With the rapid pace of advancements in additive manufacturing and techniques such as fused filament fabrication (FFF), the feedstocks used in these techniques should advance as well. While available filaments can be used to print highly customizable parts, the creation of the end part is often the only function of a given feedstock. In this study, novel FFF filaments with inherent environmental sensing functionalities were created by melt-blending poly(lactic acid) (PLA), poly(ethylene glycol) (PEG), and pH indicator powders (bromothymol blue, phenolphthalein, and thymol blue). The new PLA-PEG-indicator filaments were universally more crystalline than the PLA-only filaments (33–41% vs. 19% crystallinity), but changes in thermal stability and mechanical characteristics depended upon the indicator used; filaments containing bromothymol blue and thymol blue were more thermally stable, had higher tensile strength, and were less ductile than PLA-only filaments, while filaments containing phenolphthalein were less thermally stable, had lower tensile strength, and were more ductile. When the indicator-filled filaments were exposed to acidic, neutral, and basic solutions, all filaments functioned as effective pH sensors, though the bromothymol blue-containing filament was only successful as a base indicator. The biodegradability of the new filaments was evaluated by characterizing filament samples after aging in soil and soil slurry mixtures; the amount of physical deterioration and changes in filament crystallinity suggested that the bromothymol blue filament degraded faster than PLA-only filaments, while the phenolphthalein and thymol blue filaments saw decreases in degradation rates.

Although direct ink writing (DIW) allows the rapid fabrication of unique 3D printed objects, the resins—or “inks”—available for this technique are in short supply and often offer little functionality, leading to the development of new, custom inks. However, when creating new inks, the ability of the ink to lead to a successful print, or the “printability,” must be considered. Thus, this work examined the effect of filler composition/concentration, printing parameters, and lattice structure on the printability of new polysiloxane inks incorporating high concentrations (50–70 wt%) of metallic and ceramic fillers as well as emulsions. Results suggest that strut diameter and spacing ratio have the most influence on the printability of DIW materials and that the printability of silica- and metal-filled inks is more predictable than ceramic-filled inks. Additionally, higher filler loadings and SC geometries led to stiffer printed parts than lower loadings and FCT geometries, and metal-filled inks were more thermally stable than ceramic-filled inks. The findings in this work provide important insights into the tradeoffs associated with the development of unique and/or multifunctional DIW inks, printability, and the final material’s performance.

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We present the δ 11 B of well-preserved brachiopod fossils coupled with geochemical modeling to examine how seawater boron responded to abrupt and dynamic climate changes in the Late Paleozoic. The Late Carboniferous, a time of major coal formation and glacioeustatic sea level changes, is characterized by relatively stable brachiopod δ 11 B of 15-17‰, similar to values seen in modern brachiopods. Brachiopod δ 11 B dropped by~5‰ in the early Permian and then restabilized at a new value of 10‰ within a few million years. Mass balance models of seawater δ 11 B reproduced the overall trends in our brachiopod data but failed to capture the large drop in δ 11 B in the early Permian. Published seawater 87 Sr/ 86 Sr and δ 44/40 Ca data based on brachiopod shells also shift to lower values in the early Permian, suggesting a common control on all three seawater isotope systems. The Permian terrestrial record of evaporites and eolian deposits suggests a prolonged reduced delivery of dissolved weathering products to the ocean, accounting for the change in seawater 87 Sr/ 86 Sr. This reduced weathering, in turn, led to increased atmospheric CO 2 and lowered seawater pH, which may have significantly decreased major removal mechanisms for seawater calcium and boron leading to declines in both isotope systems. We propose that boron removal via coprecipitation in carbonates and adsorption onto clay minerals was significantly diminished due to a reduction in the availability of the borate aqueous species caused by lowered seawater pH. Plain Language Summary A great way to understand the effects of climate changes happening today is to look at how climate changes affected Earth systems in the past. One of the most extreme climate changes happened roughly 290 million years ago during the early Permian period. Prior to this time, all of the continents on Earth had come together to form the supercontinent Pangea, which caused major changes in ocean circulation and climate patterns around the equator. In the Carboniferous, the low-latitude environment was very wet, but in the Permian it became very arid, meaning there was less rainwater to dissolve rocks on the continents and deliver their dissolved salts to the oceans. To see how the oceans responded to these changes, we measured boron isotope ratios (11 B/ 10 B) in shell fossils. Boron isotopes usually change because of differences in ocean inputs/outputs or because of changes in ocean pH. The boron isotopes, along with strontium and calcium isotopes, changed significantly during the Carboniferous-Permian transition. This suggests that all of the isotopes changed because of the same processes. We argue that a reduction of dissolved salts delivered to the ocean by rivers caused the pH in the ocean to become more acidic.