Intelligent composite materials and devices are attracting a great interest owing to their potential impact on various future life applications. To meet the growing demand for multifunctional materials, the development and validation of visible sensing behavior is highly desirable, but the development of a single multifunctional wearable sensing material still remains a challenge to be achieved. To reach this goal, here we present a wearable intelligent fabric with piezoresistivity and mechanoluminescence ability based on a layer-structured graphene-based conductive cotton fabric and SrAlO:Eu, Dy/polyurethane foamed coating. The presence of the foamed coating structure endows the flexible composite fabric with a controllable positive/negative piezoresistivity (gauge factor from -2.5 to 17) and a bright mechanoluminescence ability that can be used in the darkness without additional batteries. Three-dimensional chromaticity diagrams have also been developed as advanced tools to quantitatively assess the luminescence, whose lightness, during the bending cycles, is highly repeatable with value in the range from ~25 to ~55. The multifunctional layered composite sensor provides multiple output signals which can be accurately recognized and assigned to independent triggering events, opening up new opportunities in advanced wearable devices based on commercial fabrics.

Active packaging systems, interacting directly with the enclosed food, can delay or inhibit those phenomena responsible for food quality decay, contributing to the food shelf-life extension. In this work a vinyl resin-based coating containing free or loaded eugenol (EG) in Santa Barbara Amorphous (SBA)15 mesoporous silica nanoparticles is designed to coat flexible aluminium foils to obtain an antimicrobial material. Thermogravimetric analysis shows a good loading capacity of eugenol in SBA15 (48% wt/wt). SEM analysis shows a good dispersion of free EG in the hosting polymeric matrix, whereas some EG/SBA15 particles aggregations are observed in the material. Water contact angle highlights a higher hydrophobicity of the eugenol based-materials (>90°) compared to the pristine vinyl coating (85°). Electrochemical impedance spectroscopy highlights no corrosion phenomena of the VIN/5%(EG/SBA15) coating and corrosion phenomena of the VIN/5%EG coating after 7 days of exposure to lactic acid pH = 4. Finally, the two active coatings are studied to evaluate their antibacterial activity using the ISO 22196. Interestingly, results demonstrate that when eugenol is loaded in the SBA15 mesoporous silica nanoparticles the antimicrobial activity of the material significantly increases against both foodborne pathogens and food spoilage bacteria, achieving the highest microbial growth reduction on S. aureus (R = 3.62 log).

Laser-fabrication of graphene from cellulose-based feedstock materials often requires extensive preprocessing. This work demonstrates laser fabrication of porous, 3D graphene from a new class of marine-based sustainable materials-chitosan biopolymers. The biopolymer films contain only chitosan, acetic acid, glycerol, and water. Fourier transform infrared spectroscopy studies indicate that the cured chitosan films still retain a significant water content (?30%), enabling production of flexible films. A simple 3-step laser fabrication process is presented using low-cost infrared (CO, 2.1 W) and visible (405 nm, 0.5 W) hobbyist laser engravers, with measured sheet resistance values as low as 40 ohms sq.. Transient electrochemical detection of an inner sphere redox molecule is demonstrated using a graphene-like carbon working electrode fabricated on a water-soluble chitosan substrate.

Three-dimensional printed polymers offer unprecedented advantages for prosthetic applications, namely in terms of affordability and customisation. This work thus investigates the possibility of designing an additively manufactured prosthetic foot using continuous fibre-reinforced polymers as an alternative to composite laminate ones. A numerical approach was thus proposed and validated as a possible design tool for additively manufactured composite feet. This approach was based on explicit separate simulations of the infill, aiming to capture its homogenised engineering constants. The approach was validated on simple sandwich specimens with a different infill geometry: stiffness predictions were within the experimental standard deviation for 3D simulations. Such an approach was thus applied to redesign a laminated component of a foot prosthesis inspired by a commercial one with new additive technology. The new component was about 83% thicker than the reference one, with 1.6 mm of glass fibre skins out of about 22 mm of the total thickness. Its stiffness was within 5% of the reference laminated one. Overall, this work showed how additive manufacturing could be used as a low-cost alternative to manufacturing affordable prosthetic feet.

