Sandwich Configuration Research Articles

Mechanical performance of sandwich composites with additively manufactured triply periodic minimal surface cellular structured core

Sandwich composite structures are comprised of a low-density core (commonly honeycomb) and facesheets. They are typically used in applications that require lightweight for efficient design, such as in the marine and aerospace industries. This work investigates the feasibility of adopting triply periodic minimal surface (TPMS) cellular structures as the core for sandwich composites. Sandwich structures were manufactured using a carbon fiber-reinforced polymer (CFRP) facesheet and three different 304 L stainless steel core structures (honeycomb, gyroid TPMS, and diamond TPMS). Three mechanical tests, namely edgewise compression, three-point bend, and impact test, were carried out to evaluate the performance of each sandwich configuration. The experimental results of the non-traditional sandwich configurations were compared against those of a honeycomb core sandwich composite. The edgewise compression test showed that the ultimate edgewise compressive strength increased by 7% when the honeycomb core was replaced by the gyroid core and reduced by 2% when the diamond core replaced the honeycomb core. The three-point bend test showed that the traditional honeycomb core sandwich configuration had a higher shear yield stress when compared to the non-traditional sandwich structures. The shear yield stress was reduced by 54% when non-traditional sandwich cores were used. The shear ultimate stress was reduced by 41% and 37% when the honeycomb core was replaced by the gyroid and diamond structure, respectively. Impact test results, on the other hand, showed that the peak force recorded during the impact event was reduced, while the absorbed energy was increased when non-traditional cores were used. Peak force was reduced by 28% and 39%, while the absorbed energy was increased by 9% and 16% when the honeycomb core was replaced by the gyroid and diamond cores, respectively.

Pre-incubation with OATP1B1 and OATP1B3 inhibitors potentiates inhibitory effects in physiologically relevant sandwich-cultured primary human hepatocytes

Organic anion transporting polypeptides (OATP)1B1 and OATP1B3 are liver-specific transport proteins that express on the basolateral membrane of human hepatocytes and mediate hepatic uptake of many drugs, including statins. They are important determinants of transporter-mediated drug-drug interactions (DDIs). It has been reported that pre-incubation with some OATP1B1 and OATP1B3 inhibitors potentiates the inhibitory effects, yielding reduced IC50 values. The US FDA draft guidance has recently recommended to use the lower IC50 values after inhibitor-preincubation to assess OATP1B1 and OATP1B3-mediated DDIs. However, it remains unknown whether the potentiation effects of inhibitor-preincubation on IC50 values occur in a physiologically relevant cell model. The current study was designed to determine the IC50 values of OATP1B1 and OATP1B3 inhibitors everolimus (EVR), sirolimus (SIR), and dasatinib against OATP1B substrates in physiologically relevant primary human hepatocytes with or without inhibitor-preincubation and to compare the OATP-mediated DDI prediction using data from primary human hepatocytes and that reported previously in transporter-expressing cell lines. Primary human hepatocytes were cultured in a sandwich configuration. Accumulation of [3H]-CCK-8 (1 µM, 1.5 min), [3H]-rosuvastatin (0.5 µM, 2 min) and [3H]-pitavastatin (1 µM, 0.5 min) was determined in human sandwich-cultured hepatocytes (SCH) in the presence of vehicle control or an inhibitor with or without inhibitor-preincubation at designated concentrations, and was utilized to determine the IC50 values for these inhibitors. R-value models were used to predict OATP-mediated DDIs. Pre-incubation with EVR at a clinically relevant concentration of 0.2 µM significantly reduced accumulation of [3H]-CCK-8 and [3H]-rosuvastatin even after washing. Reduced IC50 values following inhibitor pre-incubation were observed for all three inhibitors using [3H]-CCK-8 and [3H]-rosuvastatin as substrates in human SCH. The IC50 values after inhibitor-preincubation were lower or comparable in transporter-expressing cell lines compared with that in human SCH. For dasatinib, R-values from both cell lines and human SCH were greater than the US FDA cut-off value of 1.1. For EVR, R values from cell lines were 1.23 and were lowered to near 1.1 (1.08–1.09) in human SCH. For SIR, R values from either cell type were less than the cut-off values of 1.1. In conclusion, the current study is the first to report that pre-incubation with OATP1B inhibitors potentiates inhibitory effects in physiologically relevant primary human hepatocytes, supporting the rationale of the current US FDA draft guidance of including an inhibitor-preincubation step when assessing OATP-mediated DDIs in vitro. IC50 values after inhibitor-preincubation in transporter-expressing cell lines may be used for DDI prediction for the purpose of mitigating false-negative OATP-mediated DDI prediction.

Experimental investigation of a highly efficient, low-cost PVC-Rollers Sandwich (PVC-RS) seismic isolation

This paper focuses on the large-scale experimental investigation of a novel, highly efficient, low-cost and easily constructible seismic isolation system, defined as PVC-Rollers Sandwich (PVC-RS) seismic isolation. The proposed system is based on the placement of spherical roller bearings between two PVC surfaces in a sandwich configuration. This configuration triggers a desirable rolling behaviour between the rollers and the PVC surfaces, thus isolating the motion of the structure from the ground excitation. The large-scale shaking table investigation of the seismic response of a scaled-down masonry and a scaled-down steel model of a seismically isolated prototype structure using PVC-RS has unveiled the activation of the rolling behaviour of the structure at a desirably low acceleration amplitude of 0.05g-0.1g. The reliability of this low-acceleration response of the structure was confirmed for ground motion excitations of different amplitudes and frequency characteristics. The experimentally tested variation on the amount, the material and the diameter of the roller bearings allows for the implementation of different design alternatives of the presented system, according to the seismic design requirements and the seismic performance objectives for each location.

Thermomechanical characterization of metal-polyurethane bonded joints: effect of manufacturing parameters and working temperature

ABSTRACT Metal-elastomer bonded joints are typical of different industrial applications, specifically pallet truck wheels, where the solid elastomeric layer is bonded to the metal body. This paper focuses on the effect of manufacturing parameters and working temperature, on the shear strength of a metal-elastomer bonded joint. Through a comprehensive experimental test plan, the paper investigates the effect of thermal conditioning of the adhesive, shot peening of the metal adherend, type of solvent-based adhesive, and working temperature of the joint. The test plan uses a TAST-like specimen with a sandwich configuration (metal-elastomer-metal), loaded in order to originate a nearly pure-shear stress state. The results show which parameters influence most the shear strength of the joint helping the designer in maximizing the load-carrying capacity of the joint.

Hydration-induced reversible deformation of the pine cone

The scales of pine cones undergo reversible deformation due to hydration changes in order to optimize seed dispersal. This improves the survivability of the pine. The reversible flexing of the scales is caused by two tissue layers arranged in a sandwich configuration: a layer composed of sclereid cells and a sclerenchyma layer. They expand differentially upon hydration (and contract upon dehydration) due to differences in the structure that are analyzed here for Torrey pine (Pinustorreyana) cones. In addition to this well-known mechanism by which the cellulose microfibrils in the scales vary their angle with the wood cell axis, we confirm the presence of a porosity gradient in the sclereid cells and calculate, using a model consisting of three layers, the stresses generated upon dehydration taking into account the effect of hydration on the elastic modulus. Our quantitative analysis reveals that this gradient structure can significantly decrease the stress concentrations due to the mismatch between the two layers, and show that this is an ingenious design to increase the interfacial toughness to improve the robustness of pine cone scales. We also show that each individual layer of sclereid cells and sclerenchyma fibers undergoes bending when hydrated separately, and suggest that the two layers operate synergistically to effect the required deformation for seed release. A synthetic bioinspired analog consisting of hydrogels with different porosities is used to confirm this principal actuation mechanism. These findings may inspire the materials science and mechanical engineering communities to develop more robust, biocompatible and energy-efficient actuation systems. Statement of significanceSome biological structures can exhibit reversible deformation enabled by water inflow and outflow of their structure. We analyse the reversible motion of pine cone scales. The dehydration produces their flexure and opening, resulting in the release of seeds and their dispersal, when conditions are right. This process is reversible, and rehydration of the pine cone recloses the scales. The processes of flexing and straightening are governed by shrinking and swelling which are directed by differences in the arrangement of cellulose microfibrils in a bilayer construct. We demonstrate that the scales are more complex than a simple bilayer structure and that they actually have gradients, which significantly reduce the internal stresses and ensure their integrity. We analyse the process of opening and closing of the scales for a gradient structure in the Torrey pine cone using a simple idealized trilayer model. The results demonstrate a significant decrease in internal stresses produced by the gradient structure. Using the lessons learned from the pine cone, we produce a bilayer junction using hydrogels with different porosities which exhibit the same reversible bending response.

