Robotic Cell Rotation Based on the Minimum Rotation Force

In this paper, a robotic cell rotation method based on the minimum rotation force is presented to adjust oocyte orientation in biological applications. In this method, the minimum rotation force, which can control the rotation angle (RA) of the oocyte quantitatively and generate minimum oocyte deformations, is derived through a force analysis on the oocyte in rotation. To exert this force on the oocyte, the moving trajectories (MT) of the injection micropipette (IM), are determined using mechanical properties of the oocytes. Further, by moving the IM along the designed MT, the rotation force control is achieved. To verify the feasibility of this method, a robotic rotation experiment for batch porcine oocytes are performed. Experimental results demonstrate that this system rotates the oocyte a10t an average speed of 28.6s/cell and with a success rate of 93.3%. More importantly, this method can generate much less oocyte deformations during cell rotation process compared with the manual method, while the average control error of RA in each step is only 1.2° (versus averagely 8.3° in manual operation), which demonstrates that our method can effectively reduce cell deformations and improve control accuracy of the RA. Note to Practitioners - Using an IM to rotate the oocyte is the most popular method to adjust oocyte orientations in many cellular biological applications. To rotate the oocyte precisely and reduce mechanical damages to the oocyte, the rotation force exerted on the oocyte should be estimated and controlled precisely. However, it is a challenging task and has not been resolved well. This paper calculates the minimum rotation force through the force analysis on oocyte and uses it to improve control accuracy of the RA and limit the cell deformations. Using calibrated oocyte mechanical properties, the MT of the IM corresponding to the minimum rotation force is designed. Then, by moving the IM along designed MT, the rotation force control is achieved online. This method does not rely on the force sensors and is realized on traditional micro-operation systems. Coupled with previous works, this method is able to operate batch oocytes one by one. Therefore, it can easily be applied in biological applications and replace manual operations.