Owing to their unique mechanical and thermal properties, vertically aligned carbon nanotube (VACNT) films are promising for use as advanced thermal interface materials. While there has been much research on the thermal properties of VACNT films, the mechanical modulus along the in-plane direction has received little attention. This paper reports a new technique for measuring this property using the resonant frequency shift in microfabricated resonators integrated with VACNT films. A comprehensive description of the technique includes microfabrication details, the laser Doppler methodology for extracting the resonant frequency, uncertainty analysis, and a model for data interpretation. A model accounting for the spatial variation of nanotube alignment relies on electron microscopy data and is consistent with the strong thickness dependence of the modulus data. The modulus of 0.5-100 μm-thick multi-walled nanotube films varies from 8 to 300 MPa, which is a promising value for a variety of applications including thermal interfaces.
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