The additive manufacturing of energetic materials has received worldwide attention. Here, an ink formulation is developed with only 10 wt% of polymers, which can bind a 90 wt% nanothermite using a simple direct‐writing approach. The key additive in the ink is a hybrid polymer of poly(vinylidene fluoride) (PVDF) and hydroxy propyl methyl cellulose (HPMC) in which the former serves as an energetic initiator and a binder, and the latter is a thickening agent and the other binder, which can form a gel. The rheological shear‐thinning properties of the ink are critical to making the formulation at such high loadings printable. The Young's modulus of the printed stick is found to compare favorably with that of poly(tetrafluoroethylene) (PTFE), with a particle packing density at the theoretical maximum. The linear burn rate, mass burn rate, flame temperature, and heat flux are found to be easily adjusted by varying the fuel/oxidizer ratio. The average flame temperatures are as high as ≈2800 K with near‐complete combustion being evident upon examination of the postcombustion products.
A wide range of applications rely on the ability to integrate electrically conductive microstructures with microfluidic channels. To bypass the planar geometric restrictions of conventional microfabrication processes, researchers have recently explored the use of “Direct Laser Writing (DLW)”—a submicron‐scale additive manufacturing (or “3D printing”) technology—for creating conductive microfeatures with fully 3D configurations. Despite considerable progress in the development of DLW‐compatible photomaterials, thermal post‐processing requirements to support electrical conductivity remain a critical barrier to microfluidics integration. In this work, novel graphene‐laden photocomposites are investigated to enable DLW‐based printing of true 3D conductive microstructures directly inside of enclosed microchannels (i.e., in situ). Photoreactive composite materials comprising reduced graphene oxide (rGO) particle concentrations of up to 10 wt% exhibited high compatibility with DLW, with minimal optical interference at critical wavelengths. Developed rGO‐photocomposites revealed an ultimate DC conductivity of 9.85 ± 0.48 × 10−5 S m−1. Experimental results for DLW of 3D microcoils (1 wt% rGO; wire diameter = 10 µm; coil diameter = 40 µm) revealed an impedance of 2.71 ± 0.12 MΩ at 2 MHz. In addition, results for in situ DLW of geometrically sophisticated rGO‐laden microstructures suggest utility of the presented approach for potential 3D microelectronics‐based microfluidic applications.
Solid propellant additives have a long history of modulating burning rate by introducing materials with high thermal diffusivities to better concentrate and transfer heat to nearby areas. However, recent studies have demonstrated a counterintuitive result in that additives with thermally insulating properties—notably SiO2 particles—can also enhance the propagation rate in solid propellants. In this work, high-speed microscopy and thermometry were performed on 3D printed solid propellant films containing both thermally conducting (graphite) and insulating (SiO2) particles to investigate the role of these additives on film propagation rate. It was found that addition of SiO2 particles increased the effective surface area of the reaction front through inhomogeneous heat transfer in the films, and that such corrugation of the reaction front area on the micrometer scale manifests itself as a global increase in the propagation rate on the macro scale. Graphite additive was observed to have a substantially lower burning surface area and propagation rate, suggesting that the effect of reaction front surface area is larger than the effect of thermal diffusivity for low-weight percent additives in solid propellants.
Equitable global access to vaccines requires overcoming challenges associated with complex immunization schedules and their associated economic burdens that hinder delivery in under‐resourced environments. The rabies vaccine, for example, requires multiple immunizations for effective protection and each dose is cost prohibitive, and therefore inaccessibility disproportionately impacts low‐ and middle‐income countries. In this work, an injectable hydrogel depot technology for sustained delivery of commercial inactivated rabies virus vaccines is developed. In a mouse model, it is shown that a single immunization of a hydrogel‐based rabies vaccine elicited comparable antibody titers to a standard prime‐boost bolus regimen of a commercial rabies vaccine, despite these hydrogel vaccines comprising only half of the total dose delivered in the bolus control. Moreover, these hydrogel‐based vaccines elicited similar antigen‐specific T‐cell responses and neutralizing antibody responses compared to the bolus vaccine. Notably, it is demonstrated that while the addition of a potent clinical Toll‐like receptor 4 (TLR4) agonist adjuvant to the gels slightly improved binding antibody responses, inclusion of this adjuvant to the inactivated virion vaccine is detrimental to neutralizing responses. Taken together, these results suggest that these hydrogels can enable an effective regimen compression and dose‐sparing strategy for improving global access to vaccines.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.