Thanks to the advancements in micro- and nanomechatronics techniques, the capability to inject foreign materials into target locations inside biosamples has become increasingly crucial. However, technical problems, like orientation and penetration, make manual microinjection challenging, while most available automated platforms are too targeted and often fail to support reconfiguration for different injection tasks. In this article, we first review the state-of-the-art in microinjection techniques for biomedical applications. Then, to solve the aforementioned problems, we report an autonomous omnidirectional microinjection (AOM) system based on effortless updates of manual injection hardware with experiments. Future perspectives on the system are outlined with the possibility of multiplying daily genetic screens and the potential of widespread usage in laboratories and clinics.

Objective: Zebrafish larva heart microinjection is a widely used technique in cardiac disease study. Compared with intensively researched rotation control of spherical or nearly spherical targets with clear structures, such as cells and embryos, 3-D rotation control of zebrafish larva demands new techniques due to its non-transparent structures and irregular outlines. Methods: In this paper, we present a vision-servo system to automate the rotation process of zebrafish larva body. A switched control strategy is adopted to rotate zebrafish larva about the optical axis by using two micropipettes. Precisely rolling about larva body is performed which involves a custom-designed rotational micromanipulator. A vision detection and online tracking algorithm is also developed to meet the requirement of visual servoing. With designed rotation control strategy, zebrafish larva heart can be adjusted to a desired orientation, which is often towards the injection pipette tip. Results: Experimental results show that the designed system is capable of achieving high success rate of 94% about z-axis rotation and 100% about x-axis with 50 trails. The system also performs an average speed of 44s/larva with a satisfied rotation accuracy of 0.5 in horizontal plane and 2.5 about its roll axis. Conclusion: The proposed strategy is effective in flexibly manipulating larvae in 3-D. Significance: The developed 3-D rotation control scheme is able to be applied to injection of various organs in zebrafish larva body for different experimental requirements.

This paper develops a model predictive control (MPC) framework to co-optimize switching sequences and control inputs for switched linear systems subject to persistent dwell-time (PDT) constraints. As a class of time constraints, PDT has been demonstrated to be more general and flexible than others like dwell-time or average dwell-time. Although time constraints are widely used in applications for safety and stability concerns, MPC of switched systems with time constraints often formulates a mixed- integer nonlinear program which cannot obtain the optimal solution in polynomial time, and thus suffers from the loss of recursive feasibility and stability. To address this problem, we propose several novel techniques: (i) the construction of the terminal sets based on two constraint admissible PDT contractive sets, (ii) the introduction of PDT and historical constraints, (iii) the use of two non-globally optimal solutions, and (iv) the prolonged prediction horizon. It is the first time that MPC approaches are applied to the co-optimization problem of switched systems under time constraints with guaranteed recursive feasibility and stability.

Precise rotational positioning of end-effectors under microscopy is crucial for robotic micromanipulation. However, the end-effector is presently limited to a fixed orientation, which is manually set before a given micromanipulation task, lacking accuracy and versatility of in situ reorientation. In this article, we present a unified framework for rotationally positioning the end-effector in three dimensions by establishing a general rotational model, developing a detection method within the limited field of view under microscopy, and designing a three-loop control strategy that adapts to different experimental requirements and model parameters. In experiments, a standard angled micropipette was used as the end-effector to verify the validity of the proposed methods. The performance was evaluated experimentally where the micropipette was robotically rotated to an arbitrarily desired orientation with an average orientation error less than $2^\circ$ . In the experiments of sperm manipulation, the in situ micropipette orientation control capability improved the success rate of sperm immobilization and achieved dexterous robotic sperm orientation for facile aspiration.

The zebrafish has been proven to be a significant model organism in various research fields. For investigating the in vivo properties of biologics within zebrafish with developed organs, an automated zebrafish larva organ injection system is crucially needed. However, current zebrafish larva manipulation techniques cannot accomplish this operation efficiently and continuously. Methods: In this paper, we present a novel zebrafish larva manipulation technique with two key steps in the microinjection system: orienting and aspirating zebrafish larvae automatically. The orientation control is realized in a customized microfluidic chip, after which the larva moves tailfirst until reaching the channel exit. Then a dynamic model of larva aspiration is established and an adaptive robust controller is designed. Results: Experimental results demonstrate that high success rate can be reached and damage to larva body is reduced. Conclusion: The presented strategy is capable of orienting and aspirating zebrafish larvae smoothly and efficiently. Significance: The proposed methods have the advantage of low cost, easy implementability and good stability.

Proper alignment of the end-effector is a critical procedure that determines the success of micromanipulation, such as robotic cell manipulation. Presently, end-effector alignment is performed manually and suffers from large misalignment error and inconsistency. Manual alignment often undesirably moves the end-effector (e.g., a glass micropipette) out of the limited field of view under microscopy and risks breaking the fragile end-effector. This article presents automated end-effector alignment in robotic micromanipulation. A rotational degree of freedom was added to a standard micromanipulator with translational degrees of freedom. The kinematic model of end-effector’s rotation was established, and the unknown model parameters were calibrated. To accommodate model uncertainty and parameter variations, a sliding mode controller was designed to achieve end-effector alignment. Experimental results demonstrate that the robotic alignment technique achieved an accuracy of 0.5 $\pm 0.3^{\circ }$ and a time cost of 17.9 $\pm$ 7.3 s, both significantly less than manual alignment. The developed controller based on kinematic modeling and sliding mode control achieved a higher success rate and significantly less time cost for end-effector alignment than the PID controller. Standard micropipettes were used as the end-effectors for sperm immobilization and oocyte penetration, important procedures in cell surgeries. The success rate of sperm immobilization was 98% by robotic micropipette alignment, higher than the success rate of 90% by manual alignment. Oocyte deformation before penetration was 28.1 $\pm$ 7.5 $\mu$ m by robotic end-effector alignment, significantly less than the deformation of 54.5 $\pm$ 13.2 $\mu$ m by manual alignment.