Bulk chemical composition contrast from attractive forces in AFM force spectroscopy

Abstract

A key application of atomic force microscopy (AFM) is the measurement of physical properties at sub-micrometer resolution. Methods such as force–distance curves (FDCs) or dynamic variants (such as intermodulation AFM (ImAFM)) are able to measure mechanical properties (such as the local stiffness, k r) of nanoscopic heterogeneous materials. For a complete structure–property correlation, these mechanical measurements are considered to lack the ability to identify the chemical structure of the materials. In this study, the measured attractive force, F attr, acting between the AFM tip and the sample is shown to be an independent measurement for the local chemical composition and hence a complete structure–property correlation can be obtained. A proof of concept is provided by two model samples comprised of (1) epoxy/polycarbonate and (2) epoxy/boehmite. The preparation of the model samples allowed for the assignment of material phases based on AFM topography. Additional chemical characterization on the nanoscale is performed by an AFM/infrared-spectroscopy hybrid method. Mechanical properties (k r) and attractive forces (F attr) are calculated and a structure–property correlation is obtained by a manual principle component analysis (mPCA) from a k r/F attr diagram. A third sample comprised of (3) epoxy/polycarbonate/boehmite is measured by ImAFM. The measurement of a 2 × 2 µm cross section yields 128 × 128 force curves which are successfully evaluated by a k r/F attr diagram and the nanoscopic heterogeneity of the sample is determined.

Experimental and Simulation Study of the Solvent Effects on the Intrinsic Properties of Spherical Lignin Nanoparticles

“…The 128 × 128 indentation force curves were exported for further analysis and reporting of data using SOFA. 76 …”

“…The amplitude-dependent force spectroscopy (IM ADFS) method was adapted to obtain the force curves (1 × 1 μm 2 with a resolution of 256 × 256 pixels) at a scan rate of 0.75 Hz in the fast scan direction. , The indentation depth ranged from 2 to 8 nm. The 128 × 128 indentation force curves were exported for further analysis and reporting of data using SOFA …”

“…The 128 × 128 indentation force curves were exported for further analysis and reporting of data using SOFA. 76 ■ RESULTS AND DISCUSSION Solvent Effects on the Size Distribution of LNPs. LNPs were prepared from SKL using the binary solvent of aqueous acetone or aqueous THF.…”

Carrier Fibers for the Safe Dosage of Nanoparticles in Nanocomposites: Nanomechanical and Thermomechanical Study on Polycarbonate/Boehmite Electrospun Fibers Embedded in Epoxy Resin

“…The reason for a more uniform localized mechanical behavior could be that the water stored inside the fibers and is bounded to BNP promotes chain scission of the PC during the curing process of the resin; this is plausible given the acceleration of thermal decomposition that the PC fibers suffer with concentrations of BNP higher than 5 wt % [ 26 ]. The existence of interphases could also be a reason for this characteristic response; interphases between BNP and PC and PC and EP were studied previously on our group [ 35 ], from which attractive forces ( F attr ) measured by Intermodulation AFM (ImAFM) account for mixed behavior of the composite in which the BNP domains remained surrounded by PC, and the PC phase was strongly permeated by EP. Moreover, the plasticizing effect that DGEBA has on PC and the diffusion of hardener molecules into the PC phase change the distribution of species in the network.…”

Long-Time Behavior of Surface Properties of Microstructures Fabricated by Multiphoton Lithography

“…Force volume mode was used with a cantilever deflection trigger of 100 nm [46]. In addition, 10 × 10 FDC indentations were recorded on 10 µm 2 in the centric area of the microstructure's top surface, to be averaged for a better signal-to-noise ratio and to compensate for inhomogeneities of the surface [45].…”