Low-cost methods of on-demand fluid flow, nematode egg separation and counting

There is an increasing interest to re-invent device technologies for use in actual field applications where resources may be limited. Numerous examples exist in the medical and agricultural industry where the demand and benefits for on-the-spot methods of sample collection, preparation, and characterization is being recognized by the scientific community. Some key attributes of devices that cater to this demand of on-the-spot testing are portability, low cost, disposability, easy fabrication and storage, simple operational procedure, and reasonable sensitivity and selectivity. Within the abovementioned realm of device technologies, the thesis attempts to provide low-cost alternative methods for two applications: (i) fluid flow in paper microfluidic devices and (ii) nematode egg separation and counting. Chapter 1 presents a technique to control and operate fluid flow between multiple paper substrates by employing a folded paper cantilever strip. The paper strip is mechanically actuated by a small fluid droplet. The technique can be scaled up to accomplish multiple colorimetric tests, and is demonstrated for the parallel detection of three analytes (glucose, nitrite, and protein). This actuator is intended for use in paper microfluidic devices to quantify levels of disease biomarkers. Chapter 2 describes a method to separate nematode eggs from soil particles followed by counting the number of eggs within a fluid suspension. Nematode eggs with similar-sized soil particles are collected from a series of soil processing steps. Conventionally, through a staining procedure and sucrose centrifugation, a relatively cleaner soil suspension with eggs is obtained that is later counted manually on a