No abstract

Use of a smartphone as an optical detector for paper microfluidic devices has recently gained substantial attention due to its simplicity, ease-of-use, and handheld capability. Utilization of a UV light source enhances the optical signal intensities, especially for the particle immunoagglutination assay that has typically utilized visible or ambient light. Such enhancement is essential for true assimilation of assays to field deployable and point-of-care applications by greatly reducing the effects by independent environmental factors. This work is the first demonstration of utilizing a UV LED (UVA) to enhance the Mie scatter signals from the particle immunoagglutination assay on the paper microfluidic devices, and subsequent smartphone detection. Smartphone's CMOS camera can recognize the UVA scatter from the paper microfluidic channels efficiently in its green channel. For Escherichia coli assay, the normalized signal intensities increased up to 50% from the negative signal with UV LED, compared to the 4-7% with ambient light. Detection limit was 10 CFU/mL. Similar results were obtained in the presence of 10% human whole blood.