THE FABRICATION OF MICRO-POROUS SILICA STRUCTURES FOR MICRO-REACTOR TECHNOLOGY

The formation of porous silica microstructures (frits) in capillaries with an internal diameter of 500 mu m has been examined for inducing e lectroosmotic flow (EOF), Capillaries with this internal diameter are normally considered too large to support efficient EOF, but the discre te pumping devices reported here are able to overcome this limitation. The formation of these structures in the capillaries has been examine d, with particular emphasis on identifying parameters within the prepa ration 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 appli ed potential of 700 V, The work offers an opportunity to extend electr oosmotic pumping to capillaries of larger internal diameter than was p reviously 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 par ts. When this technology is applied to micro-reactors, the silica stru ctures offer the dual advantages of providing a pumping mechanism whil e also retaining the catalyst in the micro-reactor.