Robotic cell manipulation using optical tweezers with limited FOV

Microscopic optics and cameras are commonly used in micromanipulation or biomanipulation workstations since they provide a large spectrum of visual details and information. The visual feedback information also improves robustness to uncertainty and accuracy of micromanipulation. Among various micromanipulation systems, optical tweezers are one of the most useful instruments that utilize a focused beam of light to manipulate biological cell or nanoparticles without physical contact. However, current optical manipulation techniques fail if the laser beam is not within the field of view (FOV) of the microscope. To solve this problem, we present a robotic control technique for optical manipulation with limited FOV of microscope. The proposed control strategy consists of a vision based control that manipulates the trapped cell to move to a desired position inside the FOV and a Cartesian-space feedback control that drives the laser beam back when it is outside the FOV. Thus, the proposed method allows the laser beam to leave the FOV during the course of manipulation and the transition from one feedback to another is smooth. The stability of the closed-loop system is analysed by using Lyapunov-like methods, with consideration of the dynamic interaction between the cell and the manipulator of the laser source. Experimental results are presented to illustrate the performance of the proposed method.