Scolaro, Rita (2016) Studio dei fenomeni di intrappolamento di sistemi microscopici indotti dalla luce in cristalli di niobato di litio. [Magistrali biennali]
Full text disponibile come:
Techniques for trapping and manipulation of particles with size as small as possible have become an important research field. One of these techniques, the so called photovoltaic tweezers, is based on the bulk photovoltaic (PV) effect which characterizes photovoltaic materials such as lithium niobate (LN) and it is interesting for its capacity to manipulate many particles in parallel using low-intensity light patterns. An illuminated photovoltaic crystal generates an evanescent electric field on its surface, which is used to produce trapping of particles by electrophoretic (EP) and dielectrophoretic (DEP) forces. In this thesis are discussed and analyzed the capabilities of Fe:LN to trap and manipulate particles as a function of the total concentration of iron present in the crystal and its degree of reduction. In particular are reported the studies of the trapping of charged and uncharged particles, respectively toner and carbon particles, dissolved in oils. For this thesis different kinds of samples are used: not only Fe:LN bulk crystals, but also Fe-diffused LN substrates. It is then presented a study on the experimental diffusion parameters, such as the maximum dopant concentration and its mean depth inside the substrate, necessary to get a good performing PV tweezers in diffused Fe:LN crystals. The studies of the efficiency of theses samples are based on the estimation of the total number of particles trapped at the surface of the material and on the resolution of the trapping process compared to the light pattern. A summary of the performance of differet samples is presented. Furthermore, for the first time, in this thesis is discussed the integration of a Fe:LN substrate for particle manipulation in a microfluidic lab-on-a-chip (LOC).
Solo per lo Staff dell Archivio: Modifica questo record