Cell out-of-plane rotation control using a cell surgery robotic system equipped with optical tweezers manipulators

Single cell surgery has been gaining increasing attention due to its extensive applications in physiological and pathological of cell research. Orientation control of biological cell is a basic and vital technique required in cell surgery procedures. By adjusting the orientation of the cell appropriately, the components and sites of interest can be captured by a microscope, such that further analysis, diagnosis, extraction and treatment can be performed. Cell rotation reduces the potential unwanted damage to components of cell during cell surgery. Currently, orientation control of biological cells is typically carried out with manual operations. With ongoing trend towards automated manipulation, a framework that can automate the multi-axis rotation of suspended biological cells is urgently needed. In this paper, we utilize two optical traps, generated by robotically controlled holographic optical tweezers (HOT), as two special manipulators to manipulate the cell for out of image plane rotation. By utilizing the T-matrix approach and experimental calibration, the relationship between the relative vertical height of the optical traps and the rotational angle is characterized. A visual feedback controller is further developed to rotate the cell to the pre-determined orientation accurately. Experiments are performed to demonstrate the effectiveness of the proposed approach.