Design and fabrication of a fully-compliant mechanism for control of cellular injection arrays

This paper reports on the design, fabrication, and testing of a fully-compliant mechanism designed for precise parallel guidance. The mechanism is designed to guide arrays of micro-scale needles for straight-line injections of thousands of culture cells simultaneously. During injection, the needle array is to be lowered into the cell culture dish. It must be guided carefully during insertion of the needles into the cells because any rotation or transverse motion of the needles during insertion can lead to tearing of the delicate cell membranes, leading to cell death. The injection system consists of a fully-compliant mechanism designed for straight-line motion, while resisting motions in other direction. Successive prototypes are shown to illustrate the process of design, and to illustrate the benefits of the final system. Prototypes were demonstrated using deep reactive ion etching of silicon wafers, as well as rapid prototyping using a three-dimensional printer in ABS polymer. The final system consists of a single, 3-D-printed part that incorporates compliance to guide the needle array over a distance of about 1.5 mm while restraining transverse deflections or rotations. Testing shows that injections performed using the system result in high cell viability, suggesting that the system appropriately restrains off-axis motions. While the system demonstrated here is designed specifically for biological research, it may be adapted to manufacturing, position control, or any other application requiring straight-line motion while minimizing transverse deflections or rotations.