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Laminated Aluminum Foil for Flexible Circuits and Much More

Picture of Laminated Aluminum Foil for Flexible Circuits and Much More
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LAF stands for Laminated Aluminum Foil - in this case I will be using household aluminum foil that is laminated with regular packing tape. It is strong, durable, and tear-resistant. It is flexible, conductive, easily cut, shaped, folded or printed on. It is cheap and easily made. It can be used for countless purposes: flexible circuits with buttons, slim durable wallets, keychains, and even origami.

In this Instructable I will show how to make LAF, and how to use it for many different purposes, especially for making flexible electronics. The example I will be giving for LAF's usefulness in flexible electronics is how to make a fully functioning flexible membrane computer numpad.

I discovered LAF's usefulness almost by accident. I was searching for a material to make a wallet out of and I stumbled upon LAF. Later I began to explore it's possibilities and saw that it had great potential in a many fields and tons of possible applications. I hope that you will also find it as useful as I have, especially because it extremely cheap and easy to make.
 
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Step 1: Materials and Tools

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For this project you will need very few materials that are cheaply and easily obtained:

Aluminum foil

Clear packing tape

Credit card or other plastic card

Smooth and clean work surface

Additional materials to make a flexible numpad:

X-Acto Knife/Craft Knife

Old keyboard (it has to still work)

Srewdriver

Step 2: Smoothing the Foil

Picture of Smoothing the Foil
Cut your foil slightly larger than the size of LAF you plan on making.
Lay it out on a smooth, clean surface, and using a credit card carefully smooth the foil.
You are going to want to stroke the foil with the card at an angle, going in one direction and then the other multiple times on one side, and then flipping it over and repeating the process on the other side in order to minimize curling. Try to make the foil as smooth as possible so that bubbles will not form later. Any dirt on the table will cause small bumps or creases in the foil which will also cause bubbles, or the foil might even tear, so make sure that your table is clean.


Step 3: Applying the Tape

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Cut a piece of tape a little longer than you need, as the spot where you first put down the tape will probably have bubbles.
Now line up the tape carefully and very carefully stick one end of it to the foil. How you place down the foil at first will decide if the tape goes down smoothly or wrinkles and creates bubbles. Hold the other end of tape in one hand and the credit card in the other hand. Make sure that the foil is held in place. You can place a heavy object on it, but i prefer to use my elbow as shown in the pictures.

Now, holding the credit card at an angle press down firmly on the tape and drag the card forward. Keep the tape slightly tensioned and make sure that the entire edge of the card is pressing down evenly on the tape. With practice you should be able to do this with barely any bubbles forming at all. You can now go on to apply as many strips as you need, I would recommend leaving a slight overlap between every two strips. Make sure that the pieces are aligned before sticking on the second piece because it is almost impossible to remove the tape without ruining the aluminum foil.

Also, depending on what you are going to be using the LAF for, you might want to put tape on the other side too, which will both greatly strengthen the LAF and insulate it electrically.

As a side note, if you are planning on applying a screen protector to a phone this is a great way to practice aligning it properly and avoiding bubbles.

Step 4: Making a Wallet

Picture of Making a Wallet
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This was actually the original inspiration for creating LAF: I wanted to make myself a wallet, and of course my first choice of material was duct tape. I tried several different designs, but in the end all of them were too thick and too stiff. This led me to look for a better material. I had seen Tyvek wallets before, but I didn't have any at the time; the only thing I had was packing tape. I couldn't laminate it directly to itself because bubbles always formed and dirt was always trapped inside, so I tried to find a thin, flexible material to laminate between the layers of tape. I thought of aluminum foil, super thin, lightweight, and dirt cheap, not to mention it looks awesome! Plus it has the added quality of blocking RFID (I do not know how well it works, so do not count on it protecting sensitive information. I only know that I cannot use my RFID bus pass while it is in this wallet.)

Now that I had found my material, I went ahead and perfected the process of creating it, followed by actually making the wallet. The result was a durable, waterproof, tear-resistant, and cool looking wallet. The wallet shown here is a bit over six months old and holding up fairly well, even though it was my first attempt with this material and was not very well made. I won't explain how to make a whole wallet here, as there are countless designs and Instructables on how to make them on this site which can be easily adapted to be made out of LAF.

I will however give a few tips on working with LAF:

1) Try not to crease the LAF where you do not want a crease to show: it will stay there. (This is only an aesthetic point, creases will have no effect on the finished product.)

2) With time the edges of tape will probably start peeling (not from the aluminum foil, but from the tape itself in places where extra pockets were attached), so try to wrap the LAF around a corner and then attach it, not directly on to a flat surface. (See the pictures for a better explanation.)

3) When attaching extra pockets make sure that you align the tape well before setting it down. Although it is not too difficult to get it off it will weaken the adhesive and most likely wrinkle the tape.

4) Before you place a piece of tape on any part of the wallet, make sure that it is clean because you would not like to have been so careful in making sure there are no bubbles in the LAF only to see some form as you stick on an extra pocket.

Step 5: Using LAF for Flexible Circuits

Picture of Using LAF for Flexible Circuits
LAF gives us an excellent substrate for thin, flexible circuits. They can be used in all sorts of applications, from embedding in clothing to creating a unique business card to making a membrane input device. Aluminum foil is a relatively good conductor, so it can be used as is with no extra modifications. While it is very difficult to solder to (and it will ruin the tape's adhesive), it can be glued using conductive glue, which can open it to the endless possibilities of microcontrollers, leds, and any other component that you would care to attach.