Design and development of thermoregulating polymeric composite laminates occurs for application in the field of wearable prosthetics, in which the reduction of thermal discomfort is a key-issue to improve the life quality of amputee patients. They are based on an acrylic thermoset resin modified with phase change microcapsules (PCMs) and a fabric of polyamide (Perlon®) fibers coated with reduced graphene oxide (rGO). Morphological, thermal, mechanical and heat transfer properties of the resulting composite laminates are investigated. The presence of the rGO coating on the fabrics facilitates heat conduction, and increase the composite thermal diffusivity of about 70%, as compared with pristine acrylic resin and non-modified perlon fabric. The PCMs reduce about 50% the temperature increase of the composite laminate when subject to external heating. Moreover, the combination of rGO and PCMs enhances the thermal storage potential of the PCMs, contributing to further reducing the temperature fluctuations of the composite laminates. Graphical Abstract: [Figure not available: see fulltext.]

Currently, the scientific community has spent a lot of effort in developing "green" and environmentally friendly processes and products, due the contemporary problems connected to pollution and climate change. Cellulose nanocrystals (CNCs) are at the forefront of current research due to their multifunctional characteristics of biocompatibility, high mechanical properties, specific surface area, tunable surface chemistry and renewability. However, despite these many advantages, their inherent hydrophilicity poses a substantial challenge for the application of CNCs as a reinforcing filler in polymers, as it complicates their dispersion in hydrophobic polymeric matrices, such as polyurethane foams, often resulting in aggregate structures that compromise their properties. The manipulation and fine-tuning of the interfacial properties of CNCs is a crucial step to exploit their full potential in the development of new materials. In this respect, starting from an aqueous dispersion of CNCs, two different strategies were used to properly functionalize fillers: (i) freeze drying, solubilization in DMA/LiCl media and subsequent grafting with bio-based polyols; (ii) solvent exchange and subsequent grafting with bio-based polyols. The influence of the two functionalization methods on the chemical and thermal properties of CNCs was examined. In both cases, the role of the two bio-based polyols on filler functionalization was elucidated. Afterwards, the functionalized CNCs were used at 5 wt% to produce bio-based composite polyurethane foams and their effect on the morphological, thermal and mechanical properties was examined. It was found that CNCs modified through freeze drying, solubilization and bio-polyols grafting exhibited remarkably higher thermal stability (i.e., degradation stages > 100 °C) with respect to the unmodified freeze dried-CNCs. In addition, the use of the two grafting bio-polyols influenced the functionalization process, corresponding to different amount of grafted-silane-polyol and leading to different chemico-physical characteristics of the obtained CNCs. This was translated to higher thermal stability as well as improved functional and mechanical performances of the produced bio-based composite PUR foams with respect of the unmodified CNCs-composite ones (the best case attained compressive strength values three times more). Solvent exchange route slightly improved the thermal stability of the obtained CNCs; however; the so-obtained CNCs could not be properly dispersed within the polyurethane matrix, due to filler aggregation.

Currently, the most traditional manufacturing process for composite prosthetic feet is lamination. While allowing the production of light high-performance structures, the process is very expensive and limits both production rate and customisability. Additive manufacturing can be an alternative solution to cope with these limitations. This work explores the possibility to additively manufacture a prosthetic foot with the same stiffness of a laminated one. To this end, a commercially available foot is first analysed via numerical simulations. Using this reference case, a beam elements-based tool is developed and validated. The tool was then used to optimise four different designs of a possible additively manufactured prosthesis. This preliminary work resulted in two possible 3D printed foot designs that could be further analysed to potentially substitute the laminated prosthesis.

Owing to the increasing threat of pollution by electromagnetic interference (EMI) wave pollution, it is increasingly imperative to design and validate new high-performance EMI shielding materials. In recent decades, silver/polymer composites have attracted interest in the field of EMI shielding because of their unique properties such as easy processing, light weight, superior conductivity, ultrahigh shielding effectiveness and excellent mechanical properties. Based on the form of silver fillers, silver/polymer composites can be classified as silver nanoparticle/polymer, silver nanowire/polymer and silver nanoflake/polymer composites. In this review, for each class of materials, we focus on the design of the composite structure (i.e., spatial filler distribution, three-dimensional hierarchical structure, and effect of porosity) and identification of preparation strategies to maximize the EMI shielding effectiveness and overcome fatal shortcomings, such as the easy oxidation of silver and high contact resistance of silver nanowires. On account of the current progress and the state-of-the-art, the future development of silver/polymer composites is also prospected.

