Quantitative microinjection on the picoliter scale based on the gas-liquid interface positioning control

As an effective approach to manipulate intracellular material exchange, such as injection of transgenic solutions or donor cells into receptor cells, microinjection possesses the incomparable advantage of introducing precisely defined amounts of substances into the cytoplasm without altering other components of the cell. Accurate quantification is generally obtained by calibrating the relationship between the injection volume and injection pressure in advance. Shift in the injection pressure and difference of the initial condition causes large deviation of the results. This paper presents a control method that can achieve the required injection volume with fast speed and high stability based on the flow characteristics of fluids inside a micropipette. First, a targeted control strategy has been brought up to resolve the problem of difficulty in microfluid dynamics modeling and instability of conventional control methods in settling this issue. Next, gray moment operators are employed to locate target edge to subpixel values in order to obtain higher precision of the injection volume. At last, the proposed method is applied to the automated transgenic injection tasks. Regulating time is approximately from 6 to 12 seconds, control accuracy of the injection volume is 0.0182 picoliter, and average operating speed is 1.5 cells/min.