a slide glass by using an adhesive tape. Then, the mica surface
was completely covered by each silica powder, as shown in
Fig. 3(a). After the preparation of the powder layer, the friction
probe with the load cell was located on the powder layer. The
friction force of the powder layer during the movement of the
stage slider was measured by a flow load cell. The stage velocity
and vertical load of the friction probe were fixed at 1 mm/s and