Micron-Gap Rheo-optics with Parallel Plates
Solid planar plates with area up to several square centimeters can be made parallel at controllable separations from ca. 0.1 (if airborne dust is eliminated) to >500 μm. Apart from dust and surface roughness, which set the lower bound of plate-plate separation, there is no other fundamental constraint on the type of surface (metallic or dielectric; opaque or translucent) that can be studied. When conducting plates are employed, it is possible to apply an electric field in the direction normal to the plates and observe the competition between shear fields and electric fields in orthogonal directions. The large surface area should afford sufficient quantity of sample to make possible various spectroscopic and scattering experiments (especially infrared and dielectric spectroscopy in the direction normal to the plates, and x-ray and neutron reflectivity).