To realize a high performance optical subscriber network a route reconnect switch is desired which has bistability, polarization and wavelength independence and compactness. This paper proposes an electrocapillarity optical (ECO) switch, in which a micro-mirror formed by a mercury droplet is driven by electrocapillarity. This switch has a potential for use in bistable waveguide matrix switches, which are suitable for route reconnection in the optical subscriber network. A theoretical model is presented that the driving force of the electrocapillarity originates in an electrically induced gradient in the surface tension of the mercury-electrolyte interface where an electrical double layer is formed. The experimentally obtained relation between the flow velocity of a mercury droplet and the electric current in an electrocapillary system is well described by this model. A prototype of the ECO switch is made using a resin molded single-mode fiber with a slit sawed in it in which a electrocapillary system is made. Optical switching is demonstrated and possible improvements in switching performance are discussed.