Hydrodynamic trapping

Abstract: Dynamic microarrays hold great promise for advancing research in proteomics, diagnostics and drug discovery. However, this potential has yet to be fully realized due to the lack of reliable multifunctional platforms to transport and immobilize particles, infuse reagents, observe the reaction, and retrieve selected particles. We achieved all these functions in a single integrated device through the combination of hydrodynamic and optical approaches. Hydrodynamic forces allow simultaneous transportation and immobilization of large number of particles, whereas optical-based microbubble technique for bead retrieval gives dexterity in handling individual particles without complicated circuitry. Based on the criterion derived in this paper, the device was designed, and fabricated using standard photolithography and soft lithography methods. We examined the dynamics of bubble formation and dissipation in the device, and parametric studies revealed that higher power settings at short intervals were more efficient than low power settings at longer intervals for bead retrieval. We also demonstrated the capabilities of our device and its potential as a tool for screening methods such as the "one-bead-one-compound" (OBOC) combinatorial library method. Although both approaches, hydrodynamic confinement and optical-based microbubbles, are presented in one device, they can also be separately used for other applications in microchip devices.

Abstract: High-throughput single-cell measurements of cellular responses are of great importance for a variety of applications including drug testing, toxicology, and basic cell biology. We present an optimization study for trapping single cells with high efficiency in large arrays of microwells. The method is compatible with standard fluorescence microscopy equipment and is not dependent on, but is compatible with, cell adherence. We have characterized microwell occupancy by cells for a range of microwell dimensions and seeding parameters and optimized it for fibroblasts (as a model of adherent cell) and rat basophilic leukemia cells (as a model of nonadherent cell). We have been able to obtain phase-contrast and fluorescence micrographs with more than 18 000 single cells per image using a 4× objective.

Abstract: The poor efficiency of microfluidic single cell trapping is currently restricting the full potential of state-of-the-art single cell analyses. Using fluid dynamics simulations in combination with particle image velocimetry to systematically optimize trap architectures, we present a microfluidic chip with enhanced single cell trapping and on-chip culture performance. Upon optimization of trap geometries, we measured trapping efficiencies of up to 97%. Our device also enables the stable, relatively long-term culture of individual non-adherent mammalian cells in high-throughput without a significant decrease in cell viability. As a first application of this platform we demonstrate the automated separation of the two daughter cells generated upon single cell division. The reliable trapping and re-trapping of mammalian cells should for example provide the fundament for novel types of investigations in stem cell and tumour cell biology, which depend on reliable tracking of genealogical relationships such as in stem cell lineage tracking.

Abstract: The development of hydrodynamic-based microfluidic biochips has been increasing over the years. In this technique, the cells or particles are trapped in a particular region for single cell analysis (SCA) usually without any application of external force fields such as optical, electrical, magnetic or acoustic. There is a need to explore the insights of SCA in the cell's natural state and development of these techniques is highly essential for that study. Researchers have highlighted the vast potential field that needs to be explored to develop biochip devices to suit market/researcher demands. Hydrodynamic microfluidics facilitates the development of passive lab-on-chip applications. This review gives an account of the recent advances in this field, along with their mechanisms, methods and applications.