Optical tweezers have received significant attention in the past few decades and many techniques have been proposed to achieve assorted manipulation tasks on cells or micro-objects. While traditional techniques for optical tweezers utilize laser beams for direct trapping and manipulation of cells, several approaches have also been proposed to achieve grasping and manipulation of cells. Most grasping approaches, however, have failed to solve the existing difficulties in the grasping process of cells due to limited sensing capability and presence of Brownian perturbation in the micro world. In this paper, a novel human-assisted grasping technique for manipulation of biological cells is proposed to facilitate the grasping process of biological cells. In the proposed technique, several microbeads are first trapped and used as fingertips to perform a grasping task on a biological cell. Based on human observation, the positions of the laser beams that trap the microbeads are remotely and simultaneously controlled through a touchscreen, and thus generating a grasping formation of the trapped microbeads to grasp the cell. After the cell has been grasped, a simple region control technique is utilized for automated manipulation of the grasped cell. This paper offers a flexible, reliable and efficient approach for grasping and manipulation of biological cells, and thus extending the feasible applications of optical tweezers. The stability of the control system for manipulation of the grasped cell is investigated by using a Lyapunov approach, and the feasibility of the proposed human-assisted grasping and manipulation technique is demonstrated by experiment result.

In this paper, we propose a shared control approach for optical manipulation of biological cells. A robotic control methodology is developed that allows association between human and an autonomous optical cell manipulation system. Human, when applicable or necessary, is able to associate with an autonomous cell manipulation system in a stable manner, and thus guiding the system to perform the operation task effectively. While current optical cell manipulation systems are only capable of performing either autonomous task or manual operation, the proposed approach offers an opportunity for human to associate with an autonomous optical cell manipulation system, when applicable or necessary, so as to deal with complex operation tasks. The stability of the shared control system is analyzed with a Lyapunov-like method, and the effectiveness of the proposed approach is validated with experimental results.

This paper proposes an autonomous grasping technique for micro-objects using flexible micro-hands. In this control technique, a micro-hand is constructed by several fingertips which are optically trapped and actuated by using laser beams. As the fingertips are driven towards a transformable area specified around a target micro-object, a grasping configuration of fingertips is thus formed to grasp the object. In this control technique, the effect of the Brownian perturbations on maneuvering of the micro-hand is considered so as to gain insight into the real nature of micro-manipulation using optical tweezers. The stability of the control system for autonomous grasping using flexible micro-hands is investigated with a stochastic analysis, and experimental illustration is presented to demonstrate the effectiveness of the proposed control technique.

The effect of Brownian motion on maneuvering of micro-objects in a fluid medium is one of the fundamental differences between micro-manipulation and robotic manipulators in the physical world. Besides, due to the limitation of feasible sensors and actuators in micro-manipulation, current control techniques for manipulation of micro-objects or cells are mostly dependent on the physical properties of target micro-objects or cells. In this paper, we propose the first stochastic control technique to achieve simultaneous orientation and transportation of micro-objects with Brownian perturbations. Several micro-particles which are optically trapped and driven by laser beams are utilized as fingertips to first grasp a target micro-object. Cooperative control of robot-assisted stage and the fingertips is then performed to achieve the control objective, in which the target micro-object is transported toward a desired position by using the robot-assisted stage, and at the same time, it is oriented toward a desired angular position by using the fingertips. This paper provides a stochastic control framework for simultaneous orientation and transportation of micro-objects with arbitrary types in the micro-world, and thus bringing micro-manipulation using optical tweezers closer to robotic manipulation in the physical world. Rigorous mathematical formulation and stability analysis for simultaneous orientation and positioning feedback control of micro-objects in the presence of the stochastic perturbations are derived, and experimental results are also presented.

Existing control systems for optical manipulation of multiple micro-objects do not allow users to interact with the systems during manipulation to deal with unexpected events, while ensuring stability of the overall control systems. In this paper, we propose a robotic control technique for human-guided optical manipulation of multiple micro-objects using robotic tweezers. Humans, when necessary, are able to interact or intervene with an automated optical manipulation system in a stable manner, and thus guiding a group of micro-objects to be manipulated towards a desired region while ensuring collision avoidance during manipulation. Both the ability of humans, in term of decision making, when needed, and the advantages of an automated optical manipulation system which provides precise and productive manipulation of micro-objects, are consolidated into one single technique. A theoretical foundation is developed and investigated to achieve the control objective. Experimental results are presented to illustrate the effectiveness of the proposed control technique.

