Asymmetric micro-ratchets regulated drop dispensing on bamboo mimetic surface

Abstract

The precise manipulation of drops in an open fluidic system is vital for chemical and biological assays. Despite extensive research, existing approaches still suffer from the need for complex apparatuses or channels with limitations to accurately control the volume of the dispensed drops, particularly in large volumes. Inspired by the water drop rolling trend difference on the Phyllostachys pubescens leaf from rim to tip or from tip to rim, herein, we have demonstrated an open fluidic drop manipulation device using 3D printed asymmetric ratchets to regulate drop dispensing process. The substrate consisted of a hydrophilic strip pattern, which was decorated on the superhydrophobic tilted ratchets. The hydrophilic pattern provided an effective clinging area to store water. The tilt angle of the micro-ratchets adjusted the break-up process of the water bridge between the pendulous drop and the clinging water strip, controlling the final dispensed volume. Our approach offers a mechanism that can be used to independently control the drop size and emission period, demonstrating a method for highly monodisperse and flexible drop production in open microfluidic devices.