People often communicate with others using social touch interactions including hugging, rubbing, and punching. We propose a soft social-touchable interface called "Emoballoon" that can recognize the types of social touch interactions. The proposed interface consists of a balloon and some sensors including a barometric pressure sensor inside of a balloon, and has a soft surface and ability to detect the force of the touch input. In this paper, we evaluate physical features of a balloon and its appropriateness as a form of interface to input social touch interactions. We construct the prototype of Emoballoon using a simple configuration based on the features of a balloon, and evaluate the implemented prototype. The evaluation indicates that our implementation can distinguish seven types of touch interactions with 83.5% accuracy. Finally, we discuss possibilities and future applications of the balloon-made interface.
