Microfluidics and nanofluidics
By talking of micro- and nanofluidics we refer to the research and technologies dealing with small volumes of fluids, as small as micro-, nano-, pico- and even femtolitres. The need to get detailed and accurate measurements in micro-scale devices requires the application of new experimental techniques, unusual in classical fluid mechanics. One of them is micro-PIV, full field microscopic velocity measurement which uses fluorescent tracers with dimension of only several nano-meters.
The micro-PIV system developed in our lab in 2003 was one of the first ones in Poland. A later advanced version of this system was equipped with appropriate illumination an allowed us to use total internal reflection of laser light for the investigation of Brownian motion of nanoparticles at nanometric distances from the channel wall. Experiments performed helped us to verify the classical non-slip hypothesis for the tangential velocity of liquid adjacent to the solid surface. The slip boundary condition combined with electrostatic effects (ionic double-layer) and/or steric effects (attached surface active molecules) make proper description of nanoparticle mobility particularly challenging.