Understanding the formation of ice in plants is key to mitigating crop losses worldwide, particularly in light of the extreme weather oscillations arising from climate change. In contrast to ice formation in animal cells and tissues, however, our understanding of the microscopic details of ice formation within the plant cell wall remains limited. In this work, we take the first steps to address this gap through a synergistic approach combining plant biology experiments and molecular simulations. Specifically, we analyze the molecular-level details of the crosslinking of homogalacturonan (HG) pectin, comparing different microscopic mechanisms and exploring the effects of varying HG functionalisation patterns (deprotonated, protonated, methylesterified HG). We find that the extent and nature of HG crosslinking strongly influence the porosity of the cell wall, which we characterize by an experimental approach augmented by mathematical modelling. In turn, the topology of the HG network modulates the speed of ice propagation through plant tissue. We find that cold acclimation as well as supplementing extra Ca²⁺ to the plant (which enhances the HG cross-linking) lead to a similar increase in terms of frost resistance. In addition, our simulations suggest that while HG itself shows limited ice nucleating ability at the molecular scale, larger supramolecular assemblies or ordered networks may enhance ice nucleation activity to a significant extent. Interestingly, flooding the cell wall with water reverses the inhibitory effect of crosslinking on ice growth (due to the swelling of the HG network). Molecular dynamics simulations demonstrate that crosslinking controls pore size distributions and limits ice growth via the Gibbs-Thomson effect, providing a physical basis for freezing tolerance through cell wall remodeling and hydration control. These insights reveal how plants regulate ice formation and spread by tuning pectin architecture, offering promising targets for improving crop frost resistance.

In order to separate the influences of the multiple factors that contribute to ice nucleating efficiency, there is a need for model systems with chemical and physical structures that are well defined and easily varied.  The exquisite control that it offers over physical geometry at the nanoscale makes DNA origami¹ a particularly attractive model ice nucleating agent (INA).  Here we compare ice nucleation by solutions of a rectangular DNA origami tile, formed by annealing a 2.6 kbase single-stranded DNA scaffold with ninety shorter ‘staple’ oligonucleotides, to ice nucleation when these components are mixed but not annealed.  Isothermal measurements show that the molecular conformation has a dramatic effect on the ice nucleating efficiency.  For an array of droplets containing annealed, well-folded tiles the freezing rate is constant with time, consistent with the presence of large numbers of identical INAs, whereas for unannealed DNA the freezing rate decreases with time, consistent with ice nucleation dominated by rare INAs, likely formed by molecular aggregation.  A comparison of isothermal data and temperature ramp data shows an interesting phenomenon.  Despite the freezing rate measured at low temperature being higher for annealed DNA origami samples than for a significant proportion of unannealed ones, in slow temperature-ramp measurements the latter mostly freeze at higher temperatures.  By modelling the ice nucleating efficiency of the unannealed DNA using a log normal distribution, we show that our results are qualitatively as expected from classical nucleation theory. 

TBA

Clay minerals are an important fraction of airborne dust. They are built of aluminosilicate sheets that are stacked together to form platy particles. The most common types of clay minerals, namely kaolinite, illite, and smectites, among which is montmorillonite, have all been shown to act as ice-nucleating particles (INPs) for cirrus and mixed-phase clouds despite their vastly different surface properties. While kaolinite is the only one to have an alumina surface, illite and smectite just have siloxane and edge surfaces. In contrast to kaolinite, illite and smectites both possess charge-balancing ions on their surface and between the sheets, but only smectites are swelling in water and aqueous solutions with a tendency to delaminate and even exfoliate. Despite these differences, there seem to be common structural elements that are responsible for their similar ice-nucleation (IN) activity. Yet, the surfaces and surface features required for their IN activity are still uncertain. In my presentation, I will show how experimental investigations can be used to elucidate the surface structures relevant to ice nucleation in clay minerals by targeted chemical and morphological modifications and by comparing the ice-nucleation activity of similar clay mineral samples. Specifically, I will show the influence of the charge-balancing ions on the IN activity of smectites, and the role of the stacking of sheets to platelets for the IN activity of smectites and kaolinites.

Deliquescence is a phase transition in which solid substances absorb water vapor from the environment and spontaneously dissolve into an aqueous solution. A familiar example is the coarsening of table salt, which proceeds through deliquescence-induced capillary adhesion and subsequent recrystallization upon drying. Beyond its commonplace manifestations, deliquescence plays a significant role in global-scale phenomena. Sea salt aerosols, for instance, play a critical role in climate regulation via cloud formation [1]. Meanwhile salt weathering—driven by humidity-induced cycles of deliquescence and recrystallization (like a freeze-thaw cycle)—damages cultural heritage sites such as historic stone monuments [2]. With climate change causing increased atmospheric humidity, these negative impacts are expected to become more pronounced.

