Photograph of the parallel plate shear cell placed on top of an inverted confocal microscope.
Schematic representation of the shear cell as placed on top of an inverted confocal scanning laser microscope. (1) Air bearing, (2) secondary guide rod, (3) bottom translation stage, (4) motor bottom stage, (5) top cassette, (6) tilt and gap adjustments, (7) main guide rod, (8) motor top stage, (9) main frame, (10) cross adjustment lever, and (11) confocal microscope.
The bottom and top cassette. (1) Top cassette , (2) transparant window that allows for light scattering, (3) metal ring to seal the sample cell, (4) bottom cassette with a gap to fill with solvent, (5) solvent for vapor pressure, (6) microscope glass slide, and (7) paper glue mask.
Mechanism to adjust the height of the balls that support the cassettes. (1) Single point adjustment screw, (2) lever, (3) pivot of lever, (4) cassette support ball, (5) pivot of rocker, (6) rocker, and (7) grouped rocker adjustment.
(a) Example of the glass-air interface at the top side of the bottom plate imaged in reflection mode with a confocal microscope. From such an image, the position of the interface is determined by summing the intensities horizontally and determining the maximum. The most intense peak is taken as the glass-air interface. The less intense peaks are caused by interference.
Illustration defining our coordinate system. The optical axis of the microscope is along the vertical axis. The zero-velocity plane (gray) is perpendicular to this axis and lies in the plane. Its vertical position can be set at any height. The velocity direction is along the axis of the microscope. The vorticity direction is along the axis and the gradient direction along the axis.
Vertical position during a lateral displacement over a distance of of (a) an optical flat in the bottom cassette, (b) an optical flat in the top cassette, (c) a No. 1 glass slide on the bottom cassette, and (d) a No. 5 glass slide on the top cassette. Fluctuations in were only of the order of a micrometer.
Stability of the plates in when the cell was filled with silicone oils with viscosities of (a) , (b) , and (c) . Both plates are moving with in opposite directions. The change in is only of the order of a micrometer while the travel of the plates is .
The relative position of the top plate in the velocity-vorticity plane during an oscillatory movement. Panels (a) and (b) show data taken during a movement with and . Panels (c) and (d) show data taken during a movement with and . At a relatively high speed and a large amplitude, undesired movements in the vorticity direction were noted, but the effective error remained small.
The relative position of the top plate in the velocity-vorticity plane during an oscillatory movement . Panel (b) is a magnification of one of the turning points. At speeds as low as , which is lower than the minimum speed for which the shear cell was designed, the top plate did not reverse instantly at the turning points. The period that the stage paused at the turning points was sometimes as long as .
Slowly scanned confocal microscopy images of the velocity-gradient plane of a colloidal dispersion sheared at shear rates of (a) , (b) , and (c) . The applied ratio was 0.5. The gap width was approximately . The scan rate was .
Slowly scanned confocal microscopy images of the velocity-gradient plane of a colloidal dispersion sheared at a shear rate of , but with different velocity ratios, , (a) 0.33, (b) 0.5, and (c) 1.0. The gap width was approximately . The scan rate was .
Measured velocity vs height. The velocity ratio was (a) 0.33, (b) 0.5, (c) 1, or (d) 3. The different curves in each graph represent different shear rates. The curves cross at the position of the zero-velocity plane.
In time, sedimentation of the particles caused the particle volume fraction near the bottom to increase.
Confocal micrographs of a dispersion of diameter silica particles dispersed in ETPTA at during the application of a shear with . Initially, the particles were not ordered but they gradually crystallized in time. The scale bars are .
Confocal micrographs of an initially crystalline dispersion of diameter silica particles dispersed in ETPTA. At a shear rate of , the average order of a dispersion decreased. The scale bars are .
Achieved range of various parameters of our high precision parallel plate oscillating shear cell.
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