Ultrasound-assisted nanoemulgel preparation: A one-step approach for enhanced rheo-tribological properties

Abstract

This study presents a low-frequency ultrasound (20 kHz)-assisted methodology for single-step nanoemulgel fabrication that simultaneously achieves homogenization and initiates gelation, thereby eliminating the conventional two-stage process requiring separate mechanical homogenization and subsequent gelation steps, streamlining production. Nanoemulgels were formulated using sunflower oil as the dispersed phase, Tween 20 as the emulsifier, and high-acyl gellan gum as the gelling agent. The effectiveness of this approach was evaluated using optical and fluorescence microscopy for structural visualization, rheological analysis for viscoelastic property assessment, and tribological evaluation for friction behavior characterization. Ultrasonication modified the polymeric gel network architecture, enhancing its structural coordination and mechanical strength. The resulting nanoemulgels demonstrated characteristic Stribeck curve friction behavior with reduced friction coefficients, attributed to their nanoscale droplets acting as lubricating agents. Increased specific energy input during ultrasonication yielded improvements in droplet size reduction, polydispersity, network structural coordination, and friction coefficient reduction. The one-step ultrasound-assisted approach successfully achieved concurrent nanoscale homogenization and gellan gelation onset, producing nanoemulgels with distinct functional properties compared to conventional emulgels. These nanoemulgel systems demonstrate significant potential for specialized food applications, including nutrient-dense formulations enriched with lipophilic bioactive and texture-modified foods designed for dysphagia management.