Francois-Marie Allioux

Wearable triboelectric nanogenerators (TENGs) enable self‐powered health monitoring by sensing human motion and physiological signals. However, operating at the skin/device interface is usually compromised by perspiration. Here, we present a moisture‐wicking Janus bilayer TENG (MW‐JBT) that integrates directional moisture transport with dielectric‐engineered electrospun nanofibers. The Janus bilayer membrane integrates a tribo‐negative hydrophobic poly(vinylidene fluoride‐co‐hexafluoropropylene)/barium zirconate titanate‐silver core–shell nanoparticle (PVDF‐HFP/BZT‐Ag) nanocomposite layer with a hydrophilic polyurethane (PU) layer. In this architecture, the PVDF‐HFP/BZT‐Ag side functions as the charge‐generating interface, where BZT‐Ag core–shell nanoparticles promote dielectric polarization and retention, while the PU side facilitates moisture removal from the interface. Unlike conventional water‐resistant TENGs blocking moisture penetration, the asymmetric PVDF‐HFP/PU architecture establishes a capillary‐driven moisture pathway that actively removes interfacial sweat from the triboelectric surface within 4s. The optimized MW‐JBT achieves peak‐to‐peak outputs of 5.26 µA and 372 V at 100 N and 4 Hz, with a maximum power density of 17 W m ^{− 2} . Integrated into a plantar sensing system with a wireless STM32 module and a Minimal RNN classifier, the MW‐JBT achieves 88.5% accuracy for fall detection. This work provides an interface‐engineered strategy to construct wireless sensors combing self‐powered sensing and wearable comfort, enabling home‐based healthcare and rehabilitation monitoring scenarios.

Characterizing metal solubilities in post-transition-based liquid metals remains challenging due to their inherent opacity to conventional light-based analytical techniques. In this work, we present an in situ heating methodology within a transmission electron microscope that enables direct probing of the behavior of solid metal solutes within the local boundaries of liquid metal nanodroplets. Specifically, we show that the solubility of transition and precious metals in liquid state metallic solvents is dependent on the droplet size that contains them due to the internal Laplace pressure. We also show that the dissolution behaviors of solute metals in gallium–indium and gallium–indium–tin eutectic nanodroplets deviate from that of pure gallium, with solvent composition influencing solubility. Moreover, entropy-driven solubility effects are studied in multicomponent alloys that contain several solutes. The outcomes of this work are crucial for advancing liquid metal-based functionalities of soft systems, particularly for catalysis.

Hydrogen is a clean energy carrier with significant promises for a sustainable future, yet many established production routes operate under undesirable conditions or constraints, motivating the search for alternative production pathways. Here, our approach uses photothermal oxidation of liquid gallium to generate hydrogen from both freshwater and seawater. The exposure to light thermally heats up liquid gallium droplets to a temperature suitable for fast gallium-water interaction, producing gallium oxyhydroxide and hydrogen. The light exposure also boosts the reaction by breaking the oxide layer on the surface of liquid gallium immersed in water, allowing continuous interactions between the water molecules and the surface of liquid gallium droplets. The gallium oxyhydroxide that is produced can be electrochemically reduced, allowing metal regeneration, thereby enabling circular hydrogen production. In this work, we show that photothermal activation of liquid gallium provides a rapid and circular route for generating hydrogen from diverse water sources.

Liquid metals are promising unconventional solvents for dissolving metals and growing their crystals. However, how the crystals grow within these metallic solvents cannot be observed easily due to the opacity of liquid metals. Using X-ray micro-computed tomography, the three-dimensional formations of crystals inside liquid metal solvents, under different conditions, are presented. In this work, we explore the use of different liquid metals solvents for growing metallic crystals, while imaging the crystals shape and sizes inside liquid metals. We use gallium-based solvents and platinum, as the solutes and demonstrate the use of liquid metals for forming metallic crystals through modulating environmental boundary effects, controlled cooling rates, and solvent selection. It is observed that the cooling rate and composition of the reaction media will influence crystals morphologies and intermetallic phases. As a proof-of-concept, we perform hydrogen evolution reaction using metallic crystals extracted from the solvents, showcasing the potential of liquid metal-based synthesis in tailoring metallic crystals properties for enhancing catalytic activity demonstrating a strategy for engineering metallic crystals in liquid metal solvents.

Interfacial solar steam generation has emerged as a promising strategy for sustainable water desalination; however, achieving high efficiency under practical conditions remains a significant challenge. Here, a natural polyphenol‐based gel composite incorporating liquid gallium particles and graphene is presented, engineered for high‐performance solar‐driven desalination. This synergistic combination enables broadband light absorption, heat localization, and rapid water transport. Graphene and the polyphenol gel matrix enhance light absorption and solar‐to‐heat conversion, while liquid gallium serves to localize heat; the gel structure facilitates water retention and vapor escape. These features are critical for maximizing solar energy utilization and sustaining continuous water evaporation under real‐world conditions. Under one sun irradiation, the system achieves an evaporation rate of 4.8 kg m ⁻² h ⁻¹ for deionized water and 3.4 kg m ⁻² h ⁻¹ for seawater. These findings highlight the potential of such multifunctional gel composites in addressing global freshwater scarcity through scalable and energy‐efficient desalination technologies.

