Ice Nucleation Temperature Research Articles

An extreme environment-tolerant anti-icing coating

Undesired ice accumulation on outdoor infrastructures causes serious economic and safety issues, inducing the urgent demand of anti-icing coatings. However, the outdoor equipment inevitably suffers from various extreme environments, resulting in a challenge for anti-icing coatings to maintain surface structures and material properties that directly affect anti-icing performance. Herein, we develop an anti-icing coating that can tolerate a variety of extreme environments, including ultra-low (-196 ℃) or high temperature (200 ℃), strong acid (pH = 0) or alkali (pH = 14), 168-h ultraviolet (∼6-month sunlight) exposure, and 200-cycle sandpaper grinding. The tough coating can remain intact and maintain deicing performance owing to the incorporation of fluorinated amphiphilic copolymers and photo-thermal nanocarbon fibers in PDMS matrix. The coating can significantly decrease ice nucleation temperature (<-26 ℃), increase icing delay time (∼46-fold delay), and reduce ice adhesion strength (∼17.7 kPa), suggesting both excellent anti-icing and energy-saving deicing performance. This coating is highly promising to outdoor anti-icing applications for universal conditions.

Interplay between crosslinking and ice nucleation controls the porous structure of freeze-dried hydrogel scaffolds.

Freeze-drying is a process of choice to texture hydrogel scaffolds with pores formed by an ice-templating mechanism. Using state-of-the-art microscopies (cryo-EBSD, μCT, CLSM), this work evidences and quantifies the effect of crosslinking and ice nucleation temperature on the porous structure of thin hydrogel scaffolds freeze-dried at a low cooling rate. We focused on a polysaccharide-based hydrogel and developed specific protocols to monitor or trigger ice nucleation for this study. At a fixed number of intermolecular crosslinks per primary molecule (p=5), the mean pore size in the dry state decreases linearly from 240 to 170μm, when ice nucleation temperature decreases from -6°C to -18°C. When ice nucleation temperature is fixed at -10°C, the mean pore size decreases from 250 to 150μm, as the crosslinking degree increases from p=3 to p=7. Scaffold infiltration ability was quantified with synthetic microspheres. The seeding efficiency was assessed with MC3T3-E1 individual cells and HepaRG™ spheroids. These data collapse into a single master curve that exhibits a sharp transition from 100% to 0%-efficiency as the entity diameter approaches the mean pore size in the dry state. Altogether, we can thus precisely tune the porosity of these 3D materials of interest for 3D cell culture and cGMP production for tissue engineering.

Pollen derived macromolecules serve as a new class of ice-nucleating cryoprotectants

Cryopreservation of biological material is vital for existing and emerging biomedical and biotechnological research and related applications, but there remain significant challenges. Cryopreservation of cells in sub-milliliter volumes is difficult because they tend to deeply supercool, favoring lethal intracellular ice formation. Some tree pollens are known to produce polysaccharides capable of nucleating ice at warm sub-zero temperatures. Here we demonstrated that aqueous extractions from European hornbeam pollen (pollen washing water, PWW) increased ice nucleation temperatures in 96-well plates from ≈ − 13 °C to ≈ − 7 °C. Application of PWW to the cryopreservation of immortalized T-cells in 96-well plates resulted in an increase of post-thaw metabolic activity from 63.9% (95% CI [58.5 to 69.2%]) to 97.4% (95% CI [86.5 to 108.2%]) of unfrozen control. When applied to cryopreservation of immortalized lung carcinoma monolayers, PWW dramatically increased post-thaw metabolic activity, from 1.6% (95% CI [− 6.6 to 9.79%]) to 55.0% (95% CI [41.6 to 68.4%]). In contrast to other ice nucleating agents, PWW is soluble, sterile and has low cytotoxicity meaning it can be readily incorporated into existing cryopreservation procedures. As such, it can be regarded as a unique class of cryoprotectant which acts by inducing ice nucleation at warm temperatures.

How Can Ice Emerge at 0 °C?

