For my final project, I would like to keep with the biomimicry concept. Specifically, I would like to focus on mimicking the behavior of chromatophores that appear in chameleons and other animals. In these animals, their skin actually contains several chromatophores cells of varying colors. Each chromatophore is surrounded by a circular muscle that can constrict or expand. When the muscle constricts, pigment goes to the top of the chromatophore and the cell becomes a wide, flat disc. Upon relaxation, the cell is a small spot, which is difficult to detect. The color of the body is based on which pigments are being constricted at a certain time. Below are two images that represent what is happening:
Also, this video of the octopus in camouflage mode is really impressive, and it explains a little more about chromatophores: http://phys.org/news/2013-05-chameleons-creatures-colour.html. This video shows that in octopus, the can mimic its environment although it is color blind. This mimicry occurs due to chromatophore’s action of only 3 colors with reflectors. By using these three colors and reflectors, the variety of patterns can be created to camouflage.
For the project, I want to utilize shape memory material and create and interactive artwork that has both shape and color change. Shape memory materials exhibit shape change based on a certain transition temperature in which chemical structure change within the material occurs. For shape memory alloys, this temperature is the transition from Austenite structure to a Martensite structure. For shape memory polymers, this temperature is the glass transition temperature where the structure goes from a rubbery to a glassy phase. As of now, I would like to create this artwork as a “living skin”.
Also, I would like to use shape memory polymers. Shape memory polymers have an advantage in that I can cast them into any shape using 3D printing. I have successfully been able to create color change using Solar Color Dust (3). This dust is an encapsulated powder that can be easily incorporated into the matrix and cause color change based on temperature.
Also, the shape memory polymer provides an advantage in that the glass transition temperature can be changed by adjusting the chemical ratios within the material make-up. I am working on doing some more experimentation with this color changing dyes, as well as patterns.
For this project, one major drawback is finding the appropriate method of incorporating a heating element into the polymer material, whether the heating element be a shape memory alloy or wire, for example, nichrome wire. The heating element needs to be cast while the polymer is being cast, meaning it needs to be well anchored and be able to withstand 130 deg C.
The final result I desire is to incorporate shape and color through use of sensors or physical touch. Therefore, the artwork mimic’s these animals’ response to the environment in that its pattern indicates mood or defense or attraction for a mate. This work could be interesting in technical applications. For example, shape memory polymer materials are being studied to create optimal wing geometry throughout the entire flight by being able to adjust its shape. Blending shape adjustment and color would be of interest to defense applications where camouflage and optimal performance is needed.