Bio-inspired Microfluidic Devices for Passive, Directional Liquid Transport: Model-based Adaption for Different Materials

The Texas Horned lizard has the ability to harvest moisture from ambience with its skin and to transport water directionally to its snout; at the same time water is hindered to flow in opposite direction. We present a passive microfluidic device for directional liquid transport which is inspired by this natural role model. To this end, we deduce a subnatural capillary network from the measurement data of the Texas Horned lizard's skin. We adapt the network to various liquid-polymer combinations with the help of a mathematical model. Applying a CO2 laser we engrave the structures into poly(methyl methacrylate) (PMMA). By distance measurements we verify that our devices transport liquids of different contact angles in a preferential direction, while stopping it in opposite direction. The applied network of interconnected capillary channels is advantageous, when it comes to defects during production or when particles block part of the capillary channels. The proposed concept is thought to be useful for micro-analysis devices and lubrication.