The classical nucleation theory shows that bulk water freezing does not occur at temperatures above ≈ −30 °C, and that at higher temperatures ice nucleation requires the presence of some ice-binding surfaces. The temperature and rate of ice nucleation depend on the size and level of complementarity between the atomic structure of these surfaces and various H-bond-rich/depleted crystal planes. In our experiments, the ice nucleation temperature was within a range from −8 °C to −15 °C for buffer and water in plastic test tubes. Upon the addition of ice-initiating substances (i.e., conventional AgI or CuO investigated here), ice appeared in a range from −3 °C to −7 °C, and in the presence of the ice-nucleating bacterium Pseudomonas syringae from −1 °C to −2 °C. The addition of an antifreeze protein inhibited the action of the tested ice-initiating agents.

Tuning Ice Nucleation by Mussel-Adhesive Inspired Polyelectrolytes: The Role of Hydrogen Bonding

Tuning Ice Nucleation by Mussel-Adhesive Inspired Polyelectrolytes: The Role of Hydrogen Bonding

Fabrication of liquid-infused textured surfaces (LITS): The effect of surface textures on anti-icing properties and durability

Icephobic surfaces offer an effective solution to protect the infrastructures subjected to harsh cold-weather environment and increase their efficiency. Inspired by the Nepenthes pitcher plant, liquid-infused coatings have received much interest as a potential cost-effective anti-icing solution. In this paper, we developed liquid-infused textured surfaces (LITS) through chemical etching followed by a replication method. We assessed the effect of viscosity (50 and 500 cSt) and the infusion percentages of lubricant on the morphology and icephobicity of the produced surfaces. Lubricant-infused silicone surfaces are normally obtained by combining a textured surface morphology and slipperiness. We therefore evaluated the wettability, morphology, and the localized surface elasticity maps of the fabricated surfaces using a goniometer, scanning electron microscopy (SEM), and atomic force microscopy (AFM), respectively. The icephobic performance of the samples was studied by differential scanning calorimetry (DSC), push-off tests, and freezing delay time measurements. Our observations of the anti-icing nature of the produced LITS confirmed that the heat insulation effect of the lubricant lowered the ice nucleation temperature considerably compared with non-oil surfaces. The prepared LITS presented an ice adhesion strength of less than 20 kPa, four orders of magnitude lower than that of a pristine surface. Surficial microtextures are critical for reducing the rate of oil depletion through the trapping of oil within the surface microstructures. Our designed lubricant-infused surfaces present more durable and stable anti-icing characteristics over the long term than smooth lubricant-infused surfaces.

Inter-annual variability of ice nucleating particles in Mexico city

The continuous and sustained population shift from rural to urban areas is driving most of the fast-growing megacities on a global scale. Considerable pollution, gases and particulate matter, is emitted yearly into the atmosphere of megacities, with unclear impacts on the local and regional hydrological cycle. The present work evaluated the inter-annual variability of super-micron (1.0–10 μm) ice nucleating particles (INP), via immersion freezing, sampled during the dry-warm season in Mexico City on two consecutive years using the UNAM-MicroOrifice Uniform Deposit Impactor-Droplet Freezing Technique (UNAM-MOUDI-DFT). The aerosol particles emitted in Mexico City were found to act as INP via the immersion freezing mode at temperatures below −20 °C with INP concentrations ranging between 0.74 L-1 (−20 °C) and 20.42 L-1 (−30 °C). Although the INP concentration varied between the dry-warm seasons, the average concentrations between 2018 and 2019 were rather similar, with significant differences only observed at −20 °C. The large increase (>200%) in fine particulate matter -PM2.5- observed during the 2019 severe air pollution episode caused by biomass burning (BB) emissions, did not impact the super-micron INP concentrations between −20 °C and −30 °C. However, INPs at temperatures above −15 °C were found to increase during the severe pollution episode. Given that such warm ice nucleation temperatures can be linked with the presence of biological particles, the present observations suggest that the BB plumes transported into Mexico City were most likely advecting co-emitted biological particles.

