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Performances of bipolar Au/NbOx/Nb devices were investigated by correlating the material properties of electrochemically grown NbOx with resistive switching functionalities.

In the electrochemical conversion of carbon dioxide, high currents need to be employed to obtain large production rates, thus implying that mass transport of reactants and products is of crucial importance. This aspect can be investigated by employing a model that depicts the local environment for the reduction reactions. Simultaneously, electrochemical impedance spectroscopy, despite being a versatile technique, has rarely been adopted for studying the mass transport features during the carbon dioxide (CO2) electroreduction. In this work, this aspect is deeply analyzed by correlating the results of impedance spectroscopy characterization with those obtained by a bubble-induced mass transport modeling under controlled diffusion conditions on a gold rotating disk electrode. The effects of potential and rotation rate on the local environment are also clarified. In particular, it has been found that CO2 depletion occurs at high kinetics when the rotation is absent, giving rise to an increment of the competing hydrogen evolution reaction. This feature reflects in an enlargement of the diffusion resistance, which overcomes the charge transport one.

This work aims at providing a simple and effective method to optimize and improve the nitrogen-based defects into intrinsically N-doped carbon-based electrospun nanofibers (CNFs) for achieving highly active catalysts for the oxygen reduction reaction (ORR). To reach this goal, plasma treatments are investigated as an effective method to tune the distribution of the N-doping sites that are vital to improve the ORR catalytic activity of the material. Morphological, physical, chemical as well as electrochemical characterizations were performed on plasma-treated CNFs to demonstrate the effectiveness of such treatments to improve the catalytic behavior of CNFs toward ORR. Finally, Microbial Fuel Cells (MFCs) were selected to test the plasma-treated nanofibers as the cathode catalyst layer demonstrating an increase of the overall performance of the MFCs with respect to the devices using the Pt-based reference catalyst.

Sediment microbial fuel cells (SMFCs) are energy harvesting devices where the anode is buried inside marine sediment, while the cathode stays in an aerobic environment on the surface of the water. To apply this SCMFC as a power source, it is crucial to have an efficient power management system, leading to development of an effective energy harvesting technique suitable for such biological devices. In this work, we demonstrate an effective method to improve power extraction with SMFCs based on anodes alternation. We have altered the setup of a traditional SMFC to include two anodes working with the same cathode. This setup is compared with a traditional setup (control) and a setup that undergoes intermittent energy harvesting, establishing the improvement of energy collection using the anodes alternation technique. Control SMFC produced an average power density of 6.3 mW/m2 and SMFC operating intermittently produced 8.1 mW/m2. On the other hand, SMFC operating using the anodes alternation technique produced an average power density of 23.5 mW/m2. These results indicate the utility of the proposed anodes alternation method over both the control and intermittent energy harvesting techniques. The Anode Alternation can also be viewed as an advancement of the intermittent energy harvesting method.

Self-healing hydrogels may mimic the behavior of living tissues, which can autonomously repair minor damages, and therefore have a high potential for application in biomedicine. So far, such hydrogels have been processed only via extrusion-based additive manufacturing technology, limited in freedom of design and resolution. Herein, we present 3D-printed hydrogel with self-healing ability, fabricated using only commercially available materials and a commercial Digital Light Processing printer. These hydrogels are based on a semi-interpenetrated polymeric network, enabling self-repair of the printed objects. The autonomous restoration occurs rapidly, at room temperature, and without any external trigger. After rejoining, the samples can withstand deformation and recovered 72% of their initial strength after 12 hours. The proposed approach enables 3D printing of self-healing hydrogels objects with complex architecture, paving the way for future applications in diverse fields, ranging from soft robotics to energy storage., Self-healing hydrogels can mimic the damage repair behaviour of living tissues, but such hydrogels have only been processed via extrusion-based additive manufacturing technology. Here, the authors demonstrate a rapidly self-healing hydrogel which can be processed by DLP printing.

It is widely accepted that three-dimensional cell culture systems simulate physiological conditions better than traditional 2D systems. Although extracellular matrix components strongly modulate cell behavior, several studies underlined the importance of mechanosensing in the control of different cell functions such as growth, proliferation, differentiation, and migration. Human tissues are characterized by different degrees of stiffness, and various pathologies (e.g., tumor or fibrosis) cause changes in the mechanical properties through the alteration of the extracellular matrix structure. Additionally, these modifications have an impact on disease progression and on therapy response. Hence, the development of platforms whose stiffness could be modulated may improve our knowledge of cell behavior under different mechanical stress stimuli. In this review, we have analyzed the mechanical diversity of healthy and diseased tissues, and we have summarized recently developed materials with a wide range of stiffness.

Abstract High level of atmospheric carbon dioxide (CO2) concentration is considered one of the main causes of global warming. Electrochemical conversion of CO2 into valuable chemicals and fuels has promising potential to be implemented into practical and sustainable devices. In order to efficiently realize this strategy, one of the biggest efforts has been focused on the design of catalysts which are inexpensive, active and selective and can be produced through green and up-scalable routes. In this work, copper-based materials are simply synthesized via microwave-assisted process and carefully characterized by physical/chemical/electrochemical techniques. Nanoparticle with a cupric oxide (CuO) surface as well as various cuprous oxide (Cu2O) cubes with different sizes is obtained and used for the CO2 reduction reaction. It is observed that the Cu2O-derived electrodes show enhanced activity and carbon monoxide (CO) selectivity compared to the CuO-derived one. Among various Cu2O catalysts, the one with the smallest cubes leads to the best CO selectivity of the electrode, attributed to a higher electrochemically active surface area. Under applied potentials, all Cu2O cubes undergo structural and morphological modification, even though the cubic shape is retained. The nanoclusters formed during the material evolution offer abundant and active reaction sites, leading to the high performance of the Cu2O-derived electrodes. Graphic abstract

The dewetting and ordering characteristics of a lamellae-forming poly(styrene-block-methyl methacrylate) block copolymer (BCP) either alone or blended with low-molecular-weight polystyrene and poly...

