Investigating the Role of Orientation Angle on Gecko Setae Adhesion using a Dual-Axis Mems Force Sensor

A dual-axis piezoresistive MEMS force sensor was used to investigate the role of orientation angle on the adhesion of gecko hairs, called setae. Previous work showed that the lateral adhesion force of a single seta pulled parallel to a surface is highly dependant upon the "pitch" angle between the seta\´s stalk and the substrate (K. Autumn et al., 2000). This work is the first to examine the effect of the "roll" orientation angle of the stalk under similar lateral pulls along a substrate. We find that the adhesion is near the maximum value for a wide roll angle range from -43deg to +43deg, and smoothly drops off to the frictional force at plusmn 85 M These angles relate physically to the orientation and spread of a splayed tuft of spatula-shaped terminations at the end of each seta. These spatulae make intimate contact with the substrate and enhance adhesion above traditional friction forces.