Ultra-high throughput microfluidic concentrator for harvesting of Tetraselmis sp. (Chlorodendrophyceae, Chlorophyta)

Microalgae are of commercial interest for their ability to produce high-value compounds and their potential to be used as feedstock across numerous industries. The production of algal biomass and other algal-based products involves different upstream and downstream processing steps, including cultivation, harvesting, and extraction. In particular, the harvesting process involves the extraction of a condensed algal slurry from a watery growth medium. This process accounts for 20 to 30 % of the biomass production costs, creating technological and economic barriers. The conventional harvesting methods suffer from high costs, cross-contamination, and low yield. This study explores the use of a microfluidic technique, in particular, the rigid spiral microchannel, for ultra-high-throughput algae harvesting. We have designed a novel spiral channel that enables microalgae separation at high flow rates and spatial resolution, taking advantage of inertial microfluidic principles. The results from trials with surrogate microparticles and algal cells reveal that the microchannel has the potential to operate at 12 mL/min with separation efficiency >99 %. Our inertial microfluidic device operates at high flow rates as a single channel, can be multiplexed, and shows excellent potential for large-scale processing of microalgae cultures. In addition, the lower number of loops provides the system with reduced back pressure, making it more desirable for operation using a range of different pumps. Since the overall cost of microalgae dewatering is substantial at the industrial scale, the design and fabrication of low-cost devices are of great importance, similar to the one we have developed in this study.