In this study, we revisit deliquescence by examining its underlying wetting behavior and thermodynamic stability across spatial and temporal scales, drawing particular attention to its striking resemblance to the surface melting of ice crystals [3].　Using advanced optical microscopy with a height resolution on the order of an angstrom (laser confocal microscopy combined with differential interference microscopy: LCM-DIM), we investigate the unique wetting behavior of deliquescent films, as well as their thermodynamic stability against crystallization. In situ observations using LCM-DIM revealed that deliquescent films do not grow continuously in thickness toward the deliquescence point, but rather emerge through nucleation in a first-order phase transition manner. Similar discontinuous behavior was also revealed in the quasi-liquid layers that we recently visualized [4].　We further found that deliquescent films exhibit two distinct thicknesses and that there exist transitions between these two wetting states (wetting transitions). From real-space analysis of the spreading dynamics, we succeeded in estimating the thickness of the thinner film to be approximately 3 nm.

All posters will be in the Balint Room

TBA

We have known since the 18^th Century that some insects can tolerate internal ice formation yet we still know remarkably little about the underlying mechanisms. I will briefly introduce insect freeze tolerance, and our understanding of the biochemical and molecular processes with which freeze tolerance is associated. I will then describe the currently accepted Extracellular Ice Formation (EIF) model, and the strength of evidence for and against it. In my lab, we use the spring field cricket Gryllus veletis as a model freeze tolerant insect; When freeze tolerant, G. veletis has suppressed metabolic rate and accumulates putative low molecular weight cryoprotectants (especially proline, myo-inositol, and trehalose). Recently, we have been exploring cellular- and tissue-scale remodeling in preparation for freezing, and how crickets maintain functioning mitochondria after being frozen; I will show how these observations fit the EIF model. 

For further information, see coldbugs.com or contact bjs299@cornell.edu

Several species of bacteria, fungi, lichen, and insects have evolved proteins that are potent ice nucleants. Bacteria and fungi are aerosolized and uplifted to the clouds, where they contribute to cloud glaciation and precipitation. Indeed, bacteria are so powerful ice nucleants that are routinely used for the synthetic production of snow. Despite the importance of biological ice nucleation for the survival and thriving of organisms and atmospheric processes, little is known about sequence and/or structure of the ice nucleating proteins, the mechanisms by which they promote water crystallization, and what makes them so outstanding.  This presentation will discuss our approach to bridge the results of laboratory experiments, theory, numerical and molecular simulations, and artificial intelligence to elucidate the mode of action of biological ice nucleants. Our studies reveal that nature uses a common strategy among organisms in several kingdoms, “E pluribus unum” (out of many, one), to nucleate ice at temperatures close to the 0oC by assembly of ice-nucleating proteins into large functional aggregates.

Cloud ice plays a crucial role in Earth’s weather and climate system, influencing precipitation, cloud lifetime, and the radiation budget. Among mineral dust constituents, alkali feldspars – particularly perthitic varieties with complex microstructures – are the most ice-nucleation-active (INA). Their high IN activity is attributed to surface defects such as steps, pores, and cracks, which may expose (100) crystallographic facets recently identified as potential INA sites^{1, 2}. While the link between IN activity and microstructural complexity is widely recognized, the molecular mechanism remains unclear. 

Studies have shown significant variability in the IN activity of natural alkali feldspars, ranging from low IN activity in gem-quality Adularia to high INA in perthitic microcline. To investigate this, we simulate feldspar transformation by chemically and structurally modifying pristine, defect-free feldspars and measuring changes in their IN efficacy. Our previous work confirmed that chemically induced fracturing significantly enhances the initially low IN activity of K-rich alkali feldspar³. Here, we present our first results on the IN activity of hydrothermally altered K-rich alkali feldspar, using a method that closely mimics natural alteration of feldspar in aqueous environment of the Earth’s crust. 

Additionally, we modify cleaved surfaces of pristine feldspar by micromachining cavities with one wall aligned to the (100) crystallographic orientation of feldspar, using Focused Ion Beam (FIB) milling. This enables direct testing of the hypothesis that (100) facets serve as primary high-temperature INA sites in alkali feldspar. IN activity is characterized using droplet freezing assays and ice nucleation experiments in an environmental SEM. 

