Introduction: Real Thumb Drives!
I've been collecting USB drives since they started getting cheap. Every one of them still works, but unfortunately, the cases that hold them never hold up. I carry one on my keychain for a couple of months and the frame breaks off. I've seen Some others put their thumb drives into Altoids tins, but what benifit has that other than the initial Wow! factor...
I decided that I was going to cast my thumb drive into my own thumb! Unfortunately, I'd never done any type of plastics casting. Perhaps this was fortunate because I didn't know it couldn't be done! I just thought about it for a couple of weeks. Finally I decided I was going to try it. Worst that would happen is I might destroy a couple of old, obsolete thumb drives...
After a little time at the local Hobby store and discussions with the cute little salesgirl, I decided on the supplies I needed. A little experimenting and I got the technique down.
Step 1: Supplies
First I needed casting material. I could have used plaster or latex. Plaster would produce a very porous and hard mold and would likely only give me one casting. Liquid latex would give me a nice, permanent mold but would take way too much time and work by building the casting in layers. Besides, the latex would very much irritate my thumb.
What I finally decided on was a product called "instaMOLD" made by Activa Products, Inc. ($10.50US), a water based compound that would firm up in minutes and would be reusable a few times. The problem is, would it work with plastics? What kind of plastic should I use?
Searching the plastic compounds at the hobby store proved fruitless. All of them would harden too hard for what I wanted or were way too expensive. Finally it occurred to me that most of them were some form of epoxy. Why not use regular epoxy? Studying the different epoxies that were available I concluded that the longer setting epoxy would produce the more flexible result, so 12 or 30 minute epoxy would probably be my best choices. Besides, I'd want to color the epoxy before pouring it in the mold and less that 12 minutes would probably be pushing it. This time, I'm working with the 12 Minute Epoxy ($9.95US).
Lastly, I needed color... Flesh is actually kind of easy to mix. Just Pink and Yellow. Having no idea how well they would work I bought 2 bottles of Delta brand Candle & Soap Colors for $13.99US each. Note that because the colors are water-based, they will have an adverse reaction to the epoxy mixture. The epoxy won't firm up quite as hard as it would have, so we must use as little color as will produce the desired result. For my first color experiment, I used 6 drops of pink, 12 drops of yellow and a teaspoon each resin and hardener. The result was still too pink (need more yellow) and was a little too soft (actually eerily close to real skin & muscle!). I've decided that I will be using 6 drops of pink and 18 drops of yellow for the full casting (about 3 tablespoons of epoxy mix). We'll see how well it works by the end of this instructable! :)
Oh yea! We still need the USB drives don't we? Well, I've currently got two without cases and a few more that can easily become case-less. That should be enough to start with...
Finally, we need a few small dixie cups, stirring sticks and measuring spoons. The dixie cups I used were the perfect size to cast my thumb and mix the epoxy. Disposable containers always make a project like this easier. Less cleanup!
Step 2: Make the Mold
In a separate bowl, mix 4 tablespoons water with 4 tablespoons of Mold Compound. Gradually add the compound to the water as you quickly stir. This is to avoid lumps. Fully mix it together, but don't take too long. Pour the compound into a dixie cup. You will need a spoon to get it all. Tap out any bubbles and insert your thumb. You have to act quickly here since the compound sets completely in 2 to 3 minutes. Now... DON'T MOVE YOUR THUMB! Hold still for a couple of minutes. This shouldn't be too difficult.
It's important to decide the amount of compound needed before starting. You can't add more later. Starting with more water will extend the setting time, but will result in a less strong mold. I know the epoxy works well in a 50-50 mix. I might want to make more than one too. So I'll stick with what works.
Sorry, a couple of pictures didn't come out. Namely those showing pouring the compound into the Dixie cup. I think you can figure that out though.
Step 3: Casting Is Set.
After holding your thumb still for a few minutes, carefully pull the edges of the compound away from your skin. It it seperates easily, your ready.
Pull it away all around your thumb and then carefully rock your thumb to release from the compound. It should pull out cleanly.
Step 4: Mark the Epoxy Cup
Now my thumb is just over two tablespoons in area. With the drive, all I need is two tablespoons of epoxy.
Prior to mixing the epoxy, measure a tablespoon of water into a Dixie cup and mark the line of the water. Add another tablespoon of water and mark it again. This will allow us to accurately measure our epoxy and hardener. Empty the cup and dry it out with a paper towel.
Step 5: Prepare the USB Drives
If you haven't already, plug your USB drive into a USB port and mark the connector with a felt tip pen to indicate where it plugs to. We want our thumb to be close to this mark.
Step 6: Mix the Colors
Epoxy must be mixed exactly 50/50. Using 12 Minute Epoxy gives us plenty of time to work.
Pour the epoxy resin into the cup to the first line. Here is where we add the colors. I used 5 drops of pink and 12 drops of yellow. While this didn't produce a perfect skin tone, it looks pretty good.
Stir this into the resin until it's thoroughly blended. Then tap out the bubbles. Trust me, we'll be adding enough bubbles when we mix the epoxy. We want to get as much out now as we can.
Step 7: Add the Hardener.
Now our in the epoxy hardener to the second line. Mix thoroughly. Don't be too concerned with the bubbles. We've got 12 minutes from this point to work with it. Make sure that all the resin on the bottom is mixed with the hardener. Once you've got it mixed well, tap it a number of times on the table to knock out as many bubbles as you can.
Step 8: Pour the Mold!
Now we pour the mixed epoxy into the mold. If you didn't measure your own thumb right, you may not have enough. Remember, it's better to have to much than not enough. The stuff's cheap!
Step 9: Wait! Then Insert Your USB Drive.
Wait until the epoxy starts to cure. Feel the cup. If it's starting to get quite warm, it's ready.
Carefully insert the USB Drive to just before the line and hold it steady until firm. If you've got the patience of Job (Not the Mac guy), this should be fine. Otherwise use a Stationary clip!
This was a last minute solution. Thank goodness my wife knew just where one was! Just attach the clip to just past the felt marker line and let it hold the USB drive still.
Step 10: Wait Again. Then Remove From the Mold.
Wait again. Let it sit at least 15-20 minutes. Longer won't hurt anything.
Check to see if it's ready. The epoxy should be dry. Not even tacky. Pull the mold compound away from the casting. If it opens a gap it should be ready. Use the very same technique of removing the drive as you did your own thumb. If you have no plans to reuse the casting, don't worry about it. Just yank! :)
Now you may want to carefully clean any compound still on the drive. Use a soft toothbrush and water. Don't scrub too hard! It's still not fully cured!
I discovered that epoxy is quite cruel to this molding compound. It's probably because of all the water in the compound. It you compare my first cast to the second, you can see that there are many more flaws in the second cast. These should be easy enough to clean off once the epoxy is fully cured.
Since we did add a water based material into the epoxy, it's going to take a bit longer to fully cure. Let it set at least 2 days before you clean the final product. Use an Exacto Knife, Razer Blades, Diagonal Cutters, what have you to trim any warts, threads, cancerous growths. A Dremel works nicely for final touch-ups.
