The goal of this design was to create an artificial muscle capable of gripping and contracting in several directions. This is part of ongoing research for Jiefeng Sun’s doctoral thesis through Colorado State University’s Robotics Lab. I contributed to Jiefeng’s research through January and February of 2018.
In order to initiate artificial muscle movement in several different directions, it is necessary to have several internal wires within the muscle for each direction of movement.
This particular project involves the creation of an artificial muscle with three cylindrical arms connected by an inactive central silicone cylinder. I created the mold for this project in SolidWorks:
The mold was then filled with Smooth-On silicone and the initial prototype was casted, with three TCA nylon-copper actuators in the middle:
This particular muscle, when actuated with (7 volts at 1.3 amps) tended towards twisting rather than performing a motion in a single plane. To combat this issue, I decided to add ridges along the z-axis to try to prevent twisting motions:
This solution worked relatively well, however a new problem became evident. The TCA’s are difficult to keep straight once threaded through the mold. When removed from the mold, they are often bent and therefore do not actuate well, if at all.
Below is the second iteration of the Tri-Gripper Muscle. In the left-hand image, the ridges are clearly defined. In the right-hand image, the right-most TCA is clearly bent and is not contained by the silicone cylinder to which it should be parallel within.
To fix this problem, a new method of inserting the TCAs before casting must be developed! I was able to make this progress in 3 weeks of working at the CSU Robotics Lab with Jiefeng, and continued to work on other aspects of his research such as the meta-material twist structure.
Jolán von Plutzner 