Nano- and micromechanical testing
The combination of different nano- and micromechanical testing techniques with macroscale tensile and inflation experiments and in-situ testing allows establishing data sets on the multiscale mechanical behavior of biological tissues and soft materials.
Our lab is equipped with a micromechanical testing device (FT-MTA02, FemtoTools AG, Buchs, Switzerland), which enables us to measure forces in a range from few hundred nanonewtons to several millinewtons. This device is suitable, e.g., to perform tensile tests on the single collagen or polymer fibers [1] that form a material whose effective properties can be determined through macroscopic testing. Moreover, used for microindentation [2,3] it provides local properties of soft materials and tissues at the sub-millimeter length-scale. These experiments can be performed submerged in liquids to assess additional influences of the environment, or simply to keep a material (such as a hydrogel or a tissue) in a physiological condition.
Even smaller length scales can be probed with an atomic force microscope (AFM). We have a Flex-Bio AFM (Nanosurf AG, Liestal, Switzerland) mounted on top of an inverted optical microscope in our biolab, with which forces as low as tens of piconewtons can be measured. Depending on the choice of cantilever, the AFM can be used to obtain high-resolution surface maps of, e.g., topography, stiffness, and friction of both hard and soft surfaces. Additionally, the microscope environment is equipped with both temperature and CO2 control, which allows performing experiments directly on living cells and tissues.
[1] Morel A., Domaschke S., Urundolil Kumaran V., Alexeev D., Sadeghpour A., Ramakrishna S.N., Ferguson S.J., Rossi R.M., Mazza E., Ehret A.E., Fortunato G. (2018) Correlating diameter, mechanical and structural properties of poly (L-lactide) fibres from needleless electrospinning. Acta Biomater. 81, 169-183. DOI: 10.1016/j.actbio.2018.09.055
[2] Reyes Lua A.M., Hopf R. and Mazza E., 2020. Factors influencing the mechanical properties of soft elastomer substrates for traction force microscopy. Mech. Soft Mater. 2, 6. DOI: 10.1007/s42558-020-00021-8
[3] Reyes Lua, A.M. Factors influencing the analysis of cell-substrate interaction. ETH Diss. Nr. 26609 (2020).