Dr. Carmen Eger

Dr. Carmen Eger

Research Area B

Faculty of Engineering | Department of Microsystems Engineering
University of Freiburg


Surface-bound Polymer Layers by C,H-insertion for Sustainable Materials

Project description
The biological model for my project is the pinecone. Pinecones open in response to dry conditions and close in response to wet conditions. This mechanism works through a two-layer-system, in which one layer swells (and thus expands) with increasing humidity more strongly than the other. In my project, I am investigating an artificial two-layer system consisting of a polymer film and a hydrogel as an actuator: This system, similar to the seed scales of the pinecone, reacts to changing humidity by bending. Since the swelling of the material is the main driving force of this reaction, my work focuses on this phenomena and all its related parameters.

Project outcomes
The aim of this work was to develop a passive and hygroscopic actuator to be used as an executive component in an energy-efficient adaptive facade. Due to the passive water uptake and release and subsequent closing and opening of the cone, Pinus Wallichiana was the biological role model for the development of the hygroscopic actuator. The key functions of the bending mechanism of P. Wallichiana were identified based on hydration measurements and the study of the mechanical properties during swelling. It could be shown, that the structure and the function are more complex than previously described in literature. Additionally, a novel model of how the water is taken up in the pine cone was proposed. I described the development of the hygroscopic actuators which are made from hydrogel and polyester and the complex interplay of physical and chemical properties that influence the bending motion. In order to be used as executive component in an energy-efficient adaptive facade, the actuator has to fulfill relevant properties, which I also investigated and discussed. The bending motion of the resulting actuator is adjustable, reproducible, durable and the actuators are strong enough to support panels with five times their own weight. I created a model with a possible design proposal for the adaptive facade by combining the actuators with a panel and attaching them to a model house.

Supervisor and dissertation
Prof. Dr. Jürgen Rühe

Carmen Eger completed her dissertation in 2021.

Dissertation: Hygromorphic Polymeric Actuators for Smart Building Façades Inspired by Pine Cones

Current position
Material Research Engineer at Trelleborg Sealing Solutions, developing new materials and adjusting our current material recipes to meet new industry requirements. This includes working on a whole range of materials, from thermoplastic materials, high-performance plastics, elastomers to PTFE.

Publications in livMatS