All that needs to be done in order to create a circuit is to peel off certain parts of aluminum foil and leave the circuit behind. Two circuits can be sandwiched around a third, non-conductive layer with holes cut in it in order to create a sort of membrane switch. I will be using this technique in order to create a working membrane keypad. Essentially, a full keyboard could be created using this method, but I did not have the time to do so.

The main advantages of using LAF for flexible electronics are its very low price, it is easily available to everyone, and it does not require any vacuum chambers, dangerous chemicals, or any other specialized equipment. It is also possible to make a waterproof circuit in this way, although I don't know how such a circuit could be used. Kapton tape can also be used for its heat resistant properties, although it is much more expensive. Do not use LAF made with regular packing tape in any high-temperature applications: it will shrink and peel and the adhesive will be ruined.

Step 6: Making a Flexible Numpad

Taking apart the keyboard

Using a screwdriver remove all the screws on the back of the keyboard. Some of the screws may be hidden under stickers so look carefully. Inside the keyboard you will find three layers of flexible plastic with circuits on them, which you won't be needing. You will also find a silicone layer with domes on it, which you will not be needing either. The only thing you need from the keyboard is the control processor, and the usb cable that is attached to it.

Mapping the Pin Layout

In order to map the pin layout of your keyboard it is not necessary to trace the wires on the circuit, rather it is much easier to simply short out every pair of pins directly on the controller and to see what the outcome is. First, check which pins go to which layer on your keyboard and number them from left to right(see the second picture), then starting from pin one on the top layer and pin one on the bottom layer short every pair of pins with a wire while it is connected to your computer by usb. Make sure to mark all of this down in a chart. Using this information, you can mark which keys will have which pin connected to them, you can see my example in the fourth picture.

Designing the circuit

Now, try to find the most efficient way to connect each key to its pin, while remembering that you must leave a gap between "wires" and the wires themselves must be wider than about half a millimeter.

Cutting out the circuit

In order to make the circuit, we must remove some of the aluminum foil in between the wires. To achieve this we must first cut through the aluminum foil around the wires and gaps. The trickiest part of the whole process is pressing down just the right amount on the knife: enough that it will cut all the way through the aluminum foil (cutting all the way through is important because it will make peeling off the foil MUCH easier later on) but not enough to cut through tape as well (don't worry if this happens a few times at first, mostly it won't matter too much. Just make sure that your circuit doesn't fall apart.)

Marking the Keys

Make a keycap design on your computer, print it out onto a piece of LAF, and tape it onto the top of the numpad. You can see my design created in Word here, as well as the finished numpad that actually works.

Step 7: Make a Photography Background

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LAF can easily used as an elegant photography background. All that it requires is piece of one sided LAF whatever size you need.
I personally like photographs taken on a background of aluminum foil, and backing it with tape is a perfect way of making it more durable and getting rid of those annoying wrinkles in your shot.

In the picture is a work in progress dime ring on a background of LAF, with shiny side up.

Step 8: Printing on LAF

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It is possible to print on LAF with only an ordinary inkjet printer and a heat source such as a gas stove or a lighter. In the pictures you can see the cover for my flexible numpad, and also a trial of printing a color picture for use on a keychain.

In order to print on LAF, start by printing your design on an ordinary piece of paper. This is to find its exact location on the paper when it is printed. Now tape a piece of smooth aluminum foil to the paper dull side up exactly over your printed design (leaving generous margins in all directions.) Clean your aluminum foil with a soft cloth to get rid of any fingerprints, because they will interfere with ink. Now feed the paper into the printer in the same orientation as the first time and print again.

Being careful not to touch the wet ink, cut the foil of of the paper. Now hold it over a heat source for several seconds so that the ink will bake on. After a few seconds it will start smoking. Don't worry, this should stop after about a second. After it stops smoking, wait another second or two, and then take it out of the flame. The ink will now be much harder to smudge, but it is still not ready. In order to completely protect it from smudging, we have to cover it in a layer of tape. Do this as you normally would, just try not to smudge the ink.

Your printed LAF is now ready. If you plan on using it for a keychain, laminate the other side as well. If the thickness matters, you can leave it as it is. You can print on LAF in full color or in black and white, though as you can see designs which require a lot of ink tend to bleed and smudge. 

Step 9: Making a Dry Erase Board

Picture of Making a Dry Erase Board
Due to the nonporous nature of aluminum foil, it works very well as a dry erase board. We can easily make a portable, flexible dry erase board by making a piece of one sided LAF, cutting it to A4 size (or letter paper size...), hole[punching it, and then putting it in a binder.
I keep one in the front of my math binder, it is very useful for sketches and quick calculations. Make sure that you don't write with a pen or pencil on a piece of paper that is on top of the LAF, as it will leave marks.

Step 10: More Uses

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Business Cards
Using LAF, you can make cheap, unique, and durable business cards.

Keychains
By printing on LAF you can make personalized keychains with any shape and color.

Origami
LAF can be used to make simple paper models. It cannot be used for more complicated folds because it wrinkles and becomes too thick, however it holds folds quite well: crease every fold by smoothing it down with a credit card.

Emergency situations
LAF could be used to make an emergency blanket. It would be much more durable and much quieter than an ordinary emergency blanket, albeit thicker and heavier. It could also double as a reflector, or even be used to carry water.
I would really like to use this to make alternative input devices for computers and synthesizers. It looks really cool.

But I'm wondering. How are the circuits not bridged when a button is not being pressed? Maybe it would help if you show how the layers of LAF are stacked on top of each other.