Interfacial wicking flow through hierarchical structure of natural cellulose fibers for biomedical microfluidic devices

Abstract

Micro/Nanofluidics technology is a new research area focused on analyzing and controlling flow of fluids and bio-particles at nanometer and micrometer scales. In an attempt to achieve low cost fabrication and operation of microfluidic devices, the use of cotton fabric was proposed as a new platform for developing low-cost microfluidic devices. This thesis presents a novel wicking fluidic study through the hierarchical structures of textiles by multi-stage analysis of fluid flow at different structural scales, from the macro- (the three dimensional network structure of the cotton fabrics), via the micro- (the tiny segment of the textile structure, twisted multi fibers in a yarn) to the nanoscale (single fiber). The wicking flow within the cotton fabric structure and kapok fiber (as a hollow fiber and a simple model for the wicking flow) was experimentally analyzed using quantitative fluorescence microscopy data from the motion of fluorescent beads. Thereafter, in order to formulate the wicking flow through the hierarchical structure of the fibers network of the cotton fabrics and to predict how the wicking flow depends on the textile structure and basic material properties, experimental analyses based on fluorescent beads tracing with fluorescent and confocal microscopy as well as analytical analyses were carried out. The results of this study formed the foundation of new theories and novel ideas for interfacing microfluidics and nanofluidics. Additionally, the analyses prove that the wicking and the capillary action play important roles in selective mass transport in the textile structures. This phenomenon is potentially useful for biological and chemical detection in biosensors devices. The research targets application in novel passive size-based mechanical cell sorting using cotton fabric chip and fiber based enzyme-linked immunosorbent assay (ELISA).