High Quality Electroadhesives

Description

Electroadhesion is an electronically controlled adhesive technique which makes use of static electricity to cling to objects.

Electroadhesives are surprisingly simple devices that are composed of inter digitized electrodes which are insulated in a dielectric. The electrodes are then powered with high voltage (typically around 5kV). Even though electroadhesives utilize high voltage, they use very little current and are extremely inexpensive to run continuously.

The high voltage creates static electric fields around the electrodes in the pad which induces static cling to objects it contacts. It can then drop objects when power is shut off.

Electroadhesives can be used for robotic endefectors, sloping conveyors, wall climbing adhesive, soft-robotics, bulletin boards, "sticky" whiteboard/blackboards, clipboards, and more.

Details

Electroadhesives have been around for a while now. However they are not commercially available and information on them can be difficult to find. When I learned about electroadhesives I was extremely excited and I just had to make my own!

I have done a lot of research on electroadhesives and how they work.

I have developed a method for fabricating electroadhesive pads at home! The process is still being refined to ensure the best process for making high quality electroadhesives.

I am also experimenting with the silicone thickness and electrode patterns in an attempt to improve adhesion strength.

I have searched extensively and have only found a couple of instructions on how to make an electroadhesive pad. However none of these instructions provided a high quality electroadhesive that you can make at home. So I decided to share my project and provide instructions for my electroadhesives that can be made at home with easy to acquire materials.

Files

Electroadhesive Electrode Designs.dft

Electrode designs for electroadhesives V2.

dft - 754.50 kB - 12/09/2016 at 18:28

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Project Logs

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Control Box Progress
birdycrazy • 02/16/2017 at 19:04 • 0 comments

This past weekend I built the control circuit and tested it to work as intended.
I got a plastic junction box from home depot and set to work wiring everything up and securing all the parts inside. The circuits are secured with standoffs, the flyback transformer is held in the corner with velcro, and the high voltage resistors were mounted on a small piece of acrylic. I put some silicone around the top and bottom of these to prevent any potential sparking. These are the resistors I used.
Here are some pics of the box. I'm just waiting for some high voltage plugs, once I get the plugs and add them to the box, it will be finished!
Control board schematic
birdycrazy • 02/10/2017 at 17:37 • 0 comments

Just finished a circuit diagram for the electroadhesive control box,. Im going to build it this weekend. I'm not very experienced in designing circuits so please let me know if there is anything I should do to improve it.
I wanted the robot to turn it on and off automatically so I made a digital input as well as a manual switch The robot I am using uses 24v logic. when the power is turned on, the green LED will light up. when the electroadhesive is turned on either by the switch or the digital input, the red LED will light up as well.This is the flyback transformer and flyback driver I am using.
https://easyeda.com/birdcrazy135/Electroadhesives-a2e4c625bc5749d183be29fca6703a0a
silicone vs silicone mixed with corn starch
birdycrazy • 02/09/2017 at 02:31 • 0 comments

A new pad I've been working on recently finished curing, it came out quite nicely. I have tested it and it works great with no sparking! Now I just need to back it with plexiglass and cut it to shape.
This pad is designed to lift and place thermal pads. I plan to use it as a tool in a robotic assembly process.
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I originally tried to make this pad with the corn starch/silicone mixture for a faster drying time. The mixing process introduced air into the silicone and caused air bubbles to form. This pad sparks intermittently, but otherwise works (for now). You can clearly see the difference in quality between the two pads. If you zoom in the picture below you can see all the tiny bubbles in the pad. I also like how you can see the electrode pattern much more clearly in the pure silicone pad than the other one.
Modified Process.
birdycrazy • 02/07/2017 at 16:26 • 0 comments

