Seth Fraden Group

Electro-rheological fluids:

SHEETS

At lower volume fractions (<15%) we observed chains and 'sheets'

We observe labrynths of 'sheets' of particles that form when the E-field is turned on. The view is looking down the E-field, and is that seen after ~3minutes of the sample (10% volume fraction) being in the E-field. The sheets form within seconds of the E-field being turned on, and evolve into the BCT structure over hours. BCT formation is shown by the section indicated by (I) in the image above. The structure of a sheet such as indicated by (ii) in the image is shown in the image below and in the VRML file below.

The same area after ~ 3 hours in the field. Most of the sheets have transformed into BCT crystals.

(left) Two views of a 'sheet' in planes parallel to the E-field. The particles are hexagonally packed within a sheet, but are not a collection of chains of particles that are aligned with the field except at the electrode, where the botttom two layers of particles are arranged in a chainlike manner.

This is a VRML file showing the sheet structure.

(below) Another image of a 'labrynth' of sheets. The view is looking down the E-field.

Datasets

The following are downloadable binary files containing raw 3D confocal microscope data. The pixels have 8-bit values. The 3D images are arranged as streams of pixel values at (x,y,z) integer coordinates where the x index varies fastest (with the y index next). For example, the C code shown below can used to read an image into a [x][y][z] 3D array, using the file name, x size, y size and z size as arguments.

sheets (100,100,150 pixels) - data of a 15% v.f. sample showing a sheet that is bounded at an electrode at one end. The image is taken ~1 hour after an electric field of 0.5kV/mm and 400kHz was applied. The resolution of the image is 0.087mm/pixel.
BCT crystal (50,50,100 pixels) - image of a BCT crystal formed in a 15%v.f. sample, with an electric field of ~0.5kV/mm and 400kHz. The resolution is 0.104mm/pixel.
a larger BCT crystal (100,100,120 pixels) - A larger section of the above BCT crystal with the same resolution.
A high volume fraction sample showing a mix of BCT and hexagonal packing (512,512,90 pixels) - The sample is of v.f. 45% and has been in an electric field of 1kV/mm and 1MHz for ~2 hours. The image is from the middle of the sample with an electrode gap of ~85mm. The resolution is 0.090mm/pixel.