Development of specialty materials, new polymeric blends and nanocomposites are a growing field of materials research. Improved mechanical properties of these materials is one the main motivations of the research effort. Once fabricated, characterization of their nanomechanical properties is crucial, however, few characterization methods can quantitatively measure them at the same time as provide high resolution images of their surfaces.<br/>Amplitude-modulated atomic force microscopy (AM-AFM), also known as tapping mode or AC mode, is a proven, reliable, fast and gentle imaging method with widespread applications. In what follows, we will describe a dual-frequency, “bimodal” technique we have coined “AM-FM” that is capable of high speed, high topographic resolution, stiffness and dissipative imaging of a wide variety of surfaces. The name originates from operating the first resonant mode of the cantilever in AM and the second resonance is frequency modulated (FM). The FM image returns a quantitative value of the frequency shift that depends on the sample stiffness and can be applied to a variety of physical models to calculate mechanical properties of the material imaged. We will discuss our approach to quantifying tapping mode images that builds on the work in frequency modulated bimodal imaging. [1]<br/>Given the wide range of moduli that can be obtained, AM-FM imaging is suitable for investigation of samples ranging from metals and ceramics to polymers, rubbers and biological samples. The elastic modulus is an intrinsic material property and should therefore be independent of details of the imaging parameters. We will present experimental results that demonstrate this independence. AM-FM imaging technique opens up new opportunities in fast, high resolution and quantitative tapping mode imaging of polymers.<br/><br/>[1] Herruzo ET, Garcia R. Theoretical study of the frequency shift in bimodal FM-AFM by fractional calculus. Beilstein J. Nanotechnol. 2012;3:198-206.

Quantitative modulus mapping of polymer thin films using tapping mode

249th National Meeting (2015)

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