The conversion of carbon dioxide into value-added products using sunlight, also called artificial photosynthesis, represents a remarkable and sustainable approach to store solar energy, transformin...

Light processable natural polymers are highly attractive for 3D printing of biomedical hydrogels with defined geometries and sizes. However, functionalization with photo-curable groups, such as methacrylate or acrylate groups, is required. Here, we investigated a microwave-assisted process for methacrylation of chitosan to replace conventional methacrylation processes that can be time consuming and tedious. The microwave-assisted methacrylation reaction was optimized by varying the synthesis parameters such as the molar ratio of chitosan to the methacrylic agent, the launch and reaction times and process temperature. The optimized process was fast and efficient and allowed tuning of the degree of substitution and thereby the final hydrogel properties. The successful methacrylation and degree of substitution were verified by 1H NMR and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR). The influence of the degree of methacrylation on photo-rheology, mechanical stiffness, swelling degree and gel content was evaluated. Furthermore, favourable 3D printability, enzymatic degradability, biocompatibility, cell migration and proliferation were demonstrated giving promise for further applications in tissue engineering.

We report on a simple electrochemical system able to capture gaseous carbon dioxide from a gas mixture and convert it into syngas. The capture/release module is implemented via regeneration of NaOH and acidification of NaHCO3 inside a four-chamber electrochemical flow cell employing Pt foils as catalysts, while the conversion is carried out by a coupled reactor that performs electrochemical reduction of carbon dioxide using ZnO as a catalyst and KHCO3 as an electrolyte. The capture module is optimized such that, powered by a current density of 100 mA/cm2, from a mixture of the CO2–N2 gas stream, a pure and stable CO2 outlet flow of 4–5 mL/min is obtained. The conversion module is able to convert the carbon dioxide into a mixture of gaseous CO and H2 (syngas) with a selectivity for the carbon monoxide of 56%. This represents the first all-electrochemical system for carbon dioxide capture and conversion.

This work illustrates focalization performances of a silicon-based bulk acoustic wave device applied for the separation of specimens owing to micrometric dimensions. Samples are separated in the microfluidic channel by the presence of an acoustic field, which focalizes particles or cells according to their mechanical properties compared to the surrounded medium ones. Design and fabrication processes are reported, followed by focalization performance tests conducted either with synthetic particles or cells. High focalization performances occurred at different microparticle concentrations. In addition, preliminary tests carried out with HL-60 cells highlighted an optimal separation performance at a high flow rate and when cells are mixed with micro and nanoparticles without affecting device focalization capabilities. These encouraging results showed how this bulk acoustic wave device could be exploited to develop a diagnostic tool for early diagnosis or some specific target therapies by separating different kinds of cells or biomarkers possessing different mechanical properties such as shapes, sizes and densities.

A successful application of the 3D printed materials in the biomedical field requires extensive studies to ensure their biocompatibility at every step of the process. Here, different components suitable for cell applications, including a microfluidic device, were 3D printed using common resins and a deep analysis of their biocompatibility and post printed protocols was conducted.

It is shown that the frequency dependence of the phenomenological parameters entering Langmuir kinetic equation describing the surface adsorption could be related to a random distribution of relaxation times. A theoretical model based on a generalization of Langmuir isotherm, taking into account a homogeneous distribution of relaxation times is proposed for supercapacitor modeling. Its theoretical predictions agree well with experimental data derived by the analysis of Lissajous figures describing the response of an electrochemical cell excited with a well defined frequency. According to our data, the effective desorption time is a rapidly decreasing function of the frequency of the applied signal, whereas the effective adsorption coefficient is an increasing function of it. The effective relaxation time is independent of the ionic concentration, whereas the effective adsorption coefficient strongly depends on this quantity. A large increase in the adsorption coefficient is reported, for the electrochemical cells with high surface area of the electrodes.

The effect of direct or indirect binding of intercalant molecules on DNA structure is of fundamental importance in understanding the biological functioning of DNA. Here we report on self-suspended DNA nanobundles as ultrasensitive nanomechanical resonators for structural studies of DNA-ligand complexes. Such vibrating nanostructures represent the smallest mechanical resonator entirely composed of DNA. A correlative analysis between the mechanical and structural properties is exploited to study the intrinsic changes of double strand DNA, when interacting with different intercalant molecules (YOYO-1 and GelRed) and a chemotherapeutic drug (Cisplatin), at different concentrations. Possible implications of our findings are related to the study of interaction mechanism of a wide category of molecules with DNA, and to further applications in medicine, such as optimal titration of chemotherapeutic drugs and environmental studies for the detection of heavy metals in human serum., Intercalating molecules can significantly change the conformation of DNA. Here, the authors fabricated resonators fully composed of DNA forming bundles between microfabricated pillars to study the vibration property of the DNA bundles with/without intercalant molecules.

