Noshir S. Pesika, Chemical Engineering, University of California, Interfacial Science Lab, Engineering II, Room 3357, Santa Barbara, CA 93106 and Jacob N. Israelachvili, Chemical Engineering, University of California at Santa Barbara, 3357 Engineering II, Santa Barbara, CA 93106-5080.
The gecko adhesive system is composed of complex hierarchical structures, which play specific roles to achieve high adhesion and friction forces. A “crowding model” is derived based on geometrical (pillar diameter, spacing, and tilt angle) consideration of a square lattice of pillars analogous to setal arrays (the adhesive structures on the gecko feet) of geckos. The model is used to understand the crowding events that occur upon normal compression of a setal array which limit the achievable tilt angles of the pillars. Good agreement is found between experimental data and prediction based on the “crowding model”. The model is also used to predict the optimum packing density of setae (the individual pillars that make up the setal array) of approximately 14,200 setae/mm2 in agreement with the measured value of 14,400 setae/mm2. Predictions from the model can be used to guide the fabrication of synthetic dry adhesives inspired by the gecko. In addition, preliminary synthetic structures and novel fabrication techniques will be presented for the fabrication of gecko-like adhesive structures.