Ultrasonic beadtrapping for bioassays
This paper proposes a new dynamic mode of generating bioanalytical arrays based on ultrasonic trapping of microbeads in microfluidic systems. As compared to disposable glass slide microarrays, the proposed technology utilises exchangeable microbeads as the solid phase on which bioassays are performed. The use of microbeads in biochemical analysis is advantageous due to the increased surface area and thus the high binding capacity as compared to planar solid surfaces. By the integration of ultrasonic microtransducers in a microfluidic system, we have proved that it is possible to trap and manipulate microbead clusters by making use of acoustic standing wave forces. Functionalised microbeads have been trapped and moved between well-defined positions in a microchannel, thus for the first time showing trapping of microbeads within a flow-through device with individually controlled trapping sites in an array format. A device with three acoustic trapping sites was fabricated and evaluated. The lateral extension of each trapping site was essentially determined by the corresponding microtransducer dimensions, 0.8 x 0.8 mm2. The flow-through volume was approximately 1 µl and the active trapping site volumes about 100 nl each. The strength of trapping was investigated, showing that 50 % of the initially trapped beads were still trapped at a perfusion rate of 10 µl/min. Since the beads determine the chemical functionality in the device a high degree of flexibility is expected. A fluorescence based avidin bioassay was successfully performed on biotin-coated microbeads trapped in the flow-through device, providing a first proof of principle of the proposed dynamic arraying concept. The dynamic arraying is believed to be expandable to two dimensions, thus with a prospect of performing targeted and highly parallel protein analysis in microfluidics.
- Medical Engineering
Micro Structure Workshop