My friend and I are high school seniors who are currently interning with a ninth grade physics teacher at another school as part of our last senior project before we're off to college. These past few weeks we have been prototyping a project that our mentor wants to assign to his future class of freshmen, and so we have built a small, synthetic muscle. We experimented with different types and quantities of materials, but first we'll start off with instructing how to build a simple synthetic muscle.
Here are the supplies we used that you will need in order to create the muscle:
- 15-20 test fishing line
- Heat gun
- Strain,Spring, or Force Gauge
- 2 tacks, nails, or screws
- A 100 gram weight
- Power Drill
- Two paperclips
It should be noted that while this project can be completed individually, you may need a second person to assist you with some of the steps. Also, we used a force gauge and a classroom wall, but you can similarly use a wood board and a strain or spring if you don't have either of the items we used.
Step 1: Add Tacks/nails/screws
Insert one of the above tools onto a wall or a board (we used one of the walls of our engineering classroom). Make sure is not completely inserted to the wall, but well enough to remain sturdy and in place if you are using a nail or a screw.
Step 2: Set-up the Force Gauge
Place the force gauge on the screw with the hook pointing downwards.
Step 3: Place Bottom Tack/nail/screw
Have the second item ready when synthetic muscle is built. This one can be placed about a foot away from the top nail and will be connected to paperclip attached to the bottom end of the muscle later on.
Step 4: Cut Some Fishing Line
Measure and cut 14 inches of fishing line. The intended goal is to have at least a foot of fishing line because you will need to tie both ends of the fishing line to the paper clips, and that will require a bit more fishing line. The muscle will be approximately 20% of the original length because it will shrink as it coils.
Step 5: Attach Line to Paper Clips
Tie each end of the fishing line to a paper clip with about one inch of tail on each side.
Step 6: Insert Paperclip Into the Drill Chuck
Attach one paper clip into the drill chuck. Make sure you tighten the drill chuck well in order to prevent the paper clip from detaching due to a loose grip.
Step 7: Add Weight to the Bottom End of Muscle
Attach a 100 gram weight to the paper clip that is at the bottom end of the muscle. The weight should be heavy enough to slightly stretch the fishing line.
Note: Anything that weighs about 100 grams is good. You can attach it to the paper clip by opening the clip and then inserting it through a loop in the object, or you can connect the weight to the paper clip via a zip-tie.
Step 8: Prepare to Begin Coiling
Once you have completed attaching the line to the chuck and the weight, hold the drill as straightly as possible with the chuck facing downwards.
At this point, you will need a second person to assist you by having him or her place a pencil or his/her finger inside the paperclip pushing down. This will prevent the fishing line from spinning completely, which would in turn not let the fishing line coil.
Step 9: Start the Power Drill
This part may take some trial and error. You may want to start the drill at half speed, and eventually speed it up. Once the line begins coiling, return to a slightly slower speed.
As the line becomes closer to coiling completely, slow the speed of the drill and continue until it’s fully coiled. Be careful not to continue and mess up the structure of the line or to finish too early, as either mistake can result in a faulty muscle.
Step 10: Carefully Remove Paper Clip From Drill Chuck
As you being removing the paper clip from the chuck, be very careful and have your partner hold on to both paper clips tightly while you loosen the grip of the chuck. This will prevent the line from unwinding.
Step 11: Place Muscle on Force Gauge and Bottom Screw
Place one of the paper clips on the hook of the force gauge. As you place it, you still need to hold on to the bottom end of the paper clip, as it will still be prone to uncoiling if let loose.
Once it is placed on the force gauge, hook the bottom end to the bottom screw.
Step 12: Set-up Force Gauge for Measurements
Pull down from the bottom paper clip until the force gauge is at 200 grams or 2 newtons. The fishing line should be very slightly stretched but should still retain the coils. Adjust the distance between your tacks/nails/screws if you have to.
Step 13: Test Your Muscle
Heat up the fishing line with the heat gun for a few seconds. Although it is supposed to contract when heat is applied to it, you will see it retract when you apply the heat gun for the first time, and that's normal; in fact, its supposed to happen. After a few tries, you will see the muscle contracting when it is exposed to the heat and retract to its original length once it cools off.
Note: Don't apply the heat gun for any longer than 5-10 seconds or else you will melt the muscle.
Step 14: Your Synthetic Muscle Is Complete!
The fishing line should be set and retain its form, you should be able to remove synthetic muscle from the force gauge without it uncoiling. At this point, your muscle is functional and you can now add a small weight to it and observe as it pulls it up when you heat it up.