Complementing this study with in situ synchrotron X-ray diffraction, we aim to uncover the mechanism driving ice nucleation on natural alkali feldspars and the role of adsorbed water at the feldspar surface. 

All posters will be in the Balint Room

TBA

Understanding the behavior of particles during freezing is essential across a range of fields, from cryobiology and materials science to climate studies and food preservation. In this talk, I will present how we use cryoconfocal microscopy to directly observe microscale dynamics in situ during ice growth. This technique offers a unique window into the spatial and temporal evolution of particles and solutes as they interact with a moving ice front. Focusing on the interplay between solute concentration, particles, and ice growth, I will show how these microscale processes shape macroscopic outcomes. Our observations challenge some of the assumptions of classical physical models and highlight their limitations in predicting real-world behaviors. By comparing model predictions with experimental findings, we reveal key mechanisms that are often overlooked, especially in complex or multicomponent systems.

Freeze structuring (FS) is a valuable technique with exciting applications in food structure engineering. FS’s simple and scalable process allows precise control over pore morphology by manipulating ice crystal formation in suspensions via material and process parameters. However, food systems are inherently complex, heterogeneous, and polydisperse mixtures of polysaccharides, proteins, and fats. Unlike well-studied single-component systems, the interactions within multi-component mixtures during FS are challenging, limiting the broader adoption of FS for food systems.

In this work, we examine existing research on FS from various fields to identify the raw material characteristics and pre-processing strategies that influence structural outcomes in food systems, both for single components and for the holistic view of complex mixtures of these components. By enabling the direct structuring of complex mixtures without pre-purification, we aim to advance FS as a viable tool for sustainable food manufacturing. This approach underlines FS’s potential to improve resource efficiency and nutritional value, offering a path to innovative and scalable solutions for the food industry.

Ice nucleation is a critical process in the formation of ice clouds and the initiation of precipitation. A substantial body of research has previously been conducted on a range of heterogeneous ice nucleators, encompassing both laboratory experiments and fieldwork. The majority of these studies were traditionally concerned with particulate ice nucleators, but in recent years it has become apparent that ice nucleators of molecular origin can also catalyze ice nucleation, sometimes even very effectively. However, a comprehensive molecular understanding of their mechanisms of action remains elusive, underscoring the necessity for dedicated experiments towards that goal.

A comprehensive investigation was conducted into a range of naturally occurring and synthetic substances, some of which have atmospheric relevance. To this end, two experimental techniques were employed for the detection of droplet freezing. Firstly, the BINARY (Bielefeld Ice Nucleation ARraY) setup utilizing microliter-volume droplets, and secondly, the recently developed nanoBINARY (nanoliter Bielefeld Ice Nucleation ARraY) setup, which is a microfluidic apparatus employing nanoliter-volume droplets. The combination of these two devices enables the study of freezing processes over a broad temperature range, extending from the ice melting point down to the homogeneous ice nucleation limit of water droplets. The latter ability is an essential prerequisite for the study of molecular ice nucleators, which sometimes induce heterogeneous ice nucleation only at low temperatures in proximity to the homogeneous ice nucleation limit. In conjunction with the aforementioned ice nucleation experiments, the results of other experiments dedicated to the study of ice growth inhibition induced by molecular compounds adsorbed to the surfaces of existing ice crystals are presented. This objective is realized through the implementation of the sucrose-sandwich technique in conjunction with a subsequent kinetic analysis of ice recrystallisation, a process which we termed the Ice Recrystallization Rate INhibition Analysis (IRRINA) assay.

The presentation will comprise data on ice nucleation and ice growth inhibition induced by proteins as well as oligomers and polymers of natural and synthetic origin, including polyols and polysaccharides.

Cryopreservation is a critical technology for the long-term storage of biological samples, including cells, tissues, and organs, and plays a pivotal role in biomedicine fields such as cell therapy, regenerative medicine, and organ transplantation. At the microscale, the high-water content of cells and tissues (70%–90%) presents a significant challenge: ice formation, both intracellularly and extracellularly, which can lead to mechanical damage, osmotic shock, and solute accumulation. The scientific challenge of cryopreservation lies in effectively inhibiting or controlling ice formation to mitigate these damages. Traditional cryopreservation strategies rely on cryoprotective agents (CPAs) such as dimethyl sulfoxide (DMSO), which inhibit ice formation by vitrifying water. While CPAs have achieved success in preserving cell suspensions, their cytotoxicity, and inefficiency in controlling ice formation limit their application to complex biological structures like tissues and organs. Nature offers a microscale solution through ice-binding proteins (IBPs), which regulate ice nucleation and growth by controlling the site, temperature, and morphology of ice crystals. Inspired by the mechanisms of IBPs, we have developed Ice Controlling Materials (ICMs), which mimic these natural processes [1]. Unlike conventional CPAs that prevent ice formation entirely, ICMs allow controlled ice crystal formation while precisely managing their size, shape, and nucleation site. This approach alleviates ice-related damage and enhances preservation outcomes. The development of ICMs has not only advanced cryopreservation technology but also deepened our understanding of the microscale mechanisms organisms use to protect themselves from freezing damage. By leveraging these materials, efficient and safe cryopreservation of tissues and organs is being realized [2], marking a transformative step in the field.

