Study on the AFM Force Spectroscopy method for elastic modulus measurement of living cells

Mechanical force-induced morphology changes in a human fungal pathogen

“…the ratio stress/strain for a uniaxial load, where stress is the force per unit area and strain is the proportional deformation (change in length divided by original length) and is dimensionless. Figure 2f shows the Young's modulus of different ratios of PDMS to cross-linker, which are in good agreement with published values [23][24][25][26]. The stiffness of lower ratio samples (10:1 and 20:1), intermediate ratios (30:1 to 40:1), and higher ratios (45:1 and 50:1) was similar to that of medical silicone implants [27], with a Young's modulus of~1 MPa; stiff tissues such as the myocardium [7], with a Young's modulus of~0.1-0.2 MPa; and less stiff tissues such as the epithelia [5,6], with a Young's modulus of~40-70 kPa, respectively.…”

Boosted Cross-Linking and Characterization of High-Performing Self-Assembling Peptides

“…SAP scaffolds are mimicry of the extracellular matrix (ECM), provide biochemical cues triggering biological response (e.g., cell adhesion, proliferation and differentiation), and thanks to their intrinsic versatility, they can be used for studying Alzheimer's disease [7], the regeneration of spinal cord and brain injuries [8,9], in cartilage tissue engineering [10], in cell and organoid culturing [11], drug discovery [12], bioimaging and drug delivery [13]. Nonetheless, SAPs usually give yield to soft fragile hydrogels, suited for soft tissue regeneration or as fillers [14] (Figure 1): that is why recent efforts have been focused on enhancing the mechanical properties of SAP hydrogels to match those of the tissues to be regenerated [15][16][17][18][19]. While multi-functionalization (i.e., biomimetic property) and their modifications can be considered as accomplished milestones for LDLK-or RADA-based SAPs [21]], tuning their stiffness across various orders of magnitude, in order to match that one of various living tissues (Figure 1) [20], is still an open quest.…”

Measuring the Elastic Modulus of Thin Polymer Sheets by Elastocapillary Bending

“…A number of methods have been developed in recent years to address these limitations on the mechanical characterization of compliant materials on small scales. Nanoindentation, frequently conducted with an atomic force microscope (AFM) tip, has become a valuable tool for measuring the local elastic properties of nano- to microscale soft objects such as thin polymer films, − gels, − and cells. − However, interpretation of data from this technique often leads to model-dependent conclusions that are complicated by the presence of adhesion between the tip and the sample, by viscoelastic and/or poroelastic relaxation processes, and by effects from underlying rigid substrates. ,, Microtensile − and bulge tests , have been successfully exploited for mechanical characterization of thin films with small in-plane dimensions but often require significant efforts in micromachining to prepare appropriately mounted samples, or otherwise require handling and fixing of small and flexible specimens. Aspiration methods based on measuring the deformation of a sample pulled into a capillary by a known hydrostatic pressure are also useful but have so far been applied only to nearly spherical samples. − Cavitation rheologya measurement of the pressure needed to form a bubble of fluid in a materialis especially promising due to its simplicity and flexibility, though so far has not been applied to thin layers and can be complicated for brittle materials where fracture precedes elastic cavitation. − Wrinkling of thin films supported on soft and thick elastic substrates, or floating on liquid surfaces has been exploited to quantitatively characterize elastic properties of thin films, and very recently, tensile testing of thin films floating on the surface of water was reported .…”