Facile Synthesis of Fluorinated Polysilazanes and Their Durable Icephobicity on Rough Al Surfaces.

Superhydrophobic Al surfaces with excellent durability and anti-icing properties were fabricated by coating dual-scale rough Al substrates with fluorinated polysilazane (FPSZ). Flat Al plates were etched using an acidic solution, followed by immersion in boiling water to generate hierarchical micro-nano structures on their surfaces. The FPSZ coatings were synthesized by grafting 1H,1H,2H,2H-perfluorodecyltrimethoxysilane (FAS-17), a fluoroalkyl silane), onto methylpolysilazane, an organopolysilazane (OPSZ) backbone. The high water contact angle (175°) and low sliding angle (1.6°) of the FPSZ-coated sample with an FAS-17 content of 17.3 wt% promoted the efficient removal of a frozen ice column with a low ice adhesion strength of 78 kPa at −20.0 °C (70% relative humidity), which was 4.3 times smaller than that of an OPSZ-coated surface. The FPSZ-coated Al surface suppressed ice nucleation, leading to a decrease in ice nucleation temperature from −19.5 to −21.9 °C and a delay in freezing time from 334 to 4914 s at −19.0 °C compared with the OPSZ-coated Al surface. Moreover, after 40 icing–melting cycles the freezing temperature of a water droplet on the FPSZ-coated Al surface remained unchanged, whereas that on the FAS-17-coated Al surface increased from −22.3 to −20.7 °C. Therefore, the durability of the polymeric FPSZ coating was superior to that of the FAS-17 monolayer coating.

Freezing of few nanometers water droplets

Water-ice transformation of few nm nanodroplets plays a critical role in nature including climate change, microphysics of clouds, survival mechanism of animals in cold environments, and a broad spectrum of technologies. In most of these scenarios, water-ice transformation occurs in a heterogenous mode where nanodroplets are in contact with another medium. Despite computational efforts, experimental probing of this transformation at few nm scales remains unresolved. Here, we report direct probing of water-ice transformation down to 2 nm scale and the length-scale dependence of transformation temperature through two independent metrologies. The transformation temperature shows a sharp length dependence in nanodroplets smaller than 10 nm and for 2 nm droplet, this temperature falls below the homogenous bulk nucleation limit. Contrary to nucleation on curved rigid solid surfaces, ice formation on soft interfaces (omnipresent in nature) can deform the interface leading to suppression of ice nucleation. For soft interfaces, ice nucleation temperature depends on surface modulus. Considering the interfacial deformation, the findings are in good agreement with predictions of classical nucleation theory. This understanding contributes to a greater knowledge of natural phenomena and rational design of anti-icing systems for aviation, wind energy and infrastructures and even cryopreservation systems.

Potential use of smart coatings for icephobic applications: A review

The formation, adhesion, and accumulation of ice on surfaces can cause both economic and safety issues related to, for example, reduced efficiency in energy generation, increased energy consumption, as well as mechanical and electrical failures. Smart icephobic coatings have attracted significant attention because of their responsive behaviors to external stimuli. Such coatings on exposed surfaces can respond to changes in surrounding environmental conditions or stimuli, such as temperature, electrical and magnetic fields, and pH. Several smart icephobic coatings have been developed; most aim to reduce ice adhesion, decrease the temperature of ice nucleation, and delay freezing time. This review presents recent scientific progress in the realm of smart icephobic coatings. Although these approaches offer a great potential in applications requiring icephobic surface behavior, most related research remains in the early stages and requires more thorough investigation.

Spontaneous Freezing of Water between 233 and 235 K Is Not Due to Homogeneous Nucleation.

