Electrically conductive elastomeric fibres prepared using a wet-spinning process are promising materials for intelligent textiles, in particular as a strain sensing component of the fabric. However, ...these fibres, when reinforced with conducting fillers, typically result in a compromise between mechanical and electrical properties and, ultimately, in the strain sensing functionality. Here we investigate the wet-spinning of polyurethane (PU) fibres with a range of conducting fillers such as carbon black (CB), single-walled carbon nanotubes (SWCNTs), and chemically converted graphene. We show that the electrical and mechanical properties of the composite fibres were strongly dependent on the aspect ratio of the filler and the interaction between the filler and the elastomer. The high aspect ratio SWCNT filler resulted in fibres with the highest electrical properties and reinforcement, while the fibres produced from the low aspect ratio CB had the highest stretchability. Furthermore, PU/SWCNT fibres presented the largest sensing range (up to 60% applied strain) and the most consistent and stable cyclic sensing behaviour. This work provides an understanding of the important factors that influence the production of conductive elastomer fibres by wet-spinning, which can be woven or knitted into textiles for the development of wearable strain sensors.
There is an urgent need for conductive neural interfacing materials that exhibit mechanically compliant properties, while also retaining high strength and durability under physiological conditions. ...Currently, implantable electrode systems designed to stimulate and record neural activity are composed of rigid materials such as crystalline silicon and noble metals. While these materials are strong and chemically stable, their intrinsic stiffness and density induce glial scarring and eventual loss of electrode function in vivo. Conductive composites, such as polymers and hydrogels, have excellent electrochemical and mechanical properties, but are electrodeposited onto rigid and dense metallic substrates. In the work described here, strong and conductive microfibers (40–50 μm diameter) wet‐spun from liquid crystalline dispersions of graphene oxide are fabricated into freestanding neural stimulation electrodes. The fibers are insulated with parylene‐C and laser‐treated, forming “brush” electrodes with diameters over 3.5 times that of the fiber shank. The fabrication method is fast, repeatable, and scalable for high‐density 3D array structures and does not require additional welding or attachment of larger electrodes to wires. The electrodes are characterized electrochemically and used to stimulate live retina in vitro. Additionally, the electrodes are coated in a water‐soluble sugar microneedle for implantation into, and subsequent recording from, visual cortex.
Strong, flexible fibers are wet‐spun from a liquid crystalline dispersion of graphene oxide (LCGO), then coated with parylene‐C, and laser‐excised to create free‐standing stimulate electrodes with high charge injection capacity (14 mC cm−2). LCGO electrodes stimulated retina in vitro; water‐soluble microneedles are utilized to implant the flexible electrodes into cortical tissue enabling acquisition of neural activity.
Self‐assembled structures obtained from organic molecules have shown great potential for applications in a wide range of domains. In this context, short peptides prove to be a particularly versatile ...class of organic building blocks for self‐assembled materials. These species afford the biocompatibility and polymorphic richness typical of proteins while allowing synthetic availability and robustness typical of smaller molecules. At the nano‐to‐mesoscale, the architectures obtained from peptide units exhibit stability and a large variety of morphologies, the most common of which are nanotubes, nanoribbons, and nanowires. This review describes the formation of peptide‐based self‐assembled structures triggered by different stimuli (e.g., ionic strength, pH, and polarity), and the interactions that drive the assembling processes. It is surveyed how judicious molecular design is exploited to impart favourable assembling properties to afford systems with desired characteristics. A large body of literature provides the experimental and in silico data to predict self‐assembly in a given peptide system and obtain different supramolecular organizations for applications in a wide range of fields, from transport to sensing, from catalysis to drug delivery and tissue regeneration.
The self‐assembly properties of peptide nanomaterials in relation to their design and composition are surveyed in this review. It emphasizes how the morphology of peptide nanostructures can be influenced by environmental conditions, and how this dependence can be suitably exploited for the design of stimuli‐responsive systems.
The Advanced Divertor and RF tokamak eXperiment (ADX) is a compact, high-field device proposed by the MIT Plasma Science and Fusion Center and collaborators, which will address critical gaps in world ...fusion research on the pathway to fusion energy. In addition to developing and testing new divertor concepts at reactor level magnetic field strengths and power densities, ADX will test new antenna concepts for lower hybrid current drive (LHCD) and ion cyclotron range of frequency (ICRF) heating systems. In particular, ADX will be purpose-built to allow antennas to be positioned on the high magnetic field side of the torus, i.e., on the inner wall. With antennas placed at this location, plasma-wall interactions are greatly reduced and favorable RF wave physics projects to dramatic improvements in current drive efficiency and current profile control as well as very effective scenarios for RF heating and flow drive. Initial designs for the high-field-side LHCD and ICRF antennas have been completed and are analyzed to determine the loads induced during a full-current plasma disruption. While locating antennas at the inner wall is beneficial from an RF standpoint, it exposes them to a higher toroidal field which, when combined with the eddy currents caused by a disrupting plasma, will lead to higher loads. Using COMSOL Multiphysics, a model of the ADX vessel and coils is created to predict the magnetic fields, eddy currents, and loads acting on the antennas during a disruption. Structural models are then run to predict the stresses and to provide guidance for design improvement, such as determining where structural reinforcements may be necessary.
