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Articles
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Séminaire PMMH - Dominic Vella (University of Oxford)
19 marsVendredi 22 mars de 11h00 à 12h00 - Salle réunion PMMH 1Drops with deformable boundaries : Flat tops, Locomotion and Ageing
A liquid droplet placed on a rigid, planar surface has a captivating simplicity : its surface is a spherical cap and remains in equilibrium. In this talk, I'll show that the addition of a deformable boundary leads to a range of new phenomena : evaporating droplets with an elastic skin may develop flat tops, while droplets placed in a flexible channel invariably push or pull themselves to the end of the channel. Even without a complex rheology or locomotion, reaching equilibrium can happen slowly, with the droplet's contact ageing. I will discuss three specific examples, presenting a combination of theory and experiment for each.
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Séminaire PMMH - Jacques Fattaccioli (PASTEUR, ENS)
15 marsVendredi 15 mars de 11h00 à 12h00 - Salle réunion PMMH 1Bacteria on high fat diets cooperate to stay fit
During the consumption of alkanes, Alcanivorax borkumensis, a bacteria commonly found
in oil spill areas, form a biofilm around oil droplets to consume them. The role this plays
during degradation remains unclear. Using in-situ microfluidic tracking, we identify a shift
in biofilm morphology that depends on adaptation to oil consumption : longer exposure
leads to the appearance of dendritic biofilms optimized for oil consumption effected
through tubulation of the interface at localized defects in the interfacial cell ordering. To
capture the full phenomenology, we developed a model that elucidates biofilm
morphology, linking tubulation to decreased interfacial tension and increased cell
hydrophobicity.Article DOI : DOI:10.1126/science.adf3345
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Séminaire PMMH - Dominic Vella (University of Oxford)
11 marsVendredi 22 mars de 11h00 à 12h00 - Salle réunion PMMH 1Drops with deformable boundaries : Flat tops, Locomotion and Ageing
A liquid droplet placed on a rigid, planar surface has a captivating simplicity : its surface is a spherical cap and remains in equilibrium. In this talk, I'll show that the addition of a deformable boundary leads to a range of new phenomena : evaporating droplets with an elastic skin may develop flat tops, while droplets placed in a flexible channel invariably push or pull themselves to the end of the channel. Even without a complex rheology or locomotion, reaching equilibrium can happen slowly, with the droplet's contact ageing. I will discuss three specific examples, presenting a combination of theory and experiment for each.
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Séminaire PMMH - Jacques Fattaccioli (PASTEUR, ENS)
9 marsVendredi 15 mars de 11h00 à 12h00 - Salle réunion PMMH 1Bacteria on high fat diets cooperate to stay fit
During the consumption of alkanes, Alcanivorax borkumensis, a bacteria commonly found
in oil spill areas, form a biofilm around oil droplets to consume them. The role this plays
during degradation remains unclear. Using in-situ microfluidic tracking, we identify a shift
in biofilm morphology that depends on adaptation to oil consumption : longer exposure
leads to the appearance of dendritic biofilms optimized for oil consumption effected
through tubulation of the interface at localized defects in the interfacial cell ordering. To
capture the full phenomenology, we developed a model that elucidates biofilm
morphology, linking tubulation to decreased interfacial tension and increased cell
hydrophobicity.Article DOI : DOI:10.1126/science.adf3345
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Séminaire PMMH - Min-Hui LI (Chimie ParisTech )
8 marsVendredi 8 mars de 11h00 à 12h00 - Salle réunion PMMH 1Electroactive Bi-functional Liquid Crystal Elastomer Actuators
Liquid crystal elastomers (LCEs) show promising potentials as smart actuators, for example, those contracting/expanding linearly like mammalian muscles.[1] Direct heating and light illumination are the most used activation mode in LCE actuators because LCEs are based on thermotropic or phototropic liquid crystals.[1,2,3] However, in the world of actuators, electrical energy is the most convenient and the most in demand stimuli. Indeed, the nature does use electrical impulses between nerves and muscles or skins for actuation or sensing with extraordinary efficacy, and electrical stimulation is also more widely utilizable as driving forces in industrial devices. Efforts have been made to achieve electroactive LCEs (eLCEs).
In this talk, I will present a trilayer electroactive LCE (eLCE) system by combining two smart materials, LCE and ionic electroactive polymer device (i-EAD), which is bi-functional and can perform either bending or contractile deformations under low voltage stimulation.[4] By applying a voltage of ±2 V at 0.1 Hz, the redox behavior and associated ionic motion in the two conducting polymer electrodes of i-EAD provide bending deformation of the device up to a bending strain difference of 0.8% for a sample of 0.5 mm thickness. On the other hand, by applying a voltage of ± 6V at 10 Hz, the ionic current-induced Joule heating triggers the muscle-like contractile response of the central ion-conducting LCE component, a linear contraction ratio of 20% being obtained without load. Moreover, a load of 270 times of the weight of trilayer eLCE film can be left with a strain of 20%. This approach of combining two smart polymer technologies, i.e., LCE and i-EAD, in a single device, is promising for the development of smart materials with multiple degrees of freedom in soft robotics, electronic devices, and sensors.
References
[1] M.-H. Li, P. Keller P., Artificial muscles based on liquid crystal elastomers, Phil. Trans. A. 364, 2763 (2006).
[2] B. Ni, G. Liu, M. Zhang, P. Keller, M. Tatoulian, M.-H. Li, Large-Size Honeycomb-Shaped and Iris-Like Liquid Crystal Elastomer Actuators, CCS Chemistry, 4, 847 (2022).
[3] B. Ni, G. Liu, M. Zhang, M. Tatoulian, P. Keller, M.-H. Li, Customizable Sophisticated 3D Shape Changes of Large-size Liquid Crystal Elastomer Actuators, ACS Appl. Mater. Interfaces, 13, 54439 (2021).
[4] G. Liu, Y. Deng, G. Nguyen, C. Vancaeyzeele, A. Brûlet, F. Vidal, C. Plesse, M.-H. Li, Electroactive Bi-functional Liquid Crystal Elastomer Actuators, Small, 2023, 2307565.