Resumen de Nanomechanics of Organic Layers and Biomenbranes
Gerard Oncins Marco
The main objective of this work was to quantitatively measure the nanotribological properties or organic layers and rationalize them from a physicochemical point of view. To accomplish that, a wide array of samples was selected, ranging from technological coatings as alkanethiols to biological coatings as phospholipid bilayers, which can be used to functionalize miniaturized electromechanical systems. Although the studied molecules are different in nature and functionality, the intermolecular forces that determine the layers structure are the same: van der Waals, electrostatic and water-related interactions. We are interested in quantifying these interactions as a function of the intermolecular distances, the nature of the medium the molecules are immersed in (liquid or air) and also assess external factors that have specific effects on the samples. These external factors were overall tested in biological membranes (phospholipid bilayers), where temperature and the presence of ions play a decisive role in their structure. In order to achieve our objectives, two experimental techniques were mainly used. The first one is the Lateral Force Microscopy, which was implemented in our lab during the execution of this project. As the nature of the measurements we wanted to perform was quantitative, it was also necessary to implement the methods to calibrate Atomic Force Microscopy probes both vertically and laterally.Besides, as we wanted to test the biological samples in liquid environment, a new methodology to perform Lateral Force Microscopy measurements in liquid had to be implemented. The second main technique is Force Spectroscopy, which was used to complement the nanomechanical information obtained from the friction measurements and that gave us a more detailed picture of the mechanical response of layers. Our technical goal was to obtain fast, reproducible and consistent Force Spectroscopy results, fact that implied the development of a dedicated software routine and the systematic control of the probes shape.
