HYPOTHESIS:Mechanical interlocking (anchoring) of ice within surface roughness features is a primary contributor to ice adhesion, yet the interfacial region in which it occurs remains concealed between the bulk ice and the solid surface. Previous efforts to explore this hidden region have relied on 2D side-view or top-view optical and electron microscopy, or on destructive, indirect 3D replica imaging, leaving the mechanical anchoring of ice largely hypothetical and inadequately understood. We hypothesize that in situ freezing X-ray computed tomography (XCT) can non-destructively resolve the ice-solid interfacial region in three dimensions, yielding valuable information about ice mechanical interlocking at the interface. EXPERIMENTS:This study presents a multi-step approach using in situ freezing XCT for non-destructive 3D visualization and analysis of interlocked ice at the interface between ice droplets and hydrophilic, fully wetted (Wenzel state) femtosecond-laser-textured aluminum substrates (voxel size: 1.6 μm). Freezing XCT is coupled with wetting, ice adhesion, and confocal profilometry measurements to link interfacial morphology to icing behavior. FINDINGS:Freezing XCT resolved the hidden ice infiltrated and anchored within the microgrooves at two-phase (ice + substrate) interfaces, a region previously obscured or merely speculated about. Interlocked-ice volume followed the trend of functional (volume) roughness parameters of surfaces, whereas conventional height-based parameters (e.g., Sa, Ra, Sq, Rq) remained insensitive to it, exposing the shortcomings of prevailing roughness-ice adhesion correlations.

Superomniphobic surfaces, capable of repelling a wide range of liquids including low-surface-tension oils, rely on a synergy between surface chemistry and texture. For decades, these surfaces have primarily relied on per- and polyfluoroalkyl substances (PFAS) due to their low surface energy and durability. However, the persistence of PFAS in the environment and their toxicological risks have triggered global regulations to phase out their use. This transition presents substantial challenges, especially in sectors such as textiles, food packaging, and electronics, where oil and chemical resistance are essential and fluorine-free alternatives remain limited. While recent research has made progress in developing PFAS-free superhydrophobic surfaces, there remains a significant gap in understanding and designing non-fluorinated superomniphobic systems. This review provides a comprehensive overview of recent strategies for achieving superomniphobicity without fluorinated chemistry. We discuss both texture- and chemistry-based approaches, including coatings made with silica nanoparticles, treated fabrics, and metal oxide nanostructures, as well as coating-free systems that leverage advanced 3D-printing to fabricate doubly and triply re-entrant geometries. Importantly, we highlight limitations in scalability, durability, and liquid-specific performance. By identifying key material and structural design considerations, this review offers a clear perspective on current challenges and emerging opportunities for creating sustainable, high-performance, PFAS-free superomniphobic surfaces.

Understanding ice adhesion and detachment from solid surfaces is essential for the rational design of effective icephobic coatings. In this study, we present a peculiar regime of ice sliding on surfaces with a roughness in the nanometer range, demonstrating that sliding can be consistently observed on various surfaces, including glass and polysaccharide-based monolayer coatings. Such sliding can be interpreted as the macroscopic manifestation of an interfacial layer, often referred to as quasi-liquid layer or pre-molten layer. To test the hypothesis, ice sliding experiments were conducted at different pushing speeds, roughness values and temperatures, on bare and coated glass, providing information on the nanoscale surface properties and behavior of ice at the interface. As such, we pave the way to the rational design of nanoscale-smooth surfaces and materials, that take advantage of interfacial quasi-liquid layer to reduce ice adhesion. Also, polysaccharides are non-toxic and biodegradable, properties that make them suitable as sustainable environmental-friendly coatings.

To mitigate the effects of icing in industry and everyday life, significant efforts have been directed in the last decade towards the development of surfaces with low ice adhesion. Although several materials have emerged as potential candidates for the development of ultra-low ice adhesion coatings, most of them lack mechanical durability, as they are susceptible to abrasion. The present study explores the ice adhesion properties of a nickel-titanium (NiTi) shape memory alloy (SMA), which combines a relatively low elastic modulus and mechanical durability, revealing that SMAs can display icephobic properties, with ice adhesion strength down to 100 kPa, comparable to that of soft polymers. NiTi samples of varying thicknesses are characterized for their critical shear stress and interfacial toughness, highlighting the significance of sample thickness and stiffness in ice adhesion characterization. Additionally, the impact of surface roughness on ice adhesion is examined. As a metallic material, NiTi offers superior mechanical durability, opening up a novel route for durable, coatingless technologies against ice adhesion.

