Introduction: Soft Robots: Make an Artificial Muscle Arm and Gripper

Picture of Soft Robots: Make an Artificial Muscle Arm and Gripper

Using artificial air muscles, a very flexible robot arm and gripper can be made.

This soft robot is powered by compressed air and each one of the 11 muscles can be controlled by a standard infrared universal remote control or an infrared LED connected to a micro controller that can output Sony code.

This is a hack of silicone caulk. It is in fact mostly made of silicone caulk.

This robot was a test of hand cast, silicone based air muscles which I plan to use in an inexpensive prosthetic robot hand that I am working on. A laser cutter would be very useful to make the precision sheet plastic molds necessary to cast the hand muscles. The cutter could also be used to create the "bone" structure of the hand out of plastic or plywood.

The very short video shows the robot picking up an egg and moving it.

Step 1: How It Works

Picture of How It Works

I am convinced that soft robots are the way to finally create inexpensive and flexible robots that can work well with humans. They may make possible the first really practical robots for everyday use. Soft robots use flexible materials to create the frame and actuators of the robot.

The artificial air muscles for the hand and arm are made from Oogoo, an inexpensive mix of silicone caulk and corn starch that can be cast into many shapes. For this robot, the Oogoo was cast into layers to create stacked air bladders that can be expanded or contracted with pressure or vacuum.

A standard infrared universal remote can control individual muscles or pre-programmed sequences. It does this by sending signals to an air muscle controller that is controlled by robot neurons. The air muscle controller can control up to 11 air muscles using solenoid valves and a 12 volt air compressor that provides pressure or vacuum.

This is a tethered robot that has 11 air lines connected that power the air muscles. Eventually it should be possible to fit the valves and compressor on board. A less noisy compressor could also be made.

Step 2: Materials

Picture of Materials

Materials For The Robot Arm And Gripper

Plastic grocery bag

Corn starch from grocery store

Nitrile gloves

100% silicone caulk, the type that smells like vinegar. Available from Walmart, Dollar Store, or hardware store.

1/16" sheet plastic for forms and base plate. Can be phenolic, acrylic, or any smooth sheet plastic. A good source for plastics of all kinds is usplastic:

1/16" and 1/8" ID silicone hose and fittings, available from usplastic

Materials for the air controller
The air muscle controller requires various 12 volt solenoids, silicone tubing and fittings, and an air compressor. A detailed list and sources can be found here:

Materials for the Robot Neurons
The robot neurons that control the solenoids that control the muscles are made using Picaxe micro controllers. A detailed list of parts and schematics and code can be found here:

Step 3: Making the Artificial Air Muscles

Picture of Making the Artificial Air Muscles

The step 3 pic shows the 11 segments of the upper arm. The silicone tubing goes to an air chamber that constitutes one muscle. This creates four muscles that can counterbalance each other to move the arm in four directions. This was later glued to a 1/16" plastic base plate that was bolted to a large blue sheet of expanded PVC.

The second pic shows two muscle segments, top and bottom. The segments are cast in two layers with a thin sheet of polyethylene creating an air chamber that can be filled with air. A hole in the middle of each muscle chamber brings air to the chamber when all the segments are stacked and glued together.

Pic 3 shows all twenty segments of the upper arm and forearm stacked and glued and the air power lines. A 1/16" plastic plate was later glued on top with bolts protruding that allow different grippers to be bolted on.

The next step shows how the muscle segments are cast.

Other Shapes
There are probably hundreds of useful shapes of air muscles that can be cast. Here are a couple of others I have tried:

Step 4: Casting the Artificial Air Muscles

Picture of Casting the Artificial Air Muscles

Mixing the Oogoo
A 2 to 1 mix of Silicone caulk to corn starch is mixed BY VOLUME. It sets up quickly, so it is best mixed in small batches. Typically, I would mix up 2 tablespoons of silicone to 1 tablespoon of corn starch. You can add a small dab of artists oil paint to the mix if you want colors. For more details and safety info on mixing Oogoo, see here:

Casting The Artificial Muscle Segment
The second pic shows the first form which was made from two pieces of 1/16" phenolic sheet, but any sheet plastic can be used. Plywood can also be used if it is coated first with spray lacquer as a release for the Oogoo. The two pieces of phenolic have 4 bolts holding them to a plywood base.