Ice nucleation by proteins plays a crucial role in atmospheric and ecological processes, influencing cloud formation, precipitation, and biological survival strategies. While theoretical studies suggest that large molecular size and strong ice-binding affinity are key factors in potent ice nucleation, experimental validation has been limited. Here, we integrate ice nucleation measurements, physicochemical characterization, numerical modeling, and nucleation theory to provide direct evidence that efficient ice nucleation depends on two primary factors: (1) large protein size, often achieved through the functional aggregation of smaller units, and (2) a strong affinity for ice. We elucidate the hierarchical assembly mechanism of bacterial ice-nucleating proteins (INPs), which form multimers that enhance their nucleation efficiency. The environmental sensitivity of the bacterial INP assembly to pH and ionic content provides a pathway for optimizing their performance in controlled freezing applications.

Beyond bacterial systems, we identify fungal ice-nucleating proteins as smaller extracellular proteins capable of assembling into functional aggregates. This discovery highlights a similar strategy across biological kingdoms, where protein aggregation enables ice formation at relatively warm subzero temperatures. Our findings establish a framework for identifying and engineering potent ice-nucleating proteins, with implications for atmospheric science, cryopreservation, and industrial freezing technologies.

TBA

Heterogeneous vapor-liquid nucleation of water occurs when a sufficiently large number of water molecules come together at a surface, forming a cluster that does not decay but initiates condensation. In the classical view, deposition ice nucleation occurs analogously to vapor-liquid nucleation, with the difference that the water molecules form not only a cluster but a hexagonal crystal. The requirement of the crystalline structure of the cluster obviously greatly decreases the probability of nucleation, and it seems likely that an intermediate liquid phase would facilitate ice nucleation. In the pore condensation and freezing mechanism (Marcolli, 2014), the intermediate liquid phase is capillary condensed water. However, deposition ice nucleation occurs on different nonporous ice nuclei as well, suggesting that multilayer adsorbed water may in these cases act as the intermediate phase. We have developed a theoretical framework to account for the homogeneous and heterogeneous freezing of adsorbed water films and droplets. Water vapor adsorption is described using the FHH adsorption model, which is commonly used in studies of CCN activation of insoluble particles (Sorjamaa and Laaksonen, 2007), and the freezing rates are calculated using the classical nucleation theory. The theory predicts very diverse temperature dependencies of the critical supersaturation that are determined by the adsorption parameters and ice and water contact angles of the ice-nucleating materials, and the requirement that the adsorption layer thickness, or adsorbed droplet size, must be large enough to accommodate the critical ice cluster. The predictions agree remarkably well with laboratory experiments.

The suppression of ice recrystallization by ice-binding proteins (IBPs) plays a vital role in survival strategies of freeze-tolerant organisms. While the mechanisms behind ice-recrystallization inhibition (IRI) have remained elusive, the thermal hysteresis (TH) effect, a survival strategy of freeze-avoiding organisms, has a well-established underlying physical mechanism of advancing ice plane pinning by IBPs. This study formulates and substantiates a comprehensive physical model for IRI by IBPs that ties together the physical foundations of TH and IRI. We adopt the well-established framework of diffusion-limited Ostwald ripening as the fundamental basis of ice recrystallization and incorporate transient pinning by IBPs on the ice-crystal surface. Mathematical modeling and numerical simulations reveal that transient pinning homogenizes surface curvature across ice crystals, demonstrating effective IRI at a remarkably low density of ice-bound proteins. We discuss the validity of our model in view of related theory and experimental observations, quantify the impact of ice-IBP reversibility and binding kinetics, and provide a range of testable predictions on the dependence of IRI activity on experimentally accessible parameters. This research contributes to our fundamental understanding of cryoprotection by ice-binding proteins, which can facilitate further exploration and development of ice binding agents and their use in cryopreservation applications.