Compound drops impacting on a solid surface play an important role in industrial applications, such as combustion, the food industry, and drug encapsulation. An intriguing phenomenon associated with this process is the occurrence of singular jets that are up to dozens of times faster than the impact velocity. These jets break into microdroplets, which can produce aerosols and affect the quality of printing technologies. The collapsing dynamics directly determine the cavity geometry, jet velocity, and entrapments. Here, we investigate experimentally and numerically the jetting process after a coaxial water-inoil compound drop impacts onto a glass substrate with different releasing heights and volumetric ratios. After impact, the water core spreads and retracts, giving rise to a vertical jet initially made of oil. For certain values of the impacting velocity, high-speed and very thin jets are observed, the so-called singular jets. Depending on the volumetric ratio, one or two velocity peaks can be observed when varying the impact velocity, triggered by the contraction dynamics of a deep and cylindrical cavity. The self-similar time-evolution of the collapse for the first singularity regime follows a 1/2 power law in time, which can be derived from bubble pinch-off. In contrast, the collapse at the second peak follows a 2/3 power law, which can be accounted for by a balance between inertial and capillary forces.

Freezing processes involving polysaccharides are widespread, spanning from organisms resisting cold environments, to emerging applications for cryopreservation in biomedical and food technologies. Yet, many fundamental questions on these processes remain unanswered. The challenge arises both from the complexity of polysaccharides and their structure and from water, a simple molecule with unique properties; such complexity can only be understood using a strongly interdisciplinary approach spanning through physics, chemistry, materials science and engineering. This review explores the current understanding of the complex phenomena underpinning the behavior of water when interacting with polysaccharides, with a special interest at freezing conditions, when ice forms. Herein, we draw a comprehensive picture on the most relevant findings, connecting scientific knowledge from diverse fields, from chemistry to biotechnology, materials science and engineering, all linked by the interest in water-polysaccharide interactions, especially at interfaces. After introducing the key concepts related to the structure of water at the interface with polysaccharides, such as bound water, non-freezing water and quasi-liquid layer, the review compares the main techniques used to study the polysaccharide-water interaction in freezing conditions, discussing the relevant findings for a variety of polysaccharides.

Water management is crucial for the performance of anion exchange membrane water electrolyzers (AEM-WEs), to maintain membrane hydration and enable phase separation between hydrogen gas and liquid water. Therefore, careful material selection for the anode and cathode is essential to enhance reactant/product transport and optimize water management under ‘dry cathode’ conditions. This study investigates the wetting characteristics of two commercially available porous transport layers (PTLs) used in AEM-WE: carbon paper and carbon paper with a microporous layer (MPL). Wettability was measured under static, quasi-static, and dynamic conditions to assess the effect of water and electrolytes (NaOH, KOH, K 2 CO 3 ) across concentrations (up to 1 M) and operational temperatures (20 °C to 92 °C). Carbon paper exhibits mild hydrophobicity (advancing contact angles of $$\:\sim$$ 120°, however with receding contact angle $$\:\sim$$ 0°), whereas carbon paper with MPL demonstrates superhydrophobicity (advancing and receding contact angles >145° and low contact angle hysteresis), maintaining a stable Cassie-Baxter wetting state. Dynamic wetting experiments confirmed the robustness of the superhydrophobicity in carbon paper with MPL, facilitating phase separation between hydrogen gas and liquid water. The presence of supporting electrolytes did not significantly affect wettability, and the materials retained hydrophobic properties across different temperatures. These findings highlight the importance of MPLs in optimizing water transport and gas rejection within AEM-WEs, ensuring efficient and stable operation under “dry cathode” conditions. These PTLs (with and without the addition of the MPL) were integrated into AEM-WE and polarization curves were run. Preliminary data, in a specific condition, suggested the presence of the MPL within the PTL enhance AEM-WE performance.