In this work a new Single Layer Graphene (SLG) transfer technique exploiting a hot embossing process was carried out. Flexible electrolyte gated Graphene Field Effect Transistors (G-FET) were fabricated and tested electrically. A polymeric transparent foil suitable for optics and flexible electronics, Cyclic Olefin Copolymer (COC) was used as flexible substrate. Raman characterization confirmed that the new Hot Embossing Graphene Transfer (HEGT) is suitable for the deposition of SLG and the fabrication of G-FETs. A Comparison with SLG common transfer method was carried out and proven for G-FETs fabrication. The HEGT devices showed typical characteristics and maintained the same performances when the substrate was bent. This demonstrated that the HEGT allows for efficient transfer of high quality SLG on large area thus providing the opportunity for the exploitation on a large scale production process for flexible substrates.

Flexible sensors are fundamental devices for human body monitoring. The mechanical strain and physiological parameters coupled sensing have attracted increasing interest in this field. However, integration of different sensors in one platform usually involves complex fabrication process-flows. Simplification, even if essential, remains a challenge. Here, we investigate a piezoresistive and electrochemical active electrospun nanofibers (NFs) mat as the sensitive element of the wearable physiological flex sensing platform. The use of one material sensitive to the two kinds of stimuli reduces the process-flow to two steps. We demonstrate that the final NFs pH-Flex Sensor can be used to monitor the deformation of a human body joint as well as the pH of the skin. A unique approach has been selected for pH sensing, based on Electrochemical Impedance Spectroscopy (EIS). A linear dependence of the both the double layer capacitance and charge transfer re-sistance with the pH value was obtained by EIS, as well as a linear trend of the electrical resistance with the bending deformation. Gauge factors values calculated after the bending test were 45.84 in traction and 208.55 in compression mode, reflecting the extraordinary piezoresistive behavior of our nanostructured NFs.

In this work, we discuss the use of epsilon-near-zero (ENZ) metamaterials to efficiently couple light radiated by a dipolar source to an in-plane waveguide. We exploit both enhanced and directional emission provided by ENZ metamaterials to optimize the injection of light into the waveguide by tuning the metal fill factor. We show that a net increase in intensity injected into the waveguide with respect to the total power radiated by the isolated dipole can be achieved in experimentally feasible conditions. We think the proposed system may open up new opportunities for several optical applications and integrated technologies, especially for those limited by outcoupling efficiency and emission rate.

Miniaturized low-cost sensors for volatile organic compounds (VOCs) have the potentiality to become a fundamental tool for indoor and outdoor air quality monitoring, to significantly improve everyday life. Layered double hydroxides (LDHs) belong to the class of anionic clays and are largely employed for NOx detection, while few results are reported on VOCs. In this work, a novel LDH coprecipitation method is proposed. For the first time, a study comparing four LDHs (ZnAl-Cl, ZnFe-Cl, ZnAl-NO3, and MgAl-NO3) is carried out to investigate the sensing performances. As explored through several microscopy and spectroscopy analyses, LDHs show a morphology characterized by a large surface area and a three-dimensional hierarchical flowerlike architecture with micro- and nanopores that induce a fast diffusion and highly effective surface interaction of the target gases. The fabricated sensors, operating at room temperature, are able to reversibly and selectively detect acetone, ethanol, ammonia, and chlorine vapors, reaching significant sensing response values up to 6% at 21 degrees C. The results demonstrate that by changing the LDHs' composition, it is possible to modulate the sensitivity and selectivity of the sensor, helping the discrimination of different analytes, and the consequent integration on a sensor array paves the way for electronic nose development.

Novel electrocatalysts based on zinc oxide (ZnO) and biochars are prepared through a simple and scalable route and are proposed for the electrocatalytic reduction of CO₂ (CO₂RR). Materials with different weight ratios of ZnO to biochars, namely, pyrolyzed chitosan (CTO) and pyrolyzed brewed waste coffee (CBC), are synthesized and thoroughly characterized. The physicochemical properties of the materials are correlated with the CO₂RR to CO performance in a comprehensive study. Both the type and weight percentage of biochar significantly influence the catalytic performance of the composite. CTO, which has pyridinic- and pyridone-N species in its structure, outperforms CBC as a carbon matrix for ZnO particles, as evidenced by a higher CO selectivity and an enhanced current density at the ZnO_CTO electrode under the same conditions. The study on various ZnO to CTO weight ratios shows that the composite with 40.6 wt % of biochar shows the best performance, with the CO selectivity peaked at 85.8% at −1.1 V versus the reversible hydrogen electrode (RHE) and a CO partial current density of 75.6 mA cm–² at −1.3 V versus RHE. It also demonstrates good stability during the long-term CO₂ electrolysis, showing high retention in both CO selectivity and electrode activity.

Superhydrophobic surfaces display an extraordinary repulsion to water and water-based solutions. This effect emerges from the interplay of intrinsic hydrophobicity of the surface and its morphology. These surfaces have been established for a long time and have been studied for decades. The increasing interest in recent years has been focused towards applications in many different fields and, in particular, biomedical applications. In this paper, we review the progress achieved in the last years in the fabrication of regularly patterned superhydrophobic surfaces in many different materials and their exploitation for the manipulation and characterization of biomaterial, with particular emphasis on the issues affecting the yields of the fabrication processes and the quality of the manufactured devices.

