Low-Friction, Superhydrophobic, and Shape-Memory Vulcanized Rubber Microspiked Structures

Multifunctional vulcanized rubber microspiked structures are prepared by a simple hot-press process with a fine microstructured Si mold. The vulcanized rubber spiked structures reduce the friction coefficient by concentration of the load on the top of the spikes, as confirmed by a simple calculation of the relationship between the contact area and the friction force. The friction coefficient can also be controlled by elongation of the vulcanized rubber and the rubbing direction due to the changes in the arrangement of the spiked structures from hexagonal to anisotropic linear patterns without deformation of the spike structures. The vulcanized rubber spiked structures show additional functions such as superhydrophobicity and shape memory. The superhydrophobicity is realized by the fine microspiked structures, and the shape-memory effect is generated by the vulcanized rubber properties. Therefore, folded spiked structures can be recovered to their original state by heat treatment, and superhydrophobicity regenerates. These results indicate that the surface microstructures can add further functionality to these materials. The simplicity of the preparation method required for this multifunctional vulcanized rubber offers great possibilities for the creation of superior products as there are many examples of such structural designs in nature.