Boosting Long-Range Surface-Enhanced Raman Scattering on Plasmonic Nanohole Arrays for Ultrasensitive Detection of MiRNA

A fundamental challenge, particularly, in surface-enhanced Raman scattering (SERS) analysis is the detection of analytes that are distant from the sensing surface. To tackle this challenge, we herein report a long-range SERS (LR-SERS) substrate supporting an extension of electric field afforded by long-range surface plasmon resonance (LRSPR) excited in symmetrical dielectric environments. The LR-SERS substrate has a sandwich configuration with a triangle-shaped gold nanohole array embedded between two dielectrics with similar refractive indices (i.e., MgF2 and water). The finite-difference time-domain simulation was applied to guide the design of the LR-SERS substrate, which was engineered to have a wavelength-matched LRSPR with 785 nm excitation. The simulations predict that the LR-SERS substrate exhibits great SERS enhancement at distances of more than 10 nm beyond its top surface, and the enhancement factor (EF) has been improved by three orders of magnitude on LR-SERS substrates compared to that on conventional substrates. The experimental results show good agreement with the simulations, an EF of 4.1 × 105 remains available at 22 nm above the LR-SERS substrate surface. The LR-SERS substrate was further applied as a sensing platform to detect microRNA (miRNA) let-7a coupled with a hybridization chain reaction (HCR) strategy. The developed sensor displays a wide linear range from 10 aM to 1 nM and an ultralow detection limit of 8.5 aM, making it the most sensitive among the current detection strategies for miRNAs based on the SERS-HCR combination to the best of our knowledge.

Dielectric measurements on stearic acid/eicosylamine alternate layer Langmuir–Blodgett films incorporating CdS nanoparticles

Langmuir–Blodgett deposition of 16 and 15 monolayers of stearic acid/eicosylamine has been accomplished on ultrasonically cleaned aluminized quartz substrate with 50 nm thick evaporated aluminium electrodes. Alternating current (AC) impedance measurements have been performed on with the aluminium (Al) top electrode in a sandwich configuration in the range of 100 Hz to 1 MHz and in the temperature ranging between 300 K ≤ T ≤ 360 K. The impedance data were fitted using an equivalent circuit which is mainly composed of resistors and constant phase elements (CPE). Complex impedance study highlighted the presence of a non-Debye type relaxation conduction: quantum mechanical tunnelling (QMT) through the barrier separating the localized sites and correlated barrier hopping.

Hydrophobic membranes for ammonia recovery from digestates in microbial electrolysis cells: Assessment of different configurations

