NIRT: Biologically Inspired Synthetic Gecko Adhesives

Geckos have the remarkable ability to run at any orientation on just about any smooth or rough, wet or dry, clean or dirty surface. The basis for geckos' adhesive properties is in the millions of micron-scale setae on each toe of the gecko form a self-cleaning dry adhesive. The tip of each seta consists of 100 to 1000 spatulae only 100 nanometers in diameter. Our interdisciplinary team of biologists and engineers proposes to first develop models for how the natural nanostructures function in a hierarchical combination of spatulae, spatular stalks, setal stalks, setal arrays, and toe mechanics, and then develop a nanofabrication process which will allow large arrays of hair patches to be economically fabricated using self-assembly techniques.
Using insights from biological models, our work in the gecko hair project aims to develop mechanical models for gecko hair adhesion and then to design and fabricate a synthetic gecko hair array. As reported in 2002, [Sitti and Fearing 2002] and Autumn et al [2002] we have made synthetic spatulae, which have shown adhesion similar to natural spatulae in the range of 100-300 nN. These patches of bumps lacked the setal stalks, and achieved adhesion forces on the order of a few milliNewtons on an area of a square centimeter. In 2003, we fabricated high density arrays of spatular stalks [Campolo et al 2003] which showed adhesion on the order of 0.5 Newton per sq. cm. The final goal is to build arrays incorporating the necessary geometrical features which have similar adhesion to geckos, about 10 Newtons per square centimeter.