A microfluidic concentrator for cyanobacteria harvesting

Article history: Received 25 September 2016 Received in revised form 22 March 2017 Accepted 23 March 2017 Available online xxxx The dilute conditions under which microalgae suspensions are cultured have negatively impacted economical routes for cell harvesting using conventional approaches. A promising alternative has arisen, for which a microfluidic concentration approach has been developed for harvesting Cyanobacterium Synechocystis sp. PCC 6803. This method uses passive hydrodynamic forces that include inertial focusing and Dean flow, and has a number of advantages over existing methods for concentrating dilute suspensions of microalgae; the method is truly passive, and does not require additional reagents, or external fields or electronics. After injecting a cyanobacteria suspension into an optimized microchannel configuration at a pre-determined flow rate, intrinsic inertial forces generated from the structure and geometry of the microfluidic network move the cyanobacteria laterally toward a known equilibrium position in the channel cross-section. Once focused, the cyanobacteria stream can be readily separated from culture medium to obtain a concentrated product. The system design andmaterials used in the new device are chosen with an eye toward low-cost, large-scale commercial manufacture. The operating parameters for inertial focusing of the cyanobacteria suspension have been optimized to achieve high-throughput and high-efficiency harvesting. The maximum recovery efficiency achieved in a single microchannel device is 98.4± 0.2% (mean± standard deviation). For those conditions, initial results yield a concentration factor of 3.28 for a single pass, which is 98.5% of themaximumpossible value for the current design. In addition, the calculated power consumption is less than or equal to that of tradition harvesting methods for a wide range of concentration factors. It is anticipated that this highly parallelizable, robust harvesting approach will prove to be economically feasible for concentrating microalgae/cyanobacteria at commercial scales. © 2017 Elsevier B.V. All rights reserved.