Measuring Viscoelastic Master Curves at the Nanoscale in Polymer Composites

Abstract

This is an Accepted Manuscript for the Microscopy and Microanalysis 2020 Proceedings. This version may be subject to change during the production process.

Self-assembly of a barnacle cement protein into intertwined amyloid fibres and determination of their adhesive and viscoelastic properties

“…To investigate the viscoelastic properties of samples, AFM-nDMA mode combined with fast force volume was used [35,36]. The PFQNM-LC-A-CAL probe was utilized in AFM-nDMA mode at room temperature and made contact with samples at a controlled force, followed by remaining in contact for 500 ms and oscillating in a sinusoidal wave at low frequencies of 100 Hz.…”

“…As this necessitates additional measurement time for AFM-nDMA, PFQNM is initially 8, segment B) to ensure reasonable data acquisition times. This allowed the amplitude and phase of Z displacement (Z scanner) and probe deflection to be extracted, and E 0 , E 00 and tan δ to be calculated using the equation of Pittenger et al [36]. Finally, the adhesion and Young's modulus were measured in the retract curve (figure 8, segment C) as the tip was pulled away from the sample.…”

“…The combination of PFQNM and AFM-nDMA approaches enabled comprehensive characterization of rPpolcp19k-his in liquid conditions: PFQNM provided topographic images and roughness measurements in air and water, while AFM-nDMA mode measured the viscoelastic properties of the protein, determined by storage modulus, loss modulus and tan δ. Importantly, this combination of approaches allowed the properties of the assembled fibres to be determined in conditions that are closer to their native environment [35,36] and provides a more detailed, in-depth understanding of soft materials than simply measuring their mechanical properties. AFM-nDMA, in particular, takes advantage of the exquisite force sensitivity, small contact radius and nanoscale indentation depth of AFM to provide dynamic mechanical analysis and quantitative viscoelastic analysis down to 10 nm spatial resolution [35,36].…”

“…Importantly, this combination of approaches allowed the properties of the assembled fibres to be determined in conditions that are closer to their native environment [35,36] and provides a more detailed, in-depth understanding of soft materials than simply measuring their mechanical properties. AFM-nDMA, in particular, takes advantage of the exquisite force sensitivity, small contact radius and nanoscale indentation depth of AFM to provide dynamic mechanical analysis and quantitative viscoelastic analysis down to 10 nm spatial resolution [35,36].…”

“…These typically investigate elasticity and adhesion but overlook viscosity, which plays a vital role in the surface coverage and wetting ability of a protein [34]. AFM-nanodynamic mechanical analysis (AFM-nDMA) was developed in 2019 and allows the measurement of detailed viscoelastic properties of fibres in native-like conditions at the low rheological frequency range of 0.1 to 100 Hz [35,36]. The approach takes advantage of extended tip-sample contact times compared with FV, PFQNM or QI AFM modes, allowing the tip to be oscillated at a specific frequency on the sample surface, and the amplitude and phase of the cantilever deflection and Z-piezo motion to be collected for determination of the storage modulus (E 0 -the ability of material to store energy elastically), loss modulus (E 00the ability of the material to dissipate energy) and loss tangent (tan δ-the ratio between the storage and loss moduli) of a material.…”