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Engineering of biomimetic surfaces: Switchable micropatterns for controlled adhesion and touch

Final Report Summary - SWITCH2STICK (Engineering of biomimetic surfaces: Switchable micropatterns for controlled adhesion and touch)

In the course of evolution, nature has found many fascinating solutions to engineering problems. Among those, the sticking action of animals to diverse surfaces has particularly attracted the attention of several research groups worldwide. Even without secretion or glue, "dry" adhesive systems can be very reliable as the contact is split into numerous “hairy” features, creating a three-dimensional (3D) micropatterned surface.
The aim of the project was to design and develop, by an intense interplay between experiment and theory, active 3D micropatterns with innovative properties. The study encompassed new designs, new materials or material combinations coupled with an improved understanding of the relevant theory of contact mechanics. In the first phase, our studies focused on new concepts for responsive adhesive systems: an active hybrid polymer-metal system, a mechanical actuation and systems with shape memory polymers were demonstrated. As a striking result, the results were successfully implemented into an industrial robotic system to demonstrate a revolutionary new concept of pick & place handling. Such handling ability is essential e.g. for modern production lines. The main advantages over existing solutions are that our system works in vacuum and helps save energy when compared to conventional suction or electrostatic grippers. These developments – and those of a subsequent ERC Proof-of-Concept grant - paved the way for a start-up company, where the patented Gecomer technology is now being commercialized.
Our research on adhesion to soft, compliant substrates has also opened new fields of emerging applications. As a novel design concept for a 3D micropattern, the combination of a stiff stalk with a soft terminal layer was identified to overcome limitations of fibrils made from single materials. Experiments and numerical analyses disclosed design guide rules to achieve strong adhesion even to rough substrates. In collaboration with Saarland Medical School (Prof. B. Schick), tests were performed which suggest that our adhesive films can support the healing of ear drum perforations. In addition, adhesive films for wearable sensors were designed in collaboration with the Saarland Informatics Campus (Prof. J. Steimle).
Complementary to experimental studies, theoretical modeling of contact mechanisms was successfully conducted in collaboration with Prof. Norman Fleck, Cambridge University, UK, Prof. Robert McMeeking, UCSB, USA, and others. As a result, the adhesive performance and its sensitivity to changes in geometry and material is now significantly better understood. In addition, confinement effects and statistical effects within a micropatterned array were investigated. The project thus closely combined new experimental concepts with theoretical predictions on how to obtain optimum engineering solutions.