Screeding The Segment
Pic 3 shows the screeding (smoothing and leveling) with a metal straight edge after the form was filled with white Oogoo. Filling the form must be done carefully to avoid bubbles that will leave weaknesses that can blowout under pressure.

Pic 4 shows the four polyethylene plastic pieces from a grocery bag that are used as separators to create the chambers for each muscle segment. Under pressure, the Oogoo will not stick to the polyethylene leaving a chamber to be filled with air.

Pic 5 shows the final  blue layer of Oogoo that after screeding completes the cast of one muscle segment.

After the segment has set up, it is removed from the mold and a hole drilled or punched in the middle of each chamber created by the polyethylene. The center square is then cut out. This allows a space for the silicone air tubing. The segments are then glued together in a stack. Oogoo is applied carefully to the white washer around the holes. Fresh Oogoo glues old Oogoo remarkably well and fuses the silicone pieces together as if they had been cast as one piece.

Step 5: Making the Soft Robot Gripper

Picture of Making the Soft Robot Gripper

The first two pics show the gripper closed and open.

Pic 3 shows the 3/4" piece of plywood scrap that was cut out to create the form. Next to it is a 1/16" thick piece of plastic that was embedded in the cast to add stiffness.

Pic 4 shows the gripper finger after Oogoo casting.

pic 5 shows the bottom and top of the gripper muscle segments after the center square has been cut out and the air chambers punched out.

The finished gripper is bolted on to the plastic plate that is glued to the forearm. This gripper is far from an optimum configuration and so I made it to be easy to remove and replace with a better version.

Step 6: Artificial Muscle Air Controller

Picture of Artificial Muscle Air Controller

The robot air controller consists of 14 solenoid valves that can control 11 air muscles by pressure or vacuum. I originally tried using cheapo 3/16" silicone aquarium tubing for the tubes that go from the controller to the robot. Unfortunately they collapsed when under a vacuum and had to be replaced with more expensive, flexible silicone tubing. This type of tubing is translucent white and almost sticky to the touch. It has the advantage that it very flexible and it glues extremely well to Oogoo.

I have written a detailed instructable on how to make the artificial muscle controller:

The solenoids are controlled by Tinkertrons which are artificial robot neurons. I have posted the details of making the neurons and the Picaxe code for this robot here:

Step 7: Other Possibilities

Picture of Other Possibilities

Tether-less Autonomous Robots
This soft robot is tethered with eleven tubes to a fairly heavy controller. I am working on making much smaller and lighter valves out of Oogoo to replace the solenoids. I am also working to create a quiet air compressor that will be powered by a twelve volt gear motor. This should make possible fairly small, tether-less soft robots that are autonomous.

There are several robotic researchers who are using compressed air tanks or working to create gas generators that could be used instead of a compressor.

Adding Sensors
At this point the robot arm has no sensors for position, touch or object detection. They will be required for more precise movement. I am working on conductive silicone sensors that can be embedded in or around the artificial muscles. Here is one of my earlier experiments:

"Bone" Structure
This was an experiment in an almost boneless artificial muscle structure. While it could be used to create a robot worm or snake or underwater eel, it has its limitations. In some positions, the arm is wibbly-wobbly and very difficult to control. Some kind of internal bone structure  and maybe support tendons could be added to aid in achieving more precise control.

3D Printing Of Robot Muscles
The ultimate method would be to 3D print the whole soft robot structure. I am working on making a 3D printer that will print Oogoo. Until then, casting is the easiest way to go.

Future Of Soft Robots
I am convinced that soft robots are the way to go to create inexpensive and flexible robots that can work well with humans. Perhaps a combination of motors and air muscles will create affordable robots that can be more easily produced.

Spiders, snakes, squid, fish, flowers, amoebas, and never before seen forms of soft robots can be made. It is a fresh, new frontier in the field of robotics.


robowizard2000 (author)2017-09-13

Do you have template's with measurements so people can actual make this? A pdf or CAD file perhaps?

