Search

Understanding water drop impact on meshes is valuable to design passive systems for atmospheric water collection. By investigating water drop impact on hydrophobic and superhydrophobic surfaces, here, we identify the different drop impact outcomes and build outcome maps within the pertinent parameter spaces, based on Weber number and contact angles. Furthermore, we quantitatively evaluate critical factors such as the captured volume and spray characteristics of the penetrating liquid and also measure the drop rebound time, reporting that full rebound occurs on superhydrophobic meshes surfaces even at high We numbers, as the Cassie-Baxter wetting state is maintained.

Chitosan and its derivatives are interesting biopolymers for different field of analytical chemistry, especially in separation techniques. The present study was aimed at testing chitosan water soluble derivatives as dynamic coating agents for application to capillary electrophoresis. In particular, chitosan was modified following three different chemical reactions (nucleophilic substitution, reductive amination, and condensation) to introduce differences in charge and steric hindrance, and to assess the effect of these physico-chemical properties in capillary electrophoresis. The effects were tested on the capillary electrophoretic separation of the glycoforms of human transferrin, an important iron-transporting serum protein, one of which, namely disialo-transferrin (CDT), is a biomarker of alcohol abuse. Chitosan derivatives were characterized by using NMR and 1H NMR, HP-SEC-TDA, DLS, and rheology. The use of these compounds as dynamic coatings in the electrolyte running buffer in capillary electrophoresis was tested assessing the peak resolution of the main glycoforms of human transferrin and particularly of disialo-transferrin. The results showed distinct changes of the peak resolution produced by the different derivatives. The best results in terms of peak resolution were achieved using polyethylene glycol (PEG)-modified chitosan, which, in comparison to a reference analytical approach, provided an almost baseline resolution of disialo-transferrin from the adjacent peaks.

Polymeric nanofilms have been widely utilized in diverse cutting-edge technologies, yet accurately determining their elastic moduli remains challenging. Here we demonstrate that interfacial nanoblisters, which are produced by simply immersing substrate-supported nanofilms in water, represent natural platforms for assessing the mechanical properties of polymeric nanofilms using the sophisticated nanoindentation method. Nevertheless, high-resolution, quantitative force spectroscopy studies reveal that the indentation test must be performed on an effective freestanding region around the nanoblister apex and meanwhile under an appropriate loading force, to obtain load-independent, linear elastic deformations. The nanoblister stiffness increases with either decreasing its size or increasing its covering film thickness, and such size effects can be adequately rationalized by an energy-based theoretical model. The proposed model also enables an exceptional determination of the film elastic modulus. Given that interfacial blistering is a frequently occurring phenomenon for polymeric nanofilms, we envision that the presented methodology would stimulate broad applications in relevant fields.

Hypothesis: Characterizing the microstructure of an ice/surface interface and its effect on the icephobic behavior of surfaces remains a significant challenge. Introducing X-ray Computed Tomography (XCT) can provide unprecedented insights into the internal (porosity) and interfacial structures, i.e. wetting regime, between (super)hydrophobic surfaces and ice by visualizing these optically inaccessible regions. Experiments: Frozen droplets with controlled volume were deposited on top of metallic and polymeric substrates with different levels of wettability. Different modes of XCT (3D and 4D) were utilized to obtain information on the internal and interfacial structure of the ice/surface system. The results were supplemented by conventional surface analysis techniques, including optical profilometry and contact angle measurements. Findings: Using XCT on ice/surface systems, the 3D and 4D (imaging with temporal resolution) structural information can be visualized. From these datasets, qualitative and quantitative results were obtained, not only for characterizing the interface but also for analyzing the entire droplet/surface system, e.g., measurement of porosity size, shape, and location. These results highlight the potential of XCT in the characterization of both droplets and substrates and proves that the technique can aid to develop hydrophobic surfaces for use as icephobic materials.

