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Fused deposition modeling (FDM) is one of the most popular additive manufacturing (AM) technologies for reasons including its low cost and versatility. However, like many AM technologies, the FDM process is sensitive to changes in the feedstock material. Utilizing a new feedstock requires a time-consuming trial-and-error process to identify optimal settings for a large number of process parameters. The experience required to efficiently calibrate a printer to a new feedstock acts as a barrier to entry. To enable greater accessibility to non-expert users, this paper presents the first system for autonomous calibration of low-cost FDM 3D printers that demonstrates optimizing process parameters for printing complex 3D models with submillimeter dimensional accuracy. Autonomous calibration is achieved by combining a computer vision-based quality analysis with a single-solution metaheuristic to efficiently search the parameter space. The system requires only a consumer-grade camera and computer capable of running modern 3D printing software and uses a calibration budget of just 30 g of filament (~ $1 USD). The results show that for several popular thermoplastic filaments, the system can autonomously calibrate a 3D printer to print complex 3D models with an average deviation in dimensional accuracy of 0.047 mm, which is more accurate than the 3D printer’s published tolerance of 0.1–0.4 mm.

In this review, we focus on the fabrication of electrodes, using printing techniques. Generally speaking, electrodes are comprised of a metal conductor with a metal lead (sometimes the same material) for the conduction of electrical current. Different inorganic and organic materials including metal, polymers, carbon, as well as their composites thereof, have been used for electrodes on different substrates. While material-dependent characteristics, including conductivity, optical transparency, corrosion resistance and biocompatibility, determine the choice of material, printing, as the manufacturing method, offers precise control over the geometry and scale of electrodes for selective and sensitive performance. Both 2D- and 3D-printed electrodes have been widely used as sensors for electrochemical applications as well as quantification of biological compounds, establishing contact with biological surfaces and systems, finding application in medical diagnosis, therapy and treatment of various conditions. Costa et al. (Energy Storage Mater 28:216–234, 2020), Mensing et al. (Sustain Mater Technol 25:e00190, 2020) depict the difference between the 2D and 3D printing techniques which can be used for fabrication of 2D and 3D electrodes. The 3D structure of the electrode provides advantages over the 2d electrodes in terms of its catalytic properties through enhancement in its mass transfer process, adsorption efficiency and active exposure sites (Mensing et al. in Sustain Mater Technol 25:e00190, 2020).

Physical properties of aqueous KOH solutions are crucial to the design and operation of alkaline electrolyzers but have been scarcely and sometimes unreliably reported. Obtaining published data for various properties currently requires time-consuming searches and subsequent interpretation, interpolation, and extrapolation. This work collates and critically analyzes published data for a range of physical properties relevant to alkaline electrolysis, including the density, viscosity, conductivity, surface tension, oxygen/hydrogen solubility, oxygen/hydrogen diffusivity, and water vapor pressures of aqueous KOH solutions, as a function of temperature, KOH molarity, and pressure. Correlation functions, in the form of excel spreadsheets, have been developed to allow interpolation of the most reliable data and computation of desired quantities at specific temperatures, pressures, and KOH concentrations. Composite models incorporating these properties have been developed for automated computation of (i) diffusive gas crossover and (ii) gas production volumes, including (iii) water vapor content, and associated (iv) dissolved gas concentrations in the liquid electrolyte, as a function of KOH concentration, temperature, pressure, current density, and separator thickness and porosity. These spreadsheets are provided in the Supporting Information, as tools and reference points for researchers and practitioners in alkaline electrolysis.

