This roadmap includes the perspectives and visions of leading researchers in the key areas of flexible and printable electronics. The covered topics are broadly organized by the device technologies (sections 1-9), fabrication techniques (sections 10-12), and design and modeling

Copper chalcogenides are of great interest as conversion-type cathode materials due to their large specific capacity for rechargeable magnesium batteries, yet are subjected to severe capacity fading brought about by structure collapse in repetitive charge-discharge cycling. Herein, single-crystalline and (110) preferentially oriented CuSe nanoflakes are designed via a temperaturecontrolled crystal growth route under microwave irradiation. The as-prepared CuSe nanoflake cathode materials can present high reversible capacity (204 mAh g −1 at 200 mA g −1 current density), outstanding rate capability, and remarkable long-term cycling stability (≈0.095% capacity decay per cycle at 1 A g −1 within 700 cycles). The multistep reversible conversion mechanism of the CuSe nanoflake cathode materials is evidenced by ex situ X-ray photoelectron spectroscopy and X-ray diffraction. Structure evolution investigation suggests that the single-crystalline CuSe nanoflakes can exhibit relatively durable structural stability. The desirable cycling stability can be ascribed to the excellent pulverization-tolerance of the CuSe nanoflake cathode materials endowed by the multistep reversible conversion mechanism and the single-crystalline feature. Furthermore, the preferentially-oriented (110) active plane is favorable for electrochemical reactions to ensure high specific capacity. This work can afford a crystal engineering strategy to fabricate high-performance conversion-type electrode materials for rechargeable magnesium batteries.

The conversion-type copper chalcogenide cathode materials hold great promise for realizing the competitive advantages of rechargeable magnesium batteries among next-generation energy storage technologies; yet, they suffer from sluggish kinetics and low redox reversibility due to large Coulombic resistance and ionic polarization of Mg 2+ ions. Here we present an anionic Te-substitution strategy to promote the reversible Cu 0 /Cu + redox reaction in Te-substituted CuS 1−x Te x nanosheet cathodes. X-ray absorption fine structure analysis demonstrates that Te dopants occupy the anionic sites of sulfur atoms and result in an improved oxidation state of the Cu species. The kinetically favored CuS 1−x Te x (x = 0.04) nanosheets deliver a specific capacity of 446 mAh g −1 under a 20 mA g −1 current density and a good long-life cycling stability upon 1500 repeated cycles with a capacity decay rate of 0.0345% per cycle at 1 A g −1 . Furthermore, the CuS 1−x Te x (x = 0.04) nanosheets can also exhibit an enhanced rate capability with a reversible specific capacity of 100 mAh g −1 even under a high current density of 1 A g −1 . All the obtained electrochemical characteristics of CuS 1−x Te x nanosheets significantly exceed those of pristine CuS nanosheets, which can contribute to the improved redox reversibility and favorable kinetics of CuS 1−x Te x nanosheets. Therefore, anionic Te-substitution demonstrates a route for purposeful cathode chemistry regulation in rechargeable magnesium batteries.

We present a simple and efficient method for preconcentrating per- and polyfluorinated alkyl substances (PFAS) in water. Our method was inspired by the sea-spray aerosol enrichment in nature. Gas bubbles in the ocean serve to scavenge surface active material, carrying it to the air-ocean interface, where the bubbles burst and form a sea-spray aerosol. These aerosol particles are enriched in surface-active organic compounds such as free fatty acids and anionic surfactants. In our method, we in situ generate H2 microbubbles by electrochemical water reduction using a porous Ni foam electrode. These H2 bubbles pick up PFAS as they rise through the water column that contains low concentration PFAS. When these bubbles reach the water surface, they burst and produce aerosol droplets that are enriched in PFAS. Using this method, we demonstrated ∼1000-fold preconcentration for ten common PFAS in the concentration range from 1 pM to 1 nM (or ∼0.5 ng/L to 500 ng/L) in 10 min. We also developed a diffusion-limited adsorption model that is in quantitative agreement with the experimental data. In addition, we demonstrated using this method to preconcentrate PFAS in tap water, indicating its potential use for quantitative analysis of PFAS in real-world water samples.

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