Liquid transport in the networked microchannels of the skin surface

A feature of the skin of many vertebrates is the presence of open grooves with characteristic intersecting geometric patterns. Here, we measure flows within the fine channels on the human skin surface and demonstrate that this network can act as a microfluidic device to allow the surface transport of liquids. Adapting a theory for fracture networks together with a treatment of capillary flow in a single V groove, we describe a model to account for the observed flows dependent on the groove shape, depth, and density of the grooves. This approach provides a simple framework for studying the regulation of fluid transport on the skin surface or on other similarly networked microchannels.