In most manipulation techniques for optical tweezers, open-loop controllers are developed to move the laser source without consideration of the dynamic interaction between the cell and the manipulator of laser source. This paper presents a simple PD control scheme for manipulation of cell using optical tweezers. We formulate a closed-loop setpoint control problem for optical tweezers and show that simple control law is effective for closed-loop manipulation, taking into consideration of the dynamic interaction between the laser beam and the cell. The use of closed-loop feedback control helps to enhance the trapping and also reduces the possibility of photodamage. The setpoint controller is also extended to a region reaching controller, where the desired objective is generalised to a region. Though the overall dynamics that involves the interaction between the cell and the manipulator is a fourth-order system, the proposed controllers do not require the use of acceleration and its derivative or the construction of any observer. Experimental results are presented to illustrate the performance of the proposed controllers.

ASTAR (Agency for Sci., Tech. and Research, S’pore)