NanoNewton Force Sensing and Control in Microrobotic Cell Manipulation

Cellular force sensing and control techniques are capable of enhancing the dexterity and reliability of microrobotic cell manipulation systems. This paper presents a vision-based cellular force sensing technique using a microfabricated elastic cell holding device and a sub-pixel visual tracking algorithm for resolving forces down to 3.7nN during microrobotic mouse embryo injection. The technique also experimentally proves useful for in situ differentiation of healthy mouse embryos from those with compromised developmental competence without the requirement of a separate mechanical characterization process. Concerning force-controlled microrobotic cell manipulation (pick-transport-place), this paper presents the first demonstration of nanoNewton force-controlled cell micrograsping using a MEMS-based microgripper with integrated two-axis force feedback. On-chip force sensors are used for detecting contact between the microgripper and cells to be manipulated (resolution: 38.5nN) and sensing gripping forces (resolution: 19.9nN) during force-controlled grasping. The experimental results demonstrate that the microgripper and the control system are capable of rapid contact detection and reliable force-controlled micrograsping to accommodate variations in size and stiffness of cells with a high reproducibility.