Mechanical Testing of Monolayers. 1. Fourier Transform Analysis

A new technique has been developed to perform mechanical tests on monolayer films. The viscoelastic properties of the films can be understood through use of linear system theory, where the viscoelastic parameters for the film can be thought of as the response function of the system. The tangent of the phase difference (δ) between stress and strain and the modulus of the film (|E*|) are determined as a function of the frequency applied to the sample. The computation of δ and |E*| is facilitated by computing the Fourier transforms of the stress and strain signals.