I. Introduction
Opto-fluidic refers to a class of optical systems that integrate optic and fluidic functionalities. By combining fluid unique properties with optical detection methods, novel devices with advanced features can be designed [1]. For instance, i) fluids can be used to carry substances to be analyzed in highly sensitive optical microdevices; ii) fluids can also be exploited to control light propagation in optical microdevices, making them tunable, reconfigurable, and adaptive.