Muriel Scherer

Last Name

Scherer

First Name

Muriel

ORCID

0000-0003-3777-8206

Organisational unit

09455 - Isa, Lucio / Isa, Lucio

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Publications 1 - 5 of 5

Ice and air: Visualisation of freezing spread and freeze-thaw embolism in young Liriodendron tulipifera leaves
Johnson, Kate M.; Scherer, Muriel; Gerber, Dominic; et al. (2025)
Journal of Experimental Botany
Spring freezing is an unforgiving stress for young leaves, often leading to death and with consequences for tree productivity and survival. While both the water-transport system and living tissues are vulnerable to freezing, we do not currently know whether damage to one or both of these systems causes death in leaves exposed to freezing. In this study, whole saplings of Liriodendron tulipifera were exposed to freezing and thawing trajectories designed to mimic natural spring freezes. We monitored the formation of freeze-thaw xylem embolism and damage to photosynthetic tissues and found a predictable progression of ice formation across the leaf surface that was strongly influenced by leaf- vein architecture, notably the presence or absence of bundle-sheath extensions. Our results also showed that freeze-thaw embolism occurred only in the lowest vein orders where mean vessel diameter exceeded 30μm. With evidence of both freeze-thaw embolism and damage to photosynthetic tissue, we conclude that this dual-mode of lethality in leaves might be common among other wide-vesseled angiosperm leaves, potentially playing a role in limiting geographic distributions, and demonstrate that bundle sheath extensions might stall or even prevent freezing spread.
Volume expansion vs cryosuction in frost-driven fracture: a look through numerical modeling
Chao Correas, Arturo; Scherer, Muriel; Style, Robert; et al. (2025)
CFRAC 2025: The Eighth International Conference on Computational Modeling of Fracture and Failure of Materials and Structures
Exposing wet solids to cold environments can cause the liquid imbued within to freeze. Far from innocuous, the presence of these internally growing ice inclusions can greatly compromise the solid’s structural integrity as it has the potential to trigger fracture. Traditionally, the volume expansion of water upon freezing has been assumed to be the leading factor causing frost-driven fracture in wet solids. This classical line of thought hypothesizes that the increased volume of ice has to be accommodated by the permeable solid’s microstructure, hence causing it to stretch and eventually rupture. However, conclusive experimental evidence shows that frost driven fracture can also occur in wet solids imbued with liquids that contract upon freezing, hence ruling out this physical process as the sole cause. Instead, another physical mechanism has recently arisen as a contender for causing frost-driven fracture: cryosuction. This concept stands for the migration of liquid water towards the ice front due to a reduction of the liquid pressure therein. As such, cryosuction can potentially play a dual role in frost-driven fracture: (i) leading to cracking by desiccation, and (ii) allowing ice to build up within the internal crevices for as long as the supply of supercooled water holds. In this context, the present work leverages numerical models inspired by experimental evidence to weigh the contribution of these two mechanisms to the occurrence of frost-driven fracture, using hydrogels as a model for wet solids. This is done through two different approaches. Firstly, a simplified hyperelastic numerical model is used to assess the difference between the actual freezing experiments and the purely mechanical deformation required for the hydrogel to accommodate the experimentally documented ice topology, hence providing an indirect quantification of the actual cryosuction-induced hydrogel desiccation around the ice-filled crack tip. Secondly, a hygro-mechanical numerical model of the hydrogel is set up to preliminarily describe the migration of water towards the ice-filled crack as it grows in time at different speeds. As in the previous model, the crack shape is directly extracted from the experimental observations, while the liquid pressure drop at the crack lips is derived from the ice-water thermodynamic equilibrium. This model provides detailed insights into how cryosuction draws water from the bulk as the ice-filled crack grows, and it helps interpret the experimentally observed size-dependency of the desiccation-affected region near the ice-filled cracks.
Volume expansion vs cryosuction in frost-driven fracture: a look through numerical modeling
Chao Correas, Arturo; Scherer, Muriel; Style, Robert; et al. (2025)
ESMC2025 programme
Exposing hydrogels to sufficiently low temperatures can cause the liquid imbued within to freeze into ice crystals. Far from innocuous, the presence of these internally growing solid inclusions compromises the hydrogel’s structural integrity, ultimately having the potential to trigger fracture. Traditionally, the volume expansion that water undergoes upon freezing has been assumed to be the main culprit behind frost-driven fracture. This classical line of thought hypothesizes that this volume expansion has to be accommodated by the hydrogel’s microstructure, hence causing it to stretch and eventually rupture. However, conclusive ex perimental evidence has showed that frost-driven fracture can also occur in wet solids imbued in liquids that contract upon freezing for instance, thus ruling out this physical process as the sole cause. Instead, another physical mechanism has recently arisen as a contender for causing frost-driven fracture: cryosuction. This concept stands for the migration of liquid water towards the ice front driven by a reduction of the liquid pressure therein. As such, cryosuction can potentially play a dual role in frost-driven fracture: (i) leading