Chitosan is a marine-origin polysaccharide obtained from the deacetylation of chitin, the main component of crustaceans’ exoskeleton, and the second most abundant in nature. Although this biopolymer has received limited attention for several decades right after its discovery, since the new millennium chitosan has emerged owing to its physicochemical, structural and biological properties, multifunctionalities and applications in several sectors. This review aims at providing an overview of chitosan properties, chemical functionalization, and the innovative biomaterials obtained thereof. Firstly, the chemical functionalization of chitosan backbone in the amino and hydroxyl groups will be addressed. Then, the review will focus on the bottom-up strategies to process a wide array of chitosan-based biomaterials. In particular, the preparation of chitosan-based hydrogels, organic–inorganic hybrids, layer-by-layer assemblies, (bio)inks and their use in the biomedical field will be covered aiming to elucidate and inspire the community to keep on exploring the unique features and properties imparted by chitosan to develop advanced biomedical devices. Given the wide body of literature that has appeared in past years, this review is far from being exhaustive. Selected works in the last 10 years will be considered.

Several additive manufacturing (AM) technologies are nowadays available for layer-by-layer fabrication of complex parts, allowing reduction of costs and waste compared to conventional manufacturing technologies. Among all AM technologies, digital light processing (DLP), an advanced version of stereolithography (SLA), is emerging for manufacturing 3D objects using liquid photopolymers and suspensions (e.g. including ceramic and metal particles) as feedstock. In case of supsensions, the printed object can be thermally treated for debinding and sintering, producing ceramic and metal objects. DLP takes the advantage of a digital light projector, which selectively polymerizes the feedstock, printing each layer with a single exposure, thus eliminating the scanning time required in SLA. The technology can be adopted for several applications in the field of biomedical, automobile, aerospace, and electronics due to the technological advancement in projection-based manufacturing technology and the development of innovative materials in form of elastomers, shape memory polymers, and suspensions (ceramics, metals, composites, and nanocomposites). For successful manufacturing, feedstocks need to be thoroughly characterized for optimal printing. Therefore, this work presents a systematic study to characterize both pure photopolymers and suspensions, discussing two radiation-independent characteristic parameters of photopolymers, the critical energy (Ec) and the penetration depth (Dp). This also includes some of the basic theoretical aspects of light-matter interaction that can guide the manufacturing process development and optimization. Based on such findings, we present a “printing window”, identifying the boundaries for minimum and maximum radiation exposure for optimized polymerization and thus providing guidelines for the optimal printing conditions of each individual feedstock.

Mitigating icing hazards is of interest for many technological applications. One solution is to employ low ice adhesion coatings, either passively or in combination with active de-icing systems. Nevertheless, comparing different low ice adhesion surfaces can be challenging. Studies generally report the average shear stress, calculated as the ratio of applied force to the ice-substrate contact area; however, the fracture mechanism at the ice-substrate interface is rarely reported. There are two fracture mechanisms that can occur at the interface: stress-dominated and toughness-dominated. Average shear stress is only meaningful when performing adhesion tests in a stress-dominated regime; otherwise, interface stresses are underestimated and misleading. This study presents a new understanding of ice adhesion mechanisms combining experimental and numerical methods, demonstrating how the traditional ice adhesion reporting method can lead to errors up to 400%. Using a simple fracture model, the study shows that the stress-dominated fracture regime in the horizontal push test is favored by smaller ice diameter and greater ice thickness, and is also affected by the load force position. The identification of the two fracture regimes is required for the correct understanding and reproducibility of ice adhesion results, enabling better design and characterization of icephobic coatings and materials.

Understanding the underlying hydrodynamics and developing strategies to control bouncing droplets on superhydrophobic surfaces are of fundamental and practical significance. While recent efforts have mainly focused on regulating the contact time of bouncing droplets, less attention was given to manipulating droplet rebound from the perspective of energy optimization, which determines the long-term successive dynamics. Here, we investigate the impact of water droplets on superhydrophobic cones at low Weber numbers, where ideally complete rebounds arise. In sharp contrast to flat superhydrophobic surfaces, an impinging droplet on a cone-shaped superhydrophobic surface undergoes almost inversion-symmetric spreading and retracting processes with prolonged contact time, and more strikingly, it rebounds with a higher restitution coefficient. Such enhanced droplet rebound is beyond the prediction of existing theoretical models, in which the viscous boundary layer was recognized as the dominant channel of energy dissipation and, thus, an increase in the contact time would result in a lower restitution coefficient; nevertheless, numerical simulations have confirmed the increase in the restitution coefficient. The quantitative energy and flow field analyses of our numerical results reveal that the suppression of the boundary layer in early impact and the weakening of the viscous flow near the moving edge in the subsequent impact phases, which were not accounted for yet in existing theoretical models, are the causes for the enhancement of droplet rebound on superhydrophobic cones.