The extreme miniaturization in NEMS resonators offers the possibility to reach an unprecedented resolution in high-performance mass sensing. These very low limits of detection are related to the combination of two factors: a small resonator mass and a high quality factor. The main drawback of NEMS is represented by the highly complex, multi-steps, and expensive fabrication processes. Several alternatives fabrication processes have been exploited, but they are still limited to MEMS range and very low-quality factor. Here we report the fabrication of rigid NEMS resonators with high-quality factors by a 3D printing approach. After a thermal step, we reach complex geometry printed devices composed of ceramic structures with high Young’s modulus and low damping showing performances in line with silicon-based NEMS resonators ones. We demonstrate the possibility of rapid fabrication of NEMS devices that present an effective alternative to semiconducting resonators as highly sensitive mass and force sensors., NEMS devices, nano-electro-mechanical systems, by virtue of their minute size, offer ultra-high sensitivity, though at the expense of manufacturing complexity. Here, Stassi et al succeed in manufacturing high quality factor NEMS devices using high resolution 3D printing.

Bimetallic copper-tin catalysts are considered cost-effective and suitable for large-scale electrochemical conversion of CO2 to valuable products. In this work, a class of tin (Sn) modified cuprous oxide (Cu2O) is simply synthesized through a one-pot microwave-assisted solvothermal method and thoroughly characterized by various techniques. Sn is uniformly distributed on the Cu2O crystals showing a cube-within-cube structure, and CuSn alloy phase emerges at high Sn contents. The atomic ratio of Cu to Sn is found to be crucially important for the selectivity of the CO2 reduction reaction, and a ratio of 11.6 leads to the optimal selectivity for CO. This electrode shows a high current density of 47.2 mA cm−2 for CO formation at −1.0 V vs. the reversible hydrogen electrode and also displays good CO selectivity of 80–90% in a wide potential range. In particular, considerable CO selectivity of 72–81% is achieved at relatively low overpotentials from 240 mV to 340 mV. During the long-term tests, satisfactory stability is observed for the optimal electrode in terms of both electrode activity and CO selectivity. The relatively low price, the fast and scalable synthesis, and the encouraging performance of the proposed material implies its good potential to be implemented in large-scale CO2 electrolyzers.

The electrocatalytic reduction of CO2 into useful fuels, exploiting rationally designed, inexpensive, active, and selective catalysts, produced through easy, quick, and scalable routes, represents a promising approach to face today’s climate challenges and energy crisis. This work presents a facile strategy for the preparation of doped SnO2 as an efficient electrocatalyst for the CO2 reduction reaction to formic acid and carbon monoxide. Zn or Ti doping was introduced into a mesoporous SnO2 matrix via wet impregnation and atomic layer deposition. It was found that doping of SnO2 generates an increased amount of oxygen vacancies, which are believed to contribute to the CO2 conversion efficiency, and among others, Zn wet impregnation resulted the most efficient process, as confirmed by X-ray photoelectron spectroscopy analysis. Electrochemical characterization and active surface area evaluation show an increase of availability of surface active sites. In particular, the introduction of Zn elemental doping results in enhanced performance for formic acid formation, in comparison to un-doped SnO2 and other doped SnO2 catalysts. At −0.99 V versus reversible hydrogen electrode, the total faradaic efficiency for CO2 conversion reaches 80%, while the partial current density is 10.3 mA cm−2. These represent a 10% and a threefold increases for faradaic efficiency and current density, respectively, with respect to the reference un-doped sample. The enhancement of these characteristics relates to the improved charge transfer and conductivity with respect to bare SnO2.

This work describes the fabrication of silver-patterned polymeric devices via light-based 3D printing methods from a tailored resin. An acrylate resin containing silver nitrate (AgNO3) as a silver precursor is employed to generate silver nanoparticles (AgNPs) through the in situ reduction of the metallic salt. The silver-based resin is processed through a customized stereolithography SL-3D printing to fabricate structures with silver-patterned surfaces. This customized SL-printer (emitting at 405 nm) offers the possibility of adjusting the machine settings during the printing process allowing for AgNPs to be selectively generated by modifying the laser settings during the 3D printing step. Thus, the resin photopolymerization and the photoinduced formation of AgNPs-based strands can be sequentially achieved during the same printing process with the same light source and using the same printable resin. The fabricated silver-patterned devices exhibit different surface features that might be exploited in systems working in a marine environment to control biofilm proliferation. As a proof-of-concept, the antimicrobial behavior of the silver-based 3D printed device is tested against environmental bacterial mixed communities via UV-vis spectroscopy and evaluating the absorbance change. Further tests, however, would be needed to reinforce the evidence of the bacteria behavior on the silver-patterned 3D printed devices.

In this work a new microfluidic platform is designed and validated to remove analyte contamination problem in EGOFETs biosensors.

In this paper a simple three-components photopolymerizable system based on 2-hydroxyethyl methacrylate (HEMA) and poly(ethylene glycol methyl ether methacrylate) (PEGMEMA) is used for the fabrication of thermoset H-bond stabilized shape memory polymers (SMPs) via digital light processing (DLP) three-dimensional (3D) printing. A bis(acyl)phosphane oxide derivative (BAPO-γ-CyD) was used as an all-in-one photoinitiator and crosslinking agent, so that no conventional multifunctional crosslinkers are needed. Due to the high elasticity ratio between the glassy and rubbery state and the presence of thermoreversibly associating hydrogen-bonding groups, the PHEMA-co-PEGMEMA polymers show an excellent thermally triggered shape memory response (strain recovery of 99%). A prototype of a thermoresponsive airflow diverter has been fabricated, demonstrating the potential integration of such SMPs to develop smart 3D – printed devices. Moreover, the possibility to easily design the glass transition temperature of the SMPs by varying the concentration of the two photopolymerizable ingredients allows to fine-tune the formulations such that materials can be printed showing shape memory behavior at different temperatures.

