Fresnel lens optical fiber tweezers to evaluate the vitality of single algae cells

Dunaliella salina algae are trapped and studied using dual-fiber optical tweezers based on nano-imprinted Fresnel lenses. Different forms of cyclic motion of living algae inside the optical trap are observed and analyzed. A characteristic periodic motion in the 0–35 Hz frequency region reflects the algal flagella activity and is used to estimate the algal vitality, by photomovement. The trap stiffness and optical forces are measured for the case of a dead algal cell. It is shown that the dual-fiber optical tweezers can be used to study the vitality (or viability) property of single cells, a property that is essential and can be scaled up to other applications, such as sperm analysis for fertility tests.