Self-Powered Microfluidics for Point-of-Care Solutions: From Sampling to Detection of Proteins and Nucleic Acids.

Self-powered microfluidics presents a revolutionary approach to address the challenges of healthcare in decentralized and point-of-care settings where limited access to resources and infrastructure prevails or rapid clinical decision-making is critical. These microfluidic systems exploit physical and chemical phenomena, such as capillary forces and surface tension, to manipulate tiny volumes of fluids without the need for external power sources, making them cost-effective and highly portable. Recent technological advancements have demonstrated the ability to preprogram complex multistep liquid operations within the microfluidic circuit of these standalone systems, which enabled the integration of sensitive detection and readout principles. This chapter first addresses how the accessibility to in vitro diagnostics can be improved by shifting toward decentralized approaches like remote microsampling and point-of-care testing. Next, the crucial role of self-powered microfluidic technologies to enable this patient-centric healthcare transition is emphasized using various state-of-the-art examples, with a primary focus on applications related to biofluid collection and the detection of either proteins or nucleic acids. This chapter concludes with a summary of the main findings and our vision of the future perspectives in the field of self-powered microfluidic technologies and their use for in vitro diagnostics applications.

Revolutionizing sample preparation: a novel autonomous microfluidic platform for serial dilution.

Dilution is a standard fluid operation widely employed in the sample preparation process of many bio(chemical) assays. It serves multiple essential functions such as sample mixing with certain reagents at specific dilution ratios, reducing sample matrix effects, bringing target analytes within the linear assay detection range, among many others. Traditionally, sample processing is performed in laboratory settings through manual or automated pipetting. When working in resource-limited settings, however, neither trained personnel nor proper laboratory equipment are available limiting the accessibility to high-quality diagnostic tests. In this work, we present a novel standalone and fully automated microfluidic platform for the stepwise preparation of serial dilutions without the need for any active elements. Stepwise dilution is achieved using the coordinated burst action of hydrophobic burst valves to first isolate a precisely metered volume from an applied sample drop and subsequently merge it with a prefilled diluent liquid. Downstream, expansion chambers are used to mix both reagents into a homogeneous solution. The dilution module was characterized to generate accurate and reproducible (CV < 7%) dilutions for targeted dilution factors of 2, 5 and 10×, respectively. Three dilution modules were coupled in series to generate three-fold logarithmic (log5 or log10) dilutions, with excellent linearity (R2 > 0.99). Its compatibility with whole blood was furthermore illustrated, proving its applicability for automating and downscaling bioassays with complex biological matrices. Finally, autonomous on-chip serial dilution was demonstrated by incorporating the self-powered (i)SIMPLE technology as a passive driving source for liquid manipulation. We believe that the simplicity and modularity of the presented autonomous dilution platform are of interest to many point-of-care applications in which sample dilution and reagent mixing are of importance.

Precise sample metering method by coordinated burst action of hydrophobic burst valves applied to dried blood spot collection.

Dried blood spot (DBS) sampling by finger-pricking has recently gained a lot of interest as an alternative sample collection method. The reduced invasiveness, requirement of lower sample volumes and suitability for long-term storage at room temperature make DBS ideal for use in home settings or low-resource environments. However, traditional protocols often suffer from biased analysis data due to variable and not exactly known blood volumes present in the samples. In this work, a novel device has been developed to split-off precisely metered volumes from a blood drop and load them on pre-cut filter paper. Hereto, hydrophobic burst valves (HBV) were developed to temporarily retain a fluid flow, configurable to burst at pressures within a range of 175-600 Pa. By combining HBVs with different burst pressures, a volume metering system was developed to allow parallel metering of multiple pre-defined sample volumes. The system was shown to be accurate and consistent for blood volumes between 5-15 µL and for hematocrit levels spanning the range of 25-70%. Finally, a point-of-care DBS sampling device was developed combining the self-powered microfluidic SIMPLE technology. To evaluate the system's practical applicability, a validation study in the context of therapeutic drug monitoring of biologicals was performed using adalimumab-spiked blood samples. Microfluidic DBS samples showed good performance compared to the traditional DBS method with improved recovery rates (86% over 62%). This innovative metering system, allowing for parallelization and integration with complex liquid manipulations, will greatly impact the field of robust sampling, sample preparation, storage and analysis at the point-of-care.