The combination of hydrophobic membranes and microbial electrolysis cells (MEC) was assessed in two different configurations in order to recover ammonia from anaerobically digested pig slurry. Polytetrafluorethylene (PTFE) hydrophobic membranes were inserted both in an H-type three-chamber cell (MEC-H) and a two-chamber sandwich configuration MEC (MEC-S), both fitted with a cationic exchange membrane (CEM) dividing the anode and cathode compartments. The use of electrochemical techniques such as electrochemical impedance spectroscopy was applied to monitor the increase of the biofilm on the anode, related to the decrease of the charge transfer resistance. When operated in the higher organic loading rate (28 ± 5kgCODm−3d−1) the current density produced in the MEC-H was 1.40 ± 0.71 A m−2, compared to 0.61 ± 0.28 A m−2 in the MEC-S. The flux of ammonium through the CEM in the MEC-H was of 3.4 ± 1.2 g N m−2 h−1. Regarding the recovery of ammonia through the hydrophobic membrane, the flux of ammonia was of 1.5 and 0.7 g N m−2 h−1 in the MEC-H and MEC-S, respectively, mainly governed by the pH value and the ammonia concentration of the catholyte. The combination of MEC with hydrophobic membranes reveals as a suitable technology for the recovery of ammonia and treatment of high strength wastewater such as livestock manure.

Randomly positioned gold nanoparticles as fluorescence enhancers in apta-immunosensor for malaria test

A plasmon-enhanced fluorescence-based antibody-aptamer biosensor — consisting of gold nanoparticles randomly immobilized onto a glass substrate via electrostatic self-assembly — is described for specific detection of proteins in whole blood. Analyte recognition is realized through a sandwich scheme with a capture bioreceptor layer of antibodies — covalently immobilized onto the gold nanoparticle surface in upright orientation and close-packed configuration by photochemical immobilization technique (PIT) — and a top bioreceptor layer of fluorescently labelled aptamers. Such a sandwich configuration warrants not only extremely high specificity, but also an ideal fluorophore-nanostructure distance (approximately 10–15 nm) for achieving strong fluorescence amplification. For a specific application, we tested the biosensor performance in a case study for the detection of malaria-related marker Plasmodium falciparum lactate dehydrogenase (PfLDH). The proposed biosensor can specifically detect PfLDH in spiked whole blood down to 10 pM (0.3 ng/mL) without any sample pretreatment. The combination of simple and scalable fabrication, potentially high-throughput analysis, and excellent sensing performance provides a new approach to biosensing with significant advantages compared to conventional fluorescence immunoassays.Graphical abstract

P-Type NiO thin films obtained via an electrochemical-thermal route

The development of procedures for the synthesis of p-type NiO on top of non-degenerate semiconductors is of great interest due to the potential applications in several areas of microelectronics. In this work, p-type NiO films with different resistivity values are obtained by heating at different temperatures Ni(OH)2 layers electrodeposited on n-type monocrystalline Si substrates. Characterizations by X-ray diffraction and X-ray photoelectron spectroscopy have evidenced the phase change, from hexagonal β-Ni(OH)2 to cubic NiO for all treated samples, with improved crystallinity for higher heating temperatures. The effect of the electrochemical parameters and heat treatment temperatures on the thickness and surface morphology of the films was also analyzed by mechanical profilometry and scanning electron microscopy, respectively. The p-type behavior of the films and the electrical resistivity values were determined from electrical measurements using a two-point probe system in a sandwich configuration. Higher resistivity values were found for films subjected to higher heat treatment temperatures.

UHMWPE / nanodiamond nanocomposites for orthopaedic applications: A novel sandwich configuration based approach

Ultra high molecular weight polyethylene (UHMWPE) remains a primary choice of material for load bearing applications in total joint arthroplasty. Superior mechanical properties and wear resistance are unique to its performance. However, the addition of nanomaterials has improved its properties significantly. In the present study, a novel sandwich configuration has been considered to achieve unique surface and bulk properties specific to these sandwich composites. UHMWPE was reinforced at various loadings of 0.1, 0.3, 0.5, and 0.7 wt. % by surface modified Nano-diamond (ND). It is observed that the young's modulus, yield stress, fracture stress and toughness of UHMWPE were improved by 15, 31, 30, and 49.6% respectively at the optimum loading of 0.5 wt. % ND filler. The % of elongations and impact strength showed best results at 0.3 wt. % ND. Sandwich nanocomposites were prepared with the optimum loading of 0.3 & 0.5 wt. % ND and assessed for their properties and behaviour. The sectional hardness of sandwich nanocomposites revealed the cross-sectional variation of properties of the material. The reasons for diminution of the mechanical properties of nanocomposites and sandwich nanocomposites were also ascertained by rheological studies. The vibration response, damping behaviour, water contact angle and density of the composites which influence the longevity of the implant material were also assessed. The sandwich composite (PE 0.3ND - PE - PE 0.3ND) has shown better performance in all respect as compare to SW1 and SW3 composite due to good intermingling between the adjacent layers. It is concluded that the existence of ND improved the surface properties and mechanical properties of UHMWPE. However, sandwich nanocomposites have shown better properties unique unto itself.

