Adaptable end effector for atomic force microscopy based nanomanipulation

Nanomanipulation using the atomic force microscope (AFM) has been extensively investigated for many years. But the efficiency and accuracy of AFM-based nanomanipulation are still major issues due to the nonlinearities and uncertainties in nanomanipulation operations. The deformation of the cantilever caused by manipulation force is one of the most major nonlinearities and uncertainties. It causes difficulties in accurately controlling the tip position, and results in missing the position of the object. The softness of the conventional cantilevers also causes the failure of manipulation of sticky nano-objects because the tip can easily slip over the nano-objects. In this paper, an active atomic force microscopy probe is used as an adaptable end effector to solve these problems by actively controlling the cantilever's flexibility or rigidity during nanomanipulation. A control voltage is applied to the piezo layer of the adaptable end effector to exert a reverse bending moment on the cantilever to balance the bending moment caused by the interaction force during manipulation. Thus, the adaptable end effector is controlled to maintain straight shape during manipulation. A detailed model of the adaptable end effector is presented in the paper. Control of the adaptable end effector employing an optimal LQR control law is derived and implemented. The experimental results verify the validity of the model and effectiveness of the controller. The nanomanipulation results also prove the increased efficiency of AFM-based nanomanipulation using the adaptable end effector.