A class of metal-doped polyanilines (PANIs) was synthesized and investigated as electrocatalysts for the carbon dioxide reduction reaction (CO2RR). These materials show good affinity for the electrode substrate and allow to obtain stable binder-free electrodes, avoiding the utilization of expensive ionomer and additives. The emeraldine-base polyaniline (EB-PANI), in absence of metal dopant, shows negligible electrocatalytic activity and selectivity toward the CO2RR. Such behavior significantly improves once EB-PANI is doped with an appropriate cationic metal (Mn, Cu or Sn). In particular, the Sn-PANI outperforms other metal-doped samples, showing a good turnover frequency of 72.2 h−1 for the CO2RR at − 0.99 V vs the reversible hydrogen electrode and thus satisfactory activity of metal single atoms. Moreover, the Sn-PANI also displays impressive stability with a 100% retention of the CO2RR selectivity and an enhanced current density of 4.0 mA cm−2 in a 10-h test. PANI, a relatively low-cost substrate, demonstrates to be easily complexed with different metal cations and thus shows high tailorability. Complexing metal with conductive polymer represents an emerging strategy to realize active and stable metal single-atom catalysts, allowing efficient utilization of metals, especially the raw and precious ones. Graphic abstract

Traditional in vitro culture models are unable to fully reflect the organ microenvironment, due to differences in terms of cell morphology, protein expression, cell-cell and cell-matrix interactions, and drug response. In contrast, the flexibility of bioprinting modes allows for the deposition of cell-containing biomaterials in any free-form-inspired 3D structures on chip. The main purpose of this study was to design and optimize commercially available Carbopol-based 3D printing formulations, because of their many advantages, such as low-cost, the ability to produce clear and stable gels, and the water thickening. For this purpose, three different Carbopol gels (EDT 2020 NF, Ultrez 10 NF and NF-980) were tested in terms of printability and biocompatibility, with lung cancer epithelial (A549) and normal lung fibroblast (MRC-5) cells. This study demonstrates that Carbopol is a promising candidate for the 3D printing of cell-laden constructs, both in terms of rheology and printing performance.

Neural probes are in vivo brain-invasive devices that record and manipulate neural circuits using electricity, light, or drugs. The capability to shine distinct wavelengths and control their respective output locations for activation or deactivation of specific groups of neurons is desirable but remains unachieved. Here, we discuss our probe’s capability to deliver two independently controllable wavelengths (450 and 655 nm) in the location(s) of interest using nanophotonic directional couplers and ring resonators. These nanophotonics are scalable to dozens of outputs without significantly increasing the device’s lateral dimensions. Furthermore, they are entirely passive and thus do not require electrical input that results in heat generation. Besides, we integrate a high number of electrodes for a simultaneous neural activity readout. Thus, we overcome the challenges associated with multicolor illumination for neural devices by exploiting the capability of miniaturizable, passive probes to deliver two different frequencies in several areas of interest. These devices open the path towards investigating the in vivo electrical signal propagation under the individual or simultaneous activation or inhibition of distinct brain regions.

Acoustophoretic microfluidic devices are promising non-contact and high-throughput tools for particle manipulation. Although the effectiveness of this technique has been widely demonstrated for applications based on micrometer-sized particles, the manipulation and focusing of sub-micrometer ones is challenging due to the presence of acoustic streaming. In this article, our study has the aim to investigate and understand which geometrical parameters could be changed to limit the acoustic streaming effect. We numerically study the well-known rectangular cross section of a microfluidic channel and perform a parametric study of the aspect ratio for several particle sizes. The efficiency of the focusing, is explored for different sized particles in order to identify a trend for which the acoustic streaming does not drastically influence the focusing motion of the particles. The possibility to efficiently separate different solid components in liquid suspensions, i.e. the whole blood, is crucial for all applications that require a purified medium such as plasmapheresis or an increase of the concentration of specific subpopulation as the outcome, such as proteomics, cancer biomarker detections and extracellular vesicles separation.

The aim of this paper is to shed light on the application of graphene oxide (GO) membranes for the selective removal of benzene, toluene, and xylene (BTX) from wastewater. These molecules are present in traces in the water produced from oil and gas plants and are treated now with complex filtration systems. GO membranes are obtained by a simple, fast, and scalable method. The focus of this work is to prove the possibility of employing GO membranes for the filtration of organic contaminants present in traces in oil and gas wastewater, which has never been reported. The stability of GO membranes is analyzed in water solutions with different pH and salinity. Details of the membrane preparation are provided, resulting in a crucial step to achieve a good filtration performance. Material characterization techniques such as electron microscopy, x-ray diffraction, and infrared spectroscopy are employed to study the physical and chemical structure of GO membranes, while gas chromatography, UV-visible spectroscopy, and gravimetric techniques allow the quantification of their filtration performance. An impressive rejection of about 90% was achieved for 1 ppm of toluene and other pollutants in water, demonstrating the excellent performance of GO membranes in the oil and gas field.

