Microalgal Growth Assessment using Fluorinated Ethylene Propylene Microcapillaries

Efficient microalgal bioanalytical microsystems are becoming crucial to address the industrial, agricultural and environmental increasing demands. Most microalgae farming continues to depend on a significant amount of manpower in monitoring and measuring growth of microalgae in open ponds and/or photo-bioreactors. This requires specialized operators, regular sampling from open ponds or photo-bioreactors, and the use of in bulky laboratory equipment. In addition, many open ponds and water reservoirs are exposed to environmental factors such as temperature, nutrients or pH changes which may trigger algal blooms or cause difficulty in predicting microalgal growth, a critical challenge in the water industry.<br/>In this work we demonstrate the use of a melt-extruded fluorinated ethylene propylene (FEP) Teflon microfluidic film coated with PVOH as a hydrophilic “dip-stick” microcapillary for <i>in-situ</i> power-free sampling and optical monitoring of microalgal growth. We ascertained the growth of <i>Chlorella </i>for 22 days in the ‘dip stick’ microfluidic strips matched well the growth in an aerated Erlenmeyer, yielding a logistic growth with a growth rate of 0.35 day^-1 and similar to large industrial bioreactors, without the need of nutrient renewal. The optical transparency of the ‘dip stick’ strip combined with good permeability enabled simultaneous tracking of cell cycle and growth rate using simple image analysis, which can easily be carried out with a smartphone camera.<br/>Our new microanalytical solution enables micro-cultivation and individual cell monitoring over time, which may pave the way to innovative biocompatible materials for water management and also high throughput microalgal productivity assessment.