Sorry for the wait on updates, I've been quite busy lately with school starting up again and working full time while going to school. I haven't had a whole lot of time to work on the pads.
First off, I've given up on circular designs. they are just too hard to cut out of the contact paper with a clean edge. From my research online, circular designs are found to have a stronger normal force while ladder designs have a stronger shear force, but the difference in normal force isn't huge.
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Now I got Tired of it taking a week of drying time to make a single pad, so I went exploring for ways to accelerate the drying process. So I found Oogoo. Silicone I caulk, cures by absorbing the moisture in the air, Oogoo accelerates the drying process by mixing Corn Starch into the silicone. the corn starch releases moisture into the silicone and dries the silicone from the inside out. This looked like a promising solution, so I tried it.
I made many pads with different ratios of silicone to Corn Starch, with little success and much frustration. It did greatly decrease drying time to only a couple hours But the pads kept failing. The problem was that when I mixed the silicone with corn starch, I introduced air into the silicone. This caused tiny little air bubbles (and sometimes large ones) to remain when the pad was formed. These air bubbles made a week spot in the silicone where sparks would eventually break through. The pad might work for a hundred cycles or so, but would eventually start to intermittently spark and soon after, completely short and burn through the silicone. So this solution obviously will not be ideal unless I had some way to mix the corn starch in a vacuum.
This led me to believe that my previous problems with electrode gap size may not be because the silicone caulk can not withstand it, (In fact I have proven that it can withstand at least 12kv per 600um as that is the thickness of the adhesive layer.) but that I may have had a tiny air bubble stuck in there which caused it to spark. My current test pads are using a 4mm electrode width and gap.
So I decided to go back to pure silicone caulk. I modified my process so that I could remove the shelf liner off the top of the silicone before it was completely dry. This increases the contact with the air so that the silicone is able to dry faster.
It may be possible to accelerate the drying process by using a humidifier, but I have not tried this.
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I also found that the silicone sometimes has trouble pealing off the contact paper without ripping a hole in the silicone pad. So I am just making the pad on shelf liner which the silicone peals off with no trouble at all once dry. I have updated the instructions to reflect these changes.
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I am also working on a control box for the electroadhesives. It will be using a flyback transformer, supplied with a 12v power supply to generate up to about 15kv. It will have a switch to turn it on and off. It will use high voltage resistors in parallel with the electroadhesive to provide automatic release (normally I need to short the ends to remove stored charge in the pad for release). I also hope to make it flexible for use with any electroadhesive pad.
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I hope to post a demonstration video soon of the pad lifting different materials, I just need to find the time to do so.
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In January I figured that, since I would be working with these products which produce fumes, I should make an exhaust chamber for my work space. So I built an exhaust chamber out of my closet with two sheets of Plexiglass which is held on with sticky velcro. It has some ducting for exhaust through a window fan. The bottom plexiglass sheet can be swung open to allow me to work inside the chamber. It works pretty well, I can hardly smell anything when it is closed and running.
Even though it's winter, it doesn't cool off the room too much as the window is below the ducting to the chamber, this keeps hot air in the top part of the ducting to restrict cold air from leaking into the room....
Read more »
First Large Pad
birdycrazy • 12/12/2016 at 17:03 • 0 comments

This is my first successful large electroadhesive pad.
Adhesive area is approximately 153 x 98 mm.
Electrode width is 5mm.
Electrode gap is 5mm.
Power supply: Ionizer module 9-10kV.
The silicone pad is backed with plexiglass to keep the pad flat and ridged for picking up objects.
This pad is able to pick up a wide range of materials. It can only pick up light items and It seems to stick to some materials better than others, for instance, it seems to form quite a strong bond to paper but it doesn't grip to plastics too well.
I will continue experimenting to attempt to increase adhesive force. I plan to reduce the electrodes and electrode gaps to 3mm. I also plan to reduce the silicone layer to about 300 um in an attempt to get noticeably stronger adhesion. According to my research, (see links) the adhesion strength increases as the electrode gap is reduced and increases dramatically as the insulating layer gets thinner.
Improved Process
birdycrazy • 12/12/2016 at 16:37 • 0 comments

I made these to test out a new development process which uses shelf liner to smooth out the top layer. Then I let it dry for 2-3 days before removing it. This results in a very smooth surface with no wrinkles.
First Circular design
birdycrazy • 12/12/2016 at 16:30 • 0 comments

This was my first circular design. This was made with a 1mm gap as before and sparked like the others.
This Is just a basic 2 electrode design. It only has silicone on one side. I made this to test its adhesion properties with a 600um silicone layer. This pad came out pretty well and the surface of the silicone was quite smooth.
Second Attempt -- Conductive Fabric
birdycrazy • 12/12/2016 at 16:22 • 0 comments

Once I determined that aluminum foil was not suitable, I ordered some conductive fabric to try out. It worked much better than the aluminum foil. The fabric prevented the silicone from stretching and the electrodes remained intact while stretching and bending the pads relentlessly.
I had some trouble with these samples when casting the silicone, as you can see, they have many wrinkles and folds over the surface. These problems were mainly caused by my impatience when I tried to remove the pads before the silicone was fully cured.
These pads were made with 3mm electrodes and 1mm gap between electrodes. I found that the 1mm gap was too small and sparks would jump between electrodes, burning the silicone and creating a gap in the dielectric. You can see the burnt silicone in the left pad where the spark occured.
First attempt
birdycrazy • 12/12/2016 at 16:13 • 0 comments

This was my first attempt at fabricating an electroadhesive. Aluminum foil was used for the electrodes and this was my first time using silicone caulk for this project.
The major flaw I found when using aluminum foil is that it would break apart when the silicone stretched.

