Design of a micro manipulation device for cell microinjection

Survival rate of the injected cells in microinjection is greatly affected by the injecting position on cells. Here, a PDMS-based microfluidic manipulation device for cell manipulation and position-selective microinjection is presented. The device has a fixed microneedle, and the cells in it are rotatable and movable, which are controlled by micro fluidic stream and dielectrophoretic (DEP) force. The cellular microinjection is designed to be accomplished by controlling the cell to move onto the stationary micro needle. The micro fluid ejected from microchannels is used to drive the cell to rotate so that the orientation of cell can be adjusted. The DEP force can drive cells in translational motion, which can be controllably tuned via adjusting the frequency of alternating current (AC) signal applied on the microelectrodes. The micro flow state and the variation of DEP force on cells with respect to frequency and solution conductivity are quantitatively analyzed. The distribution of microfluidic flow, DEP force and traveling-wave DEP force in this device are numerically simulated. The results show that the microflow is laminar flow, ensuring the cells move smoothly and steady in the micro channels. The optimal frequency ranges for drive cells upward and downward in vertical direction are around 10³–10⁵ and 10⁶–10⁷ Hz respectively when the conductivity equals 6.5 mS/m. The theoretical analysis and simulation suggest the position and orientation of the cells can be controllably adjusted in this manipulation device which provides a more flexible and low-cost approach for accomplishing the sophisticated microinjection process.