Xanthan Gum Emulsification in Multiform Lipophilic and Hydrophilic Microdroplet Structures in a Selectively Wettability-Treated Microchannel

The emulsification of multifunctional lipophilic and hydrophilic microdroplets in microdevices presents a promising approach to food stability and nanomedicine applications. This study introduces a novel microfluidic emulsification technique using xanthan gum and mineral oil within microdroplet structures, integrated into selectively wettability-treated microchannels, to facilitate the generation of both lipophilic and hydrophilic forms. The shear-thinning behavior of xanthan gum, a characteristic feature of its polymeric solution, plays a challenging role in regulating droplet formation and stability, especially in reverse emulsifications in PDMS microchannels. This work advances the current understanding of microfluidic droplet engineering by proposing a versatile technique for reverse emulsification and studying the effects of shear thinning on the manipulation of multiform droplets. Emulsification processes involving polymeric droplets in mineral oil droplets with Span80 were studied at four different mass concentrations of xanthan gum solutions and Pluronic F-127 (1.2 wt %). The results demonstrate that the proposed method for reverse emulsification is highly versatile, enabling the generation of both lipophilic and hydrophilic polymeric droplets. Rheological analyses indicated that increasing the xanthan gum concentration from 0.1 to 0.4 wt % resulted in a 17% increase in droplet generation frequency, while an increase in the Weber number led to a 75% increase in droplet size for xanthan gum concentrations from 0.1 to 100% for 0.4 wt %.