--"wall left, open right", and
--"wall right, open left"
which in turn controls the cockroaches movement (it's not going to move left if it feels a 'wall' on the left.
I recently realized that probably a better way of controlling the cockroaches movements is by just putting one LED on each side of its head, since they run away from light. Just turn both on to make it go forward, and one on to make it turn left or right. LEDs would require a lot less power and mechanical complexity. I'm going to try it out.
Cockroach backpack paradigm being tested, cockroach responded as desired to the backpack commands
Cockroach backpack being tested, nitinol constriction moves antenna flap.
Step 1: Making the Backpack
When I put together the backpack, it was my first electronic project ever, so it ended up being excessively heavy. I used a camera flash battery to supply the pulse of current needed to contract the nitinol, but you would want to use a capacitor and a smaller battery to reduce weight. I used periplaneta americana which is strong and moves a lot. I also tried giant madagascar hissing cockroaches but they just sleep all the time and are very slow. You should buy these from animal supply places, otherwise you'll have to wait a long time for the roaches in your kitchen to get big enough (about 1.5 inches).
I used really crappy materials that I had on hand to make the backpack, it could be built a lot better with different materials. Apparently nitinol can be soldered, which I didn't know at the time, so I crimped the nitinol at its ends (pretty friggen annoying).
If you reduce the weight enough you could make it remote controlled (instead of controlled by preprogrammed commands from the basic stamp). See the remote control diagram. You could also add sensors and make the basic stamp use the sensors to control the roach.
Step 2: Making the Backpack Circuit
I made my backpack like shown below, but you should use smaller batteries anc capacitors to power the contraction of the nitinol.
You can make the backpack remote controlled (see diagram with RF receiver).
You can make the basic stamp issue preprogrammed commands (see diagram without RF receiver)
Or you can make the basic stamp use sensors to make autonomous decisions (no diagram for that).
To reduce weight, I used cardboard and taped the electronic components to it. I wire wrapped the pins of the electronics to each other.
Step 3: Attaching the Backpack
you'll need to knock out the cockroach. I had a CO2 gas outlet at school, so I hooked a hose up to it and stuck the hose into the cockroaches box. When you hear it stop running around, it's asleep.
Gently slide it out of its box onto a 'gas stage' (don't know what these are called but look at the photo). This gas stage emits CO2 so the cockroach stays asleep.
Carefully clip off the wings to avoid cutting the exoskeleton. Cut far away from the attachment point and work your way closer so as not to damage anything else.
Put a small drop of super glue onto your backpack and attach it on the second segment (see picture) of the cockroach. DO NOT use too much glue or you will glue the segments together.
Turn off the gas and let the cockroach wake up. Make sure it's in an arena or it might run off with your backpack.
To remove the backpack, knock the cockroach out again, put a tiny bit of solvent (like acetone) on the tip of something and dab it around the edges of the backpack. It will come loose.
Let the cockroack wake up and return it to its cage. See my instructable on how to care for cockroaches: