# 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.

## Key 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.