7-DoFs Rotation-Thrust Microrobotic Control for Low-Invasive Cell Pierce via Impedance Compensation

In the robot-aided biomedical field, although the cell pierce force may be decreased by sharpening injection needle and robotic control, the physical damage to the cell remains a big issue for low-invasive cell injection. This article proposes a 7-DoFs rotation-thrust (R-T) microrobotic control instead of the conventional straightforward thrust for smaller penetrated cell deformation and higher force stability, thus decreasing the physical damage to the cell. Considering fully, a beneficial resultant of shear as well as axial force based on a point-load cell model, a dynamic centering alignment strategy is designed for overcoming the eccentric fluctuation of the rotational conical micropipette. Furthermore, integrating with a shear force, a trapezoid-speed control based on impedance force compensation is developed to ensure the R-T force stability. The R-T pierce control is compared with the other two micromanipulations (straightforward and rotation) of the zebrafish embryos, respectively, under different linear velocities, rotation velocities, and cell maturities. The results validate that the proposed control is capable of diminishing the embryos' pierce deformation and force \sim30% and improving the force stability \sim70%. The pierced cell's activity is further proved by the fluorescent dye injection. This research provides a feasible way for low-invasive cell injection techniques.