped micropillars in the present work. The water droplet on the titled surfaces grows in size to roll off due to gravitation effect. Interestingly, the roll-off angles on such surfaces are as a quadratic function of specified water droplet volume, meaning quantitative droplet collection and lossless transfer can be performed on the replicated surfaces. Meanwhile, self-cleaning behavior is preserved on the surfaces. Moreover, the robust Cassie–Baxter state on the replicated surfaces against the external pressure is demonstrated with droplet compression and immersion experiments. Specifically, a droplet sitting on the replicated surface can recover its spherical shape after squeezed to a water film as thin as 0.37 mm, and the replica is remained fully spotless after it is submerged into dyed water. The proposed method for fast replica...