Erobot331 (author)2017-05-17

so cool!!!!!

sammueldavid (author)2015-11-07

like its cool and all but... what?? how do i get oogoo and likes igghhhhh

oh wellllll

Lord_Forbes (author)sammueldavid2016-07-15

Hey, maybe this helps:

Pyromaniac_65 (author)2016-06-27

Super cool

LuísRazel (author)2016-04-14


sammueldavid (author)2015-11-07


sammueldavid (author)2015-11-07


sammueldavid (author)2015-11-07

whats the point of the arm if you ccant build it as easy look i have only 100$$ to make a full robot for school not just an arm how do i really make it????????

sammueldavid (author)2015-11-07

WHATS THE POINT OF POSTING IT IF ITS HARD TO MAKE !!!!!@#$%^&&(()(*^%#@!??????>KJEQQ#$%|

JediDude6205 (author)2015-09-24

Dang this looks so familiar! I think it's based off (or from) a nova episode or something right?

maker_studio (author)2015-08-06

Cool robot!

novelchip (author)2013-06-26

Impressive work. I also am dreaming of making a soft-micro robot , possibly smaller. But for the moment I am only working on micro-pneumatic controller circuits (such as the ones made by M.Burns and other research groups . ). With such controllers you do only need a single electro-valve to control as many pneumatic lines as you want. The idea is that the single valve generates a serial train of pneumatic impulses that are then translated by a shift-register into parallel pneumatic "signals" . So with one electrovalve + one micropneumatic chip you can control as many pneumatic lines as you want. In this way all the pneumatic (which is micro-pneumatics) should fit into a volume of few cm. You don't need high-tech equipment to make such circuits. A simple CNC mill will do a good job as you can see on my first instructable. Would be cool to collaborate once I (and you) have reached further in my work .

mikey77 (author)novelchip2013-06-27


Cool idea.

I, too am working on making smaller valves and have been experimenting with servo controlled valves. The large size of valves and pumps is the only thing keeping us from making really small robots.

You have hit on one of the main problems with soft robots, each muscle requires at least one valve and valves tend to be heavy and high volume.

It does however, seem to me that any time you convert from serial to parallel, the shift register would require a valve for each output channel and the number of total valves would not be reduced.

If you could post a clear schematic that shows how less than eight valves could control eight channels it would be greatly appreciated.

jwhitten (author)mikey772015-07-08

Do you think you might achieve different results by using a non-compressible fluid, more like traditional hydraulics?

mikey77 (author)jwhitten2015-07-10

The advantage of soft robotic air muscles is that they are light and extremely flexible when bumping into humans. Stiff exoskeleton gear motor powered robots do not have that advantage.

Hydraulic soft robot muscles could be useful underwater or in the vacuum of outer space.

novelchip (author)mikey772013-06-28

Below you can find a schematic that I am trying to reproduce. Its from research work of Minsoung Rhee (mark Burns group at University Michigan)

There are 8 pneumatic output channels in the pneumatic integrated circuit.
What needs to be verified is wether there is sufficent air-flow through the output channels to actuate air-muscles. I think yes, especially if small air-muscles are used - which after all is my  aim - and also yours as I understand. I am still experimenting with building and testing such circuits. Once I have good results i will make a new instructable about it.

mikey77 (author)novelchip2013-06-29

Very cool.

Valves that are powered and controlled by air pressure could be very useful for air powered robots.

I have lately been experimenting with casting small robot muscles and valves using 3d printed molds.

If you are interested, you could PM me and we could toss around a few ideas.

We might be able to come up with some really small air powered robots.

mbear (author)2015-07-09

Just saw this on Your comment about the silent air compressor reminded me of this: How to modify a fridge compressor into a silent air compressor Maybe that will help.

mikey77 (author)mbear2015-07-10

Thank you for the link.

There are many possibilities here.

Lord Fawful (author)2012-09-02

How much can this little guy lift?

mikey77 (author)Lord Fawful2012-09-03

In the position used to lift the egg, it can lift 1 pound 2 ounces. This is with the compressor running at 2/3 speed.

jwhitten (author)mikey772015-07-08

Well, you know, if it doesn't work out as a hand, you might want to have a chat with Pfizer... ;-)

gabriellalevine (author)2013-11-15

Hey I actually have tried this exactly and have actually made 3d printable designs next week, I'll share them on an instructables... But the solenoids I got that you references totally let air through with the sparkfun pump, so I have to use this small fish tank pump that is way less strong.

