An EO pump is modeled as many cylindrical microchannels in parallel. An electric field is imposed using two electrodes on either side of the porous substrate. The flow is driven by the motion of net charge in the EDL that drags the bulk fluid by viscosity (a) image of EO pump with integrated gas recombination system (b) detailed view of flow in one pore adapted from Yao and Santiago JOCIS 2003. (c) SEM image of porous silicon based EO pump.
Pumps have been fabricated from glass-particle-packed fused silica capillaries, porous borosilicate glass, in situ polymerized porous monoliths, as well as planar and porous silicon. EO pumps can generate high pressures of more than 340 atm and large flow rates per volt and unit area 0.13 ml/min cm² V. For example we can pump 40 ml min¯¹ of solution at 100 V in a pumping structure less than 1 cm³ in total volume. We have also demonstrated that we can pump a wide variety of aqueous solutions and polar organic solvents. Some of these solvents include methanol, acetone, and acetonitrile.
We have also shown that we can capture the electrolytic gases formed at the electrodes and recombine them to reform water using Teflon coated Pt
catalysts. These pumps can be used at
any orientations (relative to gravity) so that that they can be used in
portable medical devices as well as a cooling option for laptop
Flow rate versus backpressure for porous silicon EO pumps with various thicknesses of polysilicon deposition and 0.25 μm thick SiO2 surface layer at an applied potential of 25 V.
This work has been conducted as a collaboration with Juan G. Santiago at Stanford University and Alan Myers at Intel Corporation.
1. S. YAO, A.M. MYERS, J.D. POSNER, K.A. ROSE, AND J.G. SANTIAGO. 2006. Electroosmotic Pumps Fabricated from Porous Silicon Membranes, Journal of Microelectromechanical
Systems, Journal of Microelectromechanical Systems, V15, No. 3
2. Kim, D., J.D. Posner, and J.G. Santiago. High Flow Rate per Power Pumping of Aqueous Solutions and Organic Solvents with Electroosmotic Pumps. in Electrochemical Society (ECS) Transactions, Annual Electrochemical Society Meeting 2005. October 16-21, Los Angeles, CA.