The development of stretchable electronics requires the invention of compatible high-performance power sources, such as stretchable supercapacitors and batteries. In this work, two-dimensional (2D) titanium carbide (Ti 3 C 2 T x ) MXene is being explored for flexible and printed energy storage devices by fabrication of a robust, stretchable high-performance supercapacitor with reduced graphene oxide (RGO) to create a composite electrode. The Ti 3 C 2 T x /RGO composite electrode combines the superior electrochemical and mechanical properties of Ti 3 C 2 T x and the mechanical robustness of RGO resulting from strong nanosheet interactions, larger nanoflake size, and mechanical flexibility. It is found that the Ti 3 C 2 T x /RGO composite electrodes with 50 wt % RGO incorporated prove to mitigate cracks generated under large strains. The composite electrodes exhibit a large capacitance of 49 mF/cm 2 (∼490 F/cm 3 and ∼140 F/g) and good electrochemical and mechanical stability when subjected to cyclic uniaxial (300%) or biaxial (200% × 200%) strains. The as-assembled symmetric supercapacitor demonstrates a specific capacitance of 18.6 mF/cm 2 (∼90 F/cm 3 and ∼29 F/g) and a stretchability of up to 300%. The developed approach offers an alternative strategy to fabricate stretchable MXene-based energy storage devices and can be extended to other members of the large MXene family.

Collisions and attendant shock compaction must have been important for the accretion and lithification of planetesimals, including the parent bodies of chondrites, but the conditions under which these occurred are not well constrained. A simple model for the compaction of chondrites predicts that shock intensity as recorded by shock stage should be related to porosity and grain fabric. To test this model, we studied sixteen ordinary chondrites of different groups (H, L, LL) using X-ray computed microtomography (µCT) to measure porosity and metal fabric, ideal gas pycnometry and 3D laser scanning to determine porosity, and optical microscopy (OM) to determine shock stage. These included a subsample of six chondrites previously studied using transmission electron microscopy (TEM) to characterize microstructures in olivine. Combining with previous data, results support the simple model in general, but not for chondrites with low shock-porosity-foliation (low-SPF chondrites). These include Kernouvé (H6), Portales Valley (H6/7), Butsura (H6), Park (L6), GRO 85209 (L6), Estacado (H6), MIL 99301 (LL6), Spade (H6), and Queen's Mercy (H6), among others. The data for these meteorites are best explained by high ambient heat during or after shock. Low-SPF chondrites tend to have older 40 Ar/ 39 Ar ages (~4435-4526 Ma) than other, non-low-SPF type 6 chondrites in this study. We conclude that the H, L, and LL asteroids all were shock-compacted at an early stage while warm, with collisions occurring during metamorphic heating of the parent bodies. Results ultimately bear on whether chondrite parent bodies have internal structures more akin to a metamorphosed onion shell or metamorphosed rubble pile, and on the nature of accretion and lithification processes for planetesimals.

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This work investigates the surface chemistry of H2O2 generation on a boron-doped ultrananocrystalline diamond (BD-UNCD) electrode. It is motivated by the need to efficiently disinfect liquid waste in resource constrained environments with limited electrical power. X-ray photoelectron spectroscopy was used to identify functional groups on the BD-UNCD electrode surfaces while the electrochemical potentials of generation for these functional groups were determined via cyclic voltammetry, chronocoulometry, and chronoamperometry. A colorimetric technique was employed to determine the concentration and current efficiency of H2O2 produced at different potentials. Results showed that preanodization of an as-grown BD-UNCD electrode can enhance the production of H2O2 in a strong acidic environment (pH 0.5) at reductive potentials. It is proposed that the electrogeneration of functional groups at oxidative potentials during preanodization allows for an increased current density during the successive electrolysis at reductive potentials that correlates to an enhanced production of H2O2. Through potential cycling methods, and by optimizing the applied potentials and duty cycle, the functional groups can be stabilized allowing continuous production of H2O2 more efficiently compared to static potential methods.

