From the previous section, you should have two extension muscles, each slightly longer than the designed manipulator. For this section, you need Ecoflex™ 00-10 (which comes as two jars of liquid, labeled parts A and B), and a container for mixing, alongside spoons or other mixing utensils.
Ecoflex™ silicone and mixing container we used
Measure the radius of the muscles you fabricated as well as the depth of the mold. Before placing muscles into the mold, it is necessary to fill the mold to a certain level with silicone so that the muscles can be centered in the manipulator. Specifically, this level is one muscle-radius below the halfway point of the depth of the mold. Place a mark at this level using a pen or marker.
After stirring both parts of Ecoflex™ thoroughly in their jars (using separate stirring utensils), pour equal parts A and B into the mixing container, with at least enough to fill the mold (about 1 fluid ounce was plenty for ours). Stir this mixture (using another separate stirring utensil) for a full three minutes, taking care to scrape the sides and bottom several times during mixing. Carefully pour this mixture into the mold, up to the level previously specified. Allow this to cure; although the full four hours is not necessary, the silicone must be solid enough to prevent the muscles from sinking in.
Lay the muscles into the mold on top of the previously poured silicone so that they run parallel, each running through its own channel at the ends of the mold. Prepare another batch of silicone as done previously and pour it on top of the muscles until the mold is full. After the pour has settled, use a small instrument (like the carbon rod from before) to straighten out the muscles if they have developed curves during mold pouring, and additionally to ensure the top surface is level. Let the mold sit in room temperature.
Mold with muscles laid in, prior to silicone pouring
After four hours, carefully pry the manipulator from the mold interior (a flat-head screwdriver may help).
Finished manipulator, removed from mold
Finally, using a small pair of scissors, remove the silicone from the ends of the muscles (where the channels were), careful not to pull the muscles out of the manipulator body or cut the ends of the muscles off. This is only necessary to allow an attachment point for the power supply leads during testing.