Update (4/23/2013): smaller, cheaper "mini" gripper STL file has been added. This gripper will cost less to order from a 3D printing service and won't require as much air to inflate (easier to inflate with a single pump from a squeeze bulb).
Credits: The soft robot technology in this project was originally developed in the Whitesides Group at Harvard University. For more details about the development of the technology and its uses, see the papers Soft Robotics for Chemists and Multi-Gait Soft Robot, and check their publications page for new work. These instructions, which modified the Whitesides Group's original process to be cheaper and more kid-friendly, were developed by a postdoctoral researcher (Dr. Ben Finio) in the Creative Machines Lab at Cornell University (PI: Prof. Hod Lipson). The work at Cornell was sponsored by the National Science Foundation (DRL-1030865) and the Motorola Foundation. Special thanks to the Ithaca Generator and Ithaca Sciencenter for providing audiences to help us test this project.
"Soft robots" are all the rage in the robotics research community right now. Forget what you usually think about robots and machines - gears, pulleys, circuit boards, aluminum and steel. These robots are made out of soft, stretchable rubbers and plastics, and driven by things ranging from compressed air to chemical reactions and materials that change shape due to electrical current or voltage. Existing robots include a robot worm that can survive being hit with a hammer, a rolling soccer-ball shaped robot, a gripper filled with coffee beans, and even an artificial octopus tentacle.
This project will describe how to make simple, air-powered soft robots that are made from silicone rubber, and shaped using a 3D printed mold. The project is based on a soft robotic gripper and a walking soft robot originally developed by the Whitesides Group at Harvard University. The project requires access to a 3D printer, or you can order a 3D printed mold from an online printing service like Shapeways, Sculpteo or iMaterialise.
Required Materials
*Note: all of the materials for this project are re-usable except for the silicone rubber. The tubing is very cheap (less than a dollar per foot) so it is not very economical to ship in small quantities - it can't hurt to purchase a few feet of both polyethylene and silicone tubing, in order to make multiple robots.
Credits: The soft robot technology in this project was originally developed in the Whitesides Group at Harvard University. For more details about the development of the technology and its uses, see the papers Soft Robotics for Chemists and Multi-Gait Soft Robot, and check their publications page for new work. These instructions, which modified the Whitesides Group's original process to be cheaper and more kid-friendly, were developed by a postdoctoral researcher (Dr. Ben Finio) in the Creative Machines Lab at Cornell University (PI: Prof. Hod Lipson). The work at Cornell was sponsored by the National Science Foundation (DRL-1030865) and the Motorola Foundation. Special thanks to the Ithaca Generator and Ithaca Sciencenter for providing audiences to help us test this project.
"Soft robots" are all the rage in the robotics research community right now. Forget what you usually think about robots and machines - gears, pulleys, circuit boards, aluminum and steel. These robots are made out of soft, stretchable rubbers and plastics, and driven by things ranging from compressed air to chemical reactions and materials that change shape due to electrical current or voltage. Existing robots include a robot worm that can survive being hit with a hammer, a rolling soccer-ball shaped robot, a gripper filled with coffee beans, and even an artificial octopus tentacle.
This project will describe how to make simple, air-powered soft robots that are made from silicone rubber, and shaped using a 3D printed mold. The project is based on a soft robotic gripper and a walking soft robot originally developed by the Whitesides Group at Harvard University. The project requires access to a 3D printer, or you can order a 3D printed mold from an online printing service like Shapeways, Sculpteo or iMaterialise.
Required Materials
- Ecoflex 00-30 (one "trial kit" is enough to make 5-10 robots depending on size).
- (Optional): Ecoflex 00-50, which is stiffer than Ecoflex 00-30. Using both materials (00-30 for the top layer and 00-50 for the bottom layer) can help the robot bend more easily when inflated, but this isn't required and will drive up the cost of your project. Only recommended if you plan on making a large number of robots (e.g. for an after-school program or summer camp), and need to purchase two or more Ecoflex kits anyway.
- (Optional): Food coloring. The default color of cured Ecoflex is off-white, but you can use food coloring to customize your robots.
- 1/16" ID, 1/8" OD polyethylene tubing* (part number 5181K15 at McMaster-Carr), about one foot per robot
- 1/8" ID, 1/4" OD silicone rubber tubing* (part number 5236K832 at McMaster-Carr), about one inch per robot
- Squeeze bulb: we recommend the "Polaroid Super Blower with Hi Performance Silicon Squeeze Bulb", available at Amazon.com and ritzcamera.com.
- 3D printed mold. The STL file for a basic four-leg gripper is available as an attachment to this page, and is also available on Shapeways and Thingiverse. If you have access to a CAD program (there are some free ones like Google Sketchup and 123D by Autodesk), you can also design your own molds. UPDATE 4/23/2013: I've also added a "mini" gripper STL file - smaller, cheaper to print, and easier to inflate with a single squeeze from a squeeze bulb. This file is also available on this page, Shapeways and Thingiverse. Important: be sure to order a material with a smooth surface finish (e.g. "White Strong & Flexible Polished" from Shapeways).
- Plastic cafeteria tray or metal baking tray (metal tray only required if you plan to use an oven, see below)
- Disposable rubber gloves
- Scissors
- Plastic cups
- Coffee stirrers or popsicle sticks
- Paper towels for clean-up
- (Optional) toaster oven. Do not use an oven that you also use for food.
