Optical studies of micron-scale flows

The development and the success of microfluidics in the last 15 years is mainly due to the concept of lab-on-a-chip. Those miniaturized devices, integrating one or more laboratory functions, have aroused great interest among several research areas as physics, chemistry, biology and bioengineering. The high hydrodynamic resistance the liquid experiences in a lab-on-a-chip imposes the device to be connected to pumping systems thousands of times bigger than the chip itself, thereby erasing many advantages of a millimeter-sized device. In this respect, superhydrophobic surfaces have demonstrated to be an effective tool to reduce the fluid/solid friction. This thesis is part of the wider project of setting up an innovative technique to investigate the fluid-solid slippage on such surfaces by means of optical tweezers. This work reports the steps performed along the way towards this main goal and it consists of a collection of several researches involving different scientific fields as optics, microscopy, surface science, microhydrodynamics, microfluidics and microfabrication.