In this work a simple method is described for depositing a robust yet highly porous film of anatase titania nanoparticles with a very high surface area onto the inside walls of microfluidic devices. A very high loading of 66 g of titania per liter of reactant solution was achieved. The effectiveness is demonstrated of this deposition method by producing functionalized microfluidic reactor devices and using them to photocatalytically degrade air-saturated methylene blue solutions. Experiments were performed with and without the addition of gaseous oxygen to the microreactors. The addition of oxygen dramatically enhanced the degradation rate. This highlights the necessity for supplying additional oxygen to microsystems during photocatalysis since dissolved oxygen can be rapidly depleted within the small confined space inside microreactors. With additional gaseous oxygen, the conversion rate for the photodegradation reaction of 0.1 mM methylene blue at a flow rate of 12 mu l min(-1) was 10.6 % s(-1).