dr.ir. LMC (Leonard) Sagis

dr.ir. LMC (Leonard) Sagis

Associate professor


  • 1990 MSc Chemical Engineering TU Eindhoven
  • 1994 PhD Chemical Engineering Texas A&M University


Research interests: Interface Dominated Materials

The aim of my work is to develop novel multiphase systems, such as emulsions, foam, or encapsulation systems (submicron hydrogel beads, core-shell microcapsules), and to characterize the link between the microstructure of these multiphase systems and their macroscopic properties (for example their rheology, fracture behavior, or release of functional ingredients). A major part of my investigations focus on the dynamic behavior of the interfaces in these systems (surface rheology), and the effect of this behavior on behavior on a macroscopic scale. Another part focuses on the investigation of the relation between interfacial structure and mass transfer across the interface, important for the development of effective encapsulation and controlled release systems.

The structure-function relationships established in this work are used to develop novel functional food products, such as foods with encapsulated healthy ingredients (vitamins, omega 3 fatty acids, peptides, probiotics), highly stable emulsions and foam, or controlled release systems for pharmaceutical applications. For the synthesis of these microstructured systems we rely heavily on self-assembly processes and enzymatic synthesis routes. These processes allow for a very effective design of materials with specific functionality, tailored to the needs of our industrial partners.

The motivation to focus on interfacial properties is based on the fact that emulsions or encapsulation systems tend to have very high surface to volume ratios, and their macroscopic behavior is therefore often dominated by the interfacial properties. For this reason these materials can be considered Interface Dominated Materials (IDMs). For a targeted design of IDMs with specific functional properties, a detailed understanding of the surface properties (surface tension, bending rigidity, surface rheological parameters, permeability), their relation to structural properties on molecular scales, and their relation to macroscopic behavior, is absolutely essential. For most of the systems we are studying the characteristic length scales of the interfaces are in the colloidal range, and therefore, when combined with methods for the determination of interfacial structure, and methods to determine macroscopic behavior, surface rheology plays a central role in determining the link between molecular properties of multiphase systems and their macroscopic behavior.

Classical bulk and interfacial rheological methods are insufficient to describe the dynamics of IDMs on all relevant length scales, and we have developed a multidisciplinary approach for studying these systems that combines surface rheology with nonequilibrium thermodynamics, and methods from computational physics. Such a multiscale multidisciplinary approach is essential to explore the dynamics of complex soft interface dominated materials.