Nowadays, additive manufacturing play an increasing role in the design of assistive technology. In particular, 3D printed prosthetic devices, such as artificial limbs, still lack a comprehensive characterization of the materials and biomechanical properties, especially during the daily use. This technology can therefore benefit from advanced materials, such as smart composites, that combine high strength and lightweight properties with sensing capability. They exploit different kind of sensors embedded in the composite matrix to detect stress, strain, temperature or pressure depending on the design and the application considered. These sensors are miniaturized not to modify the mechanical behaviour of the embedding material and not to compromise its structural resistance. This study focuses on the characterization of 3D printed composites with embedded Fiber Bragg Grating (FBG) optical sensors for strain measurements, with future application in the prosthetic technology. The adhesion between the optical fiber containing the FBG and composite matrix was studied through pull-out tests, as the mechanical integrity of the whole smart material and its performance is investigated with quasi-static tensile tests. Results and discussion are provided considering polyamide and acrylate coated optical fibers embedded in specifically designed 3D printed samples.

Active natural additives can be loaded into bio-active packaging films in order to impart new functionalities and to broaden their potential application fields. However, they modify the film structure and properties, thus in this chapter, the authors aim to review the influence of the incorporation of natural additives and (bio)active compounds on the properties of active films potentially used as packaging materials able to prolong the shelf-life of packaged foodstuff. The chapter is focused on the effect of several active substances on mechanical behavior and barrier properties of active packaging materials, namely on their tensile stress, elastic modulus and elongation at break as well as oxygen, water vapor and UV light barrier properties. Several categories of (bio)active compounds are reviewed and particular attention is paid to active packaging films based on both polyolefin and biodegradable/bio-based polymers ...

Despite recent progress in graphene-based aerogels, challenges such as low mechanical strength and adsorption efficiency are still remaining. Here the reduced graphene oxide (rGO)/chitosan (CS) composite aerogel microspheres (rGCAMs) with center-diverging microchannel structures were developed by electrospraying and freeze-drying method. The optimized rGCAMs exhibit a high Young's modulus of 197 kPa and can support ~75,000 times its own weight, due to the cross-linking of CS by glutaraldehyde. Meanwhile, the rGCAMs can maintain high adsorption capacity for 15 cyclic tests due to its excellent mechanical strength. The oil adsorption kinetics and isotherms of rGCAMs follow the pseudo-second-order kinetic equation and the Langmuir model, respectively. The whole adsorption process is influenced by the oil diffusion in the liquid matrix and also in the intra-particle of aerogel microspheres. Moreover, rGCAMs can also be used to separate both surfactant-stabilized water-in-oil and oil-in-water emulsions through demulsification. The high-strength, recyclable and separation-efficient rGCAMs can be a potential candidate for oily wastewater treatment.

Plasmonic nanostructures, featuring near infrared (NIR)-absorption, are rising as efficient nanosystems for in vitro photothermal (PT) studies and in vivo PT treatment of cancer diseases. Among the different materials, new plasmonic nanostructures based on CuS nanocrystals (NCs) are emerging as valuable alternatives to Au nanorods, nanostars and nanoshells, largely exploited as NIR absorbing nanoheaters. Even though CuS plasmonic properties are not linked to geometry, the role played by their size, shape and surface chemistry is expected to be fundamental for an efficient PT process. Here, CuS NCs coated with a hydrophilic mesoporous silica shell (MSS) are synthesized by solution-phase strategies, tuning the core geometry, MSS thickness and texture. Besides their loading capability, the silica shell has been widely reported to provide a more robust plasmonic core protection than organic molecular/polymeric coatings, and improved heat flow from the NC to the environment due to a reduced interfacial thermal resistance and direct electron-phonon coupling through the interface. Systematic structural and morphological analysis of the core-shell nanoparticles and an in-depth thermoplasmonic characterization by using a pump beam 808 nm laser, are carried out. The results suggest that large triangular nanoplates (NPLs) coated by a few tens of nanometers thick MSS, show good photostability under laser light irradiation and provide a temperature increase above 38 °C and a 20% PT efficiency upon short irradiation time (60 s) at 6 W/cm power density.

