Application of Inertial Focusing Microfluidics to High Concentration Microalgal Dewatering

Microalgal harvesting is an area which introduces several issues for the widespread industrial application of algal biotechnology. This is due to the inherently high energy requirements of existing technology and limitations of their application caused by microalgal cells small size and dilute culture, making industrial application in a cost-effective manner challenging. Development of new technology is required to help combat the high costs associated with microalgal harvest, which currently accounts for the largest fraction of the total microalgal processing cost.

Inertial focusing microfluidics has been successfully applied to microalgal harvesting, predominantly utilising low concentration cultures, with few examples greater than 1x10^7 cells/ml, and with limited success when applied to small microalgal species (<10μm). High concentration processing using inertial focusing has introduced challenges in achieving successful, high recovery, separation due to particle interactions interfering with the focusing performance.

The focus of our work is the development of microfluidic systems as an alternative to existing downstream processing technologies for algae, through application to high concentration cultures and consideration into device scale-up and parallelisation. Utilising spiral inertial focusing devices we have successfully achieved high efficiency concentration of small microalgae, from culture concentrations less than 1% v/v to greater than 50% v/v, through modification of normal device operation. Through device stacking, we have also shown initial success in device scale-up with promising results for future larger scale device parallelisation and scale-up for eventual
industrial application.