Design And Characterization Of A Microfluidic Device For A Preliminary Study On The Origins Of Life

How did life on Earth begin? It has been recently proposed that chemical entities that formed autocatalytic sets in mineral surfaces could have increased their fitness/complexity over time through neighborhood selection. To test this idea, a mineral surface that is swept with a “prebiotic mix” should exhibit growth of these autocatalytic sets. If non-overlapping areas of the surface are exposed, then each area should exhibit similar levels of attachment without apparent growth. A simple microfluidic device is thus proposed as an experimental model for this hypothesis. It uses a laminar-flow technique known as hydrodynamic focusing to expose a given surface to a prebiotic mix stream in a highly controlled manner. In this project, two surface-exposure protocols were developed using a 20 µM-solution of fluorescein isothiocyanate (FITC): a sweep protocol and a control experiment protocol. The sweep protocol was optimized to accommodate a non-stop 14-day experiment by injecting FITC at 0.5 µL/min, which consumes only 10 mL of reagent. Coupled with a total flanking injection rate of 6 µL/min, the FITC stream had an average width of 264±22.1 µm inside the reaction chamber. For a chamber 2-mm wide, this stream width allowed 11 overlapping stream positions within the chamber. In addition, the control protocol was developed to achieve placement of the FITC stream in non-overlapping positions within the chamber without sweeping. It did so through temporarily increasing the injection rates by two orders of magnitude. Despite this, the stream width obtained was consistent with the sweep protocol´s stream width (262±19.8 µm). The ability of microfluidic devices to provide a suitable experimental model for the origins of life question is thus shown. Using the inherent advantages of microscale flow, the proposed device constitutes the first of many prototypes that aim to test different ramifications of the neighborhood selection hypothesis.