Data for A three-row opposed gripping mechanism with bioinspired spiny toe pads

First, the toe pad base and the spine holder were fabricated using rapid prototyping by nylon PA2200. The spine (HUANQIU acupuncture needle) was installed into a slot in the spine holder. Polyurethane (PU) Vytaflex 30 (Smooth On Inc., USA) was used to create the compliant connector. Several spiny toe pads were then installed in a spiny array holder to form an array (Figure 8(b)). The total number of toe pads could vary but in this experiment, we installed ten in the array. A customized testing apparatus for the contact force test was built. The two linear stages (X-LRM150A-E03-KX14A and X-LRM050A-E03-KX14A, Zaber Technologies Inc., Canada) generate linear motions in two orthogonal axis, which are parallel and perpendicular to the testing surface, namely the x- and y-axis respectively. Two sensors (LSM250, FUTEK Advanced Sensor Technology, Inc., USA) are connected to the y-axis linear stage, which measure the contact forces of a single spiny toe pad or a toe pad array in the x- and y- direction. We chose sandpaper (P60 &P80, MATADOR Germany) as the testing surface to serve as a standard for experimental measurement. During the testing of the array, sandpaper was installed onto the acrylic board to fit the width of the array. The experimental procedure is as follows: The y-axis stage first moves a single toe pad or a toe pad array towards the sandpaper to a position where it just contacts the surface, namely the origin position. Then, the y-axis stage presses a single toe pad or a toe pad array towards the sandpaper in the –y direction for a certain distance representing as yp, reaching the compression position. After that, the x-axis and y-axis stage drags and lifts a single toe pad or a toe pad array in +x and +y axis respectively. The speed of the tangential dragging expressed as vx=0.1mm/s and the normal lifting represented as vy={0.01, 0.02, 0.03, 0.04}[mm/s] to exert different path. The test is repeated with different positions yp {0.2,0.4,0.6,0.8,1.0,1.2}[mm].