Use and fabrication of microfluidic circuits formed with submerged microjets

Thesis

We have developed a method to fabricate microfluidic circuits that facilitate static and dynamic assays in cell biology. These microfluidic arrangements are made on standard tissue-culture Petri dishes in a manner analogous to pressure washing a patio: a submerged impinging microjet (SIM) of bioinert, transparent, and gas-permeable fluorocarbon (FC-40) displaces a dish-wetting aqueous solution (typically cell media) in any predetermined 2D pattern. The media left wetting the substrate is now uniquely confined by liquid FC-40 (not solid!) walls in the desired circuit pattern. SIM fabrication brings many benefits to biomedical scientists including rapid fabrication from familiar materials, real-time circuit accessibility, excellent optics (there are no solid walls to obscure an observer’s view), bubble-free operation, and – most importantly – easy incorporation into existing workflows. SIM-printing provides great control over the fabrication resolution of microfluidic circuits and is studied first in this thesis. Varying user input parameters such as microjet velocity, flow rate, and height above the substrate provides a thorough validation of SIM-printing and highlights its resolution limitations. The main focus of this thesis, however, is studying flows inside SIM-printed circuits. In our bodies, cells are often bathed in flowing interstitial liquids. Therefore, to assay cell activity in vitro accurately, we need to predict flows precisely. As these circuits have fluid walls that morph during flow in accordance with changes in local pressure, we develop an analytical solution to this new flow problem and validate it experimentally. The unique liquid-liquid interface between commonly used aqueous-based cell media solutions and FC-40 is also examined in an effort to determine slip characteristics and effective interfacial tensions.

Authors: Stovall-Kurtz, N

• Type of award: MSc by Research
• Level of award: Masters
• Awarding institution: University of Oxford
• Language: English
• Keywords: Interfacial Tension; Liquid Jets; Fluid Dynamics; Microfluidic Devices; Two Phase Flow; Microfluidics; Fluid Flow; High-Throughput
• Subjects: Microfluidic devices