Motility assessment of green biagellated microalgae in an optical trap using back focal plane interferometry

摘要

Green biagellated microalgae have proven to be of interest in biotechnology and biomedicine due to the productionof lipids, carotenoids, and other components that have an environment dependent yield. In this work, we useback focal plane interferometry to obtain information about the behavior of microalgae held by an optical trapunder dierent conditions. It has been observed that the elongated body of a microalga entering an optical trapwill align along the beam axis and rotate counter-clockwise. The rotation is produced by the beating agella,as we conclude from our observation of non-rotation of deagellated or photodamaged cells. The dependence ofrotation frequency on growth phase of the microalgae and on optical trapping power is investigated. To studythese eects, each cell is held in the optical trap, and the laser light transmitted by the sample is collectedwith a microscope objective. Then, the back focal plane of the collection objective is imaged onto a quadrantphotodiode. The voltage outputs of the photodiode are then recorded with a computer through the use of acustom Arduino circuit, and written to a text le for post-processing.