Flexible strain sensors are fundamental devices for application in human body monitoring in areas ranging from health care to soft robotics. Stretchable piezoelectric strain sensors received an ever-increasing interest to design novel, robust and low-cost sensing units for these sensors, with intrinsically conductive polymers (ICPs) as leading materials. We investigated a sensitive element based on crosslinked electrospun nanofibers (NFs) directly collected and thermal treated on a flexible and biocompatible substrate of polydimethylsiloxane (PDMS). The nanostructured active layer based on a blend of poly(ethylene oxide) (PEO) and poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulfonate) (PEDOT:PSS) as the ICP was optimized, especially in terms of the thermal treatment that promotes electrical conductivity through crosslinking of PEO and PSS, preserving the nanostructuration and optimizing the coupling between the sensitive layer and the substrate. We demonstrate that excellent properties can be obtained thanks to the nanostructured active materials. We analyzed the piezoresistive response of the sensor in both compression and traction modes, obtaining an increase in the electrical resistance up to 90%. The Gauge Factors (GFs) reflected the extraordinary piezoresistive behavior observed: 45.84 in traction and 208.55 in compression mode, which is much higher than the results presented in the literature for non-nanostructurated PEDOT.

Memristive devices based on a resistive switching mechanism are considered very promising for nonvolatile memory and unconventional computing applications, even though many details of the switching mechanisms are not yet fully understood. Here, we report a nanostructural study by means of high-resolution transmission electron microscopy and spectroscopy techniques of a Ag/ZnO/Pt memristive device. To ease the localization of the filament position for its characterization, we propose to use the guiding effect of regular perturbation arrays obtained by FIB technology to assist the filament formation. HRTEM and EDX were used to identify the composition and crystalline structure of the so-obtained conductive filaments and surrounding regions. It was determined that the conducting paths are composed mainly of monocrystalline Ag, which remains polycrystalline in some circumstances, including the zone where the switching occurs and at secondary filaments created at the grain boundaries of the polycrystalline ZnO matrix. We also observed that the ZnO matrix shows a degraded quality in the switching zone, while it remains unaltered in the rest of the memristive device.

The need to reduce the costs of renewable energy sources such as (bio)electrochemical systems, has pushed the research towards alternative materials, especially for cathodes performing the oxygen reduction reaction, trying to maintain a catalytic efficiency close to that of platinum or platinum-based catalysts. In this work, at first, we present a manganese oxide-based catalyst in the form of xerogel, providing a complete description of the material. Later on, we present the comparison of two nanostructured manganese oxide-based catalysts, prepared from the same precursor, manganese acetate, but with different templating agents and with two different nanostructures: the xerogel previously discussed, and the nanofibers. With these two nanostructures, we prepared carbon-based electrodes, obtaining cathodes to be tested in microbial fuel cells. One of these cathodes performed very well and its performance was comparable to that of the reference which used Pt/C as catalyst.

Polydimethylsiloxane (PDMS) is a well-known biocompatible polymer employed for many applications in the biomedical field. In this study, the biocompatibility and versatility of PDMS was tested setting up a microdevice devoted to the purification and analysis of nucleic acids. The PDMS microdevice was demonstrated to successfully fulfill all requirements of genetic analyses such as genotyping and pathogen DNA identification both in multiplex and real-time PCR, suggesting the possibility to carry out a molecular test directly on-chip. Moreover, the PDMS microdevice was successfully applied to the purification and detection of disease biomarkers, such as microRNAs related to cancer or heart disease. On-chip microRNA purification was demonstrated starting from clinically relevant samples, i.e. plasma, serum, tissue biopsies. Significantly, the purification and the transcription of microRNA into cDNA occur in the same PDMS chamber, saving time and labor for the overall analysis. Again, the PDMS microdevice was confirmed as a notable candidate for compact, rapid, easy-to-use molecular tests.

The electric responses of electrochemical capacitors produced with electrodes build up of reduced graphene oxide (rGO) deposited on Fluorine-doped tin oxide (FTO) coated glass have been experimentally investigated by cyclic voltammetry measurements. According to our experimental data, the parametric curve of the current in the circuit versus the external voltage is a continuous curve without discontinuity points respect to the inversion points of the external voltage. A few equivalent electric circuits able to reproduce the electric response of the capacitor are discussed. The dependence of the area delimited by the parametric cyclic voltammetry curve on the elements of the circuit is investigated. The possible evaluation of the effective capacitance of the capacitor by the numerical evaluation of the area delimited by the parametric curve is critically discussed and the limit of the procedure is underlined. A model based on the Poisson-Nernst-Planck theory with adsorbing electrodes is developed and used to fit the experimental voltammogram. The agreement between the theoretical model and the experimental data is good, indicating the importance of the adsorption phenomenon in the electric response of electrochemical capacitor to an external electric field.

A catalyst plays a key role in the electrochemical reduction of CO2 to valuable chemicals and fuels. Hence, the development of efficient and inexpensive catalysts has attracted great interest from both the academic and industrial communities. In this work, low-cost catalysts coupling Cu and Zn are designed and prepared with a green microwave-assisted route. The Cu to Zn ratio in the catalysts can be easily tuned by adjusting the precursor solutions. The obtained Cu-Zn catalysts are mainly composed of polycrystalline Cu particles and monocrystalline ZnO nanoparticles. The electrodes with optimized Cu-Zn catalysts show enhanced CO production rates of approximately 200 μmol h-1 cm-2 with respect to those with a monometallic Cu or ZnO catalyst under the same applied potential. At the bimetallic electrodes, ZnO-derived active sites are selective for CO formation and highly conductive Cu favors electron transport in the catalyst layer as well as charge transfer at the electrode/electrolyte interface.

