Effect of Ultrasound Standing Wave-Induced Acoustophoresis in Monoglyceride Oleogel Structuration

TL;DR

This paper explores how ultrasound standing waves affect the structure of lipid-based gels by inducing changes in crystal networks.

Contribution

The study reveals new insights into how acoustophoresis influences the formation and properties of monoglyceride oleogels.

Findings

Ultrasound standing waves create local density differences and orient monoglyceride platelets.

X-ray measurements show a 23% increase in platelet correlation length and improved surface smoothness.

These results help understand mechanical changes in lipid materials due to acoustophoresis.

Abstract

Ultrasound standing waves (USW) produce a force capable
of displacing
micrometer-sized free-flowing particles in a fluid, wherein this phenomenon
is also referred to as acoustophoresis. However, the effect of acoustophoresis
on dynamically changing and growing crystal networks is unclear. An
example of such a system are monoglyceride (MG)-based oleogels, which
are free-flowing lipids (e.g., vegetable oils) structured with a lipid-crystal
network. In this work, we use MG oleogels as an example system to
investigate the acoustophoretic effect on the structuration of a growing
crystal network. For this purpose, multifaceted characterization is
conducted utilizing optical and coded excitation scanning acoustic
microscopy as well as small-angle X-ray scattering, respectively.
The optical microscopy results show that USW produces local density
differences of the structuring crystalline material and induces the
orientation of the MG platelets. X-ray diffraction measurements confirm
these findings and show a 23% average increase in MG platelet correlation
length, which can be linked to platelet thickness, as well as an increase
in the MG nanoplatelet surface smoothness. These findings produce
a foundation for better understanding the effect of acoustophoresis
in dynamically developing lipid-based materials and illuminate the
mechanical changes that arise because of USW treatment.

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