Do you know of other solenoids that might handle higher psi, or do you know how I can prevent this or how I can check for this when purchasing? Or do you know other resources for solenoids like this that might be a little stronger?

Awesome thanks this is an amazing project that inspired me to make my own pneumatic snake robot :)

mikey77 (author)gabriellalevine2013-11-15

Cool, I'd like to see them.

If you look closely at step 1 at: I used a pressure relief valve so that none of the solenoids receive more than 9 PSI which is close to their limit. When all of the solenoids are closed the air goes out through the relief valve. I used a drip valve from a drip irrigation system but a ball valve could be used and restricted to 9 PSI when the valves are closed. I also used a motor controller to run the air pump at 75 percent of its maximum.

As for valves, I have found some surplus ones that will handle 20 PSI but they are no longer available. New valves are very expensive, so check online surplus places.

If you adjust your system to limit the max pressure, you may find that 9 PSI is plenty powerful for most small to medium sized robots.

jwhitten (author)mikey772015-07-08

Is it possible that you could cascade the valves so that the escaping air pressure of one valve helps fill the next one and so on? In the days of steam locomotives, for instance, it was a common way of using the steam a "second time" by hooking the exhaust steam to a second slightly larger cylinder and using it again.

gabriellalevine (author)mikey772013-11-18

Oh great - thanks a lot! I'll get some of those valves, and additionally, if needed, decrease the power to the motor.
thanks a lot for the tips.

BTW (i attached a photo of what each 3d printed air "pillow" is composed of. I printed them on the Objet 3d printer which can print "tango plus" , a flexible rubber material. But it is expensive. Anyhow, I've made them by hand thus far and will post my work to instructables once i get something working. )

would this work :

mikey77 (author)gabriellalevine2013-11-20

It might work, but a better, easier to adjust valve would be 0-30PSI.

Less expensive is the valves I used. I got them from a hardware store. These are drip valves for water that reduce the flow using micro channels. Raintree drip irrigation fittings (couplers, Tees, elbows, drip valves, stop valves) for 3/16" tubing available from

kd8bxp (author)2015-05-24

Saw the video, and it reminded me a lot of the mid-50s Robby the Robot arms.

Very cool retro look. :-)

nschreiber0813 (author)2015-01-12

Dear: Mike

Just to let you know my progress is tremendous with my robot arm. It is also very unsuccessful just to let you know I have decided that oogoo is not the best way to approach this for me. Right now I am using duct tape and it is more successful but not quite. It is too stiff and too much other things not the best way to approach this. Basically what I am trying to ask is what materials could I use other than oogoo. I need something strong, flexible, and non sticky. Something like rubber without the mess. Believe me I can't stand working with oogoo anymore with so little success. I have twenty attempts but all of them deem wrong. Can you please help me I am so stuck? here is my progress. Wish me good luck.

From: Noah

P.S. Duct tape is too stiff no bubbles form in case you are wondering.

mikey77 (author)nschreiber08132015-01-14

I do not understand why you are trying to cast multiple muscles when as far as I can tell, you have not cast a successful single muscle. You are trying to run without first learning how to walk. See some of my earlier instructables that show how to cast simpler muscles. Any kind of casting is going to be messy and require that you learn new skills and have a great deal of patience. That is how things get done.

That said, you could try the only other way that is not as messy but would still require skills to implement it. Google otherlab, and you will find that they are using coated fabrics and sewing them together to make artificial muscles. You might try something like that with coated fabrics or vinyl sheet material and maybe you could glue them together.

Good luck.

nschreiber0813 (author)mikey772015-01-15

Perfect thank you.

nschreiber0813 (author)2014-12-18

Dear: Mike

You should know I am trying to build your robot except do a few modifications. You see instead of building a robot arm I am trying to build a 3d printing robot arm that is soft. So far I am running into a lot of problems. I am trying to figure out how you casted the arm. I built this mold and this was the results. Where did I go wrong? I followed all your steps including putting plastic on top of the mold. Please help me?

From: Noah

mikey77 (author)nschreiber08132014-12-19

I am always happy to see anyone try do duplicate some part of any of my instructables. It almost never happens.