Microbial fuel cells (MFCs) are bio-electrochemical devices able to directly transduce chemical energy, entrapped in an organic mass named fuel, into electrical energy through the metabolic activity of specific bacteria. During the last years, the employment of bio-electrochemical devices to study the wastewater derived from the food industry has attracted great interest from the scientific community. In the present work, we demonstrate the capability of exoelectrogenic bacteria used in MFCs to catalyze the oxidation reaction of honey, employed as a fuel. With the main aim to increase the proliferation of microorganisms onto the anode, engineered electrodes are proposed. Polymeric nanofibers, based on polyethylene oxide (PEO-NFs), were directly electrospun onto carbon-based material (carbon paper, CP) to obtain an optimized composite anode. The crucial role played by the CP/PEO-NFs anodes was confirmed by the increased proliferation of microorganisms compared to that reached on bare CP anodes, used as a reference material. A parameter named recovered energy (Erec) was introduced to determine the capability of bacteria to oxidize honey and was compared with the Erec obtained when sodium acetate was used as a fuel. CP/PEO-NFs anodes allowed achieving an Erec three times higher than the one reached with a bare carbon-based anode.

In order to power remote sensors and/or data transmission devices in an aquatic environment, sedimentary microbial fuel cells and floating microbial fuel cells have been proposed in the literature, representing a continuous source of renewable and sustainable energy. However, both classes of devices are characterized by large dimensions and are immobilized in the environment within which they are working. Accordingly, when portability and small dimensions are strict requirements, these configurations cannot be exploited. The present work proposes a novel, compact and cost-effective floating set-up based on small-scale microbial fuel cells. A method for in situ anodic biofilm formation was validated through experiments conducted in laboratory and in a real marine environment. Carbon felt-based anodic electrodes were used to build different replicas of floating microbial fuel cells. Their overall performance was evaluated during two field measurement campaigns carried out in the Mediterranean Sea. The study demonstrated a high stability of the floating microbial fuel cells even in a real, uncontrolled environment. The devices were able to continuously produce electricity using seawater as fuel and electrolyte. This study suggests that these devices can be used as portable power supplies for sensors in a complex environment such as the open sea due to the easy preparation of anodic electrodes, together with the simple architecture of floating microbial fuel cells.

A tin-modified copper foam for the efficient and selective reduction of CO2 to CO is reported. We employ a cost-efficient electrodeposition route to form a three-dimensional porous dendrite architecture, in which each dendrite possesses a copper core and a copper oxide/tin oxide shell. The sparse tin species on the electrode surface play a key role to achieve excellent faradaic efficiencies for CO formation with a maximum value of 94%. We demonstrate high CO partial current densities of 4.7 mA cm−2 and 7.9 mA cm−2 at applied potentials of -0.8 V and -1.1 V vs. the reversible hydrogen electrode, respectively. The high activity for electrochemical CO2 reduction is attributed to the unique hierarchical porous structure, which offers abundant electrochemically active sites and facilitates mass transport.

Two Photon Polymerization (2PP) is a powerful additive manufacturing technology already employed in the field of micro-/nano- engineering. The resolution achieved by 2PP 3D printing systems is in the range of hundreds of nanometers, but the printing volume is limited to few mm3 and printing times are not negligible. Therefore, it cannot be considered economically efficient with respect to standard clean room technologies or other Stereolitography (SL) techniques. A possible solution to this limitation is the embedding of micro-/nano- features fabricated by 2PP inside a low-resolution object obtained by SL printers. Moreover, 2PP optimized strategies should be adopted to maximize the resolution and maintain a high printing velocity. In this work, a suspended microfilter obtained by a 2PP system has been successfully integrated in a 3D printed microfluidic structure. The microchannel was fabricated by a standard SL printer using a low-cost 3D printing resin, while the suspended microfilter was obtained using a 2PP Micro-3-Dimensional Structuring System (M3D) and a drop of Femtobond D resin. An innovative printing strategy was carried out to maximize the 2PP resolution and optimize the fabrication time. In particular, the X,Y plan was exploited to build the high-resolution mesh, thus obtaining a suspended microfilter that has a final pores size of 4 μm on a considerable area of 0.5 mm2 in an only 30 min process. Finally, the microfluidic filtration system was carried out and its efficiency was evaluated employing size-controlled fluorescent microparticles.

This paper presents a critical review and the state of the art of graphene porous membranes, a brand-new technology and backdrop to discuss its potential application for efficient water desalination in low salinity water injection (LSWI). LSWI technology consists in injecting designed, adequately modified, filtered water to maximize oil production. To this end, desalination technologies already available can be further optimized, for example, via graphene membranes, to achieve greater efficiency in water-oil displacement. Theoretical and experimental applications of graphene porous membranes in water desalination have shown promising results over the last 5-6 years. Needless to say, improvements are still needed before graphene porous membranes become readily available. However, the present work simply sets out to demonstrate, at least in principle, the practical potential graphene membranes would have in hydrocarbon recovery processes.

