The fabrication of micro-porous silica structures for micro-reactor technology

Abstract

The formation of porous silica microstructures (frits) in capillaries with an internal diameter of 500 µm has been examined for inducing electroosmotic flow (EOF). Capillaries with this internal diameter are normally considered too large to support efficient EOF, but the discrete pumping devices reported here are able to overcome this limitation. The formation of these structures in the capillaries has been examined, with particular emphasis on identifying parameters within the preparation stage that might give rise to variation in the porosity of the frit. The initial results showed that the induced electroosmotic flow rate increased with frit length (to an optimum of 50 mm) with an applied potential of 700 V. The work offers an opportunity to extend electroosmotic pumping to capillaries of larger internal diameter than was previously thought ideal. It offers a number of potential advantages in the area of fluid propulsion, including the electric control of flow rates, the plug like nature of the flow, and the absence of moving parts. When this technology is applied to micro-reactors, the silica structures offer the dual advantages of providing a pumping mechanism while also retaining the catalyst in the micro-reactor.