Explanation of the high conductivity of HCl protonated polyaniline films

A very high conductivity of polyaniline (PANI) salts can be achieved but different authors provide different explanations of the conduction mechanism. To clarify the problem, we studied the contribution of each type of charge to the total conductivity. The conductivity (1.9–3.5) S cm-1 was found using ohmic gold contacts on a PANI sample applied to glass. In contrast, the conductivity of 8.0 × 10-7 S cm−1 was determined from the volt-ampere characteristic measured on the Au/PANI/Si/In structure in a sandwich configuration. The impedance spectra show that in this structure only polarons and holes participate in the charge transfer while ions only cause sample polarization. Conductivity of 3 × 10-7 S cm−1 caused by ions was determined from the dielectric spectra. Since the sum of all contributions is very low compared to the measured total conductivity, a new mechanism of conductivity is proposed that explains the importance of hydrogen and chlorine molecules for charge transfer.

Tumor-cell detection, labeling and phenotyping with an electron-doped bifunctional signal-amplifier

Cancer cell enumeration and phenotyping can predict the prognosis and the therapy efficacy in patients, yet it remains challenging to detect the rare tumor cells. Herein, we report an octopus-inspired, bifunctional aptamer signal amplifier-based cytosensor (OApt-cytosensor) for sensitive cell analysis. By assembling high-affinity antibodies on an electrode surface, the target cells could be specifically captured and thus been sandwiched by the cell surface marker-specific DNA aptamers. These on-cell aptamers function as electrochemical signal amplifiers by base-selective electronic doping with methylene blue. Such a sandwich configuration enables highly sensitive cell detection down to 10 cells/mL (equal to ~1–2 cells at a sampling volume of 150 μL), even in a large excess of nontarget blood cells. This approach also reveals the cell-surface markers and tracks the cellular epithelial-to-mesenchymal transition induced by signaling regulators. Furthermore, the electron-doped aptamer shows remarkable cell fluorescent labeling that guides the release of the captured cells from electrode surface via electrochemistry. These features make OApt-cytosensor a promising tool in revealing the heterogeneous cancer cells and anticancer drug screening at the single-cell level.

The Use of Near-Infrared Light-Emitting Fluorescent Nanodiamond Particles to Detect Ebola Virus Glycoprotein: Technology Development and Proof of Principle.