to cracking by desiccation, and (ii) allowing ice to build up within the internal crevices for as long as the supply of supercooled water holds. In this context, the present work leverages numerical models inspired by experimental evidence to weigh the contribution of these two mechanisms to the occurrence of frost-driven fracture in hydrogels. This is done through two different approaches. Firstly, a simplified hyper-elastic numerical model is used to assess the differ ence between the actual freezing experiments and the hydrogel deformation merely due to the experimentally documented presence of ice, hence providing an indirect quantification of the actual cryosuction-induced hydrogel desiccation around the ice-filled crack tip. Secondly, a hygro-mechanical numerical model of the hydrogel is set up to preliminarily describe the migration of water towards the ice-filled crack as it grows in time at different speeds. As in the previous model, the crack shape is directly extracted from the experimental observations, while the liquid pressure drop at the crack lips is derived from the ice-water thermodynamic equilibrium. This model provides detailed insights into how cryosuction draws water from the bulk as the ice-filled crack grows, and it helps interpret the experimentally observed size-dependency of the desiccation-affected region near the ice-filled cracks.
Engineering Electrode Rinse Solution Fluidics for Carbon-Based Reverse Electrodialysis Devices
Platek-Mielczarek, Anetta; Lang, Johanna; Töpperwien, Feline; et al. (2023)
ACS Applied Materials & Interfaces
Natural salinity gradients are a promising source of so-called "blue energy", a renewable energy source that utilizes the free energy of mixing for power generation. One promising blue energy technology that converts these salinity gradients directly into electricity is reverse electrodialysis (RED). Used at its full potential, it could provide a substantial portion of the world's electricity consumption. Previous theoretical and experimental works have been done on optimizing RED devices, with the latter often focusing on precious and expensive metal electrodes. However, in order to rationally design and apply RED devices, we need to investigate all related transport phenomena─especially the fluidics of salinity gradient mixing and the redox electrolyte at various concentrations, which can have complex intertwined effects─in a fully functioning and scalable system. Here, guided by fundamental electrochemical and fluid dynamics theories, we work with an iron-based redox electrolyte with carbon electrodes in a RED device with tunable microfluidic environments and study the fundamental effects of electrolyte concentration and flow rate on the potential-driven redox activity and power output. We focus on optimizing the net power output, which is the difference between the gross power output generated by the RED device and the pumping power input, needed for salinity gradient mixing and redox electrolyte reactions. We find through this holistic approach that the electrolyte concentration in the electrode rinse solution is crucial for increasing the electrical current, while the pumping power input depends nonlinearly on the membrane separation distance. Finally, from this understanding, we designed a five cell-pair (CP) RED device that achieved a net power density of 224 mW m-² CP-¹, a 60% improvement compared to the nonoptimized case. This study highlights the importance of the electrode rinse solution fluidics and composition when rationally designing RED devices based on scalable carbon-based electrodes.
Cryosuction vs volume expansion in freezing hydrogels: A numerical study
Chao Correas, Arturo; Scherer, Muriel; Style, Robert; et al. (2025)
Exposing wet solids to cold environments can cause the aqueous phase to freeze and form ice crystals, potentially compromising the solid’s structural integrity by triggering fracture. The traditional line of thought assumed that the primary cause of frost-driven fracture is volume expansion during the water-to-ice transition: in order to accommodate the expanding ice, the solid stretches and ultimately ruptures. However, experiments have shown that frost-driven fracture can also occur with liquid phases that contract upon solidification, hence ruling out volume expansion as the sole cause. In this regard, recent empirical evidence has identified cryosuction as the driving force in frost-driven fracture for hydrogels. This mechanism involves the migration of liquid phase towards the ice front, and it can promote fracture mainly in two ways: (i) causing cracks by desiccation, and (ii) feeding further ice build-up within the newly created internal crevices. The present work leverages numerical models inspired by experimental evidence to weigh the importance of these two mechanisms in frost-driven fracture, using hydrogels as a material model. Two different approaches are used here. Firstly, an empirically verified hyperelastic model is set up to predict the deformation state for a given ice topology and compare it against the corresponding experimental measurements. This way, the cryosuction-induced desiccation in the surroundings of the ice-filled crack tip can be indirectly quantified. Secondly, a hygro-mechanical numerical model is set up to describe the migration of water toward the ice-filled crack. Once again, the crack shape is extracted from experimental observations, whereas the liquid pressure drop at the crack lips is derived from the ice-water thermodynamic equilibrium. This multiphysics model yields detailed insights into how cryosuction draws water from the bulk as the ice-filled cracks grow, and it helps to interpret the experimentally observed size-dependence of the desiccation-affected region near such cracks.

Publications 1 - 5 of 5

Muriel Scherer

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