A dataset of high-resolution microCT scans of primate skulls (crania and mandibles) and certain postcranial elements was collected to address questions about primate skull morphology. The sample consists of 489 scans taken from 431 specimens, representing 59 species of most Primate families. These data have transformative reuse potential as such datasets are necessary for conducting high power research into primate evolution, but require significant time and funding to collect. Similar datasets were previously only available to select research groups across the world. The physical specimens are vouchered at Harvard’s Museum of Comparative Zoology. The data collection took place at the Center for Nanoscale Systems at Harvard. The dataset is archived on MorphoSource.org. Though this is the largest high fidelity comparative dataset yet available, its provisioning on a web archive that allows unlimited researcher contributions promises a future with vastly increased digital collections available at researchers’ finger tips.

Integration of an organic photovoltaic (PV) with carbon-based supercapacitors (SCs) into a system for solar energy harvesting and storage is interesting for off-grid applications such as mobile electronics and sensor systems. Presented here is a conversion and control circuit (CC) on a flexible polyimide substrate in an integrated flexible energy harvesting and storage device compatible with roll-to-roll manufacturing (R2R). The CC is capable of PV max power-point tracking, DC-DC voltage boost of the PV output across a bank of four SCs, and charge balancing across the bank of SCs. This system is compared to a conventional direct connection between the PV and the SCs. More energy can be harvested from the PV and stored in the SC bank when using the CC to drive the PV at peak power, boost the output voltage, and balance it across serial connection of SCs. Finally, the CC, PV, and SCs are mounted to a 3D printed substrate and circuit which is used to power a wearable sensor. Due to these benefits and ability to be integrated with R2R, the presented CC provides a practical means of improving wearable solar energy harvesting and storage systems. In the flexible electronics literature, multiple publications demonstrated novel energy materials and devices, such as thin-film flexible photovoltaics (PVs)1-10 and carbon-based supercapacitors (SCs) [11][12][13][14][15][16][17][18] that are roll-to-roll (R2R) compatible. A few publications have further integrated a PV material with SCs to form an energy device capable of solar energy harvest and storage. 17,[19][20][21][22][23][24] Although simply connecting the devices without a conversion and control circuit (CC) that controls the flow of charge and the load impedance experienced by the PV can harvest and store energy, there are three problems that arise from this configuration: (i) the PV elements are operated inefficiently at suboptimal voltage-current conditions, far from the maximum-power point (MPP), (ii) undercharging the SCs due to low PV output voltage, and (iii) unbalanced charge storage across a bank of SCs with the risk of overcharging some while undercharging other SCs as well as a low usable combined capacity. These problems result in an inefficient and impractical energy device. In large PV systems, a CC typically mitigates these problems. However, such CCs use a discrete design with stiff bus bars or rigid circuit boards, which are incompatible with the flexible film design of the rest of the system. The lack of availability of a R2R-compatible CC has limited the realization of a R2R energy fabric for practical applications such as wearable sensors and the internet of things (IoT). 25 Many techniques have been developed to enable R2R-compatible packaging of CCs. Within the CC architecture, switching-mode DC-DC boost converters have been given considerable attention. For example, Z-folded flexible planar transformers have been developed that allow R2R production. 26 Planar geometries of flexible foils for use as low-profile inductors 27 and flip-chip flex-ci...

Electrochemical disinfection (ECD) has become an important blackwater disinfection technology. ECD is a promising solution for the 2 billion people without access to conventional sanitation practices and in areas deficient in basic utilities (e.g., sewers, electricity, waste treatment). Here, we report on the disinfection of blackwater using potential cycling compared to potentiostatic treatment methods in chloride-containing and chloride-free solutions of blackwater (i.e., untreated wastewater containing feces, urine, and flushwater from a toilet). Potentiodynamic treatment is demonstrated to improve disinfection energy efficiency of blackwater by 24% and 124% compared to static oxidation and reduction methods, respectively. The result is shown to be caused by electrochemical advanced oxidation processes (EAOP) and regeneration of sp2-surface-bonded carbon functional groups that serve the dual purpose of catalysts and adsorption sites of oxidant intermediates. Following 24 h electrolysis in blackwater, electrode fouling is shown to be minimized by the potential cycling method when compared to equivalent potentiostatic methods. The potential cycling current density is 40% higher than both the static oxidative and reductive methods. This work enhances the understanding of oxygen reduction catalysts using functionalized carbon materials and electrochemical disinfection anodes, both of which have the potential to bring a cost-effective, energy efficient, and practical solution to the problem of disinfecting blackwater.