Technology & Hardware
How a pneumatic soft actuator gets made
A practical walkthrough of the fabrication sequence for a simple pneumatic bending actuator, useful to anyone planning a first prototype or deciding what a soft robotics product line must document.
01
Step one: define the bend and the mold
Begin with the motion required, such as a finger curling to grip a small object. Decide length, chamber count and wall thickness, then model a two-part mold, one for the chambered body and one for a thinner strain-limiting base. Print the molds and note the elastomer you plan to use. Worked example: a forty-millimeter finger with five connected chambers, sized so the thin base layer resists stretching and forces the body to curl instead of balloon. Record every dimension, because later failures will trace back to these choices.
02
Step two: cast, cure and bond the layers
Mix the elastomer by the manufacturer's ratio, degas it if possible and pour it into the chambered mold. Let it cure fully, then cast the base layer with an embedded inextensible element such as paper or fabric. Join the cured body to the base with a thin uncured film of the same material. In the finger example, alignment matters most at this stage, since a skewed bond makes the curl twist sideways. Label each batch with date, mix ratio and cure conditions so any inconsistency can be compared against the documented process later.
03
Step three: connect air, test and revise
Insert tubing into the inlet and seal it with adhesive, then pressurize slowly with a hand pump or regulated source. Observe where the finger bends first, whether any chamber leaks and how far the tip travels. Increase pressure only in small increments and stop at the first sign of bulging. For the worked finger, photograph each pressure step against a grid, then adjust wall thickness or chamber spacing in the mold file. Repeat the build once with a single change. That disciplined loop turns a one-off sample into a repeatable, documentable component.