Effective control of post-operative inflammation after tissue repair remains a clinical challenge. A tissue repair patch that could appropriately integrate into the surrounding tissue and control inflammatory responses would improve tissue healing. A collagen-based hybrid tissue repair patch has been developed in this work for the local delivery of an anti-inflammatory drug. Dexamethasone (DEX) was encapsulated into PLGA microspheres and then co-electrocompacted into a collagen membrane. Using a simple process, multiple drugs can be loaded into and released from this hybrid composite material simultaneously, and the ratio between each drug is controllable. Anti-inflammatory DEX and the anti-epileptic phenytoin (PHT) were co-encapsulated and released to validate the dual drug delivery ability of this versatile composite material. Furthermore, the Young’s modulus of this drug-loaded collagen patch was increased to 20 KPa using a biocompatible riboflavin (vitamin B2)-induced UV light cross-linking strategy. This versatile composite material has a wide range of potential applications which deserve exploration in further research.

Shortages of personal protective equipment (PPE) at the start of the COVID-19 pandemic caused medical workers to reuse medical supplies such as N95 masks. While ultraviolet germicidal irradiation (UVGI) is commonly used for sterilization, UVGI can also damage the elastomeric components of N95 masks, preventing effective fit and thus weakening filtration efficacy. Although PPE shortage is no longer an acute issue, the development of sterilizable and reusable UV-resistant elastomers remains of high interest from a long-term sustainability and health perspective. Here, graphene nanosheets, produced by scalable and sustainable exfoliation of graphite in ethanol using the polymer ethyl cellulose (EC), are utilized as UV-resistant additives in polyurethane (PU) elastomer composites. By increasing the graphene/EC loading up to 1 wt %, substantial UV protection is imparted by the graphene nanosheets, which strongly absorb UV light and hence suppress photoinduced degradation of the PU matrix. Additionally, graphene/EC provides mechanical reinforcement, such as increasing Young’s modulus, elongation at break, and toughness, with negligible changes following UV exposure. These graphene/EC–PU composites remain mechanically robust over at least 150 sterilization cycles, enabling safe reuse following UVGI. Beyond N95 masks, these UVGI-compatible graphene/EC–PU composites have potential utility in other PPE applications to address the broader issue of single-use waste.

A surface electromyogram (sEMG) electrode collects electrical currents generated by neuromuscular activity by a noninvasive technique on the skin. It is particularly attractive for wearable systems for various human activities and health care monitoring. However, it remains challenging to discriminate EMG signals from isotonic (concentric/eccentric) and isometric movements. By applying nanotechnology, we provide a coiled carbon nanotube (CNT) yarn-integrated sEMG device to overcome sEMG-based motion recognition. When the arm was contracted at different angles, the sEMG-derived root mean square amplitude signals were constant regardless of the angle of the moving arm. However, the coiled CNT yarn-derived open circuit voltage (OCV) signals proportionally increased when the arm’s angle increased, and presented negative and positive values depending on the moving direction of the arm. Moreover, isometric contraction is characterized by the onset of EMG signals without an OCV signal, and isotonic contraction is determined by both EMG signals and OCV signals. Taken together, the integration of EMG and coiled CNT yarn electrodes provides complementary information, including the strength, direction, and degree of muscle movement. Therefore, we suggest that our system has high potential as a wearable system to monitor human motions in industrial and human system applications.

Grass shrimp (Palaemonetes pugio) represent a potential link in the transfer of methylmercury (MeHg) from salt marsh sediments to transient young-of-the-year (YOY) fish. Across six salt marshes subject to varying degrees of Hg contamination, MeHg concentration in grass shrimp was significantly correlated with MeHg in sediment (p< 0.05, R2= 0.81). Bioenergetic models show that grass shrimp alone account for 12–90% of MeHg observed in YOY striped bass and 6–22% of MeHg in YOY summer flounder. Direct accumulation of MeHg from grass shrimp to YOY fish increased with MeHg levels in grass shrimp and sediment. However, in the most contaminated salt marshes with the highest levels of MeHg in grass shrimp and sediment, indirect accumulation of MeHg from grass shrimp by YOY summer flounder, whose diet is dominated by benthic forage fish (mummichog), is predicted to plateau because higher concentrations of MeHg in grass shrimp are offset by a lower proportion of grass shrimp in the mummichog diet. Our results demonstrate that grass shrimp are an important trophic link in the bioaccumulation of MeHg in salt marsh food webs and that MeHg accumulation in YOY fish varies with both the concentration of MeHg in salt marsh sediments and benthic food web structure.