The introduction of inorganic materials into biopolymers has been envisioned as a viable option to modify the optical and structural properties of these polymers and promote their exploitation in different application fields. In this work, the growth of Al2O3 in freestanding ~30-?m-thick poly(butylene succinate) (PBS) films by sequential infiltration (SIS) at 70 °C via trimethylaluminum (TMA) and H2O precursors was investigated for the first time. The incorporation of Al2O3 into the PBS matrix was clearly demonstrated by XPS analysis and SEM-EDX cross-sectional images showing a homogeneous Al2O3 distribution inside the PBS films. Raman measurements on infiltrated freestanding PBS show a reduction of the signal related to the ester carbonyl group as compared to pristine freestanding PBS films. Accordingly, FTIR and NMR characterization highlighted that the ester group is involved in polymer-precursor interaction, leading to the formation of an aliphatic group and the concomitant rupture of the main polymeric chain. Al2O3 mass uptake as a function of the number of SIS cycles was studied by infiltration in thin PBS films spin-coated on Si substrates ranging from 30 to 70 nm. Mass uptake in the PBS films was found to be much higher than in standard poly(methyl methacrylate) (PMMA) films, under the same process conditions. Considering that the density of reactive sites in the two polymers is roughly the same, the observed difference in Al2O3 mass uptake is explained based on the different free volume of these polymers and the specific reaction mechanism proposed for PBS. These results assessed the possibility to use SIS as a tool for the growth of metal oxides into biopolymers, paving the way to the synthesis of organic-inorganic hybrid materials with tailored characteristics.

This paper describes the design and manufacturing process of an advanced socket for upper limb prostheses. This device uses synergies between smart materials such as phase change materials (PCM), reduced graphene oxide (rGO) and a 3D printed metastructure to improve ergonomics and thermal comfort. Virtual prototyping was combined with traditional fabrication techniques to obtain a biocompatible, user-centered device, whose main advantage is an improved thermal behavior. Besides feasibility and biocompatibility tests, the paper describes the results of a preliminary trial involving a volunteer with upper limb amputation. It was observed that the use of an inner metastructure provides basic mechanical stability and improves resin flowability. The combination of PCM and rGO delay the increase in inner socket temperature during physical exercise on a treadmill, which induced a feeling of freshness and dryness and improved the comfort for the user. These findings, despite their preliminary nature, suggest that advanced modifications of the materials and technologies involved in the production of prosthetic sockets are able to generate appreciable benefits in terms of usability.

Chitosan-based hybrid nanocomposites, containing cellulose nanocrystals (CNCs), graphene oxide (GO), and borate as crosslinking agents, were successfully prepared by solution-casting technique. The synergistic effect of the two fillers, and the role of the cross-linker, in enhancing the structural and functional properties of the chitosan polymer, was investigated. XPS results confirm the chemical interaction between borate ions and hydroxyl groups of chitosan, GO, and CNCs. The morphological characterization shows that the GO sheets are oriented along the casting surface, whereas the CNC particles are homogenously distributed in the sample. Results of tensile tests reveal that the presence of graphene oxide enhances the elastic modulus, tensile strength, elongation at break, and toughness of chitosan, while cellulose and borate induce an increase in the elastic modulus and stress at the yield point. In particular, the borate-crosslinked chitosan-based sample containing 0.5 wt% of GO and 0.5 wt% of CNCs shows an elongation at a break value of 30.2% and a toughness value of 988 J*m-3 which are improved by 124% and 216%, respectively, compared with the pristine chitosan. Moreover, the water permeability results show that the presence of graphene oxide slightly increases the water barrier properties, whereas the borate and cellulose nanocrystals significantly reduce the water vapor permeability of the polymer by about 50%. Thus, by modulating the content of the two reinforcing fillers, it is possible to obtain chitosan-based nanocomposites with enhanced mechanical and water barrier properties which can be potentially used in various applications such as food and electronic packaging.

In this work, mesoporous silica nanoparticles (MSN) hybridized with an organosilane are grafted with hyper-crosslinked poly(vinylbenzyl chloride) (PVBC), which is anchored into the mesopores and onto the external surface of MSN. The obtained nanoparticles are characterized by a MSN-templated hierarchical porosity composed of micropores, mesopores and macropores originated from the hyper-crosslinking of the PVBC phase, with a microporous fraction reaching up to 28% of the total pore volume. Tested for the adsorption of a model dye (Rhodamine 6G, Rh6G), these nanoparticles result much more efficient in Rh6G adsorption with respect to plain MSN, showing a Rh6G uptake of about 125 mg/g in highly concentrated solutions (1000 mg/L) and quite complete removal (about 98%) of the dye in more diluted conditions (30 mg/L) with comparable efficiency in repeated adsorption cycles. Overall results demonstrate the key role of the hierarchical porosity of the hyper-crosslinked PVBC-grafted MSN to tailor their adsorption properties.