View all 9 project logs

Build Instructions

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Step 1

(Note: Instructions subject to change as process is improved) These are difficult to make and there is a lot that could go wrong during the process. I recommend starting with a couple small pads to learn the process before attempting to make a large one.

Be sure to read the directions and fully understand them before trying to make one of these electroadhesive pads.

Make the stencil

- Cut out a piece of con-tact paper to the size of a piece of regular letter paper (or whatever size your printer takes)

- Try to straighten out the con-tact paper a bit by curling it .

- Place the con-tact paper in your inkjet printer so that it will

print on the paper side (not the plastic side).

- Choose an electrode design from the included file or make your own. Print the design you want onto the con-tact paper

- Tape down the con-tact paper over a cutting board and cut the electrode design out of the contact paper.

Step 2

Apply the etch resist

- Cut out some conductive fabric. It should be cut a bit larger than your chosen electrode design. I recommend about 1-2 inches larger on all sides than the electrode design. If there are folds in the fabric, remove them by ironing it on low/synthetics setting.

- Cut out piece of con-tact paper large enough to cover one side of the conductive fabric. Peal off the paper, and stick it to one side of the fabric. Make sure the fabric is flat and smooth when the contact paper is placed on it.

- Now take the stencil you made in the previous step, peal off the paper, and lay it down (paper side up) on a flat surface. Take off the paper carefully and adjust the stencil electrodes to their correct positions. Take the piece of conductive fabric and place the uncovered side down on top of the stencil. Make sure that the electrode design is positioned correctly on the fabric.

For large designs I found that it can be easier to first make a masking tape "mat" sticky side up, then stick the plastic side of your stencil onto the masking tape before pealing off the paper backing. Manipulate the stencil electrode designs to their correct positions on the masking tape and stick it to the masking tape. This will keep the electrodes in their proper positions. once the electrodes are all positioned on the masking tape, peal the paper off the con-tact paper and stick the uncovered side of the conductive fabric on the stencil. Now remove the masking tape, being careful not to pull the stencil from the fabric.

- After your stencil is attached to the fabric, it is time to apply the etch resist. I used nail polish as an etch resist (doesn't matter what kind. I used the cheapest I could find). Use a brush to paint the nail polish over the stencil. Put it on nice and thick, as thick as you can! You can never put it on thick enough!

- let the nail polish thoroughly dry for at least 60 minutes, or more if needed.

Step 3

Clean up and patch the etch resist.

- Once the nail polish is dry, peal off the stencil and the con-tact paper on the back as well. If nail polish is not fully dry, when the stencil is pulled off it, will pull off some of the nail polish on the electrodes as well.

- Under a light check out the both sides of the fabric, you should be able to see your electrode design in nail polish. If it looks like there is nail polish connecting 2 electrodes where it shouldn't, you will have to use nail polish remover to clean up the short. Place a paper towel under the fabric and use a small brush to apply nail polish remover to the shorted area, rub the area thoroughly to try to remove the nail polish on both sides.

Discussions

mnant wrote 09/29/2019 at 16:58

Hello,

How much voltage do you need to get a paper to stick on the surface of the electroadhesive pad?

Are you sure? yes | no

PointyOintment wrote 07/13/2018 at 10:16

This is an application of dielectrophoresis, right?

Are you sure? yes | no

Eric Hertz wrote 03/29/2017 at 09:25

Ah hah! I think I recognize this from an old flat-bed pen-plotter that somehow magically held the paper down to the surface. Always wondered how they pulled it off.

Are you sure? yes | no

PointyOintment wrote 07/13/2018 at 10:13

My HP 7210A has that. They called it Autogrip. However, when I cursorily looked at the board that drives it, it looked like it operates at or near mains voltage. I didn't see any transformer, just a couple of capacitors and resistors, and maybe a diode or two.

