LAUSR

Automated manipulation of single cells is required in both biological and clinical applications. In clinical infertility treatments, a single motile sperm is immobilized and inserted into an egg cell for in vitro fertilization. Sperm immobilization is essential to ease the ensuing pick-up procedure, and importantly, it prevents the sperm tail from beating inside the egg cell, which causes a lower fertilization rate. For immobilizing a motile sperm, the sperm tail must be accurately positioned and aligned with the manipulation tool (e.g., laser spot). Manual immobilization using laser ablation has stringent skill requirements, and is not able to accurately position the sperm tail to the center of the laser spot for immobilization. This letter presents a visual servo system that is capable of accurately positioning the tail of a motile sperm relative to the laser spot for automated sperm immobilization. A visual servo control strategy was developed to estimate and compensate for the motion of the sperm tail. Experimental results showed that the visual servo controller achieved a positioning accuracy of 1.7 $\mu$m, independent of sperm speed or swimming direction. By quantitatively evaluating the effect of laser energy on sperm immobilization, a consistent immobilization success rate of 100% was achieved (based on experiments on 900 sperms) with a throughput five times that of manual operation. Experimental results confirmed that this automated immobilization technique did not induce damage to sperm DNA.