Soft Robotics - Week 5 (02/21/2025)

Silicone - Part 2

This week, we were challenged to design and create our own silicone molds and cast our own silicone soft robot. I took inspiration from my research last week and attempted to recreate an origami inspired silicone actuator that was developed by researchers at ​Zhejiang University.

The first step was to create a 3D model of the mold to print on the 3D printers. This mold consists of a tray for the top and the bottom, and then a core and shell for the body of the actuator.

Lessons Learned:

1. ​Review the research paper more in depth and look at all the diagrams and charts, because chances are - the necessary dimensions are already there. In this case, I made the piece too big and the walls too thick. 
2. TinkerCAD is not a great 3D modeling tool for precision. Next time, borrow a laptop to use fusion instead. 
3. Plan enough time for printing and reprinting. Chances are, the mold will need to be reprinted.

The second step was to pour the three parts - body, top, and bottom.

Lessons Learned:

1. 100 grams is a lot less than you think.
2. Narrow angled channels are hard to pour into quickly
3. Residual silicone can be reused in a second pour to reduce wasted materials

The third step was to de-mold the body and punch holes through the fins to provide air flow through the chambers. The researchers included the cavities in their mold, but for time sake, I simply pierced holes with a wood working hole puncher from the shop.

Challenges:

1. Angled castings are hard to de-mold, the mold broke in a few places during the process
2. Due to the multi pour, there were a couple tears and air bubbles that needed to be filled in 

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The fourth step was to adhere the body to the top by pouring some more silicone into the top mold and placing the body into the wet uncured new silicone. There was a lot of trimming and cleaning to do during this process. since the bottom side of the body was flat, I attached that side to the top, so while I was waiting for this part to cure, I could use that time to trim the uneven top for a more secure adhesion to the bottom piece later.

The fifth step was to de-mold the body + top, and adhere it to the bottom piece. This part was straightforward and honestly at this point, we just have to pray to the gods that everything works out.

Testing the final piece

The tiny fan that I purchased off of amazon does not provide enough suction so I'd like to test it out with the vacuum pump by the soft lab cabinet, but out of curiosity, I also tried inflating it with the sphygmomanometer which does create an interesting look.
Although during this process, a tear appeared, which I did not notice until after the video was filmed, but you can see as the tear is created and enlarged. I did end up going in with some sil-poxy to close it up, but I will be working gently with this piece moving forward.

If I get a chance to hook this up to the vacuum pump, I will upload the video below.