Electrochromic materials enable reversible color changes under an applied electric field, making them valuable for smart windows and optoelectronic devices. Among these materials, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) has been extensively studied due to its broad electrochromic modulation range and solution processability. However, its electrochromic efficiency is limited by the insulating PSS component, which restricts charge transport. In this study, we explore the incorporation of electrically conductive liquid-state gallium nanoparticles (Ga NPs) into PEDOT:PSS to enhance its electrochromic performance. Electrochemical analyses revealed that the resulting composite exhibited enhanced switching kinetics and comparable optical transparency to pristine PEDOT:PSS films. The performance enhancement is attributed to the liquid state of Ga NPs, which facilitates the rapid oxidation and reduction of the interfacial Ga oxide layer. The cracked structure of the oxide layer enabled fast carrier exchange, while allowing efficient charge storage within the oxide. Notably, PEDOT:PSS with Ga NPs demonstrated the shortest response and recovery times recorded for PEDOT:PSS-based materials to date. These findings highlight the potential of Ga NP incorporation to significantly improve the electrochromic performance of PEDOT:PSS, offering promise for energy-efficient smart coatings and optoelectronic applications.

Mechanical agitation effectively breaks up bulk liquid metal into small particles that can be used for various applications. Although voltage is known to reduce surface tension in gallium (Ga)-based liquid metals and affects sonication-induced fragmentation, this effect remains unexplored. This study employs ultra-high-speed imaging (as high as 100,000 frames per second) to investigate particle formation under different liquid metal surface tension values influenced by the applied negative, zero, and positive voltages. Negative voltage enhanced particle generation, nearly doubling the solution turbidity compared to the zero-voltage case. Negative voltage and secondary metal inclusion [indium, zinc (Zn), and tin] in liquid Ga reduced the surface tension, increased particle generation, and decreased the particle size. Surface characterization confirms compositional differences, revealing distinct migration and oxidation behaviors of the secondary metals. Notably, Ga-Zn particles undergo significant migration of Zn to the surface, forming Ga-Zn oxide structures. A proof-of-concept demonstration highlights the difference in annealed synthesized particles for photocatalysis, illustrating one potential application of the process. The findings provide insights into voltage-assisted sonication synthesis, enabling the controlled design of liquid metal particles for various applications.

Carbon-carbon (C─C) bond formation is a key step in diverse chemical processes and requires high-performance catalysts to enable energy-efficient technologies. Here, we present liquid Pd catalysts, formed by dissolving Pd in liquid Ga, for high-turnover C─C coupling reactions. The liquid Pd catalyst achieved a turnover frequency of 2.5 × 10 ⁸ hour ⁻¹ for a model coupling reaction at 70°C, surpassing all reported Pd catalysts by 1000-fold. Our results show that Pd atoms in the Ga matrix are liquid-like, exhibiting unique electronic and interfacial properties that substantially lower the energy barrier and enhance reaction kinetics. The system retained full activity over five cycles and showed no Pd leaching, highlighting the transformative potential of liquid-phase metals to advance high-throughput and sustainable C─C bond-forming strategies.

The naturally self‐limiting oxide formed on the surface of liquid metals can be exfoliated and transferred onto various substrates. This oxide layer with a thickness of a few nanometers is typically highly transparent and can be engineered for applications in large‐area optoelectronics. While the incorporation of solvated elements into the interfacial oxide of post‐transition metal‐based liquid metals is demonstrated for n‐doping, achieving p‐doping in such ultrathin oxide layers remains a significant challenge. In this study, the use of dissolved indium (In), platinum (Pt), gold (Au), palladium (Pd), and copper (Cu) in gallium (Ga)‐based alloys is investigated to create a high‐entropy liquid metal system. This allows the exfoliation of a p‐doped ultrathin oxide layer, predominantly composed of gallium oxide (Ga₂O₃). The incorporation of these post‐transition metals in this high‐entropy system results in their atomic dispersion, with Cu exhibiting limited surface presence. The atomically dispersed Pt, Au, and Pd metals scavenge oxygen during exfoliation at moderate temperatures and release them during cooling down, promoting the emergence of trivalent metallic In in Ga oxide layer. This work presents a novel doping strategy at moderate temperatures to achieve p‐doped liquid‐metal‐derived ultrathin Ga₂O₃ layers, which maintain high transparency.