The spontaneous freezing of microdroplets around 233 K has long been regarded as the occurrence of homogeneous ice nucleation. The corresponding temperature has been directly regarded as the homogeneous ice nucleation temperature, which is an intrinsic character of water. However, many recent investigations indicate that the spontaneous freezing may be still induced by surfaces of the water microdroplets or the residual impurities inside. Therefore, it is highly desired to reveal with solid evidence the exact origin of the spontaneous freezing. Here we show with no ambiguity that the spontaneous freezing between 233 and 235 K is actually triggered by the surface of microdroplets, as the nucleation rate is found to be proportional to the surface area of droplets, via systematically investigating the freezing of water droplets with varying sizes under various cooling rates followed by a new approach in data analysis. The conclusion is further consolidated by published experimental data from other groups when using our data analysis approach. This study is critical for understanding the sources of "no-man's land" and features of homogeneous nucleation, as well as studying the structure and properties of deeply supercooled liquid water.

Comparison of the freezing behavior of two liverwort species – Conocephalum salebrosum and Marchantia polymorpha subsp. ruderalis

Extracellular ice formation as a dehydrating agent is generally acknowledged as an important element of freezing avoidance in frost hardy plants, preventing the development of lethal ice crystals within living cells. While many reports on extracellular ice formation do exist for vascular plants, not much is known on ice formation for liverworts. In this study, ice formation was studied for two liverwort species occurring in climate zones with winter freezing, Conocephalum salebrosum and Marchanthia polymorpha L. subsp. ruderalis, together with taxon-specific ice nucleating temperature and seasonal concentration of ice nucleating agents. Samples were collected in late autumn from various sites in south west Germany. Afterwards the collected liverwort specimen were cultivated and acclimated in pots in the inner courtyard of the State Museum of Natural History Stuttgart, Germany. Ice formation was observed in the environmental scanning electron microscope (ESEM) within the air chambers of both species, with ice crystals growing out of the air chamber pores, as well as random ice crystal formation on various sites on the ventral side for both taxa. The growing ice sheets led to dehydration particularly of the parenchymatous cells. For both taxa, the observations support the relevance of extracellular ice formation for surviving freezing conditions but the experiments also indicate a better adaptation of C. salebrosum to frost.

Low-temperature acclimation and legacy effects of summer water deficits in olive freezing resistance.

Low temperatures and drought are the main environmental factors affecting plant growth and productivity across most of the terrestrial biomes. The objective of this study was to analyze the effects of water deficits before the onset of low temperatures in winter to enhance freezing resistance in olive trees. The study was carried out near the coast of Chubut, Argentina. Plants of five olive cultivars were grown outdoor in pots and exposed to different water deficit treatments. We assessed leaf water relations, ice nucleation temperature (INT), cell damage (LT50), plant growth and leaf nitrogen content during summer and winter in all cultivars and across water deficit treatments. Leaf INT and LT50 decreased significantly from summer to winter within each cultivar and between treatments. We observed a trade-off between resources allocation to freezing resistance and vegetative growth, such that an improvement in resistance to sub-zero temperatures was associated with lower growth in tree height. Water deficit applied during summer increased the amount of osmotically active solutes and decreased the leaf water potentials. This type of legacy effect persists during the winter after the water deficit even when treatment was removed by natural rainfalls.

A Microfluidic Device for Automated High Throughput Detection of Ice Nucleation of Snomax®.

Measurement of ice nucleation (IN) temperature of liquid solutions at sub-ambient temperatures has applications in atmospheric, water quality, food storage, protein crystallography and pharmaceutical sciences. Here we present details on the construction of a temperature-controlled microfluidic platform with multiple individually addressable temperature zones and on-chip temperature sensors for high-throughput IN studies in droplets. We developed, for the first time, automated droplet freezing detection methods in a microfluidic device, using a deep neural network (DNN) and a polarized optical method based on intensity thresholding to classify droplets without manual counting. This platform has potential applications in continuous monitoring of liquid samples consisting of aerosols to quantify their IN behavior, or in checking for contaminants in pure water. A case study of the two detection methods was performed using Snomax® (Snomax International, Englewood, CO, USA), an ideal ice nucleating particle (INP). Effects of aging and heat treatment of Snomax® were studied with Fourier transform infrared (FTIR) spectroscopy and a microfluidic platform to correlate secondary structure change of the IN protein in Snomax® to IN temperature. It was found that aging at room temperature had a mild impact on the ice nucleation ability but heat treatment at 95 °C had a more pronounced effect by reducing the ice nucleation onset temperature by more than 7 °C and flattening the overall frozen fraction curve. Results also demonstrated that our setup can generate droplets at a rate of about 1500/min and requires minimal human intervention for DNN classification.

