In order to create an interesting and interactive diorama we wanted to find a creature which had a variety of interesting behaviors we could recreate. Bioluminescent jellyfish seemed like the obvious solution! You can read about lots of interesting bioluminescent creatures and their behaviors here.
To create the glow found in bioluminescent jellyfish we used black light tracer known as "T-900 Series Blue Aqueous Tracer" available here. To activate the tracer you need uv light, for this we used UV LEDs from DigiKey.
The other major part of this project was movement of the creature. This was accomplished with Flexinol brand muscle wire.
EcoFlex Soft Silicone
T-900 Series Blue Aqueous Tracer
Step 1: Mixing EcoFlex Silicone Rubber
To create an item with this, the two parts are mixed in equal portions. Before measuring out the two portions, make sure to thoroughly mix each part. The silicone separates if not used for a while, and thoroughly mixing each part ensures best results. Make sure to use two separate stir sticks for this, otherwise the individual parts will be contaminated.
There are a variety of ways to measure the individual parts. For this project, a pair of large syringes were used. Small measuring cups also work well, but are better suited for mixing larger quantities.
The two parts are poured together into a mixing cup, and then thoroughly mixed using a stir stick. Make sure to stir such that the bottom, sides and corners of the mixing container are agitated, otherwise there will be some unmixed part of the silicone. This may affect the cure, and could cause part of the final product to simply be a sticky liquid, rather than a smooth form. Two minutes of mixing is usually sufficient.
Once mixed, let the silicone sit for a few minutes. Bubbles will form after mixing, though this isn't immediately obvious. Letting the silicone sit allows these bubbles to form and rise to the surface. If this part is ignored, then any product placed in a close form will have bubbles embedded in it. (The best option is to place the mixed silicone in a vacuum chamber, but this is probably outside most people's collection of tools).
Step 2: Creating Jellyfish Bell - Part I
For this step, we used the following items:
1. Ecoflex Supersoft 00-30 silicone
2. Two bowls of slightly different diameter
3. Two 35 ml syringes
4. Disposable stir sticks and mixing cups
Prior to mixing and pouring the silicone, determine the amount needed. To do this, pour some water in the larger bowl, and press the smaller bowl inside, allowing any excess water to drain out. Once this step is finished, suck the remaining water into one of the syringes, noting how much volume there is. With our bowls, this needed to be done twice: the volume ended up being ~45 ml. Erring on the side of having too much, we mixed 50 ml of silicone.
Step 3: Working With SMA
Step 4: The First Movement
Step 5: Making It Blink and Glow
Step 6: Making and Attaching Tentacles
Pour enough silicone to make a sheet about 1/16" thick. Once cured, peel the sheet from the form. Using an X-Acto knife, slice individual tentacles roughly 1/8" wide. Taper the cut so that it is a point at the tip of the tentacle.
Tentacles will be attached to the stiffening wire in the bell using 30 gauge wire. Thread a short piece of wire through the top of the top of each tentacle. Once finished, thread the wire around the ring, twist to secure and clip any excess. When finished, the jellyfish should look complete.
Step 7: User Interface
While a simple button could be employed to trigger the burglar alarm, this didn't convey the reason why this jellyfish has this behavior. Rather, we wanted the viewer to pretend to be the attacker. To do this, we opted to trigger the burglar alarm with a accelerometer embedded in a plush jellyfish. The viewer picks up the plush jellyfish, and can gently shake it, as if he or she was attacking it. In order to sense a shake, the 3 axes of the accelerometer are looked at individually for sudden changes in orientation. Our silicone jellyfish then responds appropriately by flashing the burglar alarm. This effectively converts interaction from passive observation (after pushing a button) to an active interaction. We feel this approach grabs the viewer's attention, and is a particularly good way to get small children interested in the piece.
The accelerometer can be attached to the arduino using simple wires. If available, a long ribbon cable works and looks much better.
A However, any plush jellyfish can be used as an input device. Simply cut open the seam, and push the accelerometer in. The L shape of the accelerometer and connector effectively wedges the device into the stuffing. The seam could be sewed shut; we opted to leave it open.