Device with a self-aligned microgap for studying microscale flows

With the increasing interest in pressure-driven liquid flows in confined geometries, there emerges a need for the development of suitable devices for microrheological studies. The standard rheometry with macrogaps, however, has inherent disadvantages in adapting itself into a microscale version. On the other hand, compliance-based apparatuses are inappropriate for high-shear flows because of their extremely low load capacity and small allowable strain and strain rate. In this article, a self-aligned device that involves a pair of parallel disks with the bottom one fixed and the top one floated is presented. A concentrated load is applied at the center of the floating plate, for adjusting the gap size and centering the top plate. The applied load is balanced by the upward force inside the liquid film resulting from viscous flow. Due to the complete axisymmetry in terms of the geometry and the stress field, the top plate will be self-aligned in reference to the bottom plate. The self-alignment mechanism and the design principle of the device were verified using experiments with water as a testing liquid.