Prenatal alcohol exposure (PAE) can produce deficits in a wide range of cognitive functions but is especially detrimental to behaviors requiring accurate spatial information processing. In open field environments, spatial behavior is organized such that animals establish “home bases” marked by long stops focused around one location. Progressions away from the home base are circuitous and slow, while progressions directed toward the home base are non‐circuitous and fast. The impact of PAE on the organization of open field behavior has not been experimentally investigated. In the present study, adult female and male rats with moderate PAE or saccharin exposure locomoted a circular high walled open field for 30 minutes under lighted conditions. The findings indicate that PAE and sex influence the organization of open field behavior. Consistent with previous literature, PAE rats exhibited greater locomotion in the open field. Novel findings from the current study indicate that PAE and sex also impact open field measures specific to spatial orientation. While all rats established a home base on the periphery of the open field, PAE rats, particularly males, exhibited significantly less clustered home base stopping with smaller changes in heading between stops. PAE also impaired progression measures specific to distance estimation, while sex alone impacted progression measures specific to direction estimation. These findings support the conclusion that adult male rats have an increased susceptibility to the effects of PAE on the organization of open field behavior. The current study is the first to examine the effects of moderate PAE on rat movement organization in the open field. Several measures of performance consistent with spatial disorientation were observed in the moderate PAE group. Additionally, adult male rats showed an increased susceptibility to the effects of moderate PAE. This behavioral analysis may provide a sensitive and reliable way to clinically detect FASD, allowing protective interventions to begin earlier in development.

One of the key challenges of room temperature aqueous CO2electrolysis technology is the carbon losses because of carbonate formation. It is desirable if carbonate ions could be utilized concurrently for a useful process. Herein, we devise a strategy that enables in-situ electroreduction and assisted CO2storage using a by-product of that reduction process and carbonate ions. By employing a Ag catalyst deposited on a gas diffusion layer, we demonstrate CO2electroreduction and concurrent storage via mineralisation using seawater, as well as other calcium containing electrolytes. For example, CO2electroreduction in 0.6 M Na2SO4containing 400 ppm Ca electrolyte results in a Faradaic conversion efficiency to CO of ∼90 % at - 1.4 V vs. RHE (∼60 ± 6 mA cm−2), and concurrently stored CO2as calcium carbonate. This bioinspired work offers a new avenue where CO2storage is incorporated in a sustainable CO2electroreduction technology.

Peptidoglycan (PG) is a major component of the cell wall in Enterococcus faecalis. Accurate analysis of PG composition provides crucial insights into the bacterium’s cellular functions and responses to external stimuli, but this analysis remains challenging because of various chemical modifications to PG-repeat subunits. We characterized changes to the PG composition of E. faecalisgrown as planktonic bacteria and biofilm by developing “stable isotope labeling by amino acids in bacterial culture” (SILAB), optimized for bacterial cultures with incomplete amino acid labeling. This comparative analysis by mass spectrometry was performed by labeling E. faecalisin biofilm with heavy Lys (l-[13C6,2D9,15N2]Lys) and planktonic bacteria with natural abundance l-Lys, then mixing equal amounts of bacteria from each condition, and performing cell wall isolation and mutanolysin digestion necessary for liquid chromatography and mass spectrometry. An analytical method was developed to determine muropeptide abundances using correction factors to compensate for incomplete heavy Lys isotopic enrichment (98.33 ± 0.05%) and incorporation (83.23 ± 1.16%). Forty-seven pairs of PG fragment ions from isolated cell walls of planktonic and biofilm samples were selected for SILAB analysis. We found that the PG in biofilm showed an increased level of PG cross-linking, an increased level of N-deacetylation of GlcNAc, a decreased level of O-acetylation of MurNAc, and an increased number of stem modifications by d,d- and l,d-carboxypeptidases.

