Solute effects on the dynamics and deformation of emulsion droplets during freezing.

Soft or rigid particles, suspended in a liquid melt, interact with an advancing solidification front in various industrial and natural processes, such as fabrication of particle-reinforced-composites, growth of crystals, cryopreservation, frost heave, and growth of sea ice. The particle dynamics relative to the front determine the microstructure as well as the functional properties of the solidified material. Previous studies have extensively investigated the interaction of foreign objects with a moving solid-liquid interface in pure melts while in most real-life systems, solutes or surface active impurities are almost always present.

Complex Composites Built through Freezing.

Using a limited selection of ordinary components and at ambient temperature, nature has managed to produce a wide range of incredibly diverse materials with astonishingly elegant and complex architectures. Probably the most famous example is nacre, or mother-of-pearl, the inner lining of the shells of abalone and certain other mollusks. Nacre is 95% aragonite, a hard but brittle calcium carbonate mineral, that exhibits fracture toughness exceedingly greater than that of pure aragonite, when tested in the direction perpendicular to the platelets.

Multiple objects interacting with a solidification front.

The interaction of objects suspended in a liquid melt with an advancing solidification front is of special interest in nature and engineering sciences. The front can either engulf the object into the growing crystal or repel it. Therefore, the object-front confrontation can have a strong influence on the microstructure and mechanical or functional properties of the solidified material.

Unveiling Cells' Local Environment during Cryopreservation by Correlative Spatial and Thermal Analyses.

Cryopreservation is the only fully established procedure to extend the lifespan of living cells and tissues, a key to activities spanning from fundamental biology to clinical practice. Despite its prevalence and impact, the central aspects of cryopreservation, such as the cell's physicochemical environment during freezing, remain elusive. Here we address that question by coupling microscopic directional freezing to visualize cells and their surroundings during freezing with the freezing-medium phase diagram.

Ice-templated poly(vinylidene fluoride) ferroelectrets.

Ferroelectrets are piezoelectrically-active polymer foams that can convert externally applied loads into electric charge for sensor or energy harvesting applications. Existing processing routes used to create pores of the desired geometry and degree of alignment appropriate for ferroelectrets are based on complex mechanical stretching and chemical dissolution steps. In this work, we present the first demonstration of the use of freeze casting as a cost effective and environmentally friendly approach to produce polymeric ferroelectrets.

Wall friction and Janssen effect in the solidification of suspensions.

We address the mechanical effect of rigid boundaries on freezing suspensions. For this we perform the directional solidification of monodispersed suspensions in thin samples and we document the thickness h of the dense particle layer that builds up at the solidification front. We evidence a change of regime in the evolution of h with the solidification velocity V with, at large velocity, an inverse proportionality and, at low velocity, a much weaker trend.

A temperature-controlled stage for laser scanning confocal microscopy and case studies in materials science.

If confocal microscopy is an ubiquitous tool in life science, its applications in chemistry and materials science are still, in comparison, very limited. Of particular interest in these domains is the use of confocal microscopy to investigate temperature-dependent phenomena such as self-assembly, diffusio- or thermophoresis, or crystal growth. Several hurdles must be solved to develop a temperature-controlled stage for laser scanning confocal microscopy, in particular regarding the influence of an elevated temperature gradient close to the microscope objective, which most people try very hard to avoid.

Five-dimensional imaging of freezing emulsions with solute effects.

The interaction of objects with a moving solidification front is a common feature of many industrial and natural processes such as metal processing, the growth of single crystals, the cryopreservation of cells, or the formation of sea ice. Interaction of solidification fronts with objects leads to different outcomes, from total rejection of the objects to their complete engulfment. We imaged the freezing of emulsions in five dimensions (space, time, and solute concentration) with confocal microscopy.

Corrigendum: Strong, tough and stiff bioinspired ceramics from brittle constituents.

This corrects the article DOI: 10.1038/nmat3915.

Polyproline as a Minimal Antifreeze Protein Mimic That Enhances the Cryopreservation of Cell Monolayers.

Tissue engineering, gene therapy, drug screening, and emerging regenerative medicine therapies are fundamentally reliant on high-quality adherent cell culture, but current methods to cryopreserve cells in this format can give low cell yields and require large volumes of solvent "antifreezes". Herein, we report polyproline as a minimum (bio)synthetic mimic of antifreeze proteins that is accessible by solution, solid-phase, and recombinant methods. We demonstrate that polyproline has ice recrystallisation inhibition activity linked to its amphipathic helix and that it enhances the DMSO cryopreservation of adherent cell lines.

Interaction of Multiple Particles with a Solidification Front: From Compacted Particle Layer to Particle Trapping.

The interaction of solidification fronts with objects such as particles, droplets, cells, or bubbles is a phenomenon with many natural and technological occurrences. For an object facing the front, it may yield various fates, from trapping to rejection, with large implications regarding the solidification pattern. However, whereas most situations involve multiple particles interacting with each other and the front, attention has focused almost exclusively on the interaction of a single, isolated object with the front.

