Interfacial rheology
where Most commonly, the measurement of dilational interfacial rheology is conducted with an optical tensiometer combined to a pulsating drop module.
[3] Typical measurements include performing a frequency sweep for the solution to study the kinetics of the surfactant.
In another measurement method suitable especially for insoluble surfactants, a Langmuir trough is used in an oscillating barrier mode.
In this case, two barriers that limit the interfacial area are being oscillated sinusoidally and the change in surface tension measured.
The Boussinesq number, Bo, depicts how sensitive a measurement method is for detecting the interfacial viscoelasticity.
This method is often used in combination with a Langmuir trough in order to be able to conduct the experiment as a function of the packing density of the molecules or particles.
[8] Interfacial rheology has been employed to understand the structure-function relationship of these physiological interfaces, how compositional deviations cause diseases such as infant respiratory distress syndrome or dry eye syndrome, and has helped to develop therapies like artificial pulmonary surfactant replacements and eye drops.
Surfactants and surface active polymers used are for stabilising emulsions and foams in food and cosmetic industries.
Proteins are surface active and adsorb at the interface, where they can change conformation and influence the interfacial properties.
[11] Specialized setups that allow bulk exchange during interfacial rheology measurements are used to investigate the response of adsorbed proteins or surfactants upon changes in pH or salinity.
[12] These setups can also be used to mimic more complex conditions like the gastric environment to investigate the in vitro displacement or enzymatic hydrolysis of polymers adsorbed at oil-water interfaces to understand how respective emulsion are digested the stomach.
[13] Interfacial rheology allows the probation of bacteria adsorption and biofilm formation at liquid-air or liquid-liquid interfaces.
