Contact Resonance Force Microscopy for Viscoelastic Property Measurements: From Fundamentals to State-of-the-Art Applications

Abstract

Contact resonance force microscopy (CRFM) is an atomic force microscopy (AFM) method that evolved from a curiosity about the detection of ultrasonic vibrations with an AFM cantilever and an unaddressed need to characterize the mechanical properties of stiffer materials (elastic modulus >50 GPa). The method has matured to allow near-surface and subsurface elastic property measurements of single crystals, thin films, nanomaterials, composites, and other advanced materials. More recently, CRFM has been extended to viscoelastic property measurements, where the CR frequency and CR quality factor are utilized to quantitatively assess properties such as storage modulus, loss modulus, and loss tangent. In this Perspective, we trace the evolution of CRFM from initial discovery to elastic property measurements to viscoelastic property measurements. The techniques for extending single-point property measurements to two-dimensional property maps are then described in terms of their operational characteristics, demonstrated on calibration materials, and validated via comparisons to other viscoelastic measurement tools. The focus of the discussion then shifts to viscoelastic CRFM in nonambient conditions to highlight the challenges and developments related to thermomechanical analyses and liquid operation. The current state-of-the-art and best practices in data acquisition and analyses for viscoelastic CRFM are elucidated via a step-by-step demonstration on a wood–polymer composite. Finally, we conclude with a discussion of potential polymer science application areas that are poised to benefit from the recent advances in the ambient and nonambient CRFM methodologies. Altogether, we feel that the recent addition of CRFM to commercially available AFMs together with guides that clearly define state-of-the-art and best practices will accelerate its acceptance and adoption in polymer science via viscoelastic property measurements at unprecedented length and time scales.

Nanomechanical mapping of soft materials with the atomic force microscope: methods, theory and applications

“…Accurate determination of the contact radius r c might be problematic which led to use of reference samples with well-known mechanical properties. 23,271 The spatial resolution of a nanomechanical map obtained by CR-AFM is rather modest if compared to the spatial resolutions achieved in either FV or bimodal AFM. In general, a contact resonance AFM experiment involves the application of relatively large forces, say of a few hundreds of nN.…”

“…applied to characterize soft materials. [18][19][20][21][22][23][24][25][26] Some of the earlier methods such as force-volume 4,14,18,19 and AFM phase-imaging 16,17 are still evolving while the applications of other methods have declined. 26 The main goal of this review is to introduce the experimental approaches, the theoretical background and the capabilities of the most advanced AFM-based methods to map at very high (o10 nm) or high-spatial resolution (10-100 nm) the mechanical properties of soft materials.…”

Nanoscale DMA with the Atomic Force Microscope: A New Method for Measuring Viscoelastic Properties of Nanostructured Polymer Materials

“…Multiple non-resonant and resonant AFMbased methods exist for determining contact stiffness in the tip-sample junction. [4][5][6][7] These methods, together with the use of suitable tips, calibration, and contact mechanics models such as Derjaguin-Muller-Toporov (DMT) or Johnson-Kendall-Roberts (JKR) 8 permit extraction of sample moduli. While instrumented nanoindenters provide advantages for quantifying moduli, hardness, and other properties with high accuracy, the combination of tip radii down to 1 nm and force detection levels in the low piconewton range give AFM the unique capability of mapping topography and stiffness with sub-nanometer spatial resolution.…”

Mechanical Characterization of Methanol Plasma Treated Fluorocarbon Ultrathin Films Through Atomic Force Microscopy

“…Finally, not only can CR-AFM be used to study elastic but also viscoelastic materials (Killgore and DelRio, 2018). In order to account for the viscoelastic behavior of samples, a dashpot of dumping σ is included in parallel to k * in the model in Figure 1B (Yuya et al, 2008).…”

“…Moreover, micro-and nanoindentation do not allow one to visualize the distribution of these surface properties because of their poor spatial resolution. Alternatives methods, based on atomic force microscopy (AFM), can be used to obtain quantitative maps of mechanical properties, such as indentation modulus, damping, adhesion and energy dissipation (Passeri et al, 2013a) as well as viscoelastic moduli, i.e., storage and loss modulus, and loss tangent (Killgore and DelRio, 2018).…”