Non-Rigid HCI: A review of deformable interfaces and input

Deformable interfaces are emerging in HCI and prototypes show potential for non-rigid interactions. Previous reviews looked at deformation as a material property of shape-changing interfaces and concentrated on output. As such, deformable input was under-discussed. We distinguish de-formable from shape-changing interfaces to concentrate on input. We survey 131 papers on deformable interfaces and review their key design elements (e.g., shape, material) based on how they support input. Our survey shows that deformable input was often used to augment or replace rigid input, particularly on elastic and flexible displays. However, when shapes and materials guide interactions, deformable input was used to explore new HCI paradigms, where gestures are potentially endless, and input become analogy to sculpting, metaphor to non-verbal communication, and expressive controls are enhanced. Our review provides designers and practitioners with a baseline for designing deformable interfaces and input methodically. We conclude by highlighting under-explored areas and identify research goals to tackle in future work with deformable interfaces.