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NMR crystallography has emerged as a promising technique for the determination and refinement of atomic coordinates in crystal structures. The crystal structure of compounds containing quadrupolar nuclei, such as 27Al, can be improved by directly comparing solid-state NMR measurements to DFT computations of the electric field gradient (EFG) tensor. The non-negligible computational cost of these first-principles calculations limits the applicability of this method to all but the most well-defined structures. We developed a fast, low-cost machine learning model to predict EFG parameters based on local structural motifs and elemental parameters. We computed 8081 EFG tensors from 1681 27Al crystalline solids using DFT and benchmarked them against 105 experimentally measured 27Al sites. Surprisingly, simple local geometric features dominate the predictive performance of the resulting random-forest model, yielding an R2 value of 0.98 and an RMSE of 0.61 MHz for CQ, the quadrupolar coupling constant. This model accuracy should enable pre-refining future structural assignments before finally validating with first-principles calculations. Such a catalogue of 27Al NMR tensors can serve as a tool for researchers assigning complex NMR spectra influenced by the nuclear electric quadrupole interaction. 

ABSTRACT The growth of wearable electrophysiology is accelerating demand for gel‐free biopotential electrodes that are skin‐conformal, comfortable for extended use, and stable under typical human motion. Here we report σPOMaC, a self‐adhesive, conductive, skin‐compatible elastomer based on poly(octamethylene maleate (anhydride) citrate) (POMaC), a citrate‐derived polyester with mechanical characteristics that are easily tunable via changes to monomer ratios and curing. Although POMaC is readily processed into soft structures, achieving robust electronic conductivity that survives curing, drying, and handling remains challenging, hindering its use in bioelectronic interfaces. To address this, we co‐formulate a soft conductor, poly(3,4‐ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS), with a surfactant, 4‐dodecylbenzenesulfonic acid (DBSA), into the POMaC prepolymer to generate conductive σPOMaC composites. Because these additives affect processing parameters and material properties, such as curing time and viscoelasticity, we optimized composition and processing to jointly achieve high conductivity (50 S/cm; ∼ 0.02 Ω·cm), skin‐appropriate adhesion (0.013 ± 0.004 N/mm on PDMS), and elastomeric compliance suitable for biopotential recording. Using optimized σPOMaC, we fabricated a custom chest patch featuring conformal ECG electrodes and demonstrated clear, high‐fidelity on‐body ECG waveforms comparable in morphology and timing to simultaneous recordings made using commercial Ag/AgCl electrodes. Together, these results position σPOMaC as a material platform for gel‐free, self‐adhesive, skin‐interfaced bioelectronic electrodes, enabling simplified application and improved interface with the end‐user and reducing disposable hydrogel waste in longitudinal monitoring. 

A soft, flexible pressure sensor is developed to measure hydrostatic pressure in the ocean environment, which can be potentially integrated with many platforms including diver equipment and marine animal tags for real-time pressure monitoring.