Stochastic Control for Orientation and Transportation of Microscopic Objects Using Multiple Optically Driven Robotic Fingertips

Quang Minh Ta; Chien Chern Cheah
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.

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In Vivo Manipulation of Single Biological Cells With an Optical Tweezers-Based Manipulator and a Disturbance Compensation Controller

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

In vivo manipulation of biological cells has attracted considerable attention in recent years. This process is particularly useful for precision medicine, such as cancer target therapy. Robotics technology is becoming necessary to stably and effectively manipulate and control single target cells in a complex in vivo environment. This paper presents a robot-aided optical tweezers-based manipulation technology that serves a function in the transport of single biological cells in vivo. An enhanced disturbance compensation controller is developed to minimize the effect of fluids (e.g., blood flow) on the cell. The method has exhibited advantages of flexibility in adjusting cell tracking trajectory online and the capability to minimize steady-state error and eliminate overshoot. Simulations and experiments of tracking single target cells in living zebrafish embryos have demonstrated the effectiveness of the proposed approach in a dynamic in vivo environment.

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Stochastic Dynamic Trapping in Robotic Manipulation of Micro-Objects Using Optical Tweezers

Xiao Yan; Chien Chern Cheah; Quang Minh Ta; Quang-Cuong Pham

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.

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Optical Manipulation of Multiple Groups of Microobjects Using Robotic Tweezers

Haghighi, R.; Cheah, C.C.

Micromanipulation has received increasing attention from robotics researchers due to its wide applications in the manipulation of microobjects like biological cells and Bio-MEMS components. The demand for accurate and precise manipulation of microobjects opens up new challenges in automation of micromanipulation tasks. In this paper, we present a concurrent framework for optical manipulation of multiple groups of microobjects using robotic tweezers. The proposed framework is based on laser-stage coordination control and consists of two concurrent subschemes: 1) local coordination achieved by asynchronous manipulation of multiple groups of microobjects using laser beams and 2) global coordination achieved by manipulation of whole groups using a motorized stage. Unlike existing methods that are limited to the manipulation of a single microobject or a single group of microobjects, the proposed method considers concurrent laser-stage coordination of multiple groups of microobjects, which enhances the capability and flexibility in micromanipulation tasks. In addition, we introduce a unified social interaction function to achieve various cellular behaviors. A mathematical formulation is provided and stability analysis is presented. Using the proposed method, we are able to manipulate multiple groups of microobjects to construct time-varying microformations. Experimental results are presented to illustrate the performance of the proposed method.

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Fabrication of an On-Chip Nanorobot Integrating Functional Nanomaterials for Single-Cell Punctures

Hayakawa, T.; Fukada, S.; Arai, F.

Cell manipulations and cell surgeries are key techniques in biotechnology today. Micro/nanorobots integrated on a microfluidic chip (on-chip robot) are a promising technology for cell manipulations and cell surgeries because of their operator skill independency and robustness for external environments. These features enable high-throughput cell manipulations and cell surgeries on a microfluidic chip. However, it is difficult to apply previous on-chip robots for small cells of order ≈ 10 bm μ m because the manipulation or surgery probes of those robots are a few micrometers in size. This size has been restricted by their fabrication, employing a standard mask lithography process. We fabricated on-chip robots of nanometer size by femtosecond laser exposure (nanorobots). The processing resolutions were 270 nm (linewidth) and 600 nm (thickness). Furthermore, our fabrication technique enabled the nanorobot to have a hybrid structure integrating functional nanomaterials (hybrid nanorobot). By integrating the various functional nanomaterials on the nanorobot, we can create a new function for the nanorobot. In this study, we fabricated a hybrid nanorobot with carbon nanotubes (CNTs) of high photothermal efficiency. We demonstrated a single-cell puncture with this nanorobot by irradiating the CNTs with an infrared laser and generating heat at that point. Additionally, we demonstrated an optical manipulation of the nanorobot that makes it possible to perform a cell puncture with high spatial flexibility and high positioning accuracy.

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Observer-Based Optical Manipulation of Biological Cells With Robotic Tweezers

Cheah, C.C. ; Li, X. ; Yan, X. ; Sun, D.

While several automatic manipulation techniques have recently been developed for optical tweezer systems, the measurement of the velocity of cell is required and the interaction between the cell and the manipulator of laser source is usually ignored in these formulations. Although the position of cell can be measured by using a camera, the velocity of cell is not measurable and usually estimated by differentiating the position of cell, which amplifies noises and may induce chattering of the system. In addition, it is also assumed in existing methods that the image Jacobian matrix from the Cartesian space to image space of the camera is exactly known. In the presence of estimation errors or variations of depth information between the camera and the cell, it is not certain whether the stability of the system could still be ensured. In this paper, vision-based observer techniques are proposed for optical manipulation to estimate the velocity of cell. Using the proposed observer techniques, tracking control strategies are developed to manipulate biological cells with different Reynolds numbers, which do not require camera calibration and measurement of the velocity of cell. The control methods are based on the dynamic formulation where the laser source is controlled by the closed-loop robotic manipulation technique. The stability is analyzed using Lyapunov-like analysis. Simulation and experimental results are presented to illustrate the performance of the proposed cell manipulation methods.

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Moving Groups of Microparticles Into Array With a Robot–Tweezers Manipulation System

Haoyao Chen, Dong Sun
Significant demand for both accuracy and productivity in batch manipulation of microparticles highlights the need to develop an automatic arraying approach to placing groups of particles into a predefined array with right pairs. This paper presents our latest effort to achieve this objective using integrated robotics and holographic optical tweezers technologies, where holographic optical tweezers function as special robot end-effectors to manipulate the microparticles. Based on the physical dynamics of trapping, a potential-field-based controller is developed to drive every pair of particles to the assigned array, while preventing collisions between particles. The significance of the proposed controller lies in the capability of driving two groups of particles into a common array in right pair and controlling the interdistances between the particles in pairs. Experiments are performed to demonstrate the effectiveness of the proposed approach.

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