How to Make ECG Pads & Conductive Gel

234,285

253

44

Introduction: How to Make ECG Pads & Conductive Gel

E4C’s mission is to improve the lives of underserved communities by better preparing the gl...

It's easy to find a bedside monitor in a hospital in the developing world, but it's harder to find one in use. Western hospitals replace their electrocardiogram machines every few years and donate their used equipment. The second-hand machines work fine, with one glaring exception: They don't come with pads. The pads are disposable and often in short supply in impoverished regions.

The solution is to make ECG pads (link to E4C's how-to) from easy-to-find materials such as snap buttons and bottle caps. Robert Malkin and students at Duke University invented the trick, and our friends at Engineering World Health travel the world and demonstrate that making ECG pads and conductive gel is fun for the whole family. The materials required are bottle caps (read: beer and soft drinks) and the conductive gel is a gooey mess that kids enjoy. Incidentally, the gel is two ingredients and some changed proportions shy of homemade Playdough (another Instructable), which may also also go over well in the pediatric ward. 

Electrocardiogram (ECG, sometimes EKG for the German name) machines measure the heart rate and rhythm and indirectly assess the blood flow to the heart. They monitor electrical activity through the pads stuck to the patients' skin.

Here's how to make the the pads, and see the last step for directions for use.

Step 1: Materials

Pad materials:

1. Bottle caps
2. Nickel-plated brass sewing snap buttons, size 3
3. Flathead screwdriver
4. Utility knife (boxcutter, X-Acto or another sharp-bladed, small knife)
5. Pot, water and a stove
6. Optional: tweezers/forceps

Step 2: Boil and Peel

See that plastic lining on the inside of the cap? That's what you want. The lining is 36mm low-density polyethylene plastic. It will provide mechanical support for the electrode, which is the snap button, and help ensure that it has continuous contact with the patient's skin.

1. To get it, first boil the bottle caps in water for 30 minutes.

2. Then peel off the lining. Start the peel by prying an edge off with the screwdriver, then carefully pull the rest out with your fingers or with tweezers or forceps.

Tips:
* It may become harder to separate as the cap cools. In that case, try heating the cap in the water again for a few seconds then remove it and finish peeling.
* It's okay to use plastic liners that tore a little bit when you separated them, as long as they didn't tear in the middle.

Step 3: Assemble the Pad

1. Cut an “X” in the center of the lining to make a hole, no larger than 1cm on each line.

2. Then insert a size-3 nickel-plated brass sewing snap into it.

3. Trim the tiny corners of plastic from the edge of the button nub to help expose it more.

Congratulations, you made an ECG pad. They’re washable and reusable up to 100 times or so. See the last step for directions for use.

Step 4: Conductive Gel Materials

Now, to make the conductive gel.

Conductive gel materials:

1. Water, 1 cup
2. Salt, 2 tablespoons
3. Flour, 1 cup
4. Bleach, just a drop

Step 5: Gel Recipe

1. Mix the water and salt in the glass bottle.

2. Slowly pour in the flour. It will become gelatinous. Mix it until it the consistency is even throughout.

3. Add a drop of bleach to sterilize the gel.

Note: Just use regular white flour, not fancy whole grain flour like we used in this demo (it was all we had).

Step 6: How to Use the Pads

Directions for use:

1. Cleanse and, if necessary, shave the patient's skin where the pads will attach. Use antiseptic wipes.

2. Spread the conductive gel (which you'll make) on the spot where you plan to attach the pad, then lay the pad over it with the snap button nub facing up.

3. Tape the pad to the skin with medical tape (micropore), leaving the button nub exposed.

4. Fasten the ECG leads to the nub.

5. Then, after you've set everything up, tape it all in place. Reapply the conductive gel every 24 hours or as needed.

Cleaning: The pads are washable and reusable up to 100 times. To clean them, remove the buttons from the plastic and wipe everything with alcohol pads.

Warning: Check for allergies and to see if patient's skin reacts badly to nickel, flour or high levels of salt.

[The image is a composite made from photos by Engineering World Health]

Share

    Recommendations

    • Tiny Home Contest

      Tiny Home Contest
    • Creative Misuse Contest

      Creative Misuse Contest
    • Metalworking Contest

      Metalworking Contest

    44 Discussions

    Any substitution for flour in the conductive gel? I assume it is wheat flour because it is simply stated as flour. I am allergic to both ingestion and skin contact of gluten. Any work-arounds that would be just as conductive?

    5 replies

    If you're just doing a quick ECG, just use what early researchers used: cloth soaked in salt water. Or paper towels for convenience. As long as the towel is in contact with the electrode and your skin, conductivity is achieved.

    You can use virtually any gel since it's just a substrate to hold the salt, which is the crucial ingredient for conductivity. Some people use aloe vera gel, which unfortunately, is somewhat expensive. A more readily available solution might be corn starch (aka corn flour), which actually has twice the thickening power of wheat flour. Depending on your application, you may need to wet the electrodes with water every few hours. If you're doing a quick ECG, it's a non-issue, but if you're doing continuous monitoring, you'll want to either wet the gel every few hours (or re-apply), or use a gel that doesn't dry out as easily. I am currently experimenting with an oil-based mixture, i.e adding in some mineral oil (or any cooking oil, including lard) or petroleum jelly to prevent evaporation. I need to see if conductivity is lessened by the oil.

    here is a link to gf playdough
    http://onecreativemommy.com/gluten-free-play-dough-recipe-review-and-tips/?m

    You could try a gluten-free flour like rice, almond, taro or the others. Good luck!

    Xanthan Gum would be a better option (cheap to buy online). Just a tiny amount would be enough to create a gel and would be conductive with a little salt.

    Yes, that would be fine. You can use virtually any gel since it's just a substrate to hold the salt, which is the crucial ingredient. Depending on your application, you may need to wet the electrodes with water every few hours. If you're doing a quick ECG, it's a non-issue, but if you're doing continuous monitoring, you'll want to either wet the gel every few hours (or re-apply), or use a gel that doesn't dry out as easily. I am currently experimenting with an oil-based mixture, i.e adding in some mineral oil (or any cooking oil, including lard) or petroleum jelly to prevent evaporation. I need to see if conductivity is lessened by the oil.

    HI amigo me podrias dar tu correo, me gusto el proyecto y me gustaria hacerte varias preguntas, soy estudiante universitario.

    Awesome

    God Bless you , man!
    It was Amazing. Good Luck

    "snap buttons, size 3", what would that mean :s

    This is great, and for a good cause as well! Would this also work for EMG (muscle) sensing?

    I have never had reason to comment on this site, although I enjoy many of the instructables. This one tops them all. This could truly be life saving. Thank you, from the rest of the world.

    2 replies

    Thank you, so good of you to say. We'll pass your kind words on to our friends at Engineering World Health, too, to spread the love.

    if u used thermal electric generators. instead of battery's they, the instrument could be powered by the user instead of a external power source, as well. if u go to http://tegpower.com/pro4.htm if the full link doesnt or refuses tto work look at the base link then products page