Efficient AFM-Based Nanoparticle Manipulation Via Sequential Parallel Pushing

Atomic force microscopes (AFMs) have become a useful tool not only for imaging at the nanoscale resolution, but also a useful tool for manipulating nanoscale objects in nanoscale device prototyping and for studying molecular and cellular mechanisms in biology. This paper presents a method, called sequential parallel pushing (SPP), for efficient and automated nanoparticle manipulation. Instead of using tip scanning to fully locate the particle center, this method uses one scan line perpendicular to the pushing direction to determine the lateral coordinate of the particle center. The longitudinal position of the particle is inferred from the position where the tip loses contact with the particle through real-time analysis of vibration amplitude of the cantilever. The particle is then pushed from the determined lateral position along the current push direction toward the baseline of the target. This process is iterated until the particle reaches the target position. Experimental results show that the SPP algorithm, when compared with simple target-oriented pushing algorithms, not only reduces the number of scan lines but also decreases the number of pushing iterations. Consequently, the manipulation time has been decreased up to four times in some cases. The SPP method has been successfully applied to fabricate designed nanoscale patterns that are made of gold (10
$ \sim$
15 nm diameter) particles and of 170 latex 50-nm diameter) particles.