by Keyword: Nanoindentation

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Molina, B. G., Cuesta, S., Besharatloo, H., Roa, J. J., Armelin, E., Alemán, C., (2019). Free-standing taradaic motors based on biocompatible nanoperforated poly(lactic acid) layers and electropolymerized poly(3,4-ethylenedioxythiophene) ACS Applied Materials and Interfaces 11, (32), 29427-29435

The electro-chemo-mechanical response of robust and flexible free-standing films made of three nanoperforated poly(lactic acid) (pPLA) layers separated by two anodically polymerized poly(3,4-ethylenedioxythiophene) (PEDOT) layers has been demonstrated. The mechanical and electrochemical properties of these films, which are provided by pPLA and PEDOT, respectively, have been studied by nanoindentation, cyclic voltammetry, and galvanostatic charge-discharge assays. The unprecedented combination of properties obtained for this system is appropriated for its utilization as a Faradaic motor, also named artificial muscle. Application of square potential waves has shown important bending movements in the films, which can be repeated for more than 500 cycles without damaging its mechanical integrity. Furthermore, the actuator is able to push a huge amount of mass, as it has been proved by increasing the mass of the passive pPLA up to 328% while keeping the mass of electroactive PEDOT unaltered.

Keywords: Actuator, Artificial muscle, Conducting polymer, Nanoindentation

Pellequer, J. L., Parot, P., Navajas, D., Kumar, S., Svetli, Scheuring, S., Hu, J., Li, B., Engler, A., Sousa, S., Lekka, M., Szymo, Schillers, H., Odorico, M., Lafont, F., Janel, S., Rico, F., (2019). Fifteen years of Servitude et Grandeur to the application of a biophysical technique in medicine: The tale of AFMBioMed Journal of Molecular Recognition 32, (3), e2773

AFMBioMed is the founding name under which international conferences and summer schools are organized around the application of atomic force microscopy in life sciences and nanomedicine. From its inception at the Atomic Energy Commission in Marcoule near 2004 to its creation in 2007 and to its 10th anniversary conference in Krakow, a brief narrative history of its birth and rise will demonstrate how and what such an organization brings to laboratories and the AFM community. With the current planning of the next AFMBioMed conference in Münster in 2019, it will be 15 years of commitment to these events.

Keywords: Atomic Force Microscopy, Single molecules, Biomechanics, Force spectroscopy, High-speed AFM, Imaging, Nanoindentation, Nanomedicine, Nanotoxicology

Valero, C., Navarro, B., Navajas, D., García-Aznar, J. M., (2016). Finite element simulation for the mechanical characterization of soft biological materials by atomic force microscopy Journal of the Mechanical Behavior of Biomedical Materials , 62, 222-235

The characterization of the mechanical properties of soft materials has been traditionally performed through uniaxial tensile tests. Nevertheless, this method cannot be applied to certain extremely soft materials, such as biological tissues or cells that cannot be properly subjected to these tests. Alternative non-destructive tests have been designed in recent years to determine the mechanical properties of soft biological tissues. One of these techniques is based on the use of atomic force microscopy (AFM) to perform nanoindentation tests. In this work, we investigated the mechanical response of soft biological materials to nanoindentation with spherical indenters using finite element simulations. We studied the responses of three different material constitutive laws (elastic, isotropic hyperelastic and anisotropic hyperelastic) under the same process and analyzed the differences thereof. Whereas linear elastic and isotropic hyperelastic materials can be studied using an axisymmetric simplification, anisotropic hyperelastic materials require three-dimensional analyses. Moreover, we established the limiting sample size required to determine the mechanical properties of soft materials while avoiding boundary effects. Finally, we compared the results obtained by simulation with an estimate obtained from Hertz theory. Hertz theory does not distinguish between the different material constitutive laws, and thus, we proposed corrections to improve the quantitative measurement of specific material properties by nanoindentation experiments.

Keywords: AFM, Cell mechanics, FEM, Nanoindentation, Soft-tissue

Andreu, I., Luque, T., Sancho, A., Pelacho, B., Iglesias-García, O., Melo, E., Farré, R., Prósper, F., Elizalde, M. R., Navajas, D., (2014). Heterogeneous micromechanical properties of the extracellular matrix in healthy and infarcted hearts Acta Biomaterialia 10, (7), 3235-3242

Infarcted hearts are macroscopically stiffer than healthy organs. Nevertheless, although cell behavior is mediated by the physical features of the cell niche, the intrinsic micromechanical properties of healthy and infarcted heart extracellular matrix (ECM) remain poorly characterized. Using atomic force microscopy, we studied ECM micromechanics of different histological regions of the left ventricle wall of healthy and infarcted mice. Hearts excised from healthy (n = 8) and infarcted mice (n = 8) were decellularized with sodium dodecyl sulfate and cut into 12 μm thick slices. Healthy ventricular ECM revealed marked mechanical heterogeneity across histological regions of the ventricular wall with the effective Young's modulus ranging from 30.2 ± 2.8 to 74.5 ± 8.7 kPa in collagen- and elastin-rich regions of the myocardium, respectively. Infarcted ECM showed a predominant collagen composition and was 3-fold stiffer than collagen-rich regions of the healthy myocardium. ECM of both healthy and infarcted hearts exhibited a solid-like viscoelastic behavior that conforms to two power-law rheology. Knowledge of intrinsic micromechanical properties of the ECM at the length scale at which cells sense their environment will provide further insight into the cell-scaffold interplay in healthy and infarcted hearts.

Keywords: Atomic force microscopy, Extracellular matrix, Heart scaffold, Nanoindentation, Viscoelasticity