BackgroundThere is a dire need for rapid diagnostic tests of high sensitivity, efficiency, and point-of-test reporting capability to mitigate lethal viral epidemic outbreaks.PurposeTo develop a new operating system within the lateral flow assay (LFA) format for Ebola virus (EBOV), based on fluorescent nanodiamond particles (FNDP) nitrogen vacancy (NV) emitting near-infrared (NIR) light. Specifically, we aimed to detail technical issues and the feasibility of mobilizing FNDP-NV on nitrocellulose membranes (NCM) and capturing them at test and control lines.MethodsFNDP-NV-200nm, 400nm or 800nm were linked to anti-EBOV glycoprotein (GP) monoclonal antibodies (mAb) and tested for LFA performance by monitoring NIR emissions using an in vivo imaging system or optoelectronic device (OED). Anti-EBOV recombinant glycoprotein (GP) humanized mAb c13C6 was linked to FNDP-NV-200nm for the mobile phase; and a second anti-GP mouse mAb, 6D8, was printed on NCM at the test line. Goat anti-human IgG (GAH-IgG) served as a nonspecific antibody for conjugated FNDP-NV-200nm at the control line.ResultsFNDP-NV-200nm-c13C6 specifically and dose-dependently bound to recombinant EBOV GP in vitro and was effectively captured in a sandwich configuration at the test line by mAb 6D8. FNDP-NV-200nm-c13C6 was captured on the control line by GAH-IgG. The OED quantitative analysis of NIR (obtained in less than 1 minute) was further validated by an in vivo imaging system.ConclusionFNDP-NV-200nm performance as a reporter for EBOV GP rapid diagnostic tests suggests an opportunity to replace contemporary visual tests for EBOV GP and other highly lethal viral pathogens. Mobile, battery-operated OED adds portability, quantitative data, rapid data collection, and point-of-test reporting capability. Further development of FNDP-NV-200nm within a LFA format is justified.

Effective performance improvement of organic thin film transistors with multi-layer modifications

Organic thin film transistors (OTFTs) based on dioctylbenzothienobenzothiophene (C8BTBT) and copper (Cu) electrodes were fabricated. For improving the electrical performance of the original devices, the different modifications were attempted to insert in three different positions including semiconductor/electrode interface, semiconductor bulk inside and semiconductor/insulator interface. In detail, 4,4′,4′′-tris[3-methylpheny(phenyl)amino] triphenylamine (m-MTDATA) was applied between C8BTBTand Cu electrodes as hole injection layer (HIL). Moreover, the fluorinated copper phthalo-cyanine (F16CuPc) was inserted in C8BTBT/SiO2 interface to form F16CuPc/C8BTBT heterojunction or C8BTBT bulk to form C8BTBT/F16CuPc/C8BTBT sandwich configuration. Our experiment shows that, the sandwich structured OTFTs have a significant performance enhancement when appropriate thickness modification is chosen, comparing with original C8BTBT devices. Then, even the low work function metal Cu was applied, a normal p-type operate-mode C8BTBT-OTFT with mobility as high as 2.56 cm2/Vs has been fabricated.

Nanostructuring Synergetic Base-Stacking Effect: An Enhanced Versatile Sandwich Sensor Enables Ultrasensitive Detection of MicroRNAs in Blood.

MicroRNA (MiRNA)-based noninvasive diagnostics are hampered by the challenge in the quantification of circulating miRNAs using a general strategy. Here, we present a base-stacking effect-mediated ultrasensitive electrochemical miRNA sensor (BSee-miR) with a universal sandwich configuration. In the BSee-miR, a short DNA probe (10 nucleotides) self-assembled on a gold electrode surface could effectively capture the target miRNA synergizing with another sequence based on coaxial sandwich base-stacking, which rivals the fully complementary strength. Importantly, such a sandwich structure is flexible to incorporate signal amplification strategies (e.g., biotin-avidin) that are usually difficult to achieve in short sequence detection. Using this design, the BSee-miR achieves a broad dynamic range with a detection limit down to 7.5 fM. Furthermore, we found a high-curvature nanostructuring synergetic base-stacking effect that could improve the sensitivity of the BSee-miR by two orders of magnitude (79.3 aM). Our BSee-miR also has a single-base resolution to discriminate the highly homologous miRNAs. More importantly, this approach is universal and has been used to probe target miRNAs varying in sequences and secondary structures. Our ultrasensitive sensor could detect miRNA in cell lysates and human blood and distinguish cancer patients from normal individuals, promising a versatile tool to measure clinically relevant miRNAs for tumor diagnostics.

