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1. Gallium oxide-stabilized oil in liquid metal emulsions

   https://doi.org/10.1039/d1sm00982f  

   Shah, Najam Ul; Kong, Wilson; Casey, Nathan; Kanetkar, Shreyas; Wang, Robert Y.; Rykaczewski, Konrad (September 2021, Soft Matter)

   null (Ed.)

   Gallium based liquid metals (LM) have prospective biomedical, stretchable electronics, soft robotics, and energy storage applications, and are being widely adopted as thermal interface materials. The danger of gallium corroding most metals used in microelectronics requires the cumbersome addition of “barrier” layers or LM break-up into droplets within an inert matrix such as silicone oil. Such LM-in-oil emulsions are stabilized by native oxide on the droplets but have decreased thermal performance. Here we show that mixing of the silicone oil into an LM-air foam yields emulsions with inverted phases. We investigate the stability of these oil-in-LM emulsions through a range of processing times and oil viscosities, and characterize the impact of these parameters on the materials’ structure and thermal property relationships. We demonstrate that the emulsion with 40 vol% of 10 cSt silicone oil provides a unique thermal management material with a 10 W m −1 K −1 thermal conductivity and an exterior lubricant thin film that completely prevents corrosion of contacting aluminum. 

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2. Mechanism of Oil-in-Liquid Metal Emulsion Formation

   https://doi.org/10.1021/acs.langmuir.2c02428  

   Shah, Najam Ul; Kanetkar, Shreyas; Uppal, Aastha; Dickey, Michael D.; Wang, Robert Y.; Rykaczewski, Konrad (October 2022, Langmuir)
3. Fouling Resistant Liquid-Infused membranes for oil separations

   https://doi.org/10.1016/j.seppur.2024.130253  

   Shah, Rushabh M; Bennett, Madelyn G; Goodwin, Thomas; Ribbe, Alexander E; Hu, Weiguo; Schiffman, Jessica D (June 2025, Separation and Purification Technology)

   Bioinspired membranes offer an alternative approach to improving the fouling resistance of commercial membranes for oil separations. Here, two perfluoropolyether oils, a lower viscosity Krytox 103 (K103) and a higher viscosity Krytox 107 (K107), were infused into commercial polyvinylidene fluoride (PVDF) ultrafiltration membranes to mimic the Nepenthes pitcher plant. The transmembrane pressure required to perform long-term oil permeance tests was optimized by testing the liquid-infused membranes at different applied pressures. Crystal violet staining and variable pressure scanning electron microscopy qualitatively suggest that the oil layer remained on the membranes after the oil separation experiments were conducted. Over 5 cycles, K103- and K107- liquid-infused membranes exhibited a consistent permeance of ∼ 30000 L m-2h−1 bar−1 at 1.0 bar and ∼ 14500 L m-2h−1 bar−1 at 0.5 bar, respectively. The steady performance further supports a long-lasting oil layer persists on the membrane surface and inside membrane’s pores. Next, experiments were conducted to determine the stability of the Krytox oil post accelerated cleaning tests using bleach. No structural changes to the Krytox oils were detected by thermogravimetric analysis or nuclear magnetic resonance spectroscopy. Dynamic fouling experiments using Escherichia coli K12 revealed that the liquid-infused membranes had higher flux recovery ratios (∼95 %) than the bare PVDF control membranes (∼55 %). Our results demonstrate that liquid-infused membranes exhibit chlorine stability and superior fouling resistance, presenting a promising bioinspired membrane that can be used in pressure-driven oil separation applications. 

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4. Particle-assisted formation of oil-in-liquid metal emulsions

   https://doi.org/10.1088/1361-648X/ad6521  

   Kanetkar, Shreyas; Shah, Najam_Ul H; Krisnadi, Febby; Uppal, Aastha; Gandhi, Rohit M; Dickey, Michael D; Wang, Robert Y; Rykaczewski, Konrad (July 2024, Journal of Physics: Condensed Matter)

   Abstract Gallium-based liquid metals (LM) have surface tension an order of magnitude higher than water and break up into micro-droplets when mixed with other liquids. In contrast, silicone oil readily mixes into LM foams to create oil-in-LM emulsions with oil inclusions. Previously, the LM was foamed through rapid mixing in air for an extended duration (over 2 hours). This process first results in the internalization of oxide flakes that form at the air-liquid interface. Once a critical fraction of these randomly shaped solid flakes is reached, air bubbles internalize into the LM to create foams that can internalize secondary liquids. Here, we introduce an alternative oil-in-LM emulsion fabrication method that relies on the prior addition of SiO2 micro-particles into the LM before mixing it with the silicone oil. This particle-assisted emulsion formation process provides a higher control over the composition of the LM-particle mixture before oil addition, which we employ to systematically study the impact of particle characteristics and content on the emulsions' composition and properties. We demonstrate that the solid particle size (0.8 µm to 5 µm) and volume fraction (1% to 10%) have a negligible impact on the internalization of the oil inclusions. The inclusions are mostly spherical with diameters of 20 to 100 µm diameter and are internalized by forming new, rather than filling old, geometrical features. We also study the impact of the particle characteristics on the two key properties related to the functional application of the LM emulsions in the thermal management of microelectronics. In particular, we measure the impact of particles and silicone oil on the emulsion's thermal conductivity and its ability to prevent deleterious gallium-induced corrosion and embrittlement of contacting metal substrates. 

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5. Impact of Rheology on Formation of Oil-in-Liquid Metal Emulsions

   https://doi.org/10.1039/D4SM01361A  

   Kanetkar, Shreyas; Peri, Sai P; Mithaiwala, Husain; Krisnadi, Febby; Dickey, Michael D; Green, Matthew D; Wang, Robert Yue-Sheng; Rykaczewski, Konrad (December 2024, Soft Matter)

   To quantify how the viscosities of silicone oil (SO) and liquid metal (LM) relate to emulsion-formation (LM-in-SO versus SO-in-LM), a process was developed to produce LM pastes with adjustable viscosity... 

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