A microfluidic approach to assembling ordered microsphere arrays

Hydrodynamic flow through an array of channels has been utilized to assemble microspheres on a flat surface. The channels, about 6 νm in lateral size, were etched through a 60 νm thick silicon wafer using deep reactive ion etching (DRIE). Droplets containing 6-8 νm fluorescent polystyrene microspheres were placed on the top side of the horizontally-oriented silicon wafer, while the bottom side was connected to a syringe that draws the fluid through the channels. In this way the microspheres are guided and secured at the inlets of the channels, and remain in place when the suction ceases. This technique, which combines favorable features such as high throughput, high resolution rate and reusability, can be a powerful platform for a new generation of protein microarrays. Antigens can be bound to the microspheres as 'targets', which can then be exposed to different fluorescence-tagged antibodies so that their binding can be confirmed. This system can also be used to study the functional roles of gene fragments and their relations to human diseases. The high throughput feature will make it possible to screen a large number of DNA fragments and identify the genetic basis of various diseases effectively.