The Gripper is a Pneunet design that is based on the Slow Pneunet architecture. It is designed by Ben Finio. It has 2 variations - Gripper and Mini Gripper.
The fabrication process is described in detail on the Instructables page.
Take note of Stage 11, where extra sealing is necessary on the top layer after gluing.
From the instructables guide:
Puncture the robot from the side, at a 45 degree angle in between two of the "legs". Aim for the circular central chamber that connects the four air channels.
We found that even after applying reinforcement on top of the gripper, it is quite fragile and can tear or pop easily after curing. We recommend to only pump a small amount with the syringe to make sure there are no holes and then let it cure for at least half a day.