A method of using open optical waveguides to process photoreactive materials, particularly micro-nanoscale polymer thin films and chains. The illustrative embodiment shows a block (10) etched with a series of depressions to function as waveguides (14, 18), light source holders (22), a material-containing channel (12), and fluid input/overflow receptacles (24, 26). The waveguides and channel form a network constructed in conformity with a hexagonal grid pattern. A hinged waveguide cover (28) is attached to the block. Material is placed in the channel, a photoreactive solution, usually an azobenzene dye, added to the channel, the cover closed, and the light sources activated in different combinations and for different durations. The material is thereby altered through accepting surface accumulations of dye or by undergoing intrinsic structural change.