  In this paper we present Organic Primitives, an enabling toolbox that expands
upon the library of input-output devices in HCI and facilitates the design of
interactions with organic, fluid-based systems. We formulated color, odor and
shape changing material primitives which act as sensor-actuators that convert
pH signals into human-readable outputs. Food-grade organic molecules
anthocyanin, vanillin, and chitosan were employed as dopants to synthesize
materials which output a spectrum of colors, degrees of shape deformation, and
switch between odorous and non-odorous states. We evaluated the individual
output properties of our sensor-actuators to assess the rate, range, and
reversibility of the changes as a function of pH 2-10. We present a design
space with techniques for enhancing the functionality of the material
primitives, and offer passive and computational methods for controlling the
material interfaces. Finally, we explore applications enabled by Organic
Primitives under four contexts: environmental, cosmetic, edible, and
interspecies.
