Cooperative and mobile manipulation of multiple microscopic objects based on micro-hands and laser-stage control☆

Quang MinhTa, Chien Chern Cheah

While various techniques have been developed for manipulation of biological cells or micro-objects using optical tweezers, the performance and feasibility of these techniques are mostly dependent on the physical properties of the target objects to be manipulated. In these existing techniques, direct trapping and manipulation of the manipulated objects using laser traps are performed, and therefore, existing techniques for optical manipulation are not capable of coordinating and manipulating various types of objects in the micro-world, including untrappable micro-objects, relatively large micro-objects, and laser sensitive biological cells. In this paper, a cooperative control technique is proposed for coordinative and mobile manipulation of multiple microscopic objects using micro-hands with multiple laser-driven fingertips and robot-assisted stage control. Several virtual micro-hands are formed by coordinating multiple optically trapped micro-particles that serve as the laser-driven fingertips, and then utilized for individual and coordinative manipulation of the target micro-objects. Simultaneously, global transportation of all the grasped target objects is performed by controlling the robot-assisted stage. While it is difficult to design multi-fingered hands in micro-scale due to scaling effect, this paper presents the first result on cooperative and mobile manipulation of multiple micro-objects using multiple micro-hands with laser-driven fingertips and robot-assisted stage control. In this paper, a primary study on repositioning strategy of the laser-driven fingertips is also introduced to allow the fingertips in a grasping formation to be repositioned. Rigorous mathematical formulations and solutions are derived to achieve the control objective, and experimental results are presented to demonstrate the effectiveness of the proposed control technique.

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Development of a collision-avoidance vector based control algorithm for automated in-vivo transportation of biological cells

Xiaojian Li, Shuxun Chen, Chichi Liu, Shuk Han Cheng, Yong Wang, Dong Sun

With the rapid development of precision medicine, the in-vivo manipulation of microparticles has attracted increased attention in recent years. Collision is a main cause of the failure of in-vivo particle transportation. In this paper, an automated control approach with obstacle avoidance function is proposed for in-vivo cell transportation. In the proposed approach, a collision-avoidance vector method is utilized to avoid obstacles during the transportation of the target cell. The proposed method integrates obstacle detection and collision avoidance into a single step, hence reducing the duration of online processing while enhancing the accuracy of obstacle detection. With the proposed approach, different collision avoidance strategies are designed to suit for different transportation environments. The proposed approach exhibits the advantages of reduced online calculation, fast response, high accuracy, and disturbance compensation. Experiments are performed to demonstrate the effectiveness of the proposed controller.

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A switching controller for high speed cell transportation by using a robot-aided optical tweezers system

Xiangpeng Li, Hao Yang, Haibo Huang, Dong Sun

Rapid and efficient cell manipulation is critical to many cellular operations at the single-cell resolution. In this paper, we propose a new approach for high speed manipulation of a single suspended cell using a robot-aided optical tweezers cell manipulation system. A switching geometrical model for achieving automatic cell trapping, maintenance of optical trapping, and obstacle avoidance is developed based on an objective of confining the trapped cell inside the high speed transfer region, which can help attain high speed cell transportation velocity. With the switching geometrical model, a controller for high speed cell transportation is proposed to transfer the target cell to the destination efficiently. Experiments of manipulating human leukemia cancer NB-4 cells to the specific testing area for property characterization are performed to demonstrate the effectiveness of the proposed approach.

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Stochastic control for optical manipulation of multiple microscopic objects

Quang Minh Ta, Chien Chern Cheah

While various control techniques have been developed for optical manipulation, the Brownian movement of microscopic objects in the medium is usually ignored for simplicity of analyzing the control systems. Nevertheless, due to the universality of the Brownian movement and its effect on optical manipulation of cells or micro-objects, it is required for the Brownian effect to be properly taken into consideration so as to ensure the stability and performance of the control systems. In this paper, we derive a stochastic control technique to achieve a theoretical framework for optical manipulation of multiple microscopic objects in the presence of the Brownian perturbations. In the proposed control methodology, a region control technique and a dynamic interaction approach are developed for collision-free manipulation of the target micro-objects with random perturbations. All the target micro-objects are trapped and manipulated simultaneously while being kept inside the desired dynamic region, and at the same time, preserving a minimum distance with each other to avoid collisions. While a bounded tracking or region error exists in current control techniques for optical manipulation due to the effect of the Brownian perturbations, this paper provides a new approach which guarantees that all the target micro-objects are kept inside the desired region during the course of manipulation. Rigorous mathematical formulation has been developed for automated manipulation of multiple microscopic objects in the presence of the Brownian perturbations, and experimental results are presented to demonstrate the feasibility and effectiveness of the proposed control technique.