Additive manufacturing (3D printing) offers a flexible approach for the production of bespoke microfluidic structures such as the electroosmotic pump. Here a readily accessible fused filament ...fabrication (FFF) 3D printing technique has been employed for the first time to produce microcapillary structures using low cost thermoplastics in a scalable electroosmotic pump application. Capillary structures were formed using a negative space 3D printing approach to deposit longitudinal filament arrangements with polylactic acid (PLA) in either "face-centre cubic" or "body-centre cubic" arrangements, where the voids deliberately formed within the deposited structure act as functional micro-capillaries. These 3D printed capillary structures were shown to be capable of functioning as a simple electroosmotic pump (EOP), where the maximum flow rate of a single capillary EOP was up to 1.0 μl min
−1
at electric fields of up to 750 V cm
−1
. Importantly, higher flow rates were readily achieved by printing parallel multiplexed capillary arrays.
Fused filament fabrication (FFF)-3D printed polylactic acid capillary structure base on "body centre cubic (BCC)" log-pile like filament arrangements utilising the negative print space technique.
Launching lower hybrid (LH) waves from the high field side (HFS) of a tokamak offers significant advantages over low-field-side (LFS) launch with respect to both wave physics and plasma material ...interactions (PM!s). The higher magnetic field opens the window between wave accessibility and the condition for strong electron Landau damping, allowing LH waves from the HFS to penetrate into the core of burning plasma, while waves launched from the LFS are restricted to the periphery of the plasma. The lower parallel refractive index (n||) of the waves launched from the HFS yields a higher current drive efficiency as well. The absence of turbulent heat and particle fluxes on the HFS, particularly in double null configuration, makes it the ideal location to minimize PM! damage to the antenna structure. The quiescent scrape off layer (SOL) also eliminates the need to couple LH waves across a long distance to the separatrix, as the antenna can be located close to plasma without risking damage to the structure. The Advanced Divertor eXperiment (ADX) will include an LH launcher located on the HFS. The LH system for ADX will make use of the existing infrastructure from Alcator C-Mod, including sixteen 250-kW klystrons at 4.6 GHz (total source power of 4 MW), high-voltage power supply, and controls. The ADX vacuum vessel design includes dedicated space for waveguide runs, pressure windows, and vacuum feedthroughs for accessing the HFS wall. Compact antenna designs based on proven technologies (e.g., multijunction and four-way splitter antennas) fit within the available space on the HFS of the ADX. Wave coupling simulations of these launchers with HFS SOL density profiles showing good coupling can be obtained by adjusting the distance between the separatrix and the HFS wall. Guard limiters on each side of the LH antenna protect the structure during ramp-up, ramp-down, and off-normal events.
Oceans are regarded as a sink for anthropogenic CO2; as such seawater provides an attractive electrolyte for electrochemical CO2 reduction to value-added carbon-based fuels and chemical feedstocks. ...However, the composition of seawater is inherently complex, containing multiple cations and anions that may participate in the CO2 electroreduction reaction. Herein, examination of a nanoporous Ag electrocatalyst in seawater reveals a significant influence of calcium ions on the electrochemical CO2 reduction performance. Under the applied cathodic potential and in the presence of CO2, calcium ions in the seawater result in calcium carbonate deposition onto the nanoporous Ag, reducing active sites for CO2 electroreduction. Mitigation of calcification would promote a stable CO2 electrolysis in seawater. A first proof-of-concept self-powered hybrid CO2 electrolysis is demonstrated by the coupling of a Mg anode to a nanoporous Ag cathode in 0.6 M NaCl or seawater. A spontaneous oxidation of a Mg alloy at the anode drives cathodic reduction of AgCl to nanoporous Ag, which electrocatalytically reduces CO2 to CO. Combining galvanic and electrolytic properties in a single electrochemical cell offers a general approach for designing hybrid self-powered electrolysers. Strategies to overcome calcification such as removal of calcium from the seawater and development of anti-calcifying electrocatalysts are needed to promote practicability of seawater as an electrolyte in CO2 electroreduction technology.
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.
•CS/PF coil solutions for FNSF plasma equilibria.•Time dependent free-boundary plasma evolution simulations.•Ideal MHD stability to peeling-ballooning modes and n=1 extenal kink mode.•Plasma energy ...transport assessment.•Heating and current drive simulations for NB’s, LH, IC and EC.
The FNSF core plasma physics is examined with detailed analysis to establish the basis for the reference configuration, R=4.8m, a=1.2m, Ip=7.87 MA, and BT=7.5T, q95=6, fBS=0.52, βN<2.7 established in Ref. 1. Central solenoid (CS) and poloidal field (PF) coils are far from the plasma as in a power plant, and acceptable coil currents are determined for the rampup and flattop fiducial states. Time-dependent free-boundary plasma evolution simulations show that the FNSF plasma can be established, ramped up, and relaxed into flattop, including vertical stabilizers, internal feedback coils and feedback control on plasma current, position, and shape. A range of density (no/=1.3–1.5) and temperature (To/ =2.2–2.7) profiles are examined, indicating that energy confinement of H98=1.1–1.2 is required to provide 100% non-inductive plasma current in the FNSF. GLF23 theory based transport model predicted lower energy confinement of H98 ∼0.6–0.85. The EPED analysis shows that the pedestal temperature ranges from 4.0–4.7keV for pedestal densities of 1.7–1.0×1020/m3. The n=1 kink stability shows no-wall beta limits, using the pressure and current profiles associated with the transport and current drive sources, ranging from βN ∼2.25–2.55 depending on li. A conducting wall can extend these limits by 10–40% depending on li and wall location. At the lower beta’s of the reference plasma, a combination of 50MW of NB, 30MW of LH, 20MW of ICRF, 20MW of EC, and bootstrap current, are found to provide 100% of the plasma current with a stable current profile. Impacts on the FNSF of plasma physics are discussed and R&D challenges are highlighted.
PDF
