We developed a novel lab-on-a-chip device with the capability of rapidly antibody determination that use nano-beads as the solid carriers. The device combines a plasmon-assisted optical conveyor belt in the main microfluidic channel, which is made of gold nano-ellipses perpendicular to each other. In the presence of an external uniform electric field, the hot spots in the belt function as optical tweezers can trap and transport properly sized nano-beads with target antibody combined along a fix direction through rotating the polarization. Several branch channels intersecting the main microfluidic channel at right angles are used to transport smaller antigen modified nano-beads, which can be labeled with fluorescent dyes. When arriving at the crossings, the smaller nano-beads would be trapped by hotspots on the surface of two-dimensional ellipses arrays around the conveyor belt and can’t be transported between two ellipses due to their smaller size. So, the antibody modified nano-beads would be transported along the optical conveyor belt and encounter the trapped antigen modified ones in the ellipses arrays successively. Only those ones with specific antigen combined that stick to the antibody to be measured can be dragged by bigger nano-beads and transport with it. In light of that, we can determinate the antibody by identifying the fluorescence-labelled nano-beads at the exit of the main channel. With the capacity for parallel detection, our design offers an attractive scheme for rapid, high throughput determination of antibody in microfluidic channels, which are also ease to operate.
We developed a novel lab-on-a-chip device with the capability of rapidly pre-concentrating for Raman detection that use gold bead as the solid carrier of biomolecules. The device combines an array of patterned plasmonic surface (i.e. gold nano-ellipses), as the bead manipulation element. The purpose of gold bead manipulation is to provide sample pre-concentration in close proximity of the Raman detecting region. In the presence of an external uniform electric field, the gold ellipses create local electric field gradients (which is usually called hot spots) that capture the gold beads. The location of hot spots within a plasmonic nanostructure is polarization dependent, and inhomogeneous electric field between two adjacent nano-ellipses perpendicular to each other leads to highly unbalanced trap potential that give the chance of transferring trapped particles in a given direction through rotating the polarization. Nano-optical conveyor belts with staircase pattern of nano-ellipses were arranged with their terminus collected at detection area to gather biomolecules. With the capacity to transfer biomolecules precisely, our design offers an attractive scheme for rapid, high throughput and highly sensitive sensing of low abundance analytes.