Fog water harvesting, inspired by desert organisms, offers a sustainable and low‐cost solution to water scarcity, especially in humid coasts. Mesh‐based fog collection is gaining research attention due to its passive operation and minimal environmental impact. This study aims to develop effective, low‐cost, scalable, and easy‐to‐apply fog harvester designs while evaluating their performance under fog conditions that closely mimic real‐world scenarios. Copper is electrodeposited onto steel meshes to create a rough hydrophobic layer, and modified with a per‐ and polyfluoroalkyl substances‐free silica‐sol to reach superhydrophobicity. The modified sample achieves a water harvesting efficiency of 580 mg (cm2h)−1, a 40% improvement over uncoated steel meshes, comparable to the results of single‐drop impact studies and fog water harvesting investigations. The key considerations for fog harvesting research, emphasizing the need to calculate fog harvesting efficiency as the ratio of collected water to available atmospheric water generated in experimental setups are highlighted. Without standardized testing protocols, inconsistent results hinder progress and divert focus from real‐world applications. To address this, a methodology for a standardized protocol reflecting fog characteristics and environmental conditions is developed. This technological advancement offers a viable strategy to mitigate water scarcity through optimized fog water harvesters based on surface property design and control.

The working curve measurement in photopolymer additive manufacturing is a ubiquitous measure of the cure depth of a printing resin as a function of radiant exposure of light. The fit parameters from this measurement (the depth of light penetration D p and the critical exposure E c) are used to evaluate and report a resin's printability, optimize processing parameters, and inform print and resin quality control. Despite its widespread use, the working curve lacks a standard measurement method. Following up on our paper "Results of an Interlaboratory Study on the Working Curve in Vat Photopolymerization" from last year, an interlaboratory study on the working curve was performed using calibrated, reproducible, bandpass filtered light sources. With these light sources, the variability between labs in measured working curves was dramatically reduced from the initial interlaboratory study. Aggregate data from this experiment produced reliable D p and E c measurements at 385 nm of 39.2 ± 3.7 μm and 12.3 ± 3.0 mJ cm-2, respectively. At 405 nm the values of D p and E c are 69.3 ± 3.8 μm and 17.9 ± 2.3 mJ cm-2, respectively. The results are agnostic to the thickness measurement tool utilized by participants, ensuring broad applicability across laboratories. We also tested the generalizability of the proposed method of using a filtered light source by filtering a commercial 405 nm light source and obtaining a working curve in agreement with the aggregate data from the interlaboratory study. This interlaboratory study provides a basis for a documentary standard for the working curve, so that the entire photopolymer additive manufacturing industry can share reproducible and interoperable working curve data.

The main requirement for the development of Anion Exchange Membranes Fuel Cells (AEMFCs) and Water Electrolyzers (AEMFEs) on an industrial scale is the improvement of Anion Exchange Membranes performance. Besides good ionic conductivity, dimensional stability and mechanical properties in the wet state, the main challenge to be overcome is the improvement of AEMs chemical resistance in harsh alkaline environment. Poly(aryl piperidinium)s are among the most promising AEMs in terms of conductivity, mechanical properties, and chemical stability. Here we report the fabrication and physico-chemical characterization of composite AEMs based on poly(biphenyl piperidinium) (PBP) with the addition of zirconium oxide as a filler to improve membrane properties, including anionic conductivity, water uptake and alkali resistance. The optimal ZrO2 filler content was found to be 5 wt% of dry polymer mass. Compared to plain PBP, composite membranes exhibit increased hydroxide conductivity (from 75 to 116 mS cm(-1) at 80 degrees C), reduced water uptake (from 427 % to 278 % at 80 degrees C) and swelling ratio (from 85 to 62 % at 80 degrees C), and a limited reduction (41 %) of cationic groups after ageing in KOH 1 M for 500 h at 80 degrees C. We demonstrate that ZrO2 filler hinders Hoffman elimination reaction on the piperidinium ring.

HYPOTHESIS: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, where the stress concentration at the edge between rigid and soft areas, i.e. where discontinuities in elasticity are located, facilitates ice detachment. EXPERIMENTS:Composite model surfaces were fabricated with controlled rigid-soft ratios and discontinuity line lengths. The ice adhesion values were measured while recording the ice/substrate interface, to unravel the underpinning ice detachment mechanism. The experiments were complemented by numerical simulations that provided a better understanding of the ice detachment mechanism. FINDINGS:It was found that when a surface contains rigid and soft areas, stress is concentrated at the edge between soft and hard areas, i.e. at the discontinuity line, rather than all over the soft or rigid areas. An unexpected non-unidirectional crack propagation was observed for the first time and elucidated. When rigid and deformable materials are present, the crack occurs on the discontinuity line and propagates first 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.