Passive low ice-adhesion surfaces are frequently composed of soft materials; however, soft materials potentially present durability issues, which could be overcome by fabricating composite surfaces with patterned rigid and soft areas. Here we propose the innovative concept of discontinuity-enhanced icephobic surfaces, demonstrating that the stress concentration at the edge between rigid and soft areas facilitates ice detachment.

Complementing experimental tests with numerical simulations, it was found that on a composite surface containing rigid and soft areas, stress is concentrated at the edge between the two, i.e. at the discontinuity line, rather than all over the soft or rigid areas. As a result, ice detachment is promoted: the crack occurs first at the discontinuity line, propagates on rigid and then on soft areas. Moreover, it was demonstrated that an increase in discontinuities promotes crack initiation and leads to a reduction of ice adhesion. Remarkably, an unexpected non-unidirectional crack propagation was observed for the first time and elucidated.

Climate warming is altering hydrological processes in the cryosphere, yet these changes remain poorly understood. This study advances our understanding of fluid flow through subfreezing porous materials like snow, firn, and permafrost. Such flow involves complex interactions between interfacial flow, phase change, and thermal transfer, leading to diverse non-equilibrium phenomena from pore to field scales. We present ongoing numerical and experimental investigations into unsaturated water flow in porous ice.

At the cm-to-m scale, we employ a thermodynamic nonequilibrium infiltration model to examine refrozen structures formed during gravity-driven water infiltration in subfreezing porous media. We identify two key freezing-induced mechanisms that slow infiltration. First, a portion of infiltrating water freezes, reducing the effective infiltration rate, which can be quantified using the freezing Damköhler number. Second, secondary fingers—new flow paths forming between primary channels—decrease flow channelization, weakening infiltration efficiency through flow field homogenization.

At the mm-to-cm scale, we explore water imbibition into a subfreezing Hele-Shaw cell through experiments and modeling. Water at 0°C is injected at a constant flow rate into a radial Hele-Shaw cell cooled by a thermal-controlled aluminum block. By varying the cell gap thickness and flow rate, we analyze changes in solidification dynamics and flow. To model this process, we develop a gap-averaged two-phase Hele-Shaw flow model coupled with freezing dynamics. Finally, we compare preliminary experimental results with the model.

In-situ measurements indicate that atmospheric ice crystals are quite complex, with an array of different morphologies and degrees of surface roughness, aggregation, or attrition (Järvinen et al., 2018). We perform a series of single-column radiative transfer calculations to quantify the impact of this ice crystal complexity on the radiative heating from ice clouds in the atmosphere. Inclusion of complexity reduces this cloud-radiative heating (CRH), while temperature dependence of optical properties enhances the heating, especially for optically thin ice clouds at high altitudes. We then compare these findings from the idealized setup to optical sensitivities in a full complexity storm-resolving model, the Icosahedral Non-hydrostatic (ICON) model. ICON simulations are run for several different descriptions of ice optical properties in the atmosphere. In these more realistic simulations, the daily cycle of CRH is muted and the outgoing infrared radiation enhanced by including ice crystal complexity or temperature dependence in the optical properties. Changes in cloud-radiative heating of even a few degrees Kelvin per day have important implications for atmospheric circulations and stability. We finish with a brief overview of an effort at The University of Arizona to design the CHanneled Infrared Polarimeter (CHIRP), an infrared polarimeter that would provide observational data on ice crystal complexity using polarization measurements in 8-11.5 µm wavelength band.

Hydrogels are particularly versatile materials that are widely found in both Nature and industry. One key reason for this versatility is their high-water content, which lets them dramatically change their volume and many of their mechanical properties — often by orders of magnitude — as they swell and dry out. Currently, we lack techniques that can precisely characterize how these properties change with water content. To overcome this challenge, here we develop Gel-Freezing Osmometry (GelFrO): an extension of freezing-point osmometry. We show how GelFrO can measure a hydrogel’s mechanical response to compression and shrinkage in response to an applied osmotic pressure, while only using small, 100mL samples. Because the technique allows measurement of properties over an unusually wide range of water contents, it allows us to accurately test theoretical predictions. We find simple, power-law behavior for both mechanical and osmotic responses, while these are not well-captured by classical Flory-Huggins theory. We interpret this power-law behavior as a hallmark of a microscopic fractal structure of the gel’s polymer network and propose a simple way to connect the gel’s fractal dimension to its mechanical and osmotic properties. This connection is supported by observations of hydrogel microstructures using small-angle x-ray scattering. Finally, our results motivate simplifications to common models for hydrogel mechanics, and we propose an updated hydrogel constitutive model.