Force-feedback High-speed Atomic Force Microscope

High-speed atomic force microscopy (HSAFM) has enabled researchers to view the nanometer-scale dynamic behavior of individual biological and bio-relevant molecules at a molecular-level resolution under physiologically relevant time scales, which is the realization of a dream in life sciences. These high-speed imaging applications now extend to the cellular/bacterial systems with the use of a smaller cantilever. By reducing the sizes of the HSAFM cantilevers by a factor of ten, systems have demonstrated image speeds up to 0.1 frames per second for larger biological systems such as bacteria. However, this imaging speed is insufficient to understand many rapid large-scale biological phenomena. In this chapter, a newly developed novel HSAFM using force-feedback is introduced and discussed. This HSAFM is based on a newly developed force microscope called cantilever-based optical interfacial force microscope (COIFM). The COIFM system was originally developed to avoid snap-to-contact problem associated with conventional AFM in measuring normal and frictional forces as a function of distance between a probe and a sample. The HSAFM has been recently applied to the high-speed imaging of biological structures and to the mechanical property imaging of soft sample surfaces. This system has demonstrated topographic imaging capabilities with the imaging of Escherichia coli biofilm and planktonic cell structures. It also has the capacity to investigate the mechanical properties of soft materials while still avoiding the double-spring effect. The force-feedback HSAFM was shown to be stable for various speeds up to 5 frames per second in imaging softer adhesive biological samples. The system still uses a conventional-size self-actuation cantilever rather than using a smaller cantilever, thus avoiding arduous fabrication and signal detection with a smaller laser spot size associated with the use of a smaller cantilever. This novel force-feedback HSAFM will contribute greatly to the studies of large-scale biological phenomena.  1 To whom correspondence should be addressed. Email: [email protected]. No part of this digital document may be reproduced, stored in a retrieval system or transmitted commercially in any form or by any means. The publisher has taken reasonable care in the preparation of this digital document, but makes no expressed or implied warranty of any kind and assumes no responsibility for any errors or omissions. No liability is assumed for incidental or consequential damages in connection with or arising out of information contained herein. This digital document is sold with the clear understanding that the publisher is not engaged in rendering legal, medical or any other professional services. Byung I. Kim and Ryan D. Boehm 108