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Electroosmotic Flow - Experimental Validation

We have developed analytical models and CFD models for electroosmotic flow (EOF) in micro/nano-channels. The models were compared to experimental data and molecular simulations. iMEDD, Inc. and Oak Ridge National Laboratory (ORNL) provided us with the experimental data we compared our results to. The iMEDD experiments were performed on a nanochannel membrane made up of approximately 47,500 nanochannels in parallel. SEM images of a section of the membrane are shown below. Each channel has the same height (which varies), a length of 3.5 microns, and a width of 44 microns, with the fluid flowing through the 44 micron channel height surface.

iMedd nanopump experimental system

The reservoir and the channels in iMEDDs’ experiments. The iMEDD membrane with nanochannels across it is located in the center of the reservoir. Through the nanochannels, the liquid in one side of the reservoir is driven to the other side by electroosmosis.

SEM image of iMedd membraneSEM image of iMedd membrane

Nanopore membranes fabricated by iMEDD inc. Arrays of membranes are fabricated on a silicon wafer; on each membrane, there are vertical nanochannel arrays fabricated. The width of the channels is 44μm, and the distance between two arrays is 6μm.

Comparison of model results with experimental data

Comparison of our theoretical flow rates with the iMEDD experimental results. 1xPBS, 0.1xPBS and 0.01xPBS refer to original PBS, 10 folds diluted PBS and 100 folds diluted PBS, in respective.

The second set of data for comparison is the experimental results obtained by Ramsey et. al. at Oak Ridge National Laboratory. Ramsey et. al. measure the electroosmotic mobility of sodium tetraborate aqueous/methanol solution flowing through different single rectangular silicon nanochannels.

Comparison between the mobilities measured in ORNL experiments and the results from the model. The mobilities are drawn against the channel heights, which vary form 83nm to 1080nm. The mobilities Ramsey obtained from their experiment agreed very well with the model.

In Georgia Institute of Technology, Dr. M. Yoda et. al. uses Nano-PIV technique to study the flows at the nano- to micrometer scale experimentally. The velocity profile and mobility of fluids are measured in their experiments.

The picture (left) and sketch (right) of the crossing microchannel chip used in the Georgia tech experiments, the region of interest (ROI) is indicated in the sketch plot; and the direction of flow is from top to bottom in the sketch plot, as shown by the arrow.

Comparison of the mobility measured in the Georgia Tech experiments and the average mobility calculated from the asymptotic model.