Fabricação de microssistemas eletroforéticos integrados com detecção condutométrica sem contato capacitivamente acoplada
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2013-06-28
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Universidade Federal de Goiás
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This work describes the development ofelectrophoresis microchips integrated with capacitively coupled contactless conductivity detection (C4D). MSE were produced in poly(dimethylsiloxane) (PDMS) by soft lithography. For this purpose, high-relief masters were produced on (i) silicon substrates by photolithography, (ii) polyester films by laser printing and (iii) copper plates by wet chemical etching. The devices fabricated by photolithography were used to investigate the effects of the electrode orientation and length, the optimization of the operating and geometric parameters on the analytical performance of the detector. The results have shown that the analytical signal intensity is greater when employing electrodes with width of 2 mm, spaced by a minimal gap (1mm) and arranged in an antiparallel configuration. The optimal frequency found was 400 kHz. Furthermore, it was observed that the signal intensity increases linearly for amplitude values up to 5 Vpp. PDMS devices obtained with toner and copper masters were employed to perform eletrophoretic separations of inorganic cations using the previously optimized conditions. The alternative masters and the resulting PDMS channels were characterized according to their dimensions, surface roughness and replication fidelity. On toner masters, it was verified that the wider the line, the ticker the toner layer. For widths between 50 and 300 μm, the toner thickness ranged from 5 to 10 μm. On the other hand, the line height on copper masters was determined by the etching time. For lines with widths between 50 and 300 μm, the height ranged from 72 to 82 μm, under an etching rate of 7.6 ± 1.7 μm/min. Regarding the roughness, copper masters presented more uniform surfaces in comparison to toner masters. This difference is due to the additional heating step used to transfer the toner mask. The proposed masters have shown good replication fidelity and also excellent capability of producing multiple replicas with a single master. The main drawback found with the fabrication technology is associated with the laser printer resolution. However, the easiness of fabrication and low instrumental costare suitable to be implemented in locations with limited resources or restricted access to conventional microfabrication techniques.
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BRAGA, Laura Eulália de Paula. Fabricação de microssistemas eletroforéticos integrados com detecção condutométrica sem contato capacitivamente acoplada. 2013. 127 f. Dissertação (Mestrado em Química) - Universidade Federal de Goiás, Goiânia, 2013.