A new sustainable solution to water and air pollution based on spontaneously adsorbent materials is presented in this work. For the first time, high surface area micro/mesoporous hyper-crosslinked resins (XDV) were engineered in hydrogels and aerogels based on reduced graphene oxide (rGO) and montmorillonite (MMT). Hydrogels and aerogels were obtained through a mild and environmental-friendly procedure based on graphene oxide (GO) reduction by vitamin C and eventual lyophilization. In all systems, the XDV specific surface area (SSA) is completely exposed and exploitable for adsorption application in water and air. rGO/XDV and rGO/ MMT/XDV aerogels containing 50 wt% of XDV show hierarchical porosity and high SSA, reaching values of 1000-1200 m2/g. Hydrogels and aerogels show tuneable polar character on the basis of their composition, which is exploitable to develop customized adsorbents for water and air remediation from aromatic and polar pollutants. Indeed, while hydrogels containing MMT show high adsorption capacity towards cationic dyes such as rhodamine 6G, rGO and rGO/XDV systems show marked affinity for toluene. In all cases, the embedding of the hyper-crosslinked resins in the hydrogels and aerogels further enhances their adsorption capacity, with uptakes up to 482 mg/g of rhodamine 6G for rGO/MMT/XDV hydrogels and up to 500 mg/g of toluene vapours for rGO/ XDV aerogels. Both systems show regenerable adsorption properties with efficiency higher than 96% over 5 adsorption/desorption cycles.

In this study polyester-based thermoplastic polyurethane (TPU) samples were annealed at 110 degrees C for 0, 8, 16, and 24 h. To elucidate the relationship between the hard and soft phase separation and the shape memory properties, the samples were characterized within a rheometer, by selecting well defined thermal cycles. The results showed an enhancement of the shape recovery ratio (R-r similar to 65%) for all the annealed samples, when compared to the non-annealed TPU (R-r similar to 60%). This behavior was attributed to the modifications of hard-soft domain morphology occurring during the thermal annealing treatment, as it was shown both by differential scanning calorimetry with the shift in thermal transitions toward higher temperature, due the formation of new short-range ordered hard domains and infrared spectroscopy, with the increase in degree of phase separation. Analyzing small-angle X-ray scattering, the decrease of the invariant also confirmed the enhancement of short-range domains. The formation of these new short-range domains acted as crosslinking points in TPU's morphology leading to an increase in stiffness, presented by higher Young and storage modulus. Based on these results, a model mechanism is proposed to correlate the morphology and structure of the annealed materials with their shape memory effect.

Carbon-based aerogels (CA) with durable piezoresistive properties possess great promise for applications in wearable electronics. However, it is still a great challenge to fabricate high performance aerogel sensors due to the limits of mechanical properties. We recently developed a novel strategy to build aerogel/foam hybrid structure that can effectively enhance the mechanical properties of aerogel-based sensors. Herein, CA/polyurethane foam (PUF) composite was fabricated via in situ unidirectional freeze-drying process starting from a carbon nanotubes (CNTs)/graphene oxide (GO) aqueous dispersion stabilized with chitosan (CS) which was filled into the porosity of an open cell PUF. The resulting composite shows a microscopic anisotropy in the CA with electrical conductivity as high as 10.54 S m-1. The piezoresistive sensitivity of the resulting composite can be simply modulated over a wide range from 1.1 to 3.6 by adequately selecting its initial pre-strain. The CA/PUF composite exhibits excellent compressible resilience at the strain of 50% for at least 100 cycles. In addition, the sensor was successfully applied for detecting various human motions. These unique properties make the realized composite a promising candidate for effective flexible piezoresistive strain sensors in wearable applications.

Solid-state lithium metal batteries with higher energy density and safety are regarded as the promising next-generation energy storage devices. Porous materials hybrid with ionic liquids are becoming an important solid electrolyte due to the high ionic conductivity and enhanced interfacial compatibility. However, their poor electrochemical stability and limited Li+ transport pathways remain challenged. Herein, an ionic-liquid-X zeolite hybrid is designed as the solid composite electrolyte to settle the above issues. The three-dimensional open framework of X zeolite acts as the "reservoir" of the ionic liquid providing a solid interconnected pathway to facilitate an effective lithium transmission. This transport is supported by both the TFSI- adsorption and EMIM+ substitution in zeolite structure, which benefits the compatibility at electrolyte/lithium anode interface. The obtained composite electrolyte (Li-X-30) exhibits a superior ionic conductivity of 3.3 × 10-4 S·cm-1 and a widened electrochemical window of 5.4 V. An ultralong lifespan of the assembled solid-state LiFePO4//metallic lithium battery is achieved with an outstanding capacity retention of 96% after 850 cycles. The designed electrolyte with ultra-long cycling stability may provide inspiration for the development of frontier solid electrolytes with potential applications in K, Na and other types of energy storage systems.