Large-range high-speed dynamic-mode atomic force microscope imaging: adaptive tapping towards minimal force.

This paper presents a software-hardware integrated approach to high-speed large-range dynamic mode imaging of atomic force microscope (AFM). High speed AFM imaging is needed to interrogate dynamic processes at nanoscale such as cellular interactions and polymer crystallization process. High-speed dynamic-modes such as tapping-mode AFM imaging is challenging as the probe tapping motion is sensitive to the highly nonlinear probe-sample interaction during the imaging process. The existing hardware-based approach via bandwidth enlargement, however, results in a substantially reduction of imaging area that can be covered. Contrarily, control (algorithm)-based approach, for example, the recently developed adaptive multiloop mode (AMLM) technique, has demonstrated its efficacy in increasing the tapping-mode imaging speed without loss of imaging size. Further improvement, however, has been limited by the hardware bandwidth and online signal processing speed and computation complexity.Thus, in this paper, the AMLM technique is further enhanced to optimize the probe tapping regulation and integrated with a field programmable gate array (FPGA) platform to further increase the imaging speed without loss of imaging quality and range. Experimental implementation of the proposed approach demonstrates that the high-quality imaging can be achieved at a high-speed scanning rate of 100 Hz and higher, and over a large imaging area of over 20 µm. .