11. Soft robotics#

Objectives from Fabricademy website:

Surface interface or molding and casting , mixed techniques with pneumatic elements as latex pipes laser cutting or sewing#

Pump the Soft robot#

Document troubleshooting#

Make a video of the soft robotic working#

Make the control of the inflatables at least with the DC air motor#

Basic : thermal transfer material
Intermediate: molding and casting one model
Advance control more air chambers as the gripper with the electronic

Inspiration for Soft robot#

There are many, many examples of inflatable forms in nature, arguably most profoundly in marine environments. The properties of the ocean as well as the characteristics of salt water (salinity, pressure, density, volume, turbidity, and temperature) have resulted in marine life creating an endlessly diverse array of unique adaptations to move around gases in their environment.

From the buoyant swim bladders of sharks, to gas exchange systems of sea cucumbers, to defense mechanisms of pufferfish, there are endless examples - both on a microscopic scale as well as a whole system scale - of inflation/deflation.

I started by looking at corals for inspiration because I thought the structure of corals could work quite well for a soft robotic. Also, I wanted to highlight the dire state of coral reefs globally. This is why I chose to design the endangered brain coral Ctenella chagius through soft robotics.

World’s most critically endangered species of coral include mushroom coral (top left), branching hammer coral (top right) and brain coral (inset top right)

Additional inspiration: hemolymph in insects

Step-by-step process#

Step 1: Design the pneumatic channels of the soft robot#

Use Rhino to trace a section of the brain coral

Step 2: Testing my design with vinyl#

How to iron vinyl:
- On baking paper, draw your shape plus a rectangle on one of the sides of your shape. This will be where you insert your tube later when you inflate your robot
- Cut out the areas that you want to be inflated
- Cut 2 pieces of vinyl (of the same size) and place a piece on either side of the baking paper. Make sure the vinyl is bigger than the baking paper so that the vinyl can seal together around the edges
- Remove the plastic covering on the vinyl, if there is one
- Secure your baking paper inside the vinyl and iron***. DO NOT IRON directly on the vinyl because it will melt. Place a piece of fabric on top of the vinyl first and then iron.
- Insert your tube and blow into it to test the air flow is good and there are no holes where air is escaping
- If everything is inflating correctly and 100% sealed, place a thermal band around where the tube and the vinyl meet. Seal the band by applying heat, we used a lighter. The band will shrink when heated and seal the tube to the vinyl.

The 0.3 cm sample did not work but the next size up of 0.5 cm did. Thus I determined the minimum space I could have between my air channel (where vinyl is not sealed) and the sealed vinyl was 0.5 cm.

- Although 0.5 cm did cause inflation, the material was very stiff
- Since I wanted my design to inflate much, much more I decided to switch to silicon

Step 3: Design 3D printed mold#

Step 4: 3D printing#

Step 5: Pouring silicon into mold#

- Vacumn press
- Silicon kit (Part A and B)
- Measuring cups
- Gloves
- Stir sticks
- Mold

Note: you can determine the volume of your mold in ____. This will tell you how much silicon you need to mix. I didn’t know this until after I had already poured my silicon molds, so I just guessed how much to make.

Round 1:
I had to do 2 batches of silicon, because with my first batch I took too long to meausure/mix the silicon and so it cured before I was able to get the bubbles out. Not to worry, we still made a cool sample with it. I added in some fabric scraps I had from our “Textile as Scaffold” week.

From left to right: silicon composite in the mold; leftover silicon that I peeled from the bowl; the silicon composite once it’s cured

Round 2:

Step 6: Let dry#

Step 7: Sealing silicon pieces together#

Step 8: Test the air flow#

- It’s very difficult to add any particle in silicon and to make
- Density and suspension
- Need to be the same density

You need to combine particles when its....

Step 9: Add more silicon#

Step 10: Test the air flow again#

Lecture reflections#

“Soft Robotics”
Presented by Lily Chambers and Adriana Cabrera
Lecture 11