Chitosan films have attracted increased attention in the field of sensors because of chitosan’s unique chemico-physical properties, including high adsorption capacity, filmability and transparency. A chitosan film sensor was developed through the dispersion of an ammonia specific reagent (Nessler’s reagent) into a chitosan film matrix. The chitosan film sensor was characterized to assess the film’s properties by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). A gas diffusion device was prepared with the chitosan film sensor, enabling the collection and detection of ammonia vapor from biological samples. The chitosan film sensor color change was correlated with the ammonia concentration in samples of human serum and artificial urine. This method enabled facile ammonia detection and concentration measurement, making the sensor useful not only in clinical laboratories, but also for point-of-care devices and wherever there is limited access to modern laboratory facilities.

The substitution of perfluorinated substances (PFAS) as chemical applied in anti-adhesive and hydrophobic applications has become an urgent need, due to raising concerns for their potential hazard. In this framework, chitosan-based coatings represent a promising alternative because of their properties of non-toxicity, biodegradability, and sustainability as raw materials. Our work developed modified chitosan-based coatings, with a fine-tuning of transparency and superhydrophobicity (Figure 1). Chitosan-based fluorine-free superhydrophobic coatings were obtained via functionality modification through esterification and amidation reaction with stearoyl chloride, followed by freeze-drying and coating deposition using a novel solvent-free approach followed by thermal treatment. A full characterization of the modified-chitosan was performed to assess its chemico-physical properties and confirmed the functionality modification. The application of an innovative and sustainable deposition method demonstrates to be effective in tuning the coating properties of transparency and superhydrophobicity, combining durability under physical abrasion.

Protein analysis by capillary electrophoresis is an established benchmark technique, where electrophoretic separation performances are frequently affected by protein adsorption on capillary walls. The protein-wall interaction can be suppressed or mitigated by the application of the so-called dynamic coating agents. In this study, the potential of chitosan derivatives as dynamic coating was investigated, targeting the separation of the carbohydrate deficient transferrin (CDT), a relevant biomarker in forensic analyses to detect chronic alcohol abuse. To this aim, chitosan was derivatized through different chemical reactions, including nucleophilic substitution, reductive amination, and condensation reaction, to provide different characteristics to the dynamic coatings. After chemical and physical characterization, chitosan derivatives were tested as dynamic coating additives in the buffer separation solution of CDT. Evidence of the improvement in the CDT separation efficiency were found applying PEGmodified chitosan via nucleophilic substitution.

Controlling water transport and management is crucial for continuous and reliable system operation in harsh weather conditions. Passive strategies based on nonwetting surfaces are desirable, but so far, the implementation of superhydrophobic coatings into real-world applications has been limited by durability issues and, in some cases, lack of compliance with environmental regulations. Inspired by surface patterning observed on living organisms, in this study we have developed durable surfaces based on contrast wettability for capillary-driven water transport and management. The surface fabrication process combines a hydrophobic coating with hard-anodized aluminum patterning, using a scalable femtosecond laser microtexturing technique. The concept targets heavy-duty engineering applications; particularly in aggressive weather conditions where corrosion is prevalent and typically the anodic aluminum oxide-based coating is used to protect the surface from corrosion, the concept has been validated on anodic aluminum oxide coated aluminum alloy substrates. Such substrates with contrast wettable characteristics show long-term durability in both natural and lab-based artificial UV and corrosion tests where superhydrophobic coatings tend to degrade.

Additive manufacturing technologies are developed and utilized to manufacture complex, lightweight, functional, and non-functional components with optimized material consumption. Among them, vat polymerization-based digital light processing (DLP) exploits the polymerization of photocurable resins in the layer-by-layer production of three-dimensional objects. With the rapid growth of the technology in the last few years, DLP requires a rational design framework for printing process optimization based on the specific material and printer characteristics. In this work, we investigate the curing of pure photopolymers, as well as ceramic and metal suspensions, to characterize the material properties relevant to the printing process, such as penetration depth and critical energy. Based on the theoretical framework offered by the Beer–Lambert law for absorption and on experimental results, we define a printing space that can be used to rationally design new materials and optimize the printing process using digital light processing. The proposed methodology enables printing optimization for any material and printer combination, based on simple preliminary material characterization tests to define the printing space. Also, this methodology can be generalized and applied to other vat polymerization technologies.