Icephobicity encompasses a multifaceted definition that necessitates evaluations across various scales, from single droplets to larger ice specimens. The predominant method for evaluating icephobicity performance is ice adhesion strength (IAS) testing. Multiple geometries and scales for ice adhesion testing are proposed. The conventional key parameter derived from this test for icephobicity analysis is the peak detachment force value, which is subsequently converted to IAS (stress). Recent studies raise questions regarding this approach and challenge its adequacy for a comprehensive icephobicity assessment. To achieve a more profound understanding of the phenomena involved, this study utilizes three distinct ice adhesion test benches, all in horizontal shear geometry but under varying scales and conditions. The findings indicate that the peak force values derived from ice adhesion testing do not necessarily reflect the actual icephobicity behavior. However, force versus time evolution (obtained from force–time plots) can provide valuable insights into icephobicity, including the viscoelastic response of coatings and the underlying failure mechanisms. The beneficial aspects of force time evolution are additionally validated in the context of investigating coating durability through consecutive ice adhesion (icing/ice detachment) cycles, wherein conventional methodologies, such as wetting and morphological parameters, fail to capture the actual coating deterioration.

Bioactive films composed of Spiro-OMeTAD, a conductive molecular material (CMM), in combination with collagen have been manufactured and characterised for the first time. In-vitro cellular testing demonstrated the non-cytotoxicity of the doped Spiro-OMeTAD /Collagen films, opening the way for implantable or wearable medical devices and biosensors based on molecular materials.

HYPOTHESIS:Investigating solid-liquid interactions to determine advancing and receding contact angles, and consequently contact angle hysteresis, is crucial for understanding material wetting properties. A reliable, automated, and possibly open-source tool is desirable, to standardize and automatize the measurement and make it user-independent. EXPERIMENTS:This study introduces an open-source software, DropenVideo, as an extension of Dropen. DropenVideo automates frame-by-frame video analysis for the advancing and receding contact angle determination, by considering needle presence, contrast tuning, and compensating for missing drop edge data. Contact angles are calculated using convolution mask, circle, and polynomial fittings. An innovative feature in DropenVideo is the automatic protocol for identifying advancing and receding contact angles: (i) the advancing contact angle is determined as the average value during drop inflation; and (ii) the receding contact angle is determined from the frame of incipient motion during drop deflation. FINDINGS:Exploring the application of DropenVideo across a range of complex surfaces as representative test cases, we highlight existing challenges in interpreting wetting measurements by addressing different wetting scenarios. Our study demonstrates that employing frame-by-frame automatic analysis of contact angle measurement videos using DropenVideo significantly mitigates the potential risks of subjective bias associated with manual interpretation and enhances the precision of identified wetting characteristics.

Compound drop impacting on a solid surface is of considerable importance in industrial applications, such as combustion, food industry, and drug encapsulation. An intriguing phenomenon associated with this process is the occurrence of singular jets that are up to dozens of times faster than the impact velocity. These jets break into micro-droplets, which can produce aerosols and affect the quality of printing technologies. Here, we investigate experimentally and numerically the jetting process after a coaxial water-in-oil compound drop impacts on a glass substrate with different releasing heights and volumetric ratios. After impact, the water core spreads and retracts, giving rise to a vertical jet initially made of oil. For certain values of the impacting velocity, high speed and very thin jets are observed, the so-called singular jets. Depending on the volumetric ratio, one or two velocity peaks can be observed when varying the impact velocity, triggered by the contraction dynamics of a deep and cylindrical cavity. The self-similar time-evolution of the collapse for the first singularity regime follows a 1/2 power law in time, which can be derived from bubble pinch-off. In contrast, the collapse at the second peak follows a 2/3 power law, which can be accounted for by a balance between inertial and capillary forces.

STAR (Stearato dai processi di Trafilatura del filo di Acciaio come Risorsa) project, funded by the Italian Ministry of the Environment, has the ambition of redesigning the use and life cycle of waste stearates from the steel wire drawing industry, promoting the circular life of such materials. Waste stearate is having a strong impact on the economic and environmental sustainability of the steel wire production processes, adding up to the increasing pressure that industry has been facing in the last years: the pandemic crisis, the raw material price increase, the commercial restrictions related to the Ukraine and other regional conflicts.The short-term goal of the project is to develop a technology to be applied on a local scale and the long-term one is expanding it internationally. The benefits are both environmental, due to the reduction of waste and related impact on the environment, and economic, due to stearate valorization.First, stearate waste from wire drawing process were characterized in order to valorize them in the production of new materials or as an energy source.Samples of stearate waste were provided by wire drawing industries and the analyses showed that the humidity content was always low (0.1 – 5 %), while the volatile solids (VS) content varied from 2 to 70%, covering a very wide range and thus indicating a variable organic matter content. The mean higher heating value was 26 MJ/kg and the Chemical Oxygen Demand (COD) 500 mg O2/g and correlated well with VS. pH was strongly basic (>11).Anaerobic digestion can surely have an important role in valorization, as it allows to recover energy and to produce a stabilized digestate for which a further use can be studied, according to its properties. Preliminary BMP tests (BMP = Biomethane Potential) determined a biomethane production in the range 500-900 L/kgVS, much higher than the production from animal waste (around 400 L/kgVS). The toxicity of the digestate was assessed by Microtox® assay and was negligible. This finding supports the hypothesis that recalcitrant compounds, which do not undergo degradation in anaerobic conditions, are not toxic.