Water/ice phase transition: The role of zirconium acetate, a compound with ice-shaping properties.

Few compounds feature ice-shaping properties. Zirconium acetate is one of the very few inorganic compounds reported so far to have ice-shaping properties similar to that of ice-shaping proteins, encountered in many organisms living at low temperature. When a zirconium acetate solution is frozen, oriented and perfectly hexagonal ice crystals can be formed and their growth follows the temperature gradient.

Time-Lapse, in Situ Imaging of Ice Crystal Growth Using Confocal Microscopy.

Ice crystals nucleate and grow when a water solution is cooled below its freezing point. The growth velocities and morphologies of the ice crystals depend on many parameters, such as the temperature of ice growth, the melting temperature, and the interactions of solutes with the growing crystals. Three types of morphologies may appear: dendritic, cellular (or fingerlike), or the faceted equilibrium form.

Gas permeability of ice-templated, unidirectional porous ceramics.

We investigate the gas flow behavior of unidirectional porous ceramics processed by ice-templating. The pore volume ranged between 54% and 72% and pore size between 2.9 [Formula: see text]m and 19.

The effect of wall thickness distribution on mechanical reliability and strength in unidirectional porous ceramics.

Macroporous ceramics exhibit an intrinsic strength variability caused by the random distribution of defects in their structure. However, the precise role of microstructural features, other than pore volume, on reliability is still unknown. Here, we analyze the applicability of the Weibull analysis to unidirectional macroporous yttria-stabilized-zirconia (YSZ) prepared by ice-templating.

Mechanical properties and failure behavior of unidirectional porous ceramics.

We show that the honeycomb out-of-plane model derived by Gibson and Ashby can be applied to describe the compressive behavior of unidirectional porous materials. Ice-templating allowed us to process samples with accurate control over pore volume, size, and morphology. These samples allowed us to evaluate the effect of this microstructural variations on the compressive strength in a porosity range of 45-80%.

A meta-analysis of the mechanical properties of ice-templated ceramics and metals.

Ice templating, also known as freeze casting, is a popular shaping route for macroporous materials. Over the past 15 years, it has been widely applied to various classes of materials, and in particular ceramics. Many formulation and process parameters, often interdependent, affect the outcome.

Freezing-induced ordering of block copolymer micelles.

We demonstrate here the ordering of block copolymer micelles by ice templating, below 0 °C. We used this for the preparation of silica monoliths that present an ice-templated macroporosity, combined with a 2D hexagonal mesostructure templated by the addition of P123. We propose a mechanism triggered by the progressive freezing-induced concentration.

Strong, tough and stiff bioinspired ceramics from brittle constituents.

High strength and high toughness are usually mutually exclusive in engineering materials. In ceramics, improving toughness usually relies on the introduction of a metallic or polymeric ductile phase, but this decreases the material's strength and stiffness as well as its high-temperature stability. Although natural materials that are both strong and tough rely on a combination of mechanisms operating at different length scales, the relevant structures have been extremely difficult to replicate.

Self-assembly of faceted particles triggered by a moving ice front.

The possibility to align and organize faceted particles in the bulk offers intriguing possibilities for the design and discovery of materials and architectures exhibiting novel functional properties. The growth of ice crystals can be used to trigger the self-assembly of large, anisotropic particles and consequently to obtain three-dimensional porous materials of large dimensions in a limited amount of time. These mechanisms have not been explored so far due to the difficulty to experimentally investigate these systems.

Ice-structuring mechanism for zirconium acetate.

The control of ice nucleation and growth is critical in many natural and engineering situations. However, very few compounds are able to interact directly with the surface of ice crystals. Ice-structuring proteins, found in certain fish, plants, and insects, bind to the surface of ice, thereby controlling their growth.

Ice shaping properties, similar to that of antifreeze proteins, of a zirconium acetate complex.

The control of the growth morphologies of ice crystals is a critical issue in fields as diverse as biomineralization, medicine, biology, civil or food engineering. Such control can be achieved through the ice-shaping properties of specific compounds. The development of synthetic ice-shaping compounds is inspired by the natural occurrence of such properties exhibited by antifreeze proteins.

Reliability assessment in advanced nanocomposite materials for orthopaedic applications.

Alumina-zirconia nano-composites were recently developed as alternative bearing materials for orthopedics. Previous, preliminary reports show that such alumina-zirconia nanocomposites exhibit high crack resistance and low wear rate. In this paper, additional information is given in terms of wear, crack resistance and ageing behaviour: femoral heads are inspected after 7 million cycles of wear testing on a hip simulator, crack resistance is measured and compared to other ceramics used today in orthopedics, slow crack growth is reported under static and cyclic fatigue, and aging resistance is assessed.