Microsecond dye-regeneration kinetics was observed in efficient solid state dye-sensitized solar cells using photoelectrochemically deposited poly(3,4-ethylenedioxythiophene (PEDOT) hole conductors using transient absorption spectroscopy. The dye-regeneration rate is orders of magnitude slower than the case using the I−/I3−redox couple or commonly used small molecule hole conductor and is attributed to the low dye to PEDOT ratio within the films.

The rich electronic and band structures of monolayered crystals offer versatile physical/chemical properties and subsequently a wide range of applications. Fabrication, particularly by the top-down “exfoliation” processes, relies on the presence of weak van der Waals force between individual layers. Due to the strong chemical bonds between planes and atoms, unzipping ultrathin crystals (from one to several unit cells thick) from non-layered structures is more challenging. This work reports a technique used to prepare such ultrathin crystals from bulk non-layered structures (ɑ-/β-MnO2, ZnO, TiO2, ɑ-TiB2). The physical and optical properties of these materials are characterized and contrasted against those from their bulk phases. The work presented here represents a tool kit for the preparation of novel 2D non-layered nanomaterials, providing significant contributions to this family of materials, paving the way for even more applications. Furthermore, we show the application of these novel NCs for biosensing and electrochemical oxygen reduction.

It is challenging to hydrothermally synthesize solution-processable MoS2, as the strong van der Waals force between MoS2nanosheets induces self-assembly of agglomerates. Here, we introduce poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) into the precursor to impede aggregate formation in the hydrothermal process. A hybrid MoS2/PEDOT:PSS (MP) hydrogel is formed due to the electrostatic interactions between the negatively charged MoS2and positively charged PEDOT chains. This hydrogel can be easily dispersed in water for subsequent solution processing such as vacuum filtration to form free-standing flexible films or extrusion 3D printing to create novel patterns. The MP film with a fracture strength of 18.59 MPa displays excellent electrochemical performance in both aqueous Na2SO4electrolyte (474 mF cm–2) and solid-state PVA–H3PO4electrolyte (360 mF cm–2). Flexibility and robustness can be evidenced by high capacitance retention rates of 94 and 89% after being repeatedly bent to 180° for 5000 cycles in aqueous and solid-state electrolytes, respectively.

3D bioprinting has been increasingly employed in skin tissue engineering for manufacturing living constructs with three-dimensional spatial precision and controlled architecture. There is however, a bottleneck in the tunability of bioinks to address specific biocompatibility challenges, functional traits and printability. Here we report on a traditional gelatin methacryloyl (GelMA) based bioink, tuned by addition of an ulvan type polysaccharide, isolated from a cultivated source of a specific Australian Ulvaceanmacroalgae (Ul84). Ul84 is a sulfate- and rhamnose-rich polysaccharide, resembling mammalian glycosaminoglycans that are involved in wound healing and tissue matrix structure and function. Printable bioinks were developed by addition of methacrylated Ul84 (UlMA) to GelMA solutions. The inclusion of UlMA in the bioinks facilitated the extrusion printing process by reducing yield stress. The resultant printed structures containing ulvan exhibited improved mechanical strength and regulated the rate of scaffold degradation. The 3D printed cell-laden structures with human dermal fibroblasts demonstrated high cell viability, support of cell proliferation and dermal-like properties as evidenced by the deposition of key dermal extracellular matrix components including collagen I, collagen III, elastin and fibronectin. In vitrodegradation suggested the role of UlMA in supporting structural stability of the printed cellular structures. Taken together, the present work demonstrates progression towards a biocompatible and biofunctional ink that simultaneously delivers improved mechanical, structural and stability traits that are important in facilitating real world applications in skin tissue repair.