Icephobic materials can prevent or reduce ice formation, e.g. by ensuring easy detachment, a desirable property for those applications where ice accumulation is critical to human safety. Herein, we develop a chitosan electrolyte hydrogel to create a bio-based surface with low ice adhesion. The chitosan electrolyte hydrogel is physically crosslinked and infused with salted water at concentrations from 4.5 to 30 g/L, including that of seawater (23 g/L). Depending on salt content in the hydrogel, we could obtain very low ice adhesion down to 140 kPa (at - 10 degrees C). We hypothesize that the chitosan electrolyte hydrogel exploits the colligative properties of water avoiding the ice nucleation at the ice-hydrogel interface. To confirm the hypothesis, we investigate the chitosan electrolyte hydrogel structure by contact angles analysis, DSC, TGA, FTIR, XRD, and by rheometry for mechanical properties. We quantify the presence of non-freezing water, which creates a lubricating liquid water layer at the ice-hydrogel interface, affecting the ice detachment mechanism and lowering ice adhesion. In conclusion, the proposed chitosan electrolyte hydrogel presents a bio-based and cost-efficient strategy for ice detachment across various icing scenarios for systems operating in humid marine environments, such as offshore platforms and ships.

The interest in the development of icephobic surfaces has pushed towards the definition of standardized processes and parameters to assess ice adhesion, with the ambition of identifying an equivalent method to contact angle measurements used to assess wetting properties. Although most studies focus on the average ice adhesion strength, measured as the force per unit area required to detach ice, much less attention is paid to interfacial toughness, perhaps as its measurement is challenging. In this article, we provide a conceptual framework to correctly measure both ice adhesion strength and interfacial toughness, even using a simple push test method, laying the ground for a complete and comprehensive assessment of surface icephobicity.

Controlling surface morphology is one of the main strategies used to tune surface hydrophobic and icephobic properties. Taking advantage of coating growth by initiated chemical vapor deposition, random and ordered wrinkles were induced on a thin film of polyperfluorodecyl acrylate (pPFDA) deposited on polydimethylsiloxane (PDMS) to simultaneously modify surface chemistry and morphology. A range of wrinkles of different wavelengths were studied, and how the wrinkle characteristics change with varying coating thickness. Ordered wrinkles enhanced hydrophobicity more when compared to random wrinkles, with a noticeable effect for coating thickness on the order of hundreds of nanometers. An insight into the mechanism of surface wrinkling and its effect on freezing delay is also provided, and promising results were found on ordered wrinkles, where a freezing delay was observed.

Materials against ice formation and accretion are highly desirable for different industrial applications and daily activities affected by icing. Although several concepts have been proposed, no material has so far shown wide-ranging icephobic features, enabling durability and manufacturing on large scales. Herein, we present gradient polymers made of 1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane (V4D4) and 1H,1H,2H,2H-perfluorodecyl acrylate (PFDA) deposited in one step via initiated chemical vapor deposition (iCVD) as an effective coating to mitigate ice accretion and reduce ice adhesion. The gradient structures easily overcome adhesion, stability, and durability issues of traditional fluorinated coatings. The coatings show promising icephobic performance by reducing ice adhesion, depressing the freezing point, delaying drop freezing, and inhibiting ice nucleation and frost propagation. Icephobicity correlates with surface energy discontinuities at the surface plane resulting from the random orientation of the fluorinated groups of PFDA, as confirmed by grazing-incidence X-ray diffraction measurements. The icephobicity could be further improved by tuning the surface crystallinity rather than surface wetting, as samples with random crystal orientation show the lowest ice adhesion despite high contact angle hysteresis. The iCVD-manufactured coatings show promising results, indicating the potential for ice control on larger scales and various applications.