A powerful method to test the mechanical properties of biological
Nanoindentation for life science applications
- What is nanoindentation?
- How does nanoindentation work?
- Why nanoindentation vs. other testing methods?
- What are pertinent applications for nanoindenters?
- How are nanoindenters employed for mechanical testing in biology?
Nanoindentation is a powerful method to test the mechanical properties of biological samples
Mechanical properties are important parameters in the characterization of materials for science and engineering applications. Quantifying elastic, plastic, and viscous behavior provides direct information about material behavior, quality, and performance.
Within the scope of biological samples such as cells, tissue, or synthetic biomaterials, measuring the mechanical nature of materials is becoming increasingly important in biomedical engineering.
What is nanoindentation?
Nanoindentation is a versatile method to measure the mechanical properties of any material. Nanoindentation works by applying a load to the surface of a substrate which causes a small deformation. The resulting information is used to calculate the elastic, plastic, and viscous behavior of a material.
Nanoindenters are capable of local (small-scale) indentations making it a useful tool for assessing small, thin, and heterogeneous materials. Nanoindentation opens the possibility to investigate the hierarchical organization of biological samples spanning from the nanometer to millimeter scale or testing small volumes of precious samples.
Typically, an indentation test starts with a probe positioned slightly above the sample surface. The probe approaches the sample until contact is made. Applied Indentation (h), load (P), and time (t) are recorded while loading and unloading after which elastic models can be applied to data to calculate Young’s modulus.
A broad variety of deformation modes can be studied by changing experimental time scales, indenter tip geometry and loading conditions. Because nanoindentation applies very small forces, the technique is well suited for soft biomaterials such as hydrogels which are typically a challenge to characterize using macroscale techniques.
Nanoindentation can be also attractive in the biomedical context for smart scaffold design or as a potential diagnostic tool. The mechanical properties of cell microenvironments are known to play critical roles during ageing or regulating (patho)physiological cell & tissue function via mechanotransduction.
Why nanoindentation vs. other
testing methods ?
Measure heterogeneous samples in wet or dry conditions (across the micro to mesoscale)
Biological materials such as cells and tissue are heterogeneous in nature. Traditional bulk testing methods such as compression, tension, or rheology require large samples volumes and often elaborate sample preparation that are not amenable to measuring the complexity of physiological samples. The important mechanical interactions between cells and their neighboring matrix environments, as well as how those mechanisms give rise to larger tissue function cannot be analyzed with classical macroscale mechanical techniques. Nanoindenters directly provide information about the heterogeneity of micromechanical properties of biological samples by mapping the viscoelastic behavior across the surface of the material.
Small forces and displacements are non-destructive
To be sure, Atomic Force Microscopes (AFMs) have been utilized for micromechanical characterization, however the technical hurdles to using these machines require users to become experts which is prohibitive to product scope and time management. Furthermore, AFM sample displacements capabilities are limited to a range of 1 nm to 20 µm. Nanoindenters allow the measurement of very small forces and displacements, generally in the range of μN–mN and nm–μm, respectively. Nanoindenters can match the sensitivity of AFM forces without loss of data quality due to environmental noise.