Thin and flexible electromagnetic shielding materials have recently emerged because of their promising applications in drones, portable electronics, military defense facilities, etc. This research develops an electromagnetic interference (EMI) shielding material by a bidirectional lattice sandwich structure (BLSS), which is formed by liquid crystalline graphene oxide (LCGO) and an orthogonal pattern of spinnable multiwalled (OPSM) nanotubes in consideration of the movement of electromagnetic waves. The average EMI shielding effectiveness (SE) of the developed material with 0.5 wt % reduced LCGO (r-LCGO) and an OPSM nanotube composed of 64 layers was approximately 66.1 dB in the X-band frequency range (8.2–12.4 GHz, wavelength: 3.5–2.5 cm), which corresponds to a shielding efficiency of 99.9999%. Also, its absorption effectiveness is 99.7% of the total EMI SE, indicating that it has a remarkable ability to prevent secondary damage induced by EM reflection. The specific EMI SE (SSE/t) of the composite material considering the contribution of thickness (t) ranged from 21 953 to 2259 dB cm2/g.

Nanotechnology-based antimicrobial and antiviral formulations can prevent SARS-CoV-2 viral dissemination, and highly sensitive biosensors and detection platforms may contribute to the detection and diagnosis of COVID-19.

In this study we use a combination of ionic- and photo-cross-linking to develop a fabrication method for producing biocompatible microstructures using a methacrylated gellan gum (a polyanion) and chitosan (a polycation) in addition to lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP) as the photoinitiator. This work involves the development of a low-cost, portable 3D bioprinter and a customized extrusion mechanism for controlled introduction of the materials through a 3D printed microfluidic nozzle, before being cross-linked in situ to form robust microstructure bundles. The formed microstructures yielded a diameter of less than 1 μm and a tensile strength range of ∼1 MPa. This study is the first to explore and achieve GGMA:CHT microstructure fabrication by means of controlled in-line compaction and photo-cross-linking through 3D printed microfluidic channels.

Abstract

Freestanding flexible electrodes with high areal mass loading are required for the development of flexible high-performance lithium-ion batteries (LIBs). Currently they face the challenge of low mass loading due to the limited concentrations attainable in processable dispersions. Here, we report a simple low-temperature hydrothermal route to fabricate flexible layered molybdenum disulfide (MoS2)/reduced graphene oxide (MSG) films offering high areal capacity and good lithium storage performance. This is achieved using a self-assembly process facilitated by the use of liquid crystalline graphene oxide (LCGO) and commercial MoS2powders at a low temperature of 70 °C. The amphiphilic properties of ultralarge LCGO nanosheets facilitates the processability of large-size MoS2powders, which is otherwise nondispersible in water. The resultant film with an areal mass of 8.2 mg cm–2delivers a high areal capacity of 5.80 mAh cm–2(706 mAh g–1) at 0.1 A g–1. This simple method can be adapted to similar nondispersible commercial battery materials for films fabrication or production of more complicated constructs via advanced fabrication technologies.

A self-healing electrode is an electrical conductor that can repair internal damage by itself, similar to human skin. Since self-healing electrodes are based on polymers and hydrogels, these components are still limited by low electrical conductivity and mechanical strength. In this study, we designed an electrically conductive, mechanically strong, and printable self-healing electrode using liquid crystal graphene oxide (LCGO) and silver nanowires (AgNWs). The conductive ink was easily prepared by simply mixing LCGO and AgNWs solutions. The ultrathin (3 μm thick) electrode can be printed in various shapes, such as a butterfly, in a freestanding state. The maximum conductivity and strength of the LCGO/AgNW composite were 17 800 S/cm and 4.2 MPa, respectively; these values are 24 and 4 times higher, respectively, than those of a previously developed self-healing electrode. The LCGO/AgNW composite self-healed internal damage in ambient conditions with moisture and consequently recovered 96.8% electrical conductivity and 95% mechanical toughness compared with the undamaged state. The electrical properties of the composite exhibited metallic tendencies. Therefore, these results suggest that the composite can be used as an artificial electronic skin that detects environmental conditions, such as compression and temperature. This self-healing artificial electronic skin could be applied to human condition monitoring and robotic sensing systems.