Periodic Reporting for period 4 - Nanostress (Probing stresses at the nanoscale)
Reporting period: 2024-04-01 to 2024-09-30
Friction is responsible for an estimated 20-30% of the world's energy consumption but remains ill-understood. This is because of the difficulty of observing directly what happens at the interface: how do two (rough) surfaces contact each other, and how does the sliding change this? We develop, in this project, new tools to answer these century-old questions. To this end, we use molecules whose fluorescence depends on the environment, and notably molecules that start to fluoresce when they are confined in a frictional contact. Using optical microscopy, we can then do the contact mechanics, and observe what happens to the contacts when the surfaces start to slide with respect to each other. We also co-developed molecules that are sensitive to the local stress in the frictional contact. We can therefore now for instance understand where the difference between static and dynamic friction comes from, which is very important for understanding and predicting earthquakes. We also investigate whether the environmentally sensitive molecules can be used to measure local viscosities in polymer glasses when these go through the glass transition. Also here, a very heterogeneous (bulk) dynamics is anticipated from theory, but very few local measurements exist. Again, the fluorescent molecules open up a new window into the very old problem of the nature of the glass transition.
Friction is ubiquitous in nature and technology, yet our understanding of it remains limited. This project aimed to bridge the gap between microscopic and macroscopic descriptions of friction by developing novel experimental techniques and theoretical models. Key achievements include:
Implementation of environmentally sensitive fluorescent molecules to probe contact interfaces at the microscopic level, providing unprecedented insights into contact mechanics.
Development of a model for remote earthquake triggering based on perturbation-induced granular fluidization, bridging granular physics and seismology.
Establishment of a method for predicting frictional aging from bulk relaxation measurements, advancing understanding of time-dependent friction processes.
Visualization of multi-asperity contacts at the nanoscale using super-resolution fluorescence imaging, significantly enhancing experimental capabilities in contact mechanics.
Elucidation of the mechanisms behind Teflon's exceptional slipperiness, solving a long-standing question in materials science and tribology.
Implementation of environmentally sensitive fluorescent molecules to probe contact interfaces at the microscopic level, providing unprecedented insights into contact mechanics.
Development of a model for remote earthquake triggering based on perturbation-induced granular fluidization, bridging granular physics and seismology.
Establishment of a method for predicting frictional aging from bulk relaxation measurements, advancing understanding of time-dependent friction processes.
Visualization of multi-asperity contacts at the nanoscale using super-resolution fluorescence imaging, significantly enhancing experimental capabilities in contact mechanics.
Elucidation of the mechanisms behind Teflon's exceptional slipperiness, solving a long-standing question in materials science and tribology.
These interdisciplinary achievements have not only advanced fundamental understanding of friction across multiple scales but also opened new avenues for practical applications in lubrication, materials design, and seismic prediction. The project has fostered collaborations between physics, chemistry, and materials science, demonstrating the power of interdisciplinary approaches in tackling complex phenomena.