ABSTRACT
Optofluidics is an emerging research and technology area that combines the two disciplines of microfluidics and optics [1,2]. The integration of fluids and optics has a long history. The first effort to combine these two fields was in the late 1600s, when inventor Stephen Gray described what was called a water microscope [3]. A small hole punched through brass served as the aperture for a static water droplet. The image focusing was done by winding a thumbscrew to change the distance of an object. However, since there was no specific way to tune the lens's performance with a water droplet, the optical power of the microscope remained fixed. A tunable optical element using a liquid interface was demonstrated in 1872 [4]. To adjust the focal length, mercury contained in a small vessel was rotated, and the parabolic shape of the mercury's interface was controlled by the rotational speeds. In the early 1990s, the field of microfluidics emerged to show the potential for lab-on-a-chip applications [5] and, in the early 2000s, microfluidic elements began to be used for optical devices such as microfluidic tunable optical fibers and optical switching bubbles [6,7]. With further technology developments and advances in microfluidics for small scale liquid handling, the field of optofluidics formally began to emerge in the mid-2000s and was identified by researchers who were seeking synergies between these two areas [8,9].
