In the course of this project we have published over 10 publications in international peer-reviewed journals (most of winch top 10% in the respective research fields) shown in over 12 prestigious international conferences (via invited and contributed talks). The invited talks and numerous high-impact publications not only reflect the excellence of this work, inline with the stringent criteria set by MSCA, but also manifests the broad interest and productivity of this research line. Sill, as in any ambitious undertaking of this sort, some of the obtained results are still unpublished, although they are expected to be publicly available in the year following the end of this project.
During this action we have studied the friction and adhesion of different molecules over surfaces. Given the large scale of these systems (10nm) and also the large time-span intrinsic to the manipulation of these objects over surfaces (>100ns) one is faced with the difficulty of the impossibility to simulate such process using accurate quantum-mechanical methods and the lack of reliable inter-atomic interactions (quintessential in large scale modeling schemes such as molecular dynamics simulations). Throughout this project we have developed a method which now allow us to bridge this divide. This methodological development required a significant amount of effort and time of this project. Thanks to this effort we were able to properly describe molecular vibrations using large scale classical molecular dynamics simulations. Then using two model systems, namely single-stranded DNA molecule and pyrene chains (used in a wide range of nanoarchitectures) we have show how a detail balance of molecular vibrations are key to understand adhesion and friction processes on-surfaces. In fact this breakthrough allowed us among other results to measure for the first time the deformation of a single-strand-DNA, but also to detect in real time rotations around a single C-C bond. The former, is of utmost importance as very often defect on DNA are positioned not in the nucleotide but instead on the backbone. Most sequencing techniques rely on identification of nucleotide thus completely missing any damage present on DNA backbone. With this approach, we demonstrate the possibility accurately measure the elasticity of the backbone at a single base level, which provides a direct mean to accurately detect the presence of the aforementioned defects. Concerning the detection of the twisting around single C-C bonds, this is a long standing issue, on how to detect clock/anticlockwise rotation in what otherwise is a perfectly symmetric system. Depending on the orientation of the rotation one may control the chirality of the molecule. Here the symmetry is broken thanks to the presence of the surface, and moreover we demonstrate how this weak twist force can dramatically affect friction and on-surface motion of molecules. At last, still in the context of controlling friction/motion of molecules over surfaces we proposed simple molecular decorations which allowed us to control its motion with temperature ultimately resulting in a supra-molecular assembly with a thermal expansion coefficient that is over 100 times larger than conventional materials.
