Analysis of endoscopic injectability and post-ejection dripping of yield stress fluids: Laponite, Carbopol and Xanthan Gum

Yield stress fluids, which show reversible gel-sol transition and a decrease in viscosity via shear, are expected for endoscopic applications. However, quantitative analyses of such fluids, including pressure drop during endoscopic catheter delivery and post-delivery dripping, have not yet been conducted from a chemical engineering perspective. In this study, we fabricated an equipment setup comprising an endoscopic catheter and a model gastrointestinal (GI) duct to which different concentrations of three model yield stress fluids, specifically, laponite (LAP), Carbopol (CP), and xanthan gum (XG), were applied and compared. We clarified the tradeoff between the pressure drop through the catheter and dripping on the GI duct model. In terms of operability, LAP performed better than CP and XG. The effect of gravity on dripping, which is greatly affected by the position of a patient, was discussed. Finally, the relationship between the operability and rheological properties such as viscosity, yield stress, and restructuring time of the three materials were quantitatively studied.