SKIN
WHAT CAN A ROBOT ''SKIN'' BE?
Biological skin has numerous functions like protection, sensing, expression, and regulation. On the contrary, a robot’s skin is usually regarded as a passive and static separation between the body and the environment. In this project, we explore the design opportunities of a robot’s skin as a socially expressive medium. Inspired by living creatures, the proposed method integrates pneumatically actuated dynamic textures on soft skin, with forms and kinematic patterns generating a variety of visual and haptic expressions. We demonstrate the proposed design space with several texture-changing skin prototypes and discuss their expressive capacities.
Inspired by octopus, we implement a skin module with arrays of suction cups: the skin can delate to adhere to an environmental surface and pressurize to detach. In human-robot interaction, a robot may display affection for a person by attaching to his body or sticking to the ground and expressing resistance to being moved or picked up.
Inspired by scales, we use the beating of oriented textures on the skin to generate a continuous force toward the oriented direction. The force can be further visualized by passing an object along the skin or, by pointing the textures toward the ground plane, support locomotion by the robot. In interaction, a robot may refer to a person or object by moving the skin or passing an object toward it.
Inspired by plants’ stomata that open and close to regulate exchange, we make pores on a skin module to indicate the level of interaction exposure. The skin can control the amount of air and light to pass through and indicate the exposure level. Opening pores may increase a robot’s exposure to the environment, permitting it to acquire richer data; however, it is less protected by the reduced physical filtering.
We simulate dynamic wrinkles on the skin to display similar emotions. The skin changes from a resting lat surface indicating a robot’s "relaxed" state to a furrowed surface with haptic tension under negative air pressure, indicating the robot is "concentrated" or "nervous".
Inspired by sea anemones slowly waving their tentacles, we design a skin module with subtly moving tentacles for displaying liveliness in robots.
Here I illustrate several design concepts of expressive robot skin: skin textures could convey (1) explicit messages, such as texts, graphics, or braille; (2) affective states, such as with piloerection or bristling of hairs, blush with anger, or involuntary muscle contraction, etc; (3) human-robot relation, such as by actively touching or sticking to a person to show affection; (4) interaction mode, such as the level of readiness or exposure with skin opening up or closing; (5) temporal change, for example, the skin could grow hairs and develop wrinkles over time; (6) health and other internal states such as patches to indicate illness or overheat.
We present a design vocabulary for textures. Multiple properties of texture units can be manipulated in design to provide different haptic and visual experiences, including shape, materiality, motion, and force.
The figure shows six examples of how the structure of texture units can result in different deformation and behaviors.
Combining texture units can form a texture module. We consider distribution, configuration, resolution, and connectivity during this process to form different skin module properties.
Publication
Hu, Yuhan, and Guy Hoffman. “What Can a Robot’s Skin Be? Designing Texture‑Changing Skin for Human‑Robot Social Interaction.” ACM Transactions on Human‑Robot Interaction (2022).