Modular soft robots_3

PART 3 of 3

For PART 1 click here
For PART 2 click here
For PART 4 click here

For the third iteration I wanted to model something after the accordion structure.
This video below shows the accordion shaped actuator extending linearly

I took inspiration from this but decided to add some solid chunks of silicone in between to add some stability to the actuation.

trial 3.PNG

As seen in the CAD model above, the cuboidal blocks of silicone do not inflate. They work as internal bracing elements. The blocks also serve as channels for the proposed external restraints to pass through.

trial 3 a.PNG
Mold design for the actuator with the outer part and inner core.
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3D printed piece of the mold. The red wire seen on the left is to keep the cantilevered end of the inner core from touching the outer mold part.
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I casted only one half of the actuator first and decided to color the other half.
IMG_20180416_212801228_HDR
Fully casted actuator, there were a few tears toward the end of the casted piece so I had to cut it in half.

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As you can see, this iteration achieves a good amount of linear extension but it inflates in a  rather ugly manner. Also it doesn’t inflate evenly. I later found out from Kari that silicone has a tendency to do that, maybe the wall thicknesses were slightly uneven and once it inflates beyond a threshold, it creates microscopic tears which irreversible alters the behavior of the actuator.

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I tried inflating the actuator with external restraints (white wire attached to the actuator). As you can see it did successfully turn linear motion into bending motion. I just needed to refine the inflation aesthetics in the following iterations.

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