Enhancement of microalgae growth using magnetic artificial cilia.

Microalgae have shown great potential as a source of biofuels, food, and other bioproducts. More recently, microfluidic devices have been employed in microalgae-related studies. However, at small fluid volumes, the options for controlling flow conditions are more limited and mixing becomes largely reliant on diffusion. In this study, we fabricated magnetic artificial cilia (MAC) and implemented them in millimeter scale culture wells and conducted growth experiments with Scenedesmus subspicatus while actuating the MAC in a rotating magnetic field to create flow and mixing. In addition, surface of MAC was made hydrophilic using plasma treatment and its effect on growth was compared with untreated, hydrophobic MAC. The experiments showed that the growth was enhanced by ten and two times with hydrophobic and hydrophilic MAC, respectively, compared with control groups which contain no MAC. This technique can be used to investigate mixing and flow in small sample volumes, and the enhancement in growth can be beneficial for the throughput of screening studies. Moreover, the methods used for creating and controlling MAC can be easily adopted in labs without microfabrication infrastructures, and they can be mastered by people with little prior experience in microfluidics.