Lift Generation in Soft Porous Media

A red blood cell is about eight microns in diameter, §but it fits through capillary openings of only five §or six microns in diameter without showing any wear §and tear. It manages this tight squeeze about §100,000 times in its lifetime. How could there be so §little friction? A 70 kg human being can glide over §a compressed snow layer without sinking to the base, §however, when the motion is arrested, the skier §would sink to the base. Why is that? In fluid §mechanics it is highly unexpected for there to be a §dynamic similarity between the motions of objects §that differ in mass by many orders of magnitude. Yet §this is exactly what has been discovered in §comparing the motion of a red cell in a capillary, §the compression of fresh snow during skiing and the §passage of a train car over a track that has the §mechanical properties of a goose down pillow. These §diverse applications are unified in this book. The §book introduces a new concept that is of §extraordinarily broad interest and could have §important application in the design of soft porous §bearings with greatly increased lubrication §pressures and long life.