Saving and reducing the consumption of electrical energy is one of the major future challenges for industry and society. By using electrically powered actuating devices, for example in the field of engineering or construction, the back transformation into a mechanical movement is not efficient, since electrical energy is almost always generated from a primary energy source. It would be desirable, if the actuator directly responds to an external stimulus or an environmental change, like temperature, moisture and/or light.
In this context, the following talk presents mechanical investigations on the structurally optimized functional material Cottonid concerning moisture-driven movements. The composite is based on the biopolymer cellulose which is produced from the chemical digestion of cotton fibers. In tests with superimposed medial loading the passive movements of Cottonid-based bilayer structures in reaction to moisture absorption and desorption are evaluated qualitatively and quantitatively concerning parameters, like maximum displacement, angle of deflection and resulting force. Moisture content, mechanical behavior and microstructure are correlated with the help of scanning electron microscopy (SEM) and computed tomography (CT) to characterize process-structure-property-relationships which leads to a profound understanding of the biomechanics. Research activities in the field of biological actuators (conifer cones), wood / engineered wood are used as the scientific basis.
The results will be transferred to develop other temperature- and moisture-dependent biopolymer composites over special chemical treatments of natural fibers and directed process control. On this basis, tailor-made functional materials shall be generated in future where anisotropy and hygroscopicity can be adjusted by / through the manufacturing process. A first mechanical evaluation of the moisture-driven movements concerning the above mentioned parameters help to identify possible applications in the field of bio architecture.