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Grasping and manipulation of a micro-particle using multiple optical traps

Chien Chern Cheah, Quang Minh Ta, Reza Haghighi
In existing control techniques for optical tweezers, a target particle is directly trapped and manipulated by a single laser beam. However, a typical force generated by an optical trap is extremely small (on the order of piconewtons) and thus it is not sufficient to manipulate a large cell or object. Besides, the feasibility of optical manipulation also depends on the physical properties of the specimen. An opaque object or object with the same refractive index as the fluid media may not be trapped directly by the laser beam. Therefore, current control techniques for optical tweezers cannot be utilized to manipulate various types of cells or objects, including untrappable or large ones. In this paper, robotic control techniques are developed for optical tweezers to achieve grasping and manipulation of a microscopic particle, which is beyond the capability of a single optical trap. First, multiple laser beams are generated, and each laser beam is utilized to trap and drive one grasping particle to form a desired shape around the target particle. A grasping formation of trapped particles is thus generated to hold the target particle. Then the target particle is manipulated to a desired position by controlling the motorized stage. The proposed control strategy is particularly suitable for manipulation of large particles, or even untrappable cells or objects. Rigorous mathematical formulations have been developed to analyze the control system for grasping and manipulation of the microscopic particle. Experimental results are presented to illustrate the performance of the proposed grasping and manipulation techniques.

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Design of a robust unified controller for cell manipulation with a robot-aided optical tweezers system

Xiangpeng Li, Hao Yang, Jianjun Wang, Dong Sun

With the advantages of non-physical contact, high precision, and efficiency, optical tweezers have been increasingly used to manipulate biological cells in various biomedical applications. When trapping a cell with optical tweezers, the cell must be located within the optical trap. The lack of an efficient control technique that can automatically control cell motion while consistently locating such cell within the optical trap causes the trapped cell to escape easily, thus resulting in the failure of the manipulation task. Therefore, the development of a unified controller that can manipulate both cell trapping and cell motion simultaneously while possessing robustness to environmental disturbances is urgently needed. In this paper, we develop a novel unified controller that manipulates cell positioning and cell trapping simultaneously. First, we establish a geometric model to confine the cell within a local region around the optical trap. The connection between the cell and the optical tweezers is formulated by using the concept of cell–tweezers (C–T) coalition. Second, we develop a controller based on a defined potential field function to drive the C–T coalition to the desired state while avoiding collisions with other obstacles in the environment. Finally, we perform experiments of transferring yeast cells to demonstrate the effectiveness of the proposed approach.

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Dynamic trapping and manipulation of biological cells with optical tweezers

Xiang Li, Chien Chern Cheah, Songyu Hu, Dong Sun
Current control techniques for optical tweezers work only when the cell is located in a small neighbourhood around the centroid of the focused light beam. Therefore, the optical trapping fails when the cell is initially located far away from the laser beam or escapes from the optical trap during manipulation. In addition, the position of the laser beam is treated as the control input in existing optical tweezers systems and an open-loop controller is designed to move the laser source. In this paper, we propose a new robotic manipulation technique for optical tweezers that integrates automatic trapping and manipulation of biological cells into a single method. Instead of using open-loop control of the position of laser source as assumed in the literature, a closed-loop dynamic control method is formulated and solved in this paper. We provide a theoretical framework that bridges the gap between traditional robotic manipulation techniques and optical manipulation techniques of cells. The proposed controller allows the transition from trapping to manipulation without any hard switching from one controller to another. Simulation and experimental results are presented to illustrate the performance of the proposed controller.
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