title: Iterative control approach to high-speed force-distance curve measurement using AFM: time-dependent response of PDMS example.
abstract: Force-distance curve measurements using atomic force microscope (AFM) has been widely used in a broad range of areas. However, currently force-curve measurements are hampered the its low speed of AFM. In this article, a novel inversion-based iterative control technique is proposed to dramatically increase the speed of force-curve measurements. Experimental results are presented to show that by using the proposed control technique, the speed of force-curve measurements can be increased by over 80 times--with no loss of spatial resolution--on a commercial AFM platform and with a standard cantilever. High-speed force curve measurements using this control technique are utilized to quantitatively study the time-dependent elastic modulus of poly(dimethylsiloxane) (PDMS). The force-curves employ a broad spectrum of push-in (load) rates, spanning two-order differences. The elastic modulus measured at low-speed compares well with the value obtained from dynamic mechanical analysis (DMA) test, and the value of the elastic modulus increases as the push-in rate increases, signifying that a faster external deformation rate transitions the viscoelastic response of PDMS from that of a rubbery material toward a glassy one.
authors.affiliation: Mechanical Engineering Department, Iowa State University, Ames, IA 50011, USA. kyongsoo@iastate.edu
authors.forename: Kyong-Soo
authors.initials: KS
authors.lastname: Kim
authors.forename: Zhiqun
authors.initials: Z
authors.lastname: Lin
authors.forename: Pranav
authors.initials: P
authors.lastname: Shrotriya
authors.forename: Sriram
authors.initials: S
authors.lastname: Sundararajan
authors.forename: Qingze
authors.initials: Q
authors.lastname: Zou