Pulse-response measurement of frequency-resolved water dynamics on a hydrophilic surface using a Q-damped atomic force microscopy cantilever.

Masami Kageshima

doi:10.3762/bjnano.3.29

Abstract

The frequency-resolved viscoelasticity of a hydration layer on a mica surface was studied by pulse-response measurement of a magnetically driven atomic force microscopy cantilever. Resonant ringing of the cantilever due to its 1st and 2nd resonance modes was suppressed by means of the Q-control technique. The Fourier–Laplace transform of the deflection signal of the cantilever gave the frequency-resolved complex compliance of the cantilever–sample system. The significant viscoelasticity spectrum of the hydration layer was successfully derived in a frequency range below 100 kHz by comparison of data obtained at a distance of 300 nm from the substrate with those taken in the proximity of the substrate. A positive value of the real part of the stiffness was determined and is attributed to the reported solidification of the hydration layers.

Highlights

Liquid solvation is a phenomenon common to a large variety of liquid–solid interfaces [1]
Among the new experimental methods developed in the last few decades, atomic force microscopy (AFM), which was originally invented as an imaging method, has manifested its potential as a site-specific profiling tool of force interaction
It should be noted that, in addition to its high spatial resolution, AFM possesses a distinguished aptitude for dynamical measurements, which is Beilstein J

Summary

Introduction

Liquid solvation is a phenomenon common to a large variety of liquid–solid interfaces [1]. Using the method of exciting the AFM cantilever with a wellcharacterized magnetic force [26,27], attempts have been made to measure the frequency-resolved viscoelasticity spectrum of soft-matter systems.

Results

Conclusion