Unique wearable technologies are rapidly gaining significant interest due to the amazing achievements in advanced materials and mobile technology. Such technologies are going to provide us with a plethora of unique user experiences we've only dreamed of. Innovative products such as watches powered by solar energy, sunglasses that change color and tint, and fabrics that generate electrical energy are just the beginning of an exciting time ahead for all of us. The integration of these new materials and complex electronic devices such as circuit boards and light emitting diodes (LED's) into wearable technology is starting to provide unique user experiences when implemented into different user interfaces from everyday life use to mobile health diagnostics. However, in most situations and cases, minimizing the exposure to heat and moisture is crucial to minimizing corrosion and failure of components. Constant exposure to moisture and water (from sweat, swimming, washing clothes, etc) in wearable textiles is one of the leading causes to electronic failure in these wearable devices.
There's a crazy array of the manufacturing approaches for reducing the exposure of wearable devices to moisture and water, but we at Beyond 5 Industries wanted to share an approach with the Instructables community that the everyday hackers, tinkers, and craft hobbists alike could reasonably start using today! In this tutorial, we will show you one solution to waterproofing your electronic components by encapsulating them with a liquid silicone solution that when mixed with a curing agent can provide longer term water protection for your electronic components allowing you enhanced possiblities for designing wearables exposed to lots of moisture.
Step 1: Materials Checklist
Below are a list of supplies that are the recommended for this instructable.
Of course certain items can be completely eliminated or substituted with others.
In order to for us to focus on teaching you the encapsulation technique and to easily demonstrate the waterproofing performance, we be creating a simple electronic device soldering a simple wearable component (LilyPad LED) and attaching it to a power source with alligator clips. Once you've gotten down the encapsulation technique, go buck wild with testing different or similar simple or complex electronic devices and their performance in different water-based environments!
Here's what you're going to need:
- Corning Sylgard 184 Kit (PDMS) . This can be purchased online from a variety of locations including:
Galco Industrial Electronics
or purchased from eBay (search "Sylgard 184").
Specifications on the Sylgard 184 can be found here . Other varieties of PDMS are available.
Sylgard 184 is chosen for its transparency, waterproofing and room temperature curing properties.
- Plastic disposable containers as molds (2 are used, one to mix in and the other as the mold).
For our instructable we used small petri dishes.
- Disposable spoons (2 spoons used, one for the elastomer base and the other for the curing agent).
The spoons are used to as a measuring (scoop out the sylgard 184) and mixing tool.
- Standard solder (rosin core 60/40 lead/tin)
- 30W soldering iron (with stand)
- Desoldering pump (for any mistakes)
- The third helping hand, 3-arm holder (used as a third hand to help hold items into place)
- 6" red and black stranded wires
- Red and black insulated alligator clips
- Wire cutter and stripper (separate or combined)
- Diagonal cutters and needle nose pliers
- Batteries (used here 2 AA batteries connected in series to power LEDs)
- Battery holder with wires or snap connectors (used to house the batteries; power supply to LED)
- LEDs (used here is Lilypad LED). The specific LED's used can be found here .
- Water/clear cup or any container (used to test waterproofing of the LED immersed under water)
Step 2: Preparing LED Electronics
Strip the red wire about 1/2" on both sides. Repeat for black wire.
Solder the black wire to the negative terminal (marked "-") on the LED. Use the third hand tool to hold the LED on the right (or the left depending on your dominant hand). Use the opposite clip to hold the wire straight and steady so it doesn't move when you solder it
Loop the stripped end through the hole and solder it.
Turn over negative terminal and trim the excess strands of copper with diagonal cutters
Repeat the soldering process for red wire connected to the positive terminal (marked "+")
Again, after soldering the positive terminal, trim excess strands off the bottom.
Attach the clips. Match the red clip to the red wire and black clip to black wire.
Note: Make sure you put the insulating jacket on BEFORE soldering the clip.
If your connector has tabs to crimp down, crimp them down to secure wire before soldering. Hold the clip in the third hand on one side and hold the wire on the opposite clip of the third helping hand.
Repeat soldering for the positive clip
Attach LED to a 3V power supply. Your battery holder will probably look different. Take batteries and place them into the battery holder. Test LED by attaching the alligator clips to the battery holder. Attach red alligator clip to the positive terminal of the battery and attach black alligator clip to the negative terminal end of the battery.
Note: Be sure to check the terminals are properly setup to their respective terminals otherwise damage to LED could occur.
Be sure the LED lights up before proceeding to the next steps.
Step 3: Detach LED From Power Supply
Detach the alligator clips from the battery holder prior to proceeding to the next step.