The present work compares the influence of different polymer matrices on the performance of planar asymmetric Resistive Switching Devices (RSDs) based on silver nitrate and Ionic Liquid (IL). PolyVinyliDene Fluoride-HexaFluoroPropylene (PVDF-HFP), PolyEthylene Oxide (PEO), PolyMethyl MethAcrylate (PMMA) and a blend of PVDF-HFP and PEO were used as matrices and compared. RSDs represent perhaps the most promising electron device to back the More than Moore development, and our approach through functional polymers enables low temperature processing and gives compatibility towards flexible/stretchable/wearable equipment. The switching mechanism in all the four sample families is explained by means of a filamentary conduction. A huge difference in the cyclability and the On/Off ratio is experienced when changing the active polymers and explained based on the polymer crystallinity degree and general morphology of the prepared nanocomposite. It is worth noting that all the RSDs discussed here present good switching behaviour with reasonable endurance. The current study displays one of the most cost-effective and effortless ways to produce an RSD based on solution-processable materials.

Silicon-based materials present a high potential for dental implant applications, since silicon has been proven necessary for the correct bone formation in animals and humans. Notably, the addition of silicon is effective to enhance the bioactivity of hydroxyapatite and other biomaterials. The present work aims to expand the knowledge of the role exerted by hydrogen in the biological interaction of silicon-based materials, comparing two hydrogenated amorphous silicon coatings, with different hydrogen content, as means to enhance soft tissue cell adhesion. To accomplish this task, the films were produced by plasma enhanced chemical vapor deposition (PECVD) on titanium substrates and their surface composition and hydrogen content were analyzed by means of X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectrophotometry (FTIR) respectively. The surface energy and roughness were measured through optical contact angle analysis (OCA) and high-resolution mechanical profilometry respectively. Coated surfaces showed a slightly lower roughness, compared to bare titanium samples, regardless of the hydrogen content. The early cell responses of human keratinocytes and fibroblasts were tested on the above mentioned surface modifications, in terms of cell adhesion, viability and morphometrical assessment. Films with lower hydrogen content were endowed with a surface energy comparable to the titanium surfaces. Films with higher hydrogen incorporation displayed a lower surface oxidation and a considerably lower surface energy, compared to the less hydrogenated samples. As regards mean cell area and focal adhesion density, both a-Si coatings influenced fibroblasts, but had no significant effects on keratinocytes. On the contrary, hydrogen-rich films increased manifolds the adhesion and viability of keratinocytes, but not of fibroblasts, suggesting a selective biological effect on these cells.

In this study, we report on the facile synthesis of a novel electrocatalysts for the oxygen reduction reaction (ORR), based on reduced graphene oxide (RGO), functionalized with metallic and non-metallic elements. In particular, thanks to a fast one-pot microwave-assisted procedure, we induced, in the RGO graphene lattice, a combined doping with nitrogen and sulphur, and the simultaneous decoration with antimony oxide nanocrystals. The multi-doped–decorated material shows enhanced catalytic performance towards ORR, with respect to common nitrogen- or sulphur-doped carbon-based materials. The presence of co-doping is confirmed by transmission electron microscopy and X-ray photoelectron spectroscopy analysis. The detailed electrochemical characterization shows the simultaneous effects of dopant atoms on the catalytic behavior. In particular, the importance of nitrogen and sulphur atoms in driving the oxygen absorption, together with the role of antimony in enhancing the electrochemical performance toward the ORR, are discussed.

The aim of this work is the optimization of electrospun polymeric nanofibers as an ideal reservoir of mixed electroactive consortia suitable to be used as anodes in Single Chamber Microbial Fuel Cells (SCMFCs). To reach this goal the microorganisms are directly embedded into properly designed nanofibers during the electrospinning process, obtaining so called nanofiber-based bio-composite (bio-NFs). This research approach allowed for the designing of an advanced nanostructured scaffold, able to block and store the living microorganisms inside the nanofibers and release them only after exposure to water-based solutions and electrolytes. To reach this goal, a water-based polymeric solution, containing 5 wt% of polyethylene oxide (PEO) and 10 wt% of environmental microorganisms, is used as the initial polymeric solution for the electrospinning process. PEO is selected as the water-soluble polymer to ensure the formation of nanofiber mats offering features of biocompatibility for bacteria proliferation, environment-friendliness and, high ionic conductivity. In the present work, bio-NFs, based on living microorganisms directly encapsulated into the PEO nanofiber mats, were analyzed and compared to PEO-NFs made of PEO only. Scanning electron microscopy allowed researchers to confirm the rise of a typical morphology for bio-NFs, evidencing the microorganisms’ distribution inside them, as confirmed by fluorescence optical microscopy. Moreover, the latter technique, combined with optical density measurements, allowed for demonstrating that after electrospinning, the processed microorganisms preserved their proliferation capability, and their metabolic activity after exposure to the water-based electrolyte. To demonstrate that the energy-production functionality of exo-electrogenic microorganisms was preserved after the electrospinning process, the novel designed nanomaterials, were directly deposited onto carbon paper (CP), and were applied as anode electrodes in Single Chamber Microbial Fuel Cells (SCMFCs). It was possible to appreciate that the maximum power density reached by bio-NFs, which resulted in being double of the ones achieved with PEO-NFs and bare CP. SCMFCs with bio-NFs applied as anodic electrodes reached a current density value, close to (250 ± 5.2) mA m−2, which resulted in being stable over time and was comparable with the one obtained with carbon-based electrode, thus confirming the good performance of the whole device.