This Thesis introduces technologies for particle manipulation in bioanalytics, designed to advance integrative biology leveraging biomarker quantification. Bioanalytical information is essential for uncovering mechanisms and pathways, particularly in noncommunicable diseases, often lacking individualized therapy. Despite the availability of various tools for purifying and characterizing analytes, current methods may be unsuitable for downstream analysis or inaccessible due to high costs and the need for specialized personnel.
Microfluidics offers solutions to these challenges via innovative bioanalytical systems. This work proposes microsystems combining electrokinetic and hydrodynamic forces for versatile particle manipulation. Hydrodynamic methods allow for mechanical size-based immobilization or deflection of bioparticles, while adding electrical forces enables contactless manipulation, tunable in real time.
The Thesis presents microfluidic devices with active or passive micro-features, deploying various shapes and configurations. For dielectrophoretic (DEP) applications, three-dimensional electrodes spanning the height of microchannels allow for larger volumetric capacities and higher sample processing throughput. Addressing microfabrication challenges and optimizing SU-8 photolithography enabled the integration of metal-coated posts, passive obstacles, and traps.
This work focuses on two key aspects of bioanalytics: sample purification and bioassay automation. For sample purification, passive deterministic lateral displacement (DLD) was implemented to isolate large, fragile bone marrow (BM) cells at processing times comparable to fluorescence-activated cell sorting (FACS) while preserving viability. This system retrieved mature BM cells at high purity, representing the first solution for their non-destructive size-based separation compatible with downstream analysis. Additionally, DEP-enhanced DLD devices showed improved capabilities to sort submicrometer particles. Teardrop-shaped posts were introduced to reduce the DEP-DLD critical size by spatially shaping the electric field, a patented solution.
To advance bioassay automation, DEP modules were developed to handle beads functionalized with capture antibodies for protein quantification, supporting sequential operations including incubation, release, and clustering. DEP-DLD enabled robust spatial multiplexing to test diverse markers on differently-sized beads. To obviate the need for active pumping and serial injections, a hydrodynamic self-contained platform was developed, exploiting capillarity and paper modules storing reagents within a fully automatic bead-based multimarker assay system, requiring only sample injection by the user. This novel configuration pairs microfluidics with paper components independently adjustable to tune the assay flow and reagent release. This platform quantified kidney function biomarkers from one microliter of mouse urine or plasma within twenty minutes, effectively replicating standard ELISA results.
In conclusion, this Thesis advances a design space combining three-dimensional active and passive features within microfluidics to control particle trajectories in continuous flow. These technologies offer versatile, easy-to-use solutions with a high degree of automation, minimizing extensive sample preparation off-chip. Implementing these methods for novel bioanalytical applications opens new possibilities for biological discoveries and healthcare.