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Optical signatures of no-slip rotation in liquid films: Spiral fringes and frame permittivity effects
No full textInternational audienceSince the discovery of controlled rotation in soap films under electric fields in 2009, the rotation of suspended liquid films has drawn attention across disciplines. While prior studies identified surface charge as a primary driver-particularly in polar liquids and liquid crystals-our work introduces a new influencing factor: the permittivity of the supporting frame. We show that the frame-to-film permittivity ratio governs the transition between slip and no-slip rotational modes. Using both Particle-Image Velocimetry (PIV) and visual inspection, we characterize these modes. Although PIV offers precise measurements, we demonstrate that the two rotational states can be visually distinguished through their color patterns. Films in no-slip rotation exhibit vivid, colored spiral fringe patterns, while slip modes display steady central patterns. These spiral fringes result from white light interference between the incident wave and the portion transmitted through the film and reflected back from the second surface. When the film's thickness is below the temporal coherence length of white light, and its geometry resembles a hybrid lens-spiral-phase element, concentric fringes transform into dynamic, colored spirals. We propose that in the no-slip mode, the rotating film behaves as a lens-like spiral-phase object. The observed spiral pattern thus serves as both a qualitative signature and a physical indicator of the no-slip regime. This finding provides an accessible optical method for identifying rotational modes and offers new insights into the interplay between electromechanical forces, geometry, and optical behavior in thin liquid films.</div
Smartphone Exergames with Real-Time Markerless Motion Capture: Challenges and Trade-offs
No full textInternational audienceMarkerless Motion Capture (MoCap) using smartphone cameras is a promising approach to making exergames more accessible and cost-effective for health and rehabilitation. Unlike traditional systems requiring specialized hardware, recent advancements in AI-powered pose estimation enable movement tracking using only a mobile device. For an upcoming study, a mobile application with real-time exergames including markerless motion capture is being developed. However, implementing such technology introduces key challenges, including balancing accuracy and real-time responsiveness, ensuring proper user interaction. Future research should explore optimizing AI models for realtime performance, integrating adaptive gamification, and refining user-centered design principles. By overcoming these challenges, smartphone-based exergames could become powerful tools for engaging users in physical activity and rehabilitation, extending their benefits to a broader audience
Echo-M : Towards an Ethical Framework for Selecting Cultural Heritage Objects for Digitization in Metaverse
No full textInternational audienceLe métavers, soutenu par des technologies avancées (AR, VR, IA, blockchain), ouvre de nouvelles perspectives pour le tourisme et la préservation du patrimoine en proposant des expériences immersives. Toutefois, ce développement soulève des défis techniques et éthiques. Cet article propose le cadre ECHO-M, fondé sur des principes éthiques et une approche de décision multicritère (AHP et TOPSIS), pour guider la sélection des objets culturels à numériser et intégrer dans le métavers. Ce cadre a été testé par des expérimentations concrètes, conciliant ainsi précision technique et responsabilité éthique
Model Predictive Control for Scalable Multi-Agent Systems: A Distributed Approach
No full textInternational audienceThis poster presents the initial stages of a research project focused on developing a Distributed Model Predictive Control (DMPC) framework for scalable and dynamically evolving multi-agent systems (MAS). The work addresses the limitations of traditional centralized control methods by enabling each agent to solve a local optimization problem subject to state, input, and environmental constraints.A key aspect of the framework is the decomposition of constraints into non-coupled (e.g., input limits and obstacle avoidance) and coupled constraints (e.g., inter-agent collision avoidance), allowing for parallelized computation and modular scalability. Initial results include the successful implementation of a local MPC controller on a single robotic platform for point stabilization in an obstacle-filled environment. Future work will incorporate interaction-aware constraints and extend the approach to multi-robot coordination.The poster was presented at the Journée Régionale des Doctorants en Automatique (JRDA) 2025 in Amiens, France
