Measurement of mechanical properties of living cells using micro fingers and AFM cantilevers

A measurement system of mechanical properties of living cells using a 3-DOF micro finger with high accuracy and a micro force sensor based on AFM (Atomic Force Microscope) principle has been developed. Using this system, we measure the stiffness of human leukocyte and yeast cell. The micro finger is controlled by teleoperation under an optical microscope. The AFM cantilever is placed within the microscopic field. The micro finger approaches a target cell and holds it firmly using capillary phenomenon. Then the finger moves the cell to the AFM cantilever and presses it against the cantilever tip. Thus force is applied to the cell, and the cell is deformed. This pressing force is calculated from the measured defection of the cantilever tip. The deformation of the cell is obtained as the difference between the deflection of the cantilever tip and the moving distance of the micro finger tip. As a result we can obtain the force-deformation curve of the target cell; this curve represents its stiffness.