MICROFABRICATION, MODELING AND SIMULATION OF A MICROFLUIDIC PROTOTYPE FOR ANALYTICAL PURPOSES

PABLO A. KLER, FABIO A. GUARNIERI, CLAUDIO L. A. BERLI

San Carlos de Bariloche, Argentina

Congreso; 2006 Pan-American Advanced Studies Institute (PASI) on Nano and Biotechnology; 2006

National Science Foundation (USA)

Microfluidic chips are miniaturized analytical devices used in chemical, biological and medical applications. In most cases, fluids are conducted through microchannels by applying electric potentials and/or pressure gradients. There has been a huge interest in these devices in the past decade that led to a commercial range of products (Freemantle, 1999). Different methods to obtain microfluidic systems have been successfully developed for several materials (Madou, 2002). This growing lab-on-a-chip technology requires analytical models and numerical simulations to assist the design, control and optimization of analytical manipulation (Patankar 1998). The present work deals with the microfabrication, theoretical modeling and simulation of a microfluidic chip aimed to perform analytical assays, namely capillary electrophoresis (CE). The prototype has been manufactured integrally in glass, using commercial microscopes slides as substrates (Stjerström et al 1998, Baldwin et al 2002). In these substrates a microchannel network, and an electrode system have been fabricated using photolithographic techniques, wet etching, physical vapour deposition, and thermal bonding techniques. Wet etching was performed using photoresist as etch mask, to avoid using metals mask, simplifying the usual process in glass etching (Che-Hsin Lin et al 2001). The transport of electrolyte solution through the microchannels is based on electroosmotic flow, it is obtained using a single DC high voltage source (Flüke 415B) and electrodes at the ends of the channels (reservoirs) in order to apply the potential difference. Basic manipulations, such as sample injection and focusing, were carried out to evaluate the capability of the device.  An analytical unidirectional model was used to estimate values of flow rate and electric current for a given configuration of applied electric potentials. Also a 3D numerical simulation by finite elements method (FEM) were performed. These studies allowed us to predict values of fluid velocity and electric current for both constructive and functional parameters variations. Constructive parameters were channel dimensions, while functional parameters were applied voltage, electrolyte composition, and channel surface properties. Experimental results from the injection and focusing process were compared with those predicted by both analytical and numerical models. The magnitudes employed to carry out this comparison were the velocity and the focus width.