A trap-and-release integrated microfluidic system for dynamic microarray applications

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.high throughput screening ͉ lab-on-a-chip ͉ MEMS ͉ bead-based assay ͉ microbubble M icroarray applications are extensive, and have been successfully used in basic scientific studies (1-4), drugdiscovery (5, 6), and diagnostic purposes (7). Microarrays can be broadly classified into two categories: static and dynamic. In static microarrays, biomolecules and chemicals are immobilized as microspots on a static solid support, and can be fabricated using a variety of technologies, including printing with highspeed arrayer onto glass slides (7), photolithography using premade masks (8), or photolithography using micromirror devices (9). In the case of dynamic microarrays, instead of stationary solid supports, bio-molecules and chemicals are immobilized onto mobile substrates, usually microbeads (10, 11). Besides bead-based microarrays, dynamic microarrays also include cell-based arrays (12, 13). Compared with their static counterparts, dynamic microarrays have several advantages: (i) ability to mix-and-match the beads (or cells) to cater for the type of screening to be performed, and introduce them into the microarray on demand offer great versatility; (ii) beads (or cells) can be replaced, resulting in a reusable format that greatly reduces the cost of operation; (iii) reaction on beads tends to be faster compared with conventional planar surfaces, as microbeads have increased surface area, thus higher binding capacity. To fully realize the potential of dynamic microarrays, it will be necessary to build a platform that allows us to transport particles, to immobilize them for convenient signal d...

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