The effect of UV irradiation on the swelling properties of polymer layers as a function of the chain scission degree is studied, using white light interferometiy. The use of patternable polymeric films and their subsequent UV irradiation treatment as a means to engineer individual sensor sensitivities in chemical sensor arrays is proposed. First results with the polyhydwxy-ethyl- methacrylate (PHEMA) before and after deep UV irradiation, for three different exposure doses are presented. The relative expansion of the layer was clearly found to depend on the irradiation conditions.