Chroma

A foray into thermochromic interaction design

Color changing eye-shadow prototype as shown in ChromoSkin [1]

On ChromoSkin

ChromoSkin [1] is such an interesting paper! In this work, thermochromic pigments are interactively used in make-up to enable color changing cosmetics. The prototype is so strikingly simple yet hands-down innovative. There is no weakness in the project other than the constraints it has been designed within:

1. To use thermochromic pigments: because of this a heating circuit is needed. Adding a heating circuit implies that the user feels another stimulus (heat on the skin) which is actually extraneous to the purpose of the project- ‘adaptive color change’.
2. Needs a microcontroller: Because the project was by design to allow user-control of cosmetics, a microcontroller was needed to modulate the color of the pigment.
3. Choice of temperature range: For the same reason as above, because it was required that the color should be able to set the color, the team had rejected the subset of pigments that activate below 350C that react to human skin temperature.
4. It is a short paper: I did not notice a study on the user feedback (aesthetics, skin-friendliness, etc.) but it is outside the scope of this paper.

Dr. Kao’s (the author) works [2] are really interesting . They show that fabrication of novel interactions should not be a barrier to their imagination. In many of her papers, simple fabrication techniques have been described which truly encourage a novice researcher like me to dabble in interactive materials.

A new interaction! Chroma.

As a design exercise I decided to design a project that could address the above ‘limitations’ (they are not!!) of the ChromoSkin.

Imagine tangible interactions using thermochromic pigments that function without the need for microcontrollers! Using the same limitations of ChromoSkin we can design many more compelling and colorful interactions.

Points to consider:

1. Touch: Human touch is not just change in pressure or shear on skin, it is also change in temperature. An important point under consideration could be to map the change in pressure, temperature and time-in-contact with everyday objects (human or otherwise). Using this map would allow us to create appropriate color formats for thermochromic tactile interactions =)
2. Color+ Volume: Mercury is a commonly used thermometric liquid (and toxic!) that visibly reacts to change in temperature by changing in volume. This is because it has a high coefficient of expansion. But can we dope mercury to change color? Seems possible here. In that example the chemical composition of mercury changes but is there a way to perhaps dope mercury with existing thermochromic pigments? Not sure, needs research. Are their non-toxic fluidic alternatives to mercury? This reference [3] points to few of those fluids. Of course actual implementation would need more research in selection and specifications.
3. Inspiration: Now that we have our fluid of choice and significant inspiration from this awesome research- Venous Materials [4]; we can design interactions using thermochromic effects that not only change color but also physical configuration using microfluidics.

Quick concept art- the Chroma Ecosystem

References

[1] H.-L. (Cindy) Kao, M. Mohan, C. Schmandt, J. A. Paradiso, and K. Vega, “ChromoSkin: Towards Interactive Cosmetics Using Thermochromic Pigments,” in Proceedings of the 2016 CHI Conference Extended Abstracts on Human Factors in Computing Systems, New York, NY, USA, May 2016, pp. 3703–3706. doi: 10.1145/2851581.2890270.

[2] “ChromoSkin — Cindy Hsin-Liu Kao.” https://cindykao.com/ChromoSkin (accessed Feb. 16, 2022).

[3] “Index of /~isidoro/lab1/Thermometry.” http://webserver.dmt.upm.es/~isidoro/lab1/Thermometry/ (accessed Feb. 16, 2022).

[4] “Project Overview ‹ Venous Materials: Towards interactive, fluidic mechanisms,” MIT Media Lab. https://www.media.mit.edu/projects/prototyping-interactive-fluidic-mechanisms/overview/ (accessed Feb. 16, 2022).