Nanoindentation Techniques for Bone Mechanical Properties

Nanoindentation has emerged as a pivotal tool for probing the mechanical characteristics of bone at the tissue and sub-tissue levels. By applying controlled loads through a sharp indenter tip, often of Berkovich or spherical geometry, it is possible to derive local hardness and elastic modulus values that reflect the composite nature of bone. This technique excels in resolving the heterogeneity of bone, distinguishing between mineralised lamellar regions, less mineralised woven bone, and distinct microstructural features such as osteonal and interstitial tissue. Modern implementations integrate depth-sensing feedback to capture load-displacement curves with nanometre precision, enabling the quantification of viscoelastic recovery, plastic deformation and energy dissipation during dwell periods. Advances in indentation protocols and tip calibration have improved repeatability and comparability across laboratories, while complementary methods—such as atomic force microscopy for simultaneous topography and modulus mapping—have widened the scope for correlative analyses of composition, nanostructure and mechanics. As a result, nanoindentation has become indispensable for elucidating the roles of mineral density, collagen orientation and age-dependent changes in bone quality, with implications for understanding fracture risk, implant integration and the efficacy of therapeutic interventions.

Research from Nature Portfolio

Investigations of growing human cortical fibulae have employed microindentation to elucidate differences between juvenile and adult bone at the extracellular-matrix level. By combining quantitative microradiography and infrared microspectroscopy with indentation modulus measurements, distinct profiles of mineral maturity, crystallinity and collagen crosslinking were established for osteonal versus interstitial regions. Contrary to expectations, juvenile bone did not uniformly exhibit inferior mechanical properties; rather, age-related contrasts in indentation modulus, yield strain and tissue ductility varied according to regional microstructure. This work emphasises that intrinsic material parameters cannot be extrapolated directly from adult data when modelling the biomechanics of paediatric bone.

Nanoindentation Techniques for Bone Mechanical Properties publication trend

The graph below shows the total number of articles in nanoindentation techniques for bone mechanical properties across all publications each year (not limited to Nature Index journals).

Technical terms

Nanoindentation: A precision technique that indents a material with a sharp tip under controlled load to measure local hardness and elastic modulus at the sub-micrometre scale.

Reduced modulus: An indentation modulus that accounts for the combined elastic response of both indenter and sample, yielding a material-specific stiffness value.

Hardness: A measure of a material’s resistance to permanent indentation, reflecting both elastic and plastic deformation under load.

Osteonal tissue: Cylindrical structural units in cortical bone, consisting of concentric lamellae around a central canal, typically more organised and mineralised.

Interstitial tissue: The remnant bone matrix residing between osteons, often older and characterised by higher mineralisation.

Degree of mineralisation: The proportion of mineral content within the bone matrix, influencing its stiffness, toughness and fracture resistance.

References

1. Compositional and mechanical properties of growing cortical bone tissue: a study of the human fibula. Scientific Reports (2019).
2. Nanomechanical Characterization of Bone Quality Depending on Tissue Age via Bimodal Atomic Force Microscopy. Nanomanufacturing and Metrology (2023).
3. Nanoindentation analysis of the micromechanical anisotropy in mouse cortical bone. Royal Society Open Science (2017).
4. Computational and experimental methodology for site-matched investigations of the influence of mineral mass fraction and collagen orientation on the axial indentation modulus of lamellar bone. Journal of the Mechanical Behavior of Biomedical Materials (2013).