Devices and methods for the application of materials to an interior space of a tooth, such as the extirpated pulp chamber andor root canals of the tooth subsequent to root canal surgery. The sunscreen composition is in the form of a thixotropic gel. A free-standing film of a chemically sensitive polymer that swells when exposed to vapors of a volatile chemical is formed in-between the pair of closely-spaced wires by capillary action. The main body has a first sloping surface joining the bottom surface and at least one of the side surfaces. The embodiment may be used to fabricate an array of OLEDs on a flexible substrate. At least a portion of the cover member can be disposed proximate the at least one channel, to provide at least one hollow core waveguide.