Prediction of Current Drop in High Power Electro-Osmotic Pumps

Mena Tawfik, Thomas Hansen, Shashwat Gupta, Anirudh Thuppul, F.J. DiezDecember 2015

INTRODUCTION• Problem: Observed current drop when

a DC voltage is applied across an EO pump.

• Goal: To predict the current drop using a theoretical model.

• Tools used: a) Advection diffusion equation to

predict ion transportation.b) Superposition of diffusion limited

current and ion migration limited current

EXPERIMENTAL SETUP

A 3D model of the EO pump housing Sketch showing the experimental setup used

Reservoir

Precision Scale

Reservoir

Function Generator

Amplifier

Flow meter

PCMicroscopeCamera

ADVECTION DIFFUSION THEORY

Advection-Diffusion Equation (Ogata & Banks Solution) Diffusion equation (Cottrell solution)

TRANSIENT CURRENT

Transient current (comparison between theoretical and experimental current) without membrane.

Experimental current drop without membrane

CHALLENGES• To predict the current drop with the membrane.

• To find theoretical resistance of the porous membrane.

• Match the theoretical resistance with the experimental values.

• A hypothesis has been introduced for the inclusion of membrane effects in the transient current.

HYPOTHESIS• With the membrane in consideration, the total

current will be:I (total) =

• Now, let V (total) = V eff/electrolyte + Vmembrane. (1)

• Also, V (total) = I (total) R(total) = ((V

eff/electrolyte / Relectrolyte) + (Vmembrane/ Rmembrane)) (2)

• From (1) and (2), we find V eff/electrolyte and Vmembrane.

lfhjR(electrolyte) R (membrane)

+

FUTURE WORK• Test the hypothesis experimentally.

• Determination of theoretical resistance of the porous membrane.

• Combine all the work into a holistic theory.