A method and system of detecting whether the intensity of light incident a spatial light modulator varies periodically. The functionalized poly is useful as a component of a curable composition in which its carbon\u2014carbon double bond copolymerizes with one or more olefinically unsaturated comonomers. The first and second switching elements are made operative or inoperative as a switch in accordance with different conditions. Also, under the gravity and capillarity effect, the output speed is controlled by the number, size and shape of the guiding flow ways and the storing recesses so that each probe structure is strong, the liquid storing capacity is high, its liquid output is stable, it is easier to manufacture the guiding flow ways, and it is easy to clean. Upon connection of the cap to the distal end of the body, the cap may be inserted into a mouth of a user for chewing.