Frozen in the dark: interplay of night-time activity of xanthophyll cycle, xylem attributes, and desiccation tolerance in fern resistance to winter.

While most ferns avoid freezing as they have a tropical distribution or shed their fronds, wintergreen species in temperate and boreoalpine ecosystems have to deal with sub-zero temperatures. Increasing evidence has revealed overlapping mechanisms of desiccation and freezing tolerance in angiosperms, but the physiological mechanisms behind freezing tolerance in ferns are far from clear. We evaluated photochemical and hydraulic parameters in five wintergreen fern species differing in their ability to tolerate desiccation. We assessed frond freezing tolerance, ice nucleation temperature and propagation pattern, and xylem anatomical traits. Dynamics of photochemical performance and xanthophyll cycle were evaluated during freeze-thaw events under controlled conditions and, in selected species, in the field. Only desiccation-tolerant species, which possessed a greater fraction of narrow tracheids (<18 μm) than sensitive species, tolerated freezing. Frond freezing occurred in the field at -3.4 ± 0.9 °C (SD) irrespective of freezing tolerance, freezable water content, or tracheid properties. Even in complete darkness, maximal photochemical efficiency of photosystem II was down-regulated concomitantly with zeaxanthin accumulation in response to freezing. This was reversible upon re-warming only in tolerant species. Our results suggest that adaptation for freezing tolerance is associated with desiccation tolerance through complementary xylem properties (which may prevent risk of irreversible cavitation) and effective photoprotection mechanisms. The latter includes de-epoxidation of xanthophylls in darkness, a process evidenced for the first time directly in the field.

Supercooling as a potentially improved storage option for commercial kimchi

The supercooling degree (SD), which refers to the difference between the ice nucleation temperature and freezing point of kimchi, varies depending on the type of kimchi, manufacturer, recipe, and manufacturing season. The aim of this study is to investigate the major influencing factors for the supercooled storage of kimchi and to analyze the possibility of supercooled storage for commercial kimchi. Pearson correlation analysis determined that, in commercial kimchi manufactured between March and July 2018, the SD of kimchi correlated to the number of aerobic bacteria (P <0.01), however, was not associated with lactic acid bacteria. Moreover, the ice nucleation temperature of saline solution inoculated with aerobic bacteria was reduced from -3.03± 0.04 to -6.18± 0.11°C by 10 kGy gamma ray sterilization. Meanwhile, the ice nucleation temperatures of 1.8kg of commercial red cabbage kimchi and 500g of white cabbage kimchi manufactured in February 2020 were -3.93± 0.06°C and -3.57± 0.06°C, respectively, and they could be stored at -2.5°C for 12 weeks without freezing. Additionally, supercooled storage of kimchi at -2.5°C caused a fermentation delay effect compared to control storage at 1°C, considering the acidity and amount of lactic acid bacteria. Therefore, if the number of aerobic bacteria is controlled during the manufacturing process of kimchi, supercooled storage at temperatures below -2.5°C may extend the shelf life of kimchi. PRACTICAL APPLICATION: We have shown that aerobic bacteria are the key influencing factor for ice nucleation of kimchi during supercooled storage. Aside from the initial sterilization process, fermentation of kimchi can also be delayed by lowering the storage temperature below -2.5°C. Moreover, the method of direct cool refrigeration may have an industrial-level application.

In-line prediction of secondary drying time from measured ice nucleation temperature during lyophilization process

In-line prediction of secondary drying time from measured ice nucleation temperature during lyophilization process

The freezing behavior of aqueous n-alcohol nanodroplets.

