Physique et Mécanique des Milieux Hétérogènes

The hetero-integration of oxide semiconductors (OSs) and silicon (e.g., poly-Si and crystalline-Si) exhibits promising potential on advancing displays and 3DICs, while the inevitable hydrogen (H) doping results in a critical process incompatibility. In contrast to incumbent mitigation solutions to the H-induced micro-scale short-channel effect (SCE) and severe bias-temperature instabilities in OS field-effect transistors (FETs), a novel hetero-integration-compatible Hydrogen Evacuation Layer (HEL) is proposed to enable the thorough hydrogenation-immunity in OS FETs. The H-induced SCE is suppressed with OS channel length downscaling to 60 nm, and positive/negative bias temperature instabilities (PBTI/NBTI) and self-heating instability (SHI) are reduced to 0.03 V and 0.3 V, respectively. This paves the way for Miro- and Nano-scale OS-Si hetero-integration.

Phosphatidylinositol phosphate (PIP) lipids, enriched on the cytoplasmic leaflet of the plasma membrane, are key regulators of diverse cellular processes, often through interactions with partner proteins that regulate actin assembly. Supported lipid bilayers (SLBs) provide a powerful model system to study the interactions of PIP lipids with their partner proteins. However, despite advances in SLB preparation methods, it remains a challenge to robustly obtain fluid SLBs in which PIP lipids are both mobile and asymmetrically distributed. In this study, we report a simple and robust method to generate asymmetric SLBs containing tunable amounts of PI(4,5)P 2 . By dissolving PI(4,5)P 2 below its critical micelle concentration (CMC), we enable its spontaneous insertion into the upper leaflet of SLBs exposed to bulk solution. The mobility of PI(4,5)P 2 is confirmed using fluorescence recovery after photobleaching (FRAP). Furthermore, we demonstrate that PI(4,5)P 2 incorporated using this method retains its functionality, recruiting binding partners, actin-membrane linker ezrin, and myosin 1 motors capable of sliding actin filaments on the SLBs. Our method offers a straightforward strategy to generate asymmetric PI(4,5)P 2 -containing SLBs and is applicable to other lipid species with high CMC values.

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Active matter, exemplified by adaptive living materials such as the actomyosin cytoskeleton, can navigate material parameter space, leading to unconventional mechanical responses. In particular, it can self-drive toward elastic spinodal regimes, where inhomogeneous floppy modes induce elastic degeneracy and enable a controlled interplay between rigidity loss and recovery. Proximity to such marginal states leads to stress localization and the formation of force chains that can be actively assembled and disassembled. Here we extend the classical notion of spinodal states to active solids and demonstrate how these extreme mechanical regimes can be actively accessed. Moreover, we show that in a nonlinear setting, crossing elastic spinodals generates new energy wells and makes force channeling an intrinsic feature of the emerging microstructure.

Inspired by the formation of bigels, we developed a bond percolation model that yields multiple percolating clusters in three dimensions not only at the critical point, but also above it. Our simulations suggest that, in the thermodynamic limit, there is no upper limit to the number of percolating clusters. We show that in finite systems the maximum number of percolating clusters that can be obtained grows logarithmically with the lattice size. For equal initial densities in the thermodynamic limit, all clusters percolate at the same threshold and exhibit critical exponents consistent with the critical exponents of standard percolation. The threshold depends linearly on the initial density of species and the maximum and minimum initial densities decay exponentially with the maximal number of spanning clusters. Published by the American Physical Society 2025

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Dew Water Harvesting by Laser Micropatterning A metallic surface micropatterned with a laser achieves self-cooling capacity when it faces the night sky thanks to its enhanced infrared emissivity, which triggers water condensation similar to natural dew on leaves. The patterned microgrooves promote condensation as a continuous film rather than dispersed droplets, enabling an efficient and autonomous harvesting of dew water. More details ban be found in article number 2419472 by Pablo Pou-Álvarez and co-workers.

Emergence and growth of sand dunes result from the dynamic interaction between topography, wind flow and sediment transport. While feedbacks between these variables are well studied at the scale of a single and relatively small dune, the average effect of a periodic large-scale dune pattern on atmospheric flows remains poorly constrained, due to a pressing lack of data in major sand seas. Here, we compare local measurements of surface winds to the predictions of the ERA5-Land climate reanalysis at four locations in Namibia, both within and outside the giant linear dune field of the Namib Sand Sea. In the desert plains to the north of the sand sea, observations and predictions agree well. This is also the case in the interdune areas of the sand sea during the day. At night, however, an additional wind component aligned with the giant dune orientation is measured, in contrast to the easterly wind predicted by the ERA5-Land reanalysis.For the given dune orientation and measured wind regime, we link the observed wind deviation to the daily cycle of the turbulent atmospheric boundary layer. At night, a shallow boundary layer induces flow confinement above the giant dunes, resulting in large flow deviations, especially for the slower easterly winds. During the day, the feedback of the giant dunes on the atmospheric flow is much weaker due to the thicker boundary layer and higher wind speeds. Finally, we propose that the confinement mechanism and the associated wind deflections induced by giant dunes could explain the development of smaller-scale secondary dunes, which elongate obliquely in the interdune areas of the primary dune pattern.Published article: Gadal, C., Delorme, P., Narteau, C., Wiggs, G. F., Baddock, M., Nield, J. M., & Claudin, P. (2022). Local wind regime induced by giant linear dunes: comparison of ERA5-land reanalysis with surface measurements. Boundary-Layer Meteorology, 185(3), 309-332.                                                    

We investigate the mechanics of two asymmetric ribbons bound at one end and pulled apart at the other ends. We characterize the elastic junction near the bonding and conceptualize it as a bending boundary layer. While the size of this junction decreases with the pulling force, we observe the surprising existence of the binding angle as a macroscopic signature of the bending stiffnesses. Our results thus challenge the standard assumption of neglecting bending stiffness of thin shells at large tensile loading. In addition, we show how the rotational response of the structure exhibits a nonlinear and universal behavior regardless of the ratio of asymmetry. Leveraging the independence of the binding angle to the pulling force, we finally introduce the λ-test-a visual measurement technique to characterize membranes through simple mechanical coupling.