Flat Soft Actuators From Images




Introduction: Flat Soft Actuators From Images

About: Hi! I'm Aidan Leitch, a robotics, electronics, and 3D printing hobbyist.

Soft robotics is a growing sub-field of robotics involving using soft materials and compliant methods of actuation to maker robots. For some time I've been looking for an solution to allow people to easily create their own custom soft actuators with minimal input. Based off of the work found here: http://www.kevincgalloway.com/portfolio/zero-volu... I've written a Thingiverse Customizer script, that allows you to turn black and white images into the mold and stencil needed to create a flat soft actuator that inflates to the shape of the image.



  • Cup
  • Spoon
  • Tweezers
  • 3D printer

Step 1: Design Image

Use any image manipulation tool (I used GIMP) to create a black-and-white image. What is black will become the air chamber and what is white will become solid. Here are the rules you need to follow when designing:

  • Image has to be 100x100
  • The only colors that can be used are black and white, no grey
  • There can be no "floating" white parts. This would result in a stencil that is multiple pieces (you can have floating black parts however).
  • There must be a 5 pixel-wide border around you design.

Step 2: Customizer

Open the Customizer page on Thingiverse and add in your image. These are what the different parameters do:

  • Side Length: Since the generated actuator is a square this will be the length of all sides.
    • Side Note: You can cut your actuator later as long as it does not cut into the air chamber
  • Layer 1 Height: Since the flat actuators are made of two layers of silicone, you can choose the height of each. This is the layer that is lower in the mold.
  • Layer 2 Height: Since the flat actuators are made of two layers of silicone, you can choose the height of each. This is the layer that is higher in the mold.

When you are satisfied, press "Create Thing" and download the stencil .STL and the mold .STL.

Print them out on your 3D printer. Use 3 shells and .1mm-.2mm layer height.

Step 3: Cast Layer 1

Mix up some EcoFlex silicone. Ecoflex is a 1A:1B ration silicone, meaning you should have an equal amount of both liquids. I suggest mixing it in a paper cup with a spoon. Pour it into the mold, only up to the first brim, and let it cure for 4 hours.

Step 4: Spray Release

Snap the stencil into the mold. It should be flush with the first silicone layer. Spray a generous amount of mold release onto the exposed silicone. It should be enough that the surface looks gooey and liquidy. Let it sit for 15 minutes and then remove the stencil.

Step 5: Cast Layer 2

Mix up some more EcoFlex silicone. Fill the rest of the mold up. Let it cure for 4 hours.

Step 6: Demolding and Connection

Once layer 2 has cured, you can now peel the entire actuator out of the mold. You can check to see that the layers did not stick together on the design by rubbing it with your fingers. Take tweezers and poke a hole through the side of the actuator at the seam in between the two layers. Make sure the hole reaches the air chamber. Stick the 1/16" tubing through the hole and connect the other end to your air source. Now you can inflate!



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    6 Discussions

    I love your idea, but i was wondering if their was a way to simulate the inflation of the actuator relative to the pressure applied on the desired shape. Would love to hear back from you.

    Very nice, now I am thinking about what other shapes and functionalities could be made with this. Thanks.

    Great job indeed. But the efficiency depends on the elasticity of the silicone and, of course, the air pressure. So you cannot be sure to always have the same result. If you choose to work with a liquid, you'll get the same result each time as elasticity won't count no more.

    1 reply

    Thank you, but I'm not sure what you're talking about. Changing the durometer and air pressure can deliver more force, but with a given actuator, there will always be a consistent pressure-force curve. If I were to use a hydraulic fluid, it would transfer more force, but durometer and pressure would still have the same effect.

    Why not take a balloon and attach to a straw? If you want a particular shape, make a frame to snap round the balloon.

    1 reply

    I like your idea, but there are a few issues with it (besides the fact that it's just not what I wanted to make). Firstly, if I were to restrain a balloon with a rigid frame, then it would not be a fully soft robot. Secondly, your idea would make it difficult to make an actuator that does anything but just inflate, as the rigid frame would forbid it from bending or extending. Lastly, although restraining wireframes sound like a good idea, the inflatable tends to inflate in all other directions, making it not so useful for restricting movement. Typically soft actuators with restraints have restraints surrounding them completely. Hope this clears things up.