Lightning in a bottle: Plasma enables selective, electrolytic production of ammonia from nitrogen and water.

Emerging atomic layer semiconducting crystals such as molybdenum disulfide (MoS) are promising candidates for flexible electronics and strain-tunable devices due to their ultrahigh strain limits (up to ∼20-30%) and strain-tunable bandgaps. However, high strain levels, controllable isotropic and anisotropic biaxial strains in single- and few-layer MoS on device-oriented flexible substrates permitting convenient and fast strain tuning, remain unexplored. Here, we demonstrate a "blown-bubble" bulge technique for efficiently applying large strains to atomic layer MoS devices on a flexible substrate. As the strain increases via bulging, we achieve continuous tuning of Raman and photoluminescence (PL) signatures in single- and few-layer MoS, including splitting of Raman peaks. With proper clamping of the MoS crystals, we apply up to ∼9.4% strain in the flexible substrate, which causes a doubly clamped single-layer MoS to fracture at 2.2-2.6% strain measured by PL and 2.9-3.5% strain measured by Raman spectroscopy. This study opens new pathways for exploiting 2D semiconductors on stretchable substrates for flexible electronics, mechanical transducers, tunable optoelectronics, and biomedical transducers on curved and bulging surfaces.

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We describe a direct-write process for producing electrically conductive metal patterns at the surface of polymers. Thin films of poly(acrylic acid) (PAA) loaded with Ag ions are reduced by a scanning, atmospheric-pressure microplasma to form crystalline Ag features with a line width of 300 μm. Materials analysis reveals that the metallization occurs in a thin layer of ∼5 μm near the film surface, suggesting that the Ag ions diffuse to the surface. Sheet resistances of 1-10 Ω/sq are obtained independent of film thickness and Ag volume concentration, which is desirable for producing surface conductivity on polymers while minimizing metal loading.

Printable metal inks are typically composed of premade nanoparticles that require postdeposition thermal sintering to produce crystalline, electrically conductive features. In this paper, it is shown that particle-free Ag inks made from simple, water-soluble metal salts such as silver nitrate can be ink-jet printed and converted into electrical features with tunable resistivity at low temperature (<100 °C) by exposure to a pure argon plasma. X-ray diffraction confirms that the converted inks are crystalline, and four-point probe electrical measurements show that the sheet resistances are a function of the pressure and power in the plasma. From cross-sectional scanning electron microscopy analysis, it is found that the morphology of the converted silver layer becomes increasingly dense with increasing plasma treatment time, which explains the measured changes in sheet resistance, and that the thickness of the layer is ∼1.5 μm, which yields a minimum resistivity of ∼6 × 10−8 Ω m, approximately 3.8 times higher than bulk resistivity of silver. Interestingly, the resistivity can be varied over a span of 6 orders of magnitude which allows resistor–capacitor filter devices to be fabricated exhibiting varying cut-off frequencies from a single material and geometry.