Micro-supercapacitors powered integrated system for flexible electronics

Recently, the rapid progress of flexible electronics has attracted tremendous attention for the potential on revolutionizing human lives. Originally, flexible on-chip energy-storage devices, such as micro-supercapacitors (MSCs), have become the matchable microscale power source for wearable and portable electronics. Herein, latest advances of flexible planar MSCs and their integrated systems are briefly reviewed. Firstly, the fundamentals of flexible MSCs including planar and sandwich configuration of MSCs, one dimensional (1D) nanomaterials, 2D nanomaterials, and 2D nanocomposites electrode materials, different kinds of gel polymer electrolytes, fabrication technologies, and performance evaluation metrics are investigated. Secondly, MSCs powered integrated systems for flexible electronics with multifunction of photodetection, gas sensing, motion monitoring, body fluid monitoring, and lighting micro-LED are reviewed comprehensively. Finally, the challenges and opportunities for industrial manufacturing technology and practical applications of micro-supercapacitors powered integrated systems are briefly discussed.

Closed form solution for the energy release rate and mode partitioning of the single cantilever beam sandwich debond from an elastic foundation analysis

The goal of this paper is to derive closed form expressions for the energy release rate and mode partitioning offace/core debonds for the Single Cantilever Beam Sandwich Composite testing configuration, which is loaded with an applied shear force and/or bending moment. This is achieved by an elastic foundation approach, in which a finite length sandwich beam is treated as having a free “debonded” section and a “joined” section where a series of springs exists between the face and the substrate (core and bottom face). The elastic foundation analysis is done for a general asymmetric sandwich construction. A J-integral approach is subsequently used to derive a closed form expression for the energy release rate. It is also shown that the energy release rate is very close to the differential energy stored in the springs at the beginning of the elastic foundation, i.e. the energy released by the “broken” differential spring element as the debond propagates. In the context of this elastic foundation model, a mode partitioning measure is defined based on the transverse and axial displacements at the beginning of the elastic foundation. Since the normal springs account for the transverse compressibility of the core but not for the shear, a correction for the shear of the substrate is included by deriving the expression for the corresponding shear angle and accounting for the additional horizontal “tip” displacement. The results are compared with finite element results for a range of core materials and show very good agreement.

Eulerian thermo-mechanical simulations of heterogeneous solid propellants using an approximate projection method

We present a mathematical model that describes thermo-mechanical deformations and thermal gradients on the unsteady burning of a heterogeneous solid propellant. A scaling study shows that the deformations in solid at combustion timescales can be treated as quasi-static. The resulting thermo-mechanical formulation is formulated on a Cartesian grid and makes use of a weak form of Chorin-type projection method to deal with large difference in shear modulus of constituent materials. A one-dimensional verification study is carried out by comparing numerical simulations with those of an analytical model. In addition, convergence studies for a two-dimensional propellant sandwich configuration are presented for the stress, velocity, and reference map components. Finally, simulations are carried out for a two-dimensional random propellant pack and the time-averaged burn rate and strains are reported.

Scalable Multilayer Printing of Graphene Interfacial Layers for Ultrahigh Power Lithium‐Ion Storage

A low resistance graphene‐based interfacial layer is developed for multilayered lithium‐ion capacitor electrodes using a layer‐by‐layer printing approach, with the goal of boosting energy storage performance at ultrafast charge/discharge rates (≥100 C). The electrochemical behavior of spray printed Li4Ti5O12‐based heterostructure electrodes is investigated as a thin, discrete graphene layer is placed: 1) at the base of the Li4Ti5O12 (at the electrode/current collector interface); 2) on the top of the Li4Ti5O12 (at the electrode/separator junction); and 3) both at the base and on the top of the Li4Ti5O12 (sandwich configuration), with marked improved electrode performance at >50 C when the graphene layer is interleaved at the Li4Ti5O12/current collector interface. This best performing heterostructure negative electrode is then coupled with a spray printed activated carbon positive electrode in a lithium‐ion capacitor configuration, showing an attractive power density of ≈8000 W kg−1 at 350 C. The fabrication of double‐sided graphene/Li4Ti5O12 multilayered heteroelectrodes is successfully demonstrated over areas of 20 cm × 15 cm and in various patterned configurations.