Step 4: Preparing the PDMS Waterproofing Material
Depending on what is needing to be encapsulated, the amount of the Sylgard 184 solution can be varied.
Before you mix the two components, you should have an idea of what application and how large the device will be for your final device.
For instance, if you are interested in just encapsulating/sealing a fairly static device from water, such as an electronic coaster; a ratio of 10 parts (silicone elastomer base) to 1 part (curing agent) can be used. If the device is expected to be put through stress (squishing, pulling), then a lower ratio can be used (i.e. 5 parts silicone base to 1 part curing agent) to obtain a more rigid/tougher encapsulation.
Note: Determination of the right ratios for your particular application may require some testing/experimentation. For instance we have prepare in house small scale reference samples ranging from 3:1 all the way to 20:1 as guide for various applications .
You can prepare these small samples by mixing and curing them in a small disposable container like a soda cap.
Knowing what ratio you are interested in using (for our example we used 10 parts silicone-base to 1 part curing agent), dispense the silicone base into one of the disposable mold containers by using a disposable spoon. Scoop out the amount need using the spoon as a measuring tool. In our case, we scooped out 10 spoonful of the silicone base and put it in the container. The silicone base is quite viscous (similar to honey) so make sure the amount place in the mold container is as accurate as possible. Then scoop out with the unused spoon, 1 spoonful of the curing agent. Place this in the same mold container as the silicone base.
Note: Two separate spoons to dispense the Sylgard 184 are used since mixing the two solutions will cause the mixture to react and harden. Never mix the elastomer base with the curing agent unless you want the material to harden. Once the two solution are mixed, the reaction cannot be reversed.
Next, thoroughly mix the two components carefully using the spoon to minimize air bubbles, which will likely form during mixing. If air bubbles form, you can remove the bubbles under vacuum in a special vacuum container such as the one seen in this other Instructable for a Simple DIY Vacuum Chamber and Pump .
Next, take the LED device and with the help of the third helping hand, suspend the device inside of the mold container.
Note: Does not require the third helping hand, but any other way to suspend it would work as well.
Pour the mixture into the mold container making sure that it fully covers the area that you want to encapsulate/protect from water. For our case, we utilized a petri dish container and suspended the device and poured in the mixed PDMS solution to fully cover the area we were interested in protecting from water.
The mold is typically dried within two days (48 hrs) at room temperature conditions. This process can be speed up using a specialized heating vacuum oven as well if you have access to one (overnight or like 6-10 hours).
Note: Be sure not to touch or move the mold during the drying period.
Step 5: Removing Device From Mold Container
After 48 hrs, depending on the mold container used, you want to be able to distort the mold container or insert a thin piece of plastic/metal so that you can get in between the molded device the mold container. (This is similar to removing jello from a container).
Step 6: Trimming the PDMS Device
At this point you can trim the unwanted PDMS from the device using a utility knife/exacto knife to any shape you want. Make sure not to trim too much as to expose the device. Inspect to make sure no part of the device you want encapsulated/waterproofed is exposed. If it is repeat steps 4 and 5 to remold the device.
Step 7: Test Quality of Encapsulation and Waterproofing
Take encapsulated device and attach the alligator clips to the battery holder/power supply to make sure the LED lights up. Again making sure that the proper alligator wire terminal polarities are attached to the battery. Then take a glass filled with water and place device into the container of water. Now you have a water proof electronic device! Variations can be made to encapsulate and waterproof other electronic devices. Check out the simple performance test we ran in the next step.
Step 8: Testing LEDs With and Without Waterproofing
For a performance test, we took both an encapsulated/waterproofed LED device and a unencapsulated/not waterproofed LED device and placed them both in water to test how long they would survive over several days. We used potable water from the Seattle municipal water supply obtained from our kitchen sink.
When placed in water, both the encapsulated and unencapsulated lilypad LED's survive in the water. After exposure in water for 13 hours, both LED's still continue to work however, a noticeable level of corrosion on the electrode of the unencapsulated LED device is seen, while the waterproofed device shows no damage.
After 80 hours exposure of the devices in the water under operation, the clarity of the water has changed from clear to a light blue color. The unencapsulated device completely failed under operation. Upon closer inspection of the two LED's, the unprotected LED shows significant degradation and corrosion to the electrodes leading to the failure of the LED device. However, when the PDMS is removed from the protected LED, it can be seen that there is little to no damage to electrodes. The PDMS protected LED still shows full functionality after the same exposure to water.
Thanks everybody! We hope you enjoyed the tutorial and have got some inspiration and ideas flowing!
Feel free to shoot us any questions, comments, or feedback here on Instructables. Also, feel free to shoot us an email at firstname.lastname@example.org or check us out at Beyond 5 Industries.