That said, you should understand that soft robots are not the best way to create the ultra precise positioning that 3D printers require.

While it might be possible, the flex and downright floppiness of artificial muscles made of silicone make it extremely difficult to control the movement precisely.

Even so, you should try it anyway. What you learn could be useful for other things even if it is not useful for your original goal.

I cannot tell from your pictures what you did or did not do. The idea is to lay down a layer of Oogoo and then separate it with thin sheet of polyethylene from a second layer of Oogoo.

It might be useful to start with a single muscle instead of the multiple muscles you are trying.

Good luck.

nschreiber0813 (author)mikey772014-12-19

That solves it. I was wondering why when I did it why I wasn't understanding how it works. You should know that when I put a layer of oogoo down I made one layer of Oogoo not two. That would explain why when I put the plastic on it seemed a little funny. I also didn't put the plastic inbetween the oogoo I just put it on the top. Thank you I will give it a shot. Wish me good luck...

chubby8 (author)2014-09-04

I mixed my first batch of oogoo today. very cool stuff.
I'm going to begin to build a hand that uses air muscles,I find robots combined with prosthetics very interesting.

on a very different note, I'm also thinking of casting some oogoo insoles for my shoes, made to fit my feet perfectly. ;D

thank you, you are very inspiring.

chan2005 (author)2014-04-16

there is a nova on an arm like this

wsmith52 (author)2014-04-13

This is so cool, how many arms can you run at one time with this setup?

mikey77 (author)wsmith522014-04-15

With the controller I have now it can only run one arm at a time.

I am working on making my own valves which should make it possible to scale up the system.

gabriellalevine (author)2013-11-18

I was just also wondering if you or anyone knows where to purchase suitable valves. Or what specifically to search for? Air valves that flip when powered with over nine psi but handle over 20?

Ironsloth1993 (author)2013-07-08

Congratulations on winning Michael.

Dream Dragon (author)2012-12-29

I've been out of touch for a while but I was very impressed with your earlier experiments with air muscles. It's great to see this development.

For a light weight and simple "valve" you might want to look at musical history. Particularly the development of the ORGAN. Leather and wood would be much lighter and simpler, not to mention CHEAPER, than the precision machined metal components, and I bet you could develop the idea to use the same Oogoo material.

mikey77 (author)Dream Dragon2013-01-01

Thank you,
for the research idea.

Organ valves are very interesting and fairly simple.

You have recognized the point of the exercise: to discover simple and easy to make components that work well.

I have been experimenting with several designs of various types of electric and passive valves that are made with Oogoo.

I hope to publish an instructable on the best ones, after they have been tested in the real world.

mightysoxer (author)2012-12-23

mikey77, you are just too awesome.

Husham Samir (author)2012-10-03


CrLz (author)2012-09-24

Fantastic project! Thanks for sharing the construction, design and idea!

flic2flac (author)2012-09-21

Hello, I understand this is becoming cliché but I must say it ... AMAZING :-O

I have a PhD in biomechanics and I study the mechanics of human soft tissues. Although robotics isn't at all my field I've seen in conferences and scientific papers the concept of pneumatic muscles but never as organic, elegant ... and let's be honest ... blue as yours.

I truly believe the biomimetic approach is the way to go. I agree with you regarding the potential for human/machine (or orga/mecha) interaction of combining small electric motors and artificial pneumatic (or hydraulic) muscles.

As I see it, a scaling down of this approach i.e., build artificial muscle fibers (to be controlled in fiber bundles to form muscle groups), would allow the possibility (if the nightmarish automation and control challenges can be surpassed) of truly biomimetic robotics opening the door for applications such as prosthetics (ex. artificial sphincters - the existing are effective but very crude). Once again, UAU

godfish (author)2012-09-18

I am shocked at what you've made here this is wonderful, I only wish I could do something as cool.

sciencetor2 (author)2012-09-03

well, this is quite an amazing use of air muscles in robotics, but if you have the resources to build all this, don't you already own everything in the prize pack? Im trying to come up with a hack so i can win the stuff and get the supplies i need to finish my fully open sourced musical tesla coil.

About This Instructable




Bio: I believe that the purpose of life is to learn how to do our best and not give in to the weaker way.
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