Enhanced near-infrared organic photodetectors leveraging core–shell nanotripods
No full textInternational audienceNear-infrared (NIR) photodetectors are essential for diverse applications, including medical diagnostics, optical communication, and bioimaging. Traditional photodetectors, typically made from silicon and III–V semiconductors, struggle with large-area devices on precured or flexible substrates due to complex manufacturing and high costs. Organic photodetectors (OPDs), however, offer cost-effectiveness, flexibility, and a customizable spectral response. In this study, we report our effort to enhance NIR absorption in OPDs by incorporating core–shell structured PdCu@Au@SiO2 nanotripods (NTs) with a D3h configuration, designed for localized surface plasmon resonance (LSPR) beyond 1000 nm. Integrating these NTs into the OPD active layer significantly boosts NIR absorption, achieving a responsivity of 0.46 A/W and a dynamic range of 145 dB at 1050 nm. NT-based OPDs show superior sensitivity over the control OPD and a silicon photodetector at wavelengths of over 1000 nm. This improvement is due to the synergistic effects of LSPR and omnidirectional scattering from the PdCu@Au@SiO2 NTs, enhancing carrier generation and extraction. The improved performance highlights their potential for advanced applications such as long-range photoplethysmography and visual line-of-sight communication systems
Electrodes transparentes à base de réseaux de nanofils de cuivre : propriétés électriques de jonctions uniques
No full textInternational audienc
Design and Fabrication Of Multiplexed One-Port SAW Resonators On A Single Chip
No full textData Availability: All data supporting this study are openly available in a GitHub link:Shear horizontal surface acoustic wave (SH-SAW) sensors are considered as a viable option for label-free, sensitive, real-time, and cost-effective detection. In this paper, we present the design, the fabrication and the characterization of multiplexed SAW sensors based on a single chip SAW resonator. Operating near the industrial, scientific and medical (ISM) bands, resonators were microfabricated on 42.75° Y (ST) cut Quartz. This substrate was selected due to its traditional association with temperature stability in the design of SAW devices. Parameters like aperture, number of interdigitated electrode (IDT) pairs, IDT wavelengths, and number of reflectors were studied experimentally to enhance electrical responses. Resonance frequency, quality factor and electromechanical coupling were extracted through impedance measurements and fitted with a modified Butterworth-Van Dyke (MBVD) model. Based on these results, we propose a novel design for a multi-frequency device that can serve as a single electronic nose for complex gases detection
Approximation par des B-Splines de solutions optimales pour des problèmes LQ : une estimation a posteriori de l’erreur
No full textNous proposons une alternative à l’équation de Riccati lors de la résolution de systèmes linéaires quadratiques en contrôle optimale. Une transformation de l’équation d’état basée sur la forme de Brunoswski de ce système permet de mettre en évidence une représentation sous la forme de sorties dites plates. Le système ainsi transformé nous permet d’exprimer le problème de contrôle optimal sous la forme d’un problème variationnel. Une approximation par une B-Spline des sorties plates est proposée ainsi que la majoration a posteriori de l’erreur commise. L’intérêt de cette majoration d’erreur est qu’elle permet d’optimiser le placement des noeuds de la B-Spline afin de satisfaire une tolérance donnée
An Interlaboratory Comparison of On-Wafer S-Parameter Measurements up to 1.1 THz
No full textInternational audienceThis paper reports on an interlaboratory measurement comparison involving on-wafer S-parameter measurements from 10 GHz to 1.1 THz. Seven laboratories are involved, and each participant has measured an individual reference substrate fabricated from a high-resistivity silicon wafer in the same batch. One- and two-port co-planar waveguide (CPW) structures are designed, simulated, and fabricated. The measurements from 10 GHz to 1.1 THz, extending across six frequency bands, are conducted using different equipment in terms of vendors and specifications (e.g., probe pitch size). Despite such differences, this interlaboratory study has shown a generally good agreement between results from different participants when uncertainties are considered. The comparison with simulated reference values demonstrates agreement within 0.08 for |S11| and 2 dB for |S21| measurements of matched devices up to 1.1 THz. The measurement comparison demonstrates the need for a standardized measurement approach and, with that, a potential to achieve accurate on-wafer CPW measurements up to THz frequencies, underpinning the development of integrated circuits for such high frequencies