One of the current greatest challenges in materials science and technology is the development of safe- and sustainable-by-design coatings with enhanced functionalities, e.g. to substitute fluorinated substances raising concerns for their potential hazard on human health. Bio-based polymeric coatings represent a promising route with a high potential. In this study, we propose an innovative sustainable method for fabricating coatings based on chitosan with modified functionality, with a fine-tuning of coating properties, namely transparency and superhydrophobicity. The process consists in two main steps: i) fluorine-free modification of chitosan functional groups with stearoyl chloride and freeze-drying to obtain a superhydrophobic powder, ii) coating deposition using a novel solvent-free approach through a thermal treatment. The modified chitosan is characterized to assess its chemico-physical properties and confirm the functionality modification with fatty acid tails. The deposition method enables tuning the coating properties of transparency and superhydrophobicity, maintaining good durability.

Additive manufacturing is a layer-by-layer strategy enabling the advanced design and fabrication of complex 3D objects and structures, overcoming geometry limitations and reducing waste production compared to conventional technologies. Among various additive manufacturing technologies, digital light processing (DLP), is an additive manufacturing technology used to print photopolymer parts, using a projected light source to cure an entire layer at once. Initially developed for pure resins, recent advances have demonstrated the potential of DLP in the polymerization of ceramic and metal-loaded suspensions, enabling the fabrication of ceramic and metal components after proper debinding and sintering. Such flexibility increases the potential of DLP for different applications, ranging from dental implants and bone scaffolds to smart biomaterials for soft robotics, smart wearables, and microfluidic devices. The review provides an overview of DLP technology and its recent advances; specifically, the review covers the photopolymer properties, the ceramic and metallic feedstock preparation, and the light-matter interaction mechanism underpinning the printing and post-processing steps. Finally, a description of the current application is provided and complemented with future perspectives.

Non‐covalent interactions in supramolecular chemistry provide useful systems to understand biological processes, and self‐assembly systems are suitable assets to build‐up innovative products for biomedical applications. In this field, polyelectrolyte complexes are interesting, especially when polysaccharides are involved, due to their non‐toxicity and bio-absorbability. In this work, we investigated a polyelectrolyte formed by hyaluronic acid (HA), a negatively charged linear polysaccharide, with Chitlac (Ch), a positively charged lactose‐modified chitosan. The aim of the study was the investigation of a novel Ch–HA polyelectrolyte complex, to understand the interaction between the two polysaccharides and the stability towards enzymatic activity. By means of gel permeation chromatography–triple detector array (GPC–TDA), nuclear magnetic resonance (NMR), dynamic viscosity, Zeta Potential and scanning electron microscopy (SEM), the polyelectrolyte complex properties were identified and compared to individual polysaccharides. The complex showed monodisperse molecular weight distribution, high viscosity, negative charge, and could be degraded by specific enzymes, such as hyaluronidase and lysozyme. The results suggest a close interaction between the two polysaccharides in the complex, which could be considered a self‐assembly system.

Contact angle measurement is an effective way to investigate solid surface properties. The introduction of low-cost digital cameras, as well as software and libraries for image analysis, has made contact angle measurement potentially accessible to every laboratory. In this review, we provide a comparison of the main methods developed to evaluate contact angle from digital images, including the so-called Young-Laplace method, the circle and polynomial fittings, as well as the mask method. All methods have been implemented and compared analyzing virtual and real drop images in an open-source software, Dropen, developed as an app in MATLAB environment. The code enables single image analysis evaluation, for the robust automatic identification of the contact points and contact angle evaluation, with the goal of minimizing user inputs, automatizing the process and facilitating measurements for all users, from less experienced to advanced wetting experts. Dropen and its code are made available at BOA, the Bicocca Open Access public repository, for use and further development.

