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From stochastic thermodynamics to disordered mechanics
In the first part, I will discuss the link between thermodynamics and information theory at the microscopic scale. The usual laws of thermodynamics are known for their robustness and universality. However, when thermal fluctuations are on the same scale as the studied phenomena, these laws only describe the average behaviour. While it is impossible to macroscopically extract work from thermal fluctuations, this limit can be overcome by adapting the protocols based on the outcome of a measurement. I will present an experimental realisation of information engine, monothermal cycles which evolution is determined by the result of a measurement on the system. It is then possible to extract energy from thermal fluctuations, seemingly breaking the second Law of thermodynamics, and optimise the engine to maximise the work extraction in different regimes. These measurements are used to test recent theoretical results bounding the extracted work by the amount of information taken by the operator.
In the second part, I will focus on the intringuing mechanical properties of disordered packings of long elastic fibers. Though the mechanics of a single fiber is easily understood from its geometry and elastic modulus, assemblies show non-trivial collective responses, because contacts between fibers evolve as the assemblies deform, but also because of the irreversibility brought by friction. On the basis of compression experiments with assemblies and fibers of different sizes and material, we discuss the relevance and some limitation of previous elastic scalings, derived for wool fiber assemblies, and we highlight the important role of friction, even for purely monotonic compression.