Development and validation of methods for determination of liquid properties, volume, and flow in microfluidic devices

• Autor(a) principal: Lima, João Maria Varregoso
• Data de Publicação: 2023
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/163862
• topic: Contact angle; flow rate; microfluidics; surface tension; front track method; Wilhelmy plate method; Domínio/Área Científica::Engenharia e Tecnologia::Engenharia Mecânica

Microfluidic applications are increasing all over the world, and ensuring traceability, accuracy, and precision of the quantities to be measured in microfluidic devices is crucial. That is why new cali- bration methods in this relatively new field must be developed. Also, due to the small flow rates in- volved, different relationships between forces and liquid properties must be studied. This research focuses on understanding these interactions. Throughout this research it was stud- ied how some liquid properties like contact angle, surface tension, and refractive index change when different solids and liquids commonly used in the microfluidic world are involved and influence the measurements of flow and volume. By doing so, the aim is to contribute to a better understanding of these essential aspects in microfluidics, ultimately enhancing accuracy and precision in this field. The research was conducted at the Instituto Português da Qualidade spanning across three dis- tinct laboratories: the Laboratório de Comprimento, the Laboratório de Propriedades de Líquidos, and the Laboratório de Volume e Caudal. The study employed a diverse range of methodologies, such as the gravimetric method, interferometric method, the front track method and the Wilhelmy plate method. The primary objectives of this work consisted in determining the suitability and accuracy of those methods to accurately measure flow, volume and liquid properties like the ones listed above. It was found that, regarding flow rate measurements, the gravimetric method consistently emerged as the superior approach, consistently delivering the most reliable outcomes. Furthermore, the utilization of the Wilhelmy method for determining surface tension, and subsequently extrapolating the static contact angle, exhibited great accuracy. However, when it came to dynamic contact angle meas- urements, the results were characterized by increased uncertainty, particularly in the context of hyste- resis.