Dimensional measurements are fundamental in microfluidic device manufacturing and performance. The main focus of this study is the measurement of the connection port sizes in microfluidic devices and components and, accordingly, the possible existence of fluid leaks determined using the flow rate error. The sizes associated with three different microfluidic systems were determined using laser interferometry and through an optical measuring instrument, with metrological traceability to national length standards. It was possible to infer the method with the greatest accuracy and lowest measurement uncertainty for characterizing this kind of system. In conclusion, the results of this work directly address the current lack of dimensions measuring methods of microfluidic components by providing a comprehensive comparison of different protocols, ultimately suggesting a preferred option for immediate application within the microfluidic industry.

A new traceability methodology for roughness stylus calibration is being developed in the National Metrology Laboratory of the Portuguese Institute for Quality (IPQ) using a high-precision displacement transducer. The calibration and dissemination of roughness standards measurements is one of the activities of IPQ. A stylus instrument is used to acquire the height values of the scanned points on the surface of the roughness standard. Defined according to ISO standards, namely the ISO 21920-2:2021, the integrated software calculates the roughness parameters that quantify the surface. A set of roughness parameters, measured after stylus calibration with different standards artefacts, as defined in ISO 5436-1:2000 has been evaluated. The need for the development of a new route for the metrological traceability in roughness, with faster calibration and better accuracy was also analyzed. The use of a displacement transducer, as reference, was the studied solution.

Microfluidics is a rapidly growing technology with applications in biochemistry and life sciences. To support the ongoing growth there is a need for common metrology, quality control, and standardisation. Here measurements of wettability and surface roughness can contribute, and these quantities affect flow characteristics of devices, bonding processes in manufacturing, and special microfluidic mechanisms such as droplet formation and spreading of fluids on surfaces. To quantify wettability, an optical laboratory setup was used to measure liquid drop contact angles of three liquids on a microfluidic surface. To further quantify wettability, the Owens, Wendt, Rabel, and Kaelble model was applied to contact angle measurements to determine the total surface free energy. To quantify surface roughness, atomic force microscopy and stylus profilometry measured area roughness parameter and profile roughness parameter for four samples of microfluidic surfaces. The wettability methods successfully demonstrated measurements of contact angles, and these methods were applied to determine a value for the total surface free energy. AFM and stylus profilometry successfully determined surface roughness parameters, and the determined values agreed with the expected for the material. In conclusion, the demonstrated methods can contribute to metrology, quality control and standardisation in microfluidics.