Planar Cell Orientation Control System Using a Rotating Electric Field

In this paper, an automated cell orientation control system is proposed to reorient suspended cells in the plane, about a single axis of rotation. The system consists of a vision system, which images the suspended cell, a software system which estimates the cell orientation angle, and a rotating electric field, applied to rotate the suspended cell. The angular coordinate of the cell is used as a feedback in a closed-loop system to reorient the cell, rotating it to its desired angle. The closed-loop feedback system permits the suspended cell orientation to track reference input signals. A microscale device, energized with sinusoidal voltages, is used to generate a rotating electric field. This device was designed and fabricated using MEMS fabrication techniques. A vision-tracking algorithm to image and estimate cell orientation in real time was designed and implemented, based on the circular Hough transform. The cell is driven to its desired orientation angle with a PID controller using the estimated cell rotation angle as a feedback. Experiments have been carried out which demonstrate that the cell orientation control system performs well. A variety of tests have been performed, including step response and trajectory following. Cell orientation control may be used as one step in the general process of orienting cells for cell surgery.