Fast and high-resolution mapping of elastic properties of biomolecules and polymers with bimodal AFM

Fast, quantitative and high resolution mapping of viscoelastic properties with bimodal AFM

“…1 depicts some of the excitation and detection schemes used in bimodal AM-FM along with the main observables, A 1 , ϕ 1 , and Δf 2 and the driving force of the second mode F 2 . [26][27][28] To relate the observables with the tip-sample force we apply the virial V i and energy dissipation E dis equations [44][45][46][47][48] to some of the excited modes…”

“…In the bimodal AM-FM, the calibration of the force constant of the second mode is a critical step. 27,57 The second mode of the cantilevers was calibrated by assuming the stiffness-frequency power law relationship, k 2 = k 1 ( f 2 /f 1 ) ζ2 , where ζ 2 is an experimental calibration parameter. 58 Mapping the sample's viscoelastic properties requires the measurements to be performed in the tip-sample repulsive regime.…”

“…1,6,8,[16][17][18][19][20][21] Bimodal AFM provides a very fast, high resolution and accurate method to map the elastic properties of polymers and biomolecules. 22,23 It has been applied to determine with very high spatial resolution the elastic modulus of a large variety of materials and macromolecules such as antibodies 24 and other proteins, [25][26][27] DNA, 28,29 cells, 30,31 bone microconstituents, 32 lipid bilayers, 33,34 self-assembled monolayers, 35,36 2D materials 37 or organic semiconductor devices. 38 This technique can be operated in air or liquid.…”

Polypeptide templating for designer hierarchical materials

“…Nanomechanical characterization of silk nanofibrils. Nanomechanical properties of the peptide seeds and silk nanofibrils obtained through templated crystallization were measured by atomic force microscopy (AFM)-based bimodal tapping mode force microscopy, namely amplitude modulation-frequency modulation (AM-FM) mapping 39,40 . For the peptide seeds deposited on mica, AM-FM mapping reported Young's moduli of 4.18 ± 0.71 GPa (defined as mean ± standard deviation obtained from log-normal distribution fitting of~10,000 data points) for (GAGSGA) 2 nanowhiskers (Fig.…”

Direct Visualization of Local Spin Transition Behaviors in Thin Molecular Films by Bimodal AFM

“…This approach enabled us to detect-in a reproducible and noninvasive manner-an ≈30% decrease of the elastic modulus when going from the LS to the HS state. As it was demonstrated in several recent reports, the spatial resolution of this technique can reach the 1-10 nm range for various samples, [45,46] which opens up a unique possibility to assess mechanical properties of SCO materials at the nanoscale, with particular relevance to their possible use in nanoscale actuator devices. [26,33] The ability of AFM to provide spatially resolved information on local SCO behaviors allowed us to evidence a very homogenous phase transformation in the films, except for the vicinity of film defects, which were shown to stabilize the HS state in the form of sub-micrometric puddles.…”