  In this paper, we explore the new design space of extra-linguistic cues
inspired by graphical tropes used in graphic novels and animation to enhance
the expressiveness of social robots. To achieve this, we identified a set of
cues that can be used to generate expressions, including smoke/steam/fog, water
droplets, and bubbles. We prototyped devices that can generate these fluid
expressions for a robot and conducted design sessions where eight designers
explored the use and utility of the cues in conveying the robot's internal
states in various design scenarios. Our analysis of the 22 designs, the
associated design justifications, and the interviews with designers revealed
patterns in how each cue was used, how they were combined with nonverbal cues,
and where the participants drew their inspiration from. These findings informed
the design of an integrated module called EmoPack, which can be used to augment
the expressive capabilities of any robot platform.
