Field-deployable microfluidics for species identification in conservation

Abstract

This work explores the development of anisotropic ratchet conveyors (ARCs), a type of microfluidic system that can transport small liquid quantities in the form of droplets. ARCs derive their function from a passive, microfabricated surface pattern and applied orthogonal vibrations. A fundamental solid mechanics model is developed to describe how droplets convert a vertical vibration to horizontal droplet transport. Results demonstrate the droplet system can be modelled as a damped-harmonic-oscillator and elucidate the effect of vibration and substrate parameters on droplet behavior. An investigation of how the interface between the substrate and droplet edges affects droplet transport demonstrates that the substrate can influence resonance behavior of the droplet. These results also demonstrate that transport velocity is the result of a summation of discrete step size probabilities, as edge movement is quantized by the rung intervals. This understanding led to the development of new ARC devices that can enable controlled synchronization, sorting, and transfer of droplets. Finally, the capabilities of this system are focused on the development of a field-deployable platform for species identification. Key problems in conservation that have need for new DNA testing technologies and would substantially benefit from the application of microfluidic systems are discussed. A prototype chipset and driving unit is created that can perform an isothermal nucleic acid amplification test by delivering reagents with the ARC system. This initial foray of the ARC microfluidic system into species identification for conservation demonstrates a promising potential for this system and introduces an impactful application setting for microfluidics research that has been previously unexplored.