Micromanipulation And Control Of Biological Cells By Using A Robot-Tweezers Cell Surgery System

Cell surgery has been extensively investigated because of its extensive applications in various physiological, pathological, and pharmacological processes. However, results are mostly limited to proof-of-concept demonstrations. Research progress on cell surgery has also been impeded by the lack of an effective and efficient cell surgery system that can precisely manipulate and control the position and orientation of single cells and can analyze large numbers of cells simultaneously to increase the precision, throughput, and reliability. In this thesis, a cell surgery system that integrates robotics and optical tweezers (OTs) is developed to enable the simultaneous manipulation of batches of cells and precise control of cell position and orientation, where OTs function as special end-effectors controlled robotically to trap and manipulation biological cells. This thesis is conducted on the basis of the following three perspectives.First, an autonomous control technology is developed to control cell position accurately. The control strategy ensures that trapped cells can stay within a small neighborhood around the centroid of the optical trap;thus, a stable optical trapping of cells can be achieved during cell manipulation. A simple saturated PID controller is developed on the basis of the dynamic equation of optically trapped cells for the asymptotic regulation of cell position without requiring dynamic model parameters and cell velocity. Experimental results are presented to demonstrate the effectiveness of the proposed approach.Second, arraying cell groups into desired pairs automatically is also investigated by using holographic optical tweezers (HOTs) technology with the robot-tweezers cell manipulation system. The proposed cell pairing approach is based on artificial potential field functions and concentric circle concept. Specific potential field functions are defined to stimulate cells to the desired topology and prevent cell collisions with other obstacles. A potential field function-based controller is developed on the basis of the dynamic equation of optically trapped cells to induce multiple cell groups to multiple concentric circles for the pairing process. Pairing can be performed automatically by using the symmetry of a concentric circle, and the interdistance between any pair of two cells can be controlled on the basis of the concentric structure. Arraying yeast cell groups is experimentally examined to demonstrate the effectiveness of the proposed approach.Third, the dynamic modeling and control of multiple degrees of freedom (DOF) for cell rotation is investigated by using a controlled optical tweezers system. Two optical traps generated by robotically controlled HOTs are utilized to manipulate the cells for rotation. A general dynamic model of the trapped cell is established. In this model, cell rotational motion is considered. The relationship between the applied torques and spherical coordinates of the optical tweezers applied to cells is modeled and characterized by using a T-matrix approach. A visual tracking scheme is developed to calculate the angular velocity of cells. Feedback controllers are also established on the basis of the dynamic model of the rotated cell to perform in-plane and out-of-plane rotations of single cells. The rotation of single yeast cells are experimentally analyzed to illustrate the effectiveness of the proposed approach.In summary, the proposed robot-tweezers-based cell surgery control system provides a powerful tool for the precise control of cell position and orientation and numerous cell manipulation tasks. The autonomous cell position control system not only ensures a stable optical trapping but also acts as a vital step toward the development of cell position-based applications in cell surgery and related biomedical engineering techniques. The manipulation of arraying cell groups into desired pairs considerably improves the manipulation efficiency and measurement throughput. This study also reveals the functional mechanisms of intercellular and intracellular processes. The automated multi-DOF cell rotational control enables the full control of cell orientation, which is a basic and vital technique required by many cell surgical operations. This thesis may be used as a solid foundation for future investigations on physiological and pathological mechanisms at a single-cell level and for further advancements in cellular/subcellular-based target therapies in precision medicine.