Blood Cell Count On-a-Chip

Abstract

White blood cell (WBC) count is one of the most frequently ordered clinical tests in hospitals. There are five types of WBCs in the circulating blood, including lymphocyte, monocyte, neutrophil, eosinophil and basophil. The WBC count test enumerates not only the total number of WBCs in per volume blood, but also the percentage of each WBC type. A portable instrument for the WBC count test is currently in demand by the NASA human spaceflight, and also by the on-earth telemedicine application. However, the commercially available tests do not meet the requirement of the portable applications, because of their large instrument size and the large reagent volume consumed per test. This study describes the development of a WBC count technology optimized for portable applications. First, a sheathless microfluidic cytometer is developed for WBC count. This technology consumes only a small amount of blood (5 microlitre) and a minimal volume of reagents (50 microlitre). Second, fluorescent dye assays are developed for the WBC differential count by measuring fluorescent emissions on the microfluidic cytometer. Based on this technology, a portable instrument is built with high test accuracy (maximum error less than 10%). Furthermore, this study explores two key components for future integrating this technology into a self-contained chip. First, a microvalve actuated by thermal blood clogging is developed. This valve has a simple structure suitable for on-chip integration. Second, a micromixer is used to demonstrate the staining of blood with dye assays, and the following fluorescent detection of WBCs on the cytometer.