A Centrifugal Microfluidics Platform for Potential Application on Immobilization-Free Bead-Based Immunoassays

Abstract

In this work, we demonstrate a simple yet convenient centrifugal microfluidics, or lab-on-a-disc (LOAD) platform for bead-based immunoassays. The disc contains a network of passive valves for sample manipulation and a bead-aggregating barrier structure to instead of commonly used immobilization method. The narrow-channel structure not only provides a geometric barrier for retaining the beads, but also significantly increased fluidic resistance which results in lower flow rate and longer reaction time for each reagent in the reaction chamber. Centrifuge-forced beads densification in the small junction area and signal concentrating allows high signal sensing capability. The acceleration speed is optimized for largest signal-to-noise ratio. The device uses different rotation speed to trigger a cascade of flow events. The integrated platform contains all the necessary functional elements for conducting one-step parallel assays through a sequential protocol. For our test device, the total time required to complete an immunoassay experiment is typically under 6 minutes. Through this work we have also shown that the use of a geometric barrier for the aggregation of signaling beads is an effective approach for the enhancement of optical signals in common immunoassays. This flexible design is suitable for a broad range of bead-based immunoassays with low-cost and high-speed operation.