Desenvolvimento e caracterização de métodos alternativos para prototipagem de dispositivos microfluídicos em poli(metil metacrilato) (PMMA)

• Autor(a) principal: Lobo Júnior, Eulício de Oliveira
• Data de Publicação: 2020
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Repositório Institucional da UFG
• Texto Completo: http://repositorio.bc.ufg.br/tede/handle/tede/10756
• topic: Bioanalítica; Detecção condutométrica sem contato; Eletroforese; Microfabricação; Sistemas analíticos portáteis; Bioanalytical; Capacitively coupled contactless conductivity detection; Electrophoresis; Microfabrication; Portable analytical systems; CIENCIAS EXATAS E DA TERRA::QUIMICA

This thesis describes an unconventional and economical soft embossing process for the production of poly (methyl methacrylate) (PMMA) microfluidic devices. This process was developed in order to meet the demand of researchers interested in producing and developing their own microfluidic systems with the desired configurations. Basically, for the production of these devices, the microfluidic structure of interest was photographed on a poly (vinyl acetate) film (PVAc) deposited on a glass surface to produce a primary mold. Then this mold was used to produce a secondary embossed mold of hardened PDMS (S-PDMS), which was obtained by increasing the proportion of curing agent / monomer (1: 5) followed by thermal aging in an oven (200 ºC for 24 h). Then the S-PDMS mold was used to mold the microfluidic devices in PMMA via soft embossing at (220-230 ºC) and followed by thermal sealing at 140 ºC. Both the molding and sealing processes were carried out using metal clips to perform pressure. The proposed protocol ensured the molding of PMMA devices with excellent fidelity (> 94%). With the developed technique, electrophoretic microsystems (MSE), micro-drop generator devices and microwell plates were produced. These devices have been tested in the respective analytical techniques showing promising results. Specifically, to test the MSE a model mixture containing inorganic cations was used, and in a systematic comparison, the analytical performance obtained did not differ significantly from a commercial PMMA MSE. With micro-drop generator device micro-drops were produced in a rate of 60 micro-drops per minute (setting the flow rate at 100µL / h) with a size of 322 ± 6 μm. Electrophoretic separations and microdroplet generation were monitored using a capacitively coupled non- contact conductometric detection system or C4D. For the positioning of the C4D electrodes in the devices, a cavity was produced that allowed the electrodes to be positioned just 100 µm away from the microfluidic channels. Colorimetric glucose assays were performed on the plate containing microwells and a detection limit of 9.0 µmol L-1 was obtained. The results obtained for two artificial serum samples showed agreement with the label concentrations. An economical protocol for the production of PMMA thin film was also developed, which was applied for the production of MSEs and a microdroplet generating device, containing integrated electrodes with a distance of only 25 µm from the microfluidic channels. This strategy has the potential to improve detection limits with C4D in manufactured devices. In addition, an automated process was developed using a mini-drill (CNC) bench for the production of FIA device (flow injection analysis) with amperometric detection. Preliminary results with this device demonstrate the potential for applications such as the determination of metal ions in solution as well as the determination of carbohydrates in biological samples. The microfabrication process developed is capable of producing structures with minimum dimensions of width and height of the order of 30 µm. Thus, this thesis presents economic processes for the production of microfluidic devices with the potential for bioanalytical, environmental, forensic applications, among others. The microfabrication process uses low cost materials whose development was directed to be carried out in almost any research or even teaching laboratory of chemistry or biology. Additionally, despite using relatively simple technologies, the microfabrication process developed has the potential to achieve quality compatible with conventional microfabrication processes.