Shaping liquid on a micrometre scale using microwrinkles as deformable open channel capillaries

Abstract

Methods of shaping and manipulating liquids on small scales are important for micro-patterning, microfluidics and biosensing, and may provide fundamental insights into phenomena in confined small spaces. Here, we report a simple technique for shaping liquids into micrometre-scale filaments. Microgrooves on microwrinkles generated by thin film buckling on elastic substrates can function as open channel capillaries for liquids with appropriate wettabilities. Tuning the groove depth of the microwrinkles by modulating strain, we explore the capillary action of various liquids in microgrooves, which form liquid filaments emanating from a large reservoir. This behaviour is explained in terms of sinusoidal-geometry-dependent surface energy. Based on this concept, a regular array of liquid filaments can be formed over a large area by a simple coating method, and these filaments can be further reshaped by exploiting strain-induced nonlinear changes in microwrinkle topography. This technology shows promise for applications in micro-patterning, nano- and micro-reactors, and microfluidics.