Electrodeposition is an effective and scalable method to grow desired structures on solid surfaces, for example, to impart superhydrophobicity. Specifically, copper microcrystals can be grown using electrodeposition by controlling deposition parameters such as the electrolyte and its acidity, the bath temperature, and the potential modulation. The aim of the present work is the fabrication of superhydrophobic copper-based surfaces by electrodeposition, investigating both surface properties and assessing durability under conditions relevant to real applications. Accordingly, copper-based layers were fabricated on Au/Si(100) from Cu(BF4)2 precursor by electrodeposition, using cyclic voltammetry and square-pulse voltage approaches. By increasing the bath temperature from 22 °C to 60 °C, the growth of various structures, including micrometric polyhedral crystals and hierarchical structures, ranging from small grains to pine-needle-like dendrite leaves, has been demonstrated. Without any further physical and/or chemical modification, samples fabricated with square-pulse voltage at 60 °C are superhydrophobic, with a contact angle of 160° and a sliding angle of 15°. In addition, samples fabricated from fluoroborate precursor are carefully compared to those fabricated from sulphate precursor to compare chemical composition, surface morphology, wetting properties, and durability under UV exposure and hard abrasion. Results show that although electrodeposition from fluoroborate precursor can provide dendritic microstructures with good superhydrophobicity properties, surfaces possess lower durability and stability compared to those fabricated from the sulphate precursor. Hence, from an application point of view, fabrication of copper superhydrophobic surfaces from sulphate precursor is more recommended.

Additive manufacturing is a layer-by-layer strategy enabling the advanced design and fabrication of complex 3D objects and structures, overcoming geometry limitations and reducing waste production compared to conventional technologies. Among various additive manufacturing technologies, digital light processing (DLP), is an additive manufacturing technology used to print photopolymer parts, using a projected light source to cure an entire layer at once. Initially developed for pure resins, recent advances have demonstrated the potential of DLP in the polymerization of ceramic and metal-loaded suspensions, enabling the fabrication of ceramic and metal components after proper debinding and sintering. Such flexibility increases the potential of DLP for different applications, ranging from dental implants and bone scaffolds to smart biomaterials for soft robotics, smart wearables, and microfluidic devices. The review provides an overview of DLP technology and its recent advances; specifically, the review covers the photopolymer properties, the ceramic and metallic feedstock preparation, and the light-matter interaction mechanism underpinning the printing and post-processing steps. Finally, a description of the current application is provided and complemented with future perspectives.

Structural characterization techniques are fundamental to correlate the material macro-, nano-, and molecular-scale structures to their macroscopic properties and to engineer hierarchical materials. Here, we combine X-ray transmission with scanning small-and wide-angle X-ray scattering (sSWAXS) to investigate ultraporous and lightweight biopolymer-based foams using cellulose nanofibrils (CNFs) as building blocks. The power of multimodal sSWAXS for multiscale structural characterization of self-assembled CNFs is demonstrated by spatially resolved maps at the macroscale (foam density and porosity), at the nanoscale (foam structural compactness, CNF orientation in the foam walls, and CNF packing state), and at the molecular scale (cellulose crystallite dimensions). Specifically, we compare the impact of freeze-thawing-drying (FTD) fabrication steps, such as static/stirred freezing and thawing in ethanol/water, on foam structural hierarchy spanning from the molecular to the millimeter scale. As such, we demonstrate the potential of X-ray scattering imaging for hierarchical characterization of biopolymers.

Ice formation on surfaces is a common phenomenon occurring in the presence of water at temperatures below the freezing point, and can negatively impact many aspects of our lives. Atmospheric icing, which forms due to the natural presence of water as small liquid drops or vapor in the air, can cause damage to ground transportation, airplanes, power lines, and communication systems (e.g., telephone and cable television line operations) and other man-made structures and devices.

Drop interaction with solid surfaces upon impact has been attracting a growing community of researchers who are focusing more and more on “complex” surfaces and “complex” drops. Recently, we are observing an emerging research trend related to the investigation of compound drop impact. Compound drops consist of two or more distinct continuous phases sharing common interfaces, surrounded by a third phase. Examples are core-shell and Janus drops. In this review, we address the fundamental aspects of compound drops impact and discuss the current challenges related to experimental testing and numerical simulations of multiphase fluid systems. Furthermore, we provide a perspective on the technological relevance of understanding and controlling compound drop impact, ranging from 3D printing to liquid separation for clean water and oil remediation.

