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We developed a soft robotic skin that can change its texture to express its internal state, such as emotions. The prototype skin can animate a combination of goosebumps and spikes. This is in contrast to most socially expressive robots, which use either gestures or facial expressions to communicate. In the first prototype, we map these skin changes to the robot’s emotions to create a more effectively communicating social robotic companion.

Many animals express internal states with skin changes, such as human goosebumps, cats’ neck fur raising, dogs’ back hair, the needles of a porcupine, the spiking of a blowfish, or a bird’s ruffled feathers. In contrast, most social robots only use gestures or facial expressions to do the same. 


Skin change is a particularly useful communication channel since it operates on two channels: It is perceived not only visually, but also haptically, if the human is holding or touching the robot. This can give social robots a new channel for communicating with humans.

The soft robotic skin generates pneumatically actuated dynamic textures, deforming in response to changes in pressure inside fluidic chambers. We integrated skins with two textured shapes inspired by nature: goosebumps and spikes.


Deformation of texture module in response to the inner chamber pressure. From left to right, the pressure of the spikes channel changes from negative to positive. From bottom to top, the goosebumps channel inflates from negative pressure to positive pressure.

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The main body of the texture skin is made of an extensible elastomer (Smooth-on Ecoflex 00-30), using a mold-casting fabricating process. A plastic positive of the inner cavity and fluidic channels are fabricated using 3D-printed PLA and fixed in a mold box. The elastomer is molded to fabricate the upper part of the cavities. The bottom layer is fabricated with an inextensible film embedded in it.

We use the shape and volume of the texture, as well as the speed of the texture’s movement, to generate eight texture gestures. We presented eight texture patterns to participants in three interaction modes: online video viewing, in-person observation, and touch.

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Participants consistently perceived them as expressing specific emotions, with similar distributions across all three modes. Goosebumps convey a more positive emotion than spikes, and a higher frequency movement communicates a more aroused state.

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Hu, Yuhan, Zhengnan Zhao, Abheek Vimal, and Guy Hoffman. “Soft skin texture modulation for social robotics.” In 2018 IEEE International Conference on Soft Robotics (RoboSoft), pp. 182‑187. IEEE, 2018.

Hu, Yuhan, Guy Hoffman. “Using skin texture change to design emotion expression in social robots.”

2019 14th ACM/IEEE International Conference on Human‑Robot Interaction (HRI). IEEE, 2019

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