Kirigami Gripper

This is an OpenSCAD script for generating gripper skins like those described in this paper:
https://www.researchgate.net/publication/351538904_Grasping_with_kirigami_shells

I kind of eyeballed the initial design and wrote up a module to generate the gripper pad.
There are a number of parameters that control the shape and slots cut in the pad:

- *grip_pad_dim* = diameter of the main pad.
- *grip_pad_stretch* = amount to stretch the main pad by. 1.0 will leave it circular, 2.0 would stretch it 2X in the Y axis.

- *thickness* = thickness of the pad. I've found that 1mm and less work best.
- *arm_length,arm_hole,pad_dist,pad_dim* = control various parameters of the pull tab on either side of the pad.

- *slot_multiplier* = similar to grip_pad_stretch, used as a multiplier for the relative length of the slots with respect to the pad size. These need to be played with a bit. The slicing of the pad controls how much it will wrap when the pull-tabs are tugged on.