Actuated adhesion elements with hierarchical structure for applications on technical surfaces

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Dry adhesive surfaces provide a broad potential of application, however, their technical realisation is complex, demanding, and ambitious. The work proposed here intends to investigate actuated microstructures with hierarchical design with respect to a repeated attachment to and detachment from technical surfaces. The hierarchical structure enables the combination of different operating principles (atomic interactions, mechanic interactions) to maximise the adhesion strength. External actuation enables attachment and detachment and, in addition, allows to overcome topography which with technical surfaces typically is very pronounced. In the first phase of the project the fabrication of such micro-structured hierarchical adhesion elements by means of replication processes was shown. A controlled attachment and detachment of the adhesion elements under tensile and shear loading could be realised by pneumatic actuation. The measuring system developed for this purpose enables the determination of macroscopic forces/motions and the visual documentation of microscopic processes in the contact area. The present status of the research work allows to go over to more complex anisotropic adhesion situations. The continuation of the project applied here will focus on the investigation of anisotropic adhesion elements. The resulting adhesion which depends on the direction of force will allow a systematic control of the attachment and detachment function. The measurement data will be compared with FEM simulations in order to gain an understanding of the operating principles governing the attachment and detachment processes of such hierarchical systems as well as to deduce design rules for a technical realisation. Beyond basic scientific insight it is planned to validate the preparation processes (complexity and limitations) with regard to the sustainability of advanced adhesion systems with actuation. The decisive criterion here is the functionality of the adhesion systems on technical surfaces that can be achieved by applying replication techniques.