Research Portfolio

Microsystem Technologies - 2024

ASSURED assessment of droplet-based microfluidics: a benchmark for its future development

Abstract

Over the past 30 years, microfluidic systems have enabled new designs and scaled-down devices, such as point-of-care devices for first-line healthcare and lab-on-a-chip systems. The main advantages of microfluidic technology are miniaturization, which provides low operating energy, increased portability, enhanced device throughput, and higher-dimensional analysis of multiple analytes. However, a drawback associated with conventional microfluidic systems is the occurrence of Taylor dispersion, which leads to the movement of solutes due to variations in speed within the fluid stream, leading to inaccurate measurements of analyte detection. Furthermore, cross-contamination can lead to inaccurate results and compromised sample quality. Therefore, droplet-based microfluidics has emerged as an ideal candidate to overcome these challenges; however, it is now maturing from the proof-of-concept stage to real-world implementation. Thus, targeting key features for its future development is a must for this leap. In this regard, the ASSURED criteria (A for Affordable, S for Sensitive, S for Specific, U for User-friendly, R for Rapid and Robust, E for Equipment-free, and D for Deliverable) were adopted as a benchmark for a qualitative evaluation of the current state of droplet-based microfluidic detection systems and to pinpoint the current bottlenecks. The outcome revealed that this technology has progressed to Specific, Sensitive, Rapid and Robust features in most of the systems being presently investigated, with a huge gap regarding Affordable, Equipment-free, and Deliverable capabilities. Furthermore, the results showed that optical- and electrical-based techniques are the most promising and suitable environments for next-generation ASSURED droplet-based systems.

New
Article

IEEE Sensors Journal - 2022

On the Calibration of an Optical, High-Speed, Multiphase Microfluidic Sensor With Droplet Counting Applications in Lab-on-PCB Devices

Abstract

The integration of microfluidics and droplet-based systems has led to platforms capable of characterizing multiple phases inside microchannels which can be an asset for many industries. Furthermore, recent developments on Lab-on-a-PCB devices focus to meet design specifications such as the ASSURED criteria (Affordable, Sensitive, Specific, User-friendly, Rapid and Robust, Equipment-free, and Deliverable to end-users). However, most of these systems still present external equipment dependencies, complex setup and manufacturing processes, low reproducibility, along reduced information regarding calibration processes for ASSURED-based sensors. In this work, we developed a rapid and fully integrated calibration process for optical droplet-based Lab-on-PCB devices by means of an interfacial distance constant called λ , to obtain reliable and wide spectrum droplet detection and characterization results. To test the proposed calibration process, a low-cost optical droplet sensor was built using commonly available electronics components, consisting only of a fluid channel between a Light-Emitting Diode (LED) and a Light Dependent Resistor (LDR), which voltage variation is measured and processed with an Arduino Uno. After the proposed λ calibration of the platform, we were able to characterize different multiphase flow properties such as velocity, flow rate, droplet lengths, and volume for velocities up to 1000 droplets per second with the Mean Relative Errors (MRE) ranging from 2.4% up to 17%. The lowest MRE value was obtained using a two-phase flow system for flow from 20μL /min up to 425μL /min. In contrast, the highest MRE value we report was found for a three-phase flow system for droplets at 250μL /min.