Abstract
Microfluidic devices known also as labs-on-chip, capillary electrophoresis microchips or micro total analysis systems (µ-TAS) were introduced in 1990’s for the first time. These devices have attracted much attention over the last years. They transfer tiny quantities of samples and reagents, through a system of microchannels and microchambers manufactured on the surface of a small plate. They are made up of different materials, most often of polymers (PDMS, PMMA), glass or silicon. Microfluidic devices are applied in many areas including separations of biomolecules (DNA or proteins), DNA amplification and sequencing, chemical synthesis, single cell analysis, environmental monitoring etc. They often integrate many steps of analysis such as sample preparation, separation and detection on a small, single chip. In this paper we study electrophoresis microchips. Joule heating and its effects, i.e., the temperature growth leading to temperature gradients in microfluidic devices, lead to many problems during chip electrophoresis. Sample band dispersion (low column separation efficiency), reduction of analysis resolution, destruction of thermally labile biomolecules or formation of vapor bubbles are the negative effects of Joule heating. In our research we compare diamond, glass and PDMS microfluidic devices. Microchips of different geometries and of different materials have been analyzed by the Conventor™ software. Diamond reveals exceptionally good electro-thermo-opto-chemical parameters, is very useful in the range of biomolecular separations (such as electrophoresis) and for optical detection methods. Among them, the most important are: the highest-ever thermal conductivity coefficient, good optical transparency, very high electrical breakdown voltage, good chemical resistance and mechanical durability. Diamond microfluidic devices are very advantageous over glass or polymer microfluidic devices commonly used. They dissipate Joule heat much more efficiently because of the highest-ever thermal conductivity coefficient of diamond.