Over the past few years, the investigation of discrimination against students and researchers based on disability has become increasingly prominent, and it has broadened into a whole series of new perspectives and implications. Within this context, organisations, institutions and individuals have been promoting several actions for contrasting discriminatory bias and fostering a more inclusive environment for researchers and students with disabilities. One of the initiatives born in the wake of this movement is ResearchAbility, a multi-association initiative launched in 2018 that has become a subgroup of the Marie Curie Alumni Association since 2019. The main mission of ResearchAbility is twofold: (a) to support the careers of students and researchers with disabilities and (b) to promote research and awareness on disability and inclusive culture in the academic environment. After introducing the general context and mentioning data about students and staff with disabilities in UK academic institutions, the text introduces the ResearchAbility initiative, and describes some of its past activities and future areas of action.

Purpose: To analyse safety and efficacy of treatment based on ombitasvir/paritaprevir/ritonavir/dasabuvir plus ribavirin in the sub-group of GT1 patients older than 65 years. Methods: We collected data extracted from the ABACUS compassionate-use nationwide Italian programme, in patients with cirrhosis due to hepatitis C virus (HCV) Genotype-1 (GT1) or 4 and at high risk of decompensation. GT1-HCV-infected patients received once-daily ombitasvir/paritaprevir, with the pharmacokinetic enhancer ritonavir (25/150/100 mg) and twice-daily dasabuvir (250 mg) plus Ribavirin (RBV) (OBV/PTV/r + DSV + RBV) for 12 (GT1b) or 24 (GT1a) weeks. Endpoints were to evaluate safety and efficacy, the latter defined as HCV RNA negative 12 weeks after the end of treatment (SVR12). Results: Patients who suffered any adverse event (AE) were 74/240 (30.8%); 13/240 (5.4%) discontinued the treatment. A multivariate analysis found albumin < 3.5 g/dL (OR 2.04: 95% CI 1.0–4.2, p < 0.05) and hypertension (OR 4.6: 95% CI 2.3–9.2, p < 0.001) as variables independently associated with AE occurrence. The SVR12 was 95% (228/240). Multivariate analysis identified baseline bilirubin < 2 mg/dL (OR 4.9: 95% CI 1.17–20.71, p = 0.029) as the only variable independently associated with SVR12. Conclusion: Our findings suggest that OBV/PTV/r + DSV + RBV is safe and effective in real-life use in patients with compensated cirrhosis, HCV-GT1 infection, and age over 65.

Drop impact on solid surfaces is encountered in numerous natural and technological processes. Although the impact of single-phase drops has been widely explored, the impact of compound drops has received little attention. Here, we demonstrate a self-lubrication mechanism for water-in-oil compound drops impacting on a solid surface. Unexpectedly, the core water drop rebounds from the surface below a threshold impact velocity, irrespective of the substrate wettability. This is interpreted as the result of lubrication from the oil shell that prevents contact between the water core and the solid surface. We combine side and bottom view high-speed imaging to demonstrate the correlation between the water core rebound and the oil layer stability. A theoretical model is developed to explain the observed effect of compound drop geometry. This work sets the ground for precise complex drop deposition, with a strong impact on two- and three-dimensional printing technologies and liquid separation.

The present study explores the exploitation of ladder-like polysilsesquioxanes (PSQs) bearing reactive functional groups in conjunction with SiO2 nanoparticles (NPs) to produce UV-curable nanocomposite coatings with increased hydrophobicity and good thermal resistance. In detail, a medium degree regular ladder-like structured poly (methacryloxypropyl) silsesquioxane (LPMASQ) and silica NPs, either naked or functionalized with a methacrylsilane (SiO2@TMMS), were blended and then irradiated in the form of a film. Material characterization evidenced significant modifications of the structural organization of the LPMASQ backbone and, in particular, a rearrangement of the silsesquioxane chains at the interface upon introduction of the functionalized silica NPs. This leads to remarkable thermal resistance and enhanced hydrophobic features in the final nanocomposite. The results suggest that the adopted strategy, in comparison with mostly difficult and expensive surface modification and structuring protocols, may provide tailored functional properties without modifying the surface roughness or the functionalities of silsesquioxanes, but simply tuning their interactions at the hybrid interface with silica fillers.