*Note: all of the materials for this project are re-usable except for the silicone rubber. The tubing is very cheap (less than a dollar per foot) so it is not very economical to ship in small quantities - it can't hurt to purchase a few feet of both polyethylene and silicone tubing, in order to make multiple robots.
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Signing UpStep 1: 3D printed mold
Download the file 4-leg-gripper.stl or MiniGripper.stl from the links on introduction page (note: the units for the files are in millimeters). If you own or have access to a 3D printer, print your own mold. There are many low-cost "desktop" 3D printers available on the market, such as the Makerbot, Cube, and UP.*
If you do not have access to a 3D printer, you can order a mold from an online vendor like Shapeways, Sculpteo or iMaterialise.* Be sure to choose a material with a smooth surface finish - otherwise it will be difficult (or impossible) to remove the cured silicone rubber from your mold. Disclaimer: I tested the directions for this project printing in ABS with an UP 3D printer. I cannot guarantee that other printers or material types will work well with the silicone molding process. It might be a good idea to print a very small test container and do a test cure (follow the steps in the rest of the procedure to mix and cure the silicone rubber), to make sure you'll be able to get your robot out of the mold.
Advanced users: if you have access to CAD software, you can certainly design your own mold instead of using the files supplied here. The paper Soft Robotics for Chemists and its associated supplementary material provide a great introduction to different types and shapes of molds (and the resulting robot motion).
*Note: the 3D printing market is evolving rapidly. This project was originally posted in March 2013, and we can't predict what new 3D printers, companies and services will emerge in the future. You can always do a Google search (for example "3D printing", "3D printing service", etc) to check out what's currently available, and shop around for the best option.
If you do not have access to a 3D printer, you can order a mold from an online vendor like Shapeways, Sculpteo or iMaterialise.* Be sure to choose a material with a smooth surface finish - otherwise it will be difficult (or impossible) to remove the cured silicone rubber from your mold. Disclaimer: I tested the directions for this project printing in ABS with an UP 3D printer. I cannot guarantee that other printers or material types will work well with the silicone molding process. It might be a good idea to print a very small test container and do a test cure (follow the steps in the rest of the procedure to mix and cure the silicone rubber), to make sure you'll be able to get your robot out of the mold.
Advanced users: if you have access to CAD software, you can certainly design your own mold instead of using the files supplied here. The paper Soft Robotics for Chemists and its associated supplementary material provide a great introduction to different types and shapes of molds (and the resulting robot motion).
*Note: the 3D printing market is evolving rapidly. This project was originally posted in March 2013, and we can't predict what new 3D printers, companies and services will emerge in the future. You can always do a Google search (for example "3D printing", "3D printing service", etc) to check out what's currently available, and shop around for the best option.
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I have tried to make this using the exact same materials as you have instructed but am having trouble getting it to fold. instead the mold just wants to expand like a balloon, and one seems to expand more than the other.
I am about to increase the thickness of the side that isn't meant to expand but it is already quite thick. do you have any suggestions?
Are you using the big mold or the smaller one I uploaded recently?
http://www.youtube.com/watch?v=g210oczAqGo&feature=youtu.be
The original video from the Whitesides group is probably the best way to see one of these in action (note: I don't recommend trying this with raw eggs at home):
https://www.youtube.com/watch?v=csFR52Z3T0I
1) I've included an STL file for a smaller gripper that should be more economical - currently about $20 on Shapeways as opposed to $40 for the larger one; it will also require less silicone to fill the mold, and be easier to inflate with one pump from a squeeze bulb.
2) I've modified the directions for optional use of different materials for the top and bottom layers of the robot (Ecoflex 00-30 and 00-50 respectively). 00-50 is stiffer than 00-30 - this stiffness differential makes it easier for the appendages of the robot to curve when inflated. This can be a nice bonus but isn't required to make the project work.
Wonderful instructable, I'm exicted to try it out :D. Maybe make four, or five separate inflatable and make a whole hand out of it.
http://www.murata.com/products/micromechatronics/feature/microblower/index.html#A002
This piezoelectric microblower could make all of these soft robotic ideas easily controllable by standard electronics! I have asked DigiKey if they could carry it. Perhaps if they got several requests we could make it happen.
Great Instructable! THANKS!
Point being, we wanted to make this as cheap as possible and accessible to kids, thus the $5 squeeze bulbs*. But absolutely, if you want to do something fancier with offboard or even onboard air supply and electronics, it should be doable.
*(which in my experience can provide up to around 5-7psi with a single squeeze if hooked up directly to a pressure gauge- they are limited by their volume though, unlike an air compressor, e.g. if you hook one up to a large chamber with a pressure gauge, the pressure increase will be negligible)
You can 'toughen' it up by adding a mesh fabric into the flat layer (like in composite RTM molding)
And yes, you can add a relatively non-stretchable mesh fabric to the bottom layer (just soak it in Ecoflex and bond it as a third layer, or include it in the flat layer the first time through). This will affect the curvature of the legs. The cheapest/easiest way to do that is to just use a paper towel soaked in Ecoflex.
If you read the Whitesides papers, they actually used two materials with different stiffnesses (Ecoflex for the top layer with the channels, and I believe Sylgard for the bottom layer), this makes it easier for the legs to curve. We kept it to just one material to keep things cheap and easier for kids - but in order for that to work, the top and bottom layers (amount of material above and bellow the channels) need to be different thicknesses, or else the legs won't curve.
good job on the instructable!