Biviano Matthew D, Böni Lukas J, Berry Joseph D, Fischer Peter, Dagastine Raymond R
Department of Chemical Engineering and the Particulate Fluids Processing Centre, University of Melbourne, Parkville, VIC 3010, Australia.
Institute of Food, Nutrition and Health, ETH Zurich, Schmelzbergstrasse 7, 8092 Zurich, Switzerland.
J Colloid Interface Sci. 2021 Feb 1;583:404-413. doi: 10.1016/j.jcis.2020.09.008. Epub 2020 Sep 15.
Interfacial rheology provides insight into the mechanical properties of adsorption layers on liquid-liquid interfaces, which mediates the stability of emulsion droplets. The use of capsule compression at the scale of an emulsion droplet to probe the interfacial rheology may open up the possibility of testing the interfacial rheological properties of droplets with complex histories and extremely small volumes found in many applications.
The time dependent interfacial rheological behavior of β-lactoglobulin adsorption layers on an oil/water interface in the native and crosslinked state was extracted using small oscillatory indentation with atomic force microscopy (AFM). The results of this novel model and experimental approach were compared to the well-established techniques of interfacial shear rheology (ISR) and dilational pendant drop tensiometry that were performed on analogous interfaces.
The tan δ measured between the ISR and AFM measurements provide similar results in an overlapping frequency range, but the viscoelastic moduli G' and G'' differ by several orders of magnitude. This is most likely the result of the different flow fields and the low deformation of the AFM measurements compared to dilational and shear flow fields.
界面流变学有助于深入了解液-液界面上吸附层的力学性质，而这一性质介导了乳液滴的稳定性。在乳液滴尺度下使用胶囊压缩来探测界面流变学，可能为测试许多应用中具有复杂历史和极小体积的液滴的界面流变性质开辟可能性。
利用原子力显微镜（AFM）的小振幅振荡压痕技术，提取了天然和交联状态下β-乳球蛋白在油/水界面上吸附层随时间变化的界面流变行为。将这种新型模型和实验方法的结果与在类似界面上进行的成熟的界面剪切流变学（ISR）和拉伸悬滴张力测定技术的结果进行了比较。
在重叠频率范围内，ISR和AFM测量之间测得的损耗角正切（tan δ）提供了相似的结果，但粘弹性模量G'和G''相差几个数量级。这很可能是不同流场以及与拉伸和剪切流场相比AFM测量中低变形的结果。