Are you sure? yes | no

Morning.Star wrote 03/28/2017 at 22:53

Hi, I like this project. I've never heard of electroadhesives before but I did build a linear arc laser (http://www.sparkbangbuzz.com/tealaser/tealaser7.htm) that used a 7.5KV supply from a flyback (Although not externally coupled like yours. Thats clever!) which was strong enough to tear the foil used for the capacitors if it wasnt flat. Probably good to hold Kilos on a shear mounting like the pads. How much can they hold? Just curious :-)

Are you sure? yes | no

birdycrazy wrote 04/18/2017 at 14:13

That is cool! I will have to make me one of those someday!

I do not know what the max weight it can hold is. The adhesive strength is different for different materials. I have been able to successfully lift (normal force) 1/16" aluminum and 3/32" acrylic.

So I would estimate that it can lift about 0.4 - 0.5 grams/(cm^2 contact with pad). Shear force should be slightly stronger due to friction with the silicone and charge repulsion.

Are you sure? yes | no

Morning.Star wrote 04/18/2017 at 18:16

Thats impressive for a handful of electrons. I had an idea about sticking cardboard together using the principle, so I can make self-assembling mechanisms from geometric shapes that stick to each other. I'm not sure about the voltages involved but its interesting all the same...

If you do mess with arc lasers, buy good UV eye protection ok. It throws a lot of splash like a welder and Arc-eye is miserable. It isnt just the beam you have to worry about.

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nipuna abeysinghe wrote 01/29/2017 at 08:26

Great instructions. I have been searching the internet for weeks, looking for a method to make electroadhesives pad. Its really hard to find any good information on it. so a huge thanks.....

I'm trying to make a fabric gripper to pick and place small fabric parts. How well does the pad stick to fabric ???????

Are you sure? yes | no

birdycrazy wrote 01/29/2017 at 15:07

Hello! Thank you for your interest in my project!

I had not thought to use it on fabric, I just tried, and it will indeed lift light fabric. It will lift only the top piece from a stack of fabric cutouts. you may have trouble dropping the fabric though, as there is some residual adhesion.

Was there a particular type of fabric you were interested in? I am planing to post a video in the next week or so, of the pad lifting some different materials, I will include fabric so you can see how it works.

Are you sure? yes | no

nipuna abeysinghe wrote 01/30/2017 at 03:22

I was thinking fitting the pad to a robotic arm and using it to pick and place Denim Pockets. If you could include Denim fabric in your video that will be great. I will definitely try my hand on making it my self. Hope you could update on methods to improve adhesion.

Are you sure? yes | no

birdycrazy wrote 02/07/2017 at 17:13

Sorry for the delay on that video, I really have been quite busy lately. As for improving adhesion, generally adhesion is improved with: reduced electrode gap, reduced insulating layer, and increased voltage. But sometimes its a bit more tricky than that, for instance on rougher surfaces you want a wider electrode gap as this increases the penetration depth through the material. Because of this penetration depth, you need to make sure that it can penetrate far enough past the insulating layer in order to adhere to something. Also, once you reach a certain voltage you begin to over saturate the material you're adhering to, and increased voltage doesn't increase adhesion, I think this "peak" voltage is different in different materials.

Check out the links to the left, these are the sites where I found the best info on electroadhesives and optimizing them.

The gap size and insulating thickness are limited by the dielectric properties of the insulating material. I'm sure silicone caulk is not the best dialectic insulator, there are much better silicone products out there for this purpose. The group at NASA who did a study on optimizing electroadhesives used this silicone i think, and they spin-coated it to achieve very thin insulating layers: https://www.polytek.com/products/liquid-mold-rubbers/silicone-mold-rubbers/platinum-silicone-mold-rubbers/platsil-73-series/platsil-73-40/

My goal with this project was to make it affordable and accessible to fabricate at home.

Are you sure? yes | no

J.Guo wrote 02/13/2017 at 11:34

Hi, are you from industry, seeking robust solutions to robust electroadhesive material handling systems?

The following links are some of my published that may help you:

http://ieeexplore.ieee.org/abstract/document/7801074/

http://aip.scitation.org/doi/abs/10.1063/1.4975602

http://iopscience.iop.org/article/10.1088/0022-3727/49/41/415304/meta

Are you sure? yes | no

birdycrazy wrote 02/16/2017 at 18:10

Wow, these are great! Thank you!

Are you sure? yes | no

High Quality Electroadhesives

Description

Details

Files

Electroadhesive Electrode Designs.dft

Components

Project Logs

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Control Box Progress

Control board schematic

silicone vs silicone mixed with corn starch

Modified Process.

First Large Pad

Improved Process

First Circular design

Second Attempt -- Conductive Fabric

First attempt

Build Instructions

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Discussions

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High Quality Electroadhesives

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