We generate water-rich aerosols containing 1-propanol and 1-pentanol in a supersonic nozzle to study the effects of these solutes on the freezing behavior of water. Condensation and freezing are characterized by two complementary techniques, pressure trace measurements and Fourier Transform Infrared spectroscopy. When 1-pentanol and 1-propanol are present, condensation occurs at higher temperatures because particle formation from the vapor phase is enhanced by the decrease in interfacial free energy of mixed aqueous-alcohol critical clusters relative to those of pure water. FTIR results suggest that when ∼6 nm radius droplets freeze, the tetrahedral structure of the ice is well preserved up to an overall alcohol mole fraction of 0.031 for 1-propanol and 0.043 for 1-pentanol. In this concentration range, the ice nucleation temperature decreases continuously with increasing 1-propanol concentration, whereas the onset of freezing is not significantly perturbed by 1-pentanol up to a mole fraction of 0.03. Furthermore, once freezing starts the ice nucleation rates in the aqueous-alcohol droplets are very close to those for pure water. In contrast, at the highest mole fractions of either alcohol it is not clear whether droplets freeze to form crystalline ice since the final state of the particles cannot be adequately characterized with the available experimental techniques.

Self-lubricated anti-icing MOF coating with long-term durability

In this paper, a novel self-lubricated nanothickness MOF coating (SLNTMC) with excellent and long-term anti-icing performance is designed based on the synergistic anti-icing mechanism of hydrophobic porous micro/nanostructures and lubricating layer. The organosilicone grafted thin UiO-66-NH2 coating is prepared through a three-step reaction. SLNTMCs could reduce the ice adhesion to 9.4 kPa, and lower the freezing temperature of condensed water to -36.0 °C, due to the organosilicone layer of SLNTMC covering the ice nucleation sites on surface and reducing the water/ice adhesion, whilst combined with the porous micro/nano structures which introduce air pockets between water and surface and hinder their thermal conduction. SLNTMCs with larger MOF particle size show lower ice nucleation temperature and the organosilicone molecular weight of 4000–7700 is benefical to improve surface anti-icing performance. The SLNTMC exhibits a long-term durability, it maintains a low ice adhesion after 20 icing/de-icing cycles. Moreover, SLNTMC is a ultrathin, transparent, flexible solid thin film that could be prepared on different polymeric substrates, making them suitable for practical application having different requirements.

Influence of image analysis strategy, cooling rate, and sample volume on apparent protein cloud-point temperature determination

The protein cloud-point temperature (TCloud) is a known representative of protein–protein interaction strength and provides valuable information during the development and characterization of protein-based products, such as biopharmaceutics. A high-throughput low volume TCloud detection method was introduced in preceding work, where it was concluded that the extracted value is an apparent TCloud (TCloud,app). As an understanding of the apparent nature is imperative to facilitate inter-study data comparability, the current work was performed to systematically evaluate the influence of 3 image analysis strategies and 2 experimental parameters (sample volume and cooling rate) on TCloud,app detection of lysozyme. Different image analysis strategies showed that TCloud,app is detectable by means of total pixel intensity difference and the total number of white pixels, but the latter is also able to extract the ice nucleation temperature. Experimental parameter variation showed a TCloud,app depression for increasing cooling rates (0.1–0.5 °C/min), and larger sample volumes (5–24 μL). Exploratory thermographic data indicated this resulted from a temperature discrepancy between the measured temperature by the cryogenic device and the actual sample temperature. Literature validation confirmed that the discrepancy does not affect the relative inter-study comparability of the samples, regardless of the image analysis strategy or experimental parameters. Additionally, high measurement precision was demonstrated, as TCloud,app changes were detectable down to a sample volume of only 5 μL and for 0.1 °C/min cooling rate increments. This work explains the apparent nature of the TCloud detection method, showcases its detection precision, and broadens the applicability of the experimental setup.