Depth-Sensing Indentation as a Micro- and Nanomechanical Approach to Characterisation of Mechanical Properties of Soft, Biological, and Biomimetic Materials.

Nikolay V Perepelkin,Alexander E Kovalev,Stanislav N Gorb,Feodor M Borodich

doi:10.3390/nano10010015

Nikolay V Perepelkin, Alexander E Kovalev + Show 2 more

Open Access

https://doi.org/10.3390/nano10010015

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Abstract

Classical methods of material testing become extremely complicated or impossible at micro-/nanoscale. At the same time, depth-sensing indentation (DSI) can be applied without much change at various length scales. However, interpretation of the DSI data needs to be done carefully, as length-scale dependent effects, such as adhesion, should be taken into account. This review paper is focused on different DSI approaches and factors that can lead to erroneous results, if conventional DSI methods are used for micro-/nanomechanical testing, or testing soft materials. We also review our recent advances in the development of a method that intrinsically takes adhesion effects in DSI into account: the Borodich–Galanov (BG) method, and its extended variant (eBG). The BG/eBG methods can be considered a framework made of the experimental part (DSI by means of spherical indenters), and the data processing part (data fitting based on the mathematical model of the experiment), with such distinctive features as intrinsic model-based account of adhesion, the ability to simultaneously estimate elastic and adhesive properties of materials, and non-destructive nature.

Highlights

Characterization of properties is a necessary, and one of the most important steps whenever a new material is created or discovered
We focus the discussion on different depth-sensing indentation (DSI) approaches, their critical assessment, and our recent advances related to the development of a method for simultaneous identification of elastic and adhesive properties of materials and structures based on experimental measurements of DSI: the BG method, and its extended variant: the Extended BG (eBG) method
Among the factors that influence pull-off force readings researchers point out surface roughness of the specimen [21], quality of the probe, e.g., wear, the presence of adsorbed chemicals on the probe surface. These factors become increasingly important at nanoscale, in case of DSI done by means of atomic force microscopy (AFM)

Summary

Introduction

Characterization of properties is a necessary, and one of the most important steps whenever a new material is created or discovered. To interpret the experimental measurements and estimate stress distribution in the specimens, Cao et al [8] employed molecular dynamics and Finite Element Method (FEM) simulations that took into account the actual shape and thickness of the graphene specimens The latter papers clearly demonstrate that size effects makes it increasingly difficult to follow conventional macroscopic experimental procedures. Such experimental technique as depth-sensing indentation, can be applied without much change to various kinds of materials, including soft materials, and at various length scales. As long as the BG method takes into account adhesive effects in DSI, its scope extends beyond the scope of the Oliver–Pharr method, in particular, to the problems of indentation of soft materials, including biological ones, and indentation at micro- and nanoscale. A numerical example based on the use of the eBG method and an asymptotic model of adhesive indentation of a thin elastic coating is presented in Section 4 as well

Depth-Sensing Indentation

DSI by Sharp Indenters

The BG Method

Findings

Conclusions