Visual-Based Impedance Control of Out-of-Plane Cell Injection Systems

In this paper, a vision-based impedance control algorithm is proposed to regulate the cell injection force, based on dynamic modeling conducted on a laboratory test-bed cell injection system. The injection force is initially calibrated to derive the relationship between the force and the cell deformation utilizing a cell membrane point-load model. To increase the success rate of injection, the injector is positioned out of the focal plane of the camera, used to obtain visual feedback for the injection process. In this out-of-plane injection process, the total cell membrane deformation is estimated, based on the X - Y coordinate frame deformation of the cell, as measured with a microscope, and the known angle between the injector and the X - Y plane. Further, a relationship between the injection force and the injector displacement of the cell membrane, as observed with the camera, is derived. Based on this visual force estimation scheme, an impedance control algorithm is developed. Experimental results of the proposed injection method are given which validate the approach. Note to Practitioners-In biological cell injection, the control of injection forces is important since excessive manipulation force may destroy the membrane or tissue of the biological cell, and lead to failure of the biomanipulation task. Although the injection force is a very important factor that affects the survivability of the injected cells, research on minimally invasive cell injection, based on understanding of the mechanical properties of the cellular membrane, are rare. To resolve this problem, a methodology is presented here to regulate cell injection forces using geometry of cell deformations and micro vision feedback. With the visually measured injection force applied to an injected cell, an impedance control strategy is then developed to regulate the cell injection force through the desired impedance. One advantage of using the impedance control in micromanipulation is that tiny forces exerted on the cell membrane can be reflected in the control system by adjusting the controller impedance coefficients.