For more information, see the general gecko-hair fabrication page.
Adhesive materials that can robustly and repeatedly attach and detach from wet surfaces are valuable for applications ranging from mobile robotics to medical device design. Here, we take previously-developed gecko-foot-hair-inspired elastomer microfiber arrays with film-terminated tips that have demonstrated enhanced adhesion with respect to unpatterned materials under dry conditions and coat them with synthetic DMA-containing mussel-inspired polymers to enhance adhesion repeatedly in fully-submerged wet conditions.
Coated adhesives were fabricated first by synthesizing dopamine methacrylamide (DMA) and then from this synthesizing poly-(dopamine methacrylate-co-2-methoxyethyl acrylate) (p(DMA-co-MEA). Finally, a stamping process, as illustrated to the right, is used to transfer p(DMA-co-MEA) onto microfibrillar polyurethane arrays.
The results of characterization of these directional adhesives indicate that p(DMA-co-MEA)-coated micropatterned adhesives demonstrate as much as 23-fold adhesion enhancement on wet surfaces when compared to uncoated fibrillar structures. Adhesion enhancement is due to the intrinsic properties of p(DMA-co-MEA), the geometry of the microstructured materials, and the properties of the materials used. Controlling the thickness of the terminal film is particularly important in predicting enhanced adhesion, due to its importance in crack-trapping during pull off from a surface.
Side view optical microscopy images of two coated, patterned samples with 40 micrometer diameter fibers with differing terminal film thickness are illustrated to the right.
Benefits: Robust, reversible wet adhesives have many potential applications including:
Past Members: Paul Glass, Yigit Menguc, Metin Sitti' Washburn Group (Department of Biomedical Engineering and Chemistry, Carnegie Mellon University.)