Fabrication

Fabricating a workable SCP consists of five major steps. Refer to Bill of Materials for the supplies you'll need to get started.

1. Setting up the circuitry.

2. Twisting and coiling the thread

3. Forming the macro coils

4. Crimping

5. Heat Treating

Step 1: Setup and Circuitry

First of all, we recommend reading all instructions thoroughly before beginning your construction. The SCP is one of the more complex actuators on our website, and the assembly involves many steps that should be performed soon after one another.

The basic idea behind SCP's is to coil the conductive thread on itself until it forms macro coils. To do this, one must ensure that one end of the thread can be twisted with respect to the other. The quality of coiling has a direct effect on the performance of the actuator, and in order for coils to form as evenly as possible, it is ideal to have the thread arranged vertically, with the 50g weight hanging from the bottom.

Use the edge of a wall or table to prevent the weight from rotating (if it does, it would untwist all of your hard work!). A picture of a good setup looks as follows:

Note: Since the motor used did not come with a native way to attach a thread to it, a hole was drilled through the motor shaft and a bent paper clip used to tie the thread. The paper clip is designed as a V-shaped lock mechanism to affix the thread directly onto the axis of rotation. A closeup image of the lock mechanism is below:

Set up the circuitry as follows:

For the Arduino power source, the 3.3V pin is ideal to have a lower motor speed. Lower speeds result in slower but more consistent coil formation.

In thinking about the length of thread to use, abut 80-90 cm of string yielded an 11 cm SCP by the end of coiling, with the primary coiling phase being about 24 cm. Use this to estimate what length of thread is needed for your desired length of SCP.

Step 2: Twisting and Coiling

To verify your setup, use the pushbutton to start the motor. This will allow the motor to turn on automatically when connections are made. Wire as shown in the above diagram, then correct the wire apparatus to ensure its spin is centered on the vertical axis (or as close as possible). One can also adjust the way the motor is held or mounted to ensure its rotation is centered on the vertical axis.

Once centered, wire the switch straight and let the motor coil the string. You will see the weight starting to climb up as the string shortens.

The string will become thicker as it coils. It is important to closely watch the string as it is almost done coiling so one can observe as the coils start to form. One will start to observe coils forming, and as more and more are created it is natural to see some gaps of the coiled string and then a section of coils. If more than 7 coils form at random, or one observes unevenness on how they add onto each other, these are signs of bad coil formation.

Bad coils usually snap during the heat-treating process, so it is recommended to simply start again with a new length of thread. However, it can also be beneficial to heat treat a bad coil to learn the effect coiling can have on the end result.

As one reaches the end where there are only a few gaps, wire the switch across and do the remaining coils manually, to have better control of when the SCP is deemed finished.

Step 3: Forming the Macro coils

At this point, measure the resulting super-coiled thread to determine its midpoint. Hang the 100g weight from the middle of the string, allowing it to turn. Make sure to keep the string taught at all times to prevent uneven coil formation or damage to the thread while coiling.

Step 4: Crimping

Take a jumper wire and remove the black covering as shown in the following pictures:

Next, carefully remove the crimping on tip of the Dupont crimp onto the wire. Do so carefully as this will be used to crimp the actual string on the SCP. This can be done with circuit crimps, such that one pushes one of the edges of the crimp away from the string.

Take the metal piece we just removed from the wire and cut the tip of it. Do not cut the square cavity with two wings overlapping onto another. This will be used to attach the crimp to the wire

Lastly, crimp the piece we modified onto the wire. This will be used to crimp the SCP. Tie a knot at the tip of the SCP, carefully making sure not to let the inside of the coils against one another to prevent damage. Cut the excess off and crimp the SCP at this tip, beneath the knot. Use pliers to clamp down the crimp, but be careful not to accidentally cut the SCP doing so.

Repeat on the other side, and use tape to cover the crimp for safety purposes when finished. The knots allow for easy mounting of electrical jumper wires for powering the actuator.

Step 5: Heat Treating

The circuity used for this section is a MOSFET circuit, utilizing the Arduino board to power the SCP. Note that this is the same circuit that would be used to control the SCP regularly, but here we are allowing the SCP to start doing contractions. The voltage used should be 1.5 V per centimeter of the SCP. For 8-9 centimeters of contracting SCP, 12 V were used. You can modify the duty cycle of analogWrite() commands in the Arduino programming to control the voltage.

For heat treating, hang the 100g weight from one end of the SCP. Connect the SCP to the rest of the set up. In your Arduino code, program to pass current trough the SCP in a cycle of: 1 second on, 2 seconds off. Wait and look for signs of contractions.

Some possible scenarios during heat treating you may see are:

• If you notice that the string does not go all the way back to the resting length, increase the cool down period to prevent the string from heating up too much and breaking.

• If the SCP is contracting too little, increase the on-time in the Arduino current cycle. Do so in increment of 100 of milliseconds to prevent breakage.

• If you notice that the SCP contracts more in some sections that others, this is a sign of irregularities that were formed during the twisting/coiling process. It is likely that your SCP will be less robust and prone to breakage after a few cycles.

Once you notice the SCP doing regular cycles of contraction and relaxation, allow it to run for 15-20 cycles to settle in. Congratulations on crafting your first super-coiled polymer!