An optical switch constructed from first and second waveguides. The first and second waveguides have ends disposed across a gap such that light traversing the first waveguide enters the second waveguide when the gap is filled with a liquid having a first index of refraction, whereas light traversing the first waveguide is reflected by the gap when the gap is filled with a material having a second index of refraction that is substantially different from the first index of refraction. The gap is part of a trench that contains a liquid droplet made from a droplet material having the first index of refraction. The droplet is located in the trench and is movable between the first and second positions in the trench, the droplet filling the gap in the first position. The gap is filled with a material having the second index of refraction when the droplet is in the second position. The droplet may be moved using an electric field generated by a plurality of electrodes arranged such that an electrical potential applied between a first pair of the electrodes creates an electric field in a region of the trench containing the first position. The droplet can also be moved by differentially heating two edges of the droplet so as to create a net force on the droplet in a direction parallel to the direction of the trench. The heating can be accomplished by illuminating one edge of the droplet with light of a wavelength that is absorbed by the droplet material.