Automated manipulation of flexible nanowires with an atomic force microscope

Precise placement of individual nano scale objects is an essential requirement of nanodevices fabrication. Although the recently developed nanomanipulation technology based on Atomic force microscope (AFM) has realized automatic movement of rigid nanoparticles, it was not applicable to nanowires due to the complicated behaviors of flexible one-dimensional material. To improve the efficiency of nanowires manipulation, this work proposes a highly automated manipulation method. The new method allows automatic sample identification and manipulating vectors generation. Image processing techniques such as edge detection, filling and skeleton extraction are performed to identify the nanowires from the AFM images. Once a target position is assigned for the selected nanowire, a series of parallel pushing vectors (PPVs) are generated according to the translation and rotation strategies, which are simulated and optimized using the finite element method. Then the PPVs are continuously executed to transfer the nanowire to the target and make it in a straight shape. For multiple nanowires manipulation, a graph theory method is proposed to sort the movements of the objects. Because no intermediate scanning is needed, the time consumption of complex manipulation is greatly reduced. Experiments are carried out to verify the efficiency of the new method. The translating-rotating combined manipulation of a single silver nanowire proves the high accuracy of the proposed strategies. The successful assembly of two patterns, which are respectively formed by 12 carbon nanofibers and 50 silver nanowires, implies the reliability of the manipulation. Since the present method doesn't require additional hardware, it can be easily integrated to common AFMs.