Monitoring the Contact Stress Distribution of Gecko-Inspired Adhesives Using Mechano-Sensitive Surface Coatings.
The contact geometry of microstructured adhesive surfaces is of high relevance for adhesion enhancement. Theoretical considerations indicate that the stress distribution in the contact zone is crucial for the detachment mechanism, but direct experimental evidence is missing so far. In this work, we propose a method that allows, for the first time, the detection of local stresses at the contact area of biomimetic adhesive microstructures during contact formation, compression and detachment. We use a mechano-sensitive polymeric layer, which turns mechanical stresses into changes of fluorescence intensity. The biomimetic surface is brought into contact with this layer in a well-defined fashion using a microcontact printer, while the contact area is monitored with fluorescence microscopy in situ. Thus, changes in stress distribution across the contact area during compression and pull-off can be visualized with a lateral resolution of 1 μm. We apply this method to study the enhanced adhesive performance of T-shaped micropillars, compared to flat punch microstructures. We find significant differences in the stress distribution of the both differing contact geometries during pull-off. In particular, we find direct evidence for the suppression of crack nucleation at the edge of T-shaped pillars, which confirms theoretical models for the superior adhesive properties of these structures.
Leibniz-Institut für Polymerforschung Dresden e.V. , Hohe Str. 6, 01069 Dresden, Germany.|Department of Physical Chemistry II, University of Bayreuth , Universitätsstr. 30, 95447 Bayreuth, Germany.
Jens W
JW
Neubauer
School of Power and Mechanical Engineering, Wuhan University , South Donghu Road 8, 430072 Wuhan, China.|Max Planck Institute for Polymer Research , Ackermannweg 10, 55128 Mainz, Germany.
Longjian
L
Xue
Department of Physical Chemistry II, University of Bayreuth , Universitätsstr. 30, 95447 Bayreuth, Germany.
Johann
J
Erath
Max Planck Institute for Polymer Research , Ackermannweg 10, 55128 Mainz, Germany.
Dirk-M
DM
Drotlef
Max Planck Institute for Polymer Research , Ackermannweg 10, 55128 Mainz, Germany.|INM - Leibniz Institute for New Materials , Campus D2 2, 66123 Saarbrücken, Germany.|Chemistry Department, Saarland University , 66123 Saarbrücken, Germany.
Aránzazu Del
AD
Campo
Leibniz-Institut für Polymerforschung Dresden e.V. , Hohe Str. 6, 01069 Dresden, Germany.|Department of Physical Chemistry II, University of Bayreuth , Universitätsstr. 30, 95447 Bayreuth, Germany.|Cluster of Excellence Centre for Advancing Electronics Dresden (cfaed), Technische Universität Dresden , 01062 Dresden, Germany.
Andreas
A
Fery
adhesion; bioinspired; biomimetic; mechano-responsive; polyelectrolyte brushes; polymer brushes