Decoupling capillary force-viscous resistance trade-off by shape-gradient microgrooves wick design

Abstract

The long-distance capillary transport is fundamentally hindered by the trade-off between the capillary force and viscous resistance, which limits the wicking performance of conventional microstructure surfaces. Here, we demonstrate a shape-gradient microgroove design that effectively decouples this intrinsic trade-off by femtosecond laser-based scanning path regulation strategy. Balancing the advantages of high capillary force of the V-shape and low viscous resistance of the U-shape, long-distance wicking velocity of gradient designs efficiently improved over 40% than conventional V-shape designs. Leveraging the enhanced mechanism, segmental structures with maximized long-distance wicking velocity were further developed, reaching a 100% enhancement. The design and the decoupled method provide a paradigm and guidance for the wick structures design, with implications for thermal management, microfluidics, and beyond.