Existing control techniques for optical trapping of cells or micro-objects can only perform either positioning control or separate control of orientation and position in a sequential manner. In this paper, we propose a robotic control technique to achieve simultaneous orientation and positioning control of a microscopic object using multiple laser-driven fingertips and robotic motorized stage control. Several optically trapped micro-particles are first utilized as the laser-driven fingertips to grasp a target micro-object. Simultaneous control of the laser-driven fingertips and the robotic motorized stage is then performed to achieve the control objective, in which the target object is oriented to a desired angular position by controlling the laser-driven fingertips, and at the same time, it is manipulated to follow a desired trajectory by maneuvering the robotic stage. Rigorous mathematical formulation and solution are developed for simultaneous orientation and positioning control of a micro-object using optical tweezers.

Current control techniques for optical manipulation of multiple micro-objects employ laser tweezers to directly trap and manipulate the target microscopic objects, and thus it is not capable of coordinating and manipulating micro-objects with arbitrary types in the micro-world, including large micro-objects, laser sensitive biological cells, or optically untrappable ones. In this paper, we propose a robotic control technique for optical manipulation of multiple microscopic objects by using micro-hands with multiple fingertips. In this control technique, several micro-hands are first formed by coordinating multiple optically trapped micro-particles that serve as the laser-driven fingertips, and then utilized for grasping and coordinative manipulation of multiple micro-objects. The proposed technique offers a robotic control framework for coordination and optical manipulation of multiple microscopic objects with arbitrary types in the micro-world, including large micro-objects, lasersensitive cells, or even untrappable microscopic objects.

In existing control techniques for optical manipulation, the effect of the Brownian motion is usually disregarded for ease of analyzing the control systems. However, due to the prevalence of the Brownian motion and its effect on micro-manipulation of tiny objects, it is important for the Brownian effect to be properly taken into account so as to ensure the performance and stability of the control systems. This paper proposes a robotic control technique to achieve automated manipulation of multiple microscopic objects with the consideration of the Brownian perturbations. In this control technique, a desired dynamic region is first initiated to enclose all the trapped micro-objects. The trapped objects are then manipulated as a whole while being kept inside the desired region, and at the same time, avoiding collisions between each other during the course of manipulation. Rigorous mathematical formulation is developed to analyze the control system for automated manipulation of multiple micro-objects with stochastic perturbations. Experimental results are presented to illustrate the performance of the proposed control technique.

Various automatic manipulation techniques have been developed for manipulating micro-objects using optical tweezers. Because of the small trapping force of optical traps and increase in kinetic energy during manipulation, a trapped object may not remain trappable, especially in the presence of random Brownian perturbation. However, there is no theoretical analysis so far to help understand the effects of dynamic motion and Brownian forces on the trappability problem of optical tweezers. This paper investigates the optical manipulation of micro-objects under random perturbations. Here, we provide for the first time a theoretical and experimental analysis of the dynamic trapping problem from stochastic perspectives. We derive the relationship between trapping probability and maximum manipulation velocity. A controller with appropriate velocity bound is then proposed to ensure that the system is bound and stable. The experimental results confirm the accuracy of our theoretical analysis and illustrate the necessity and usefulness of the proposed controller.

Existing control techniques for optical tweezers utilize a single focused laser beam to directly trap and manipulate a target cell. However, a typical force generated by an optical trap is extremely small (few pico-newtons) and therefore it is not sufficient to manipulate a larger cell or object. The optical trap is also sensitive to the shape of the biological cell and the refractive index. Therefore, current automatic control techniques for optical tweezers cannot be used to manipulate a large cell or cell with irregular shape. In addition, excessive irradiation of the laser beam to the cell may also cause photodamage of even lead to death of the cell. In this paper, we propose a robotic control technique for optical tweezers to achieve automated manipulation of cell, which is beyond the capability of a single optical trap. First, multiple laser beams are generated, and each laser beam is used to trap one micro-particle to create a formation around the target cell to hold it. Then the target cell is manipulated to a desired position by controlling the motorized stage. The proposed control technique is particularly suitable for automated manipulation of sensitive biological cells, cells with large size or cells of irregular shape. Rigorous mathematical formulations have been developed to analyze the control system for automated cell manipulation. Experimental results are presented to illustrate the performance of the proposed controller.