The design of physical interfaces has been constrained by the relative akinesis of the material world. Current advances in materials science promise to change this. In this paper, we present a foundation for the design of shape-changing surfaces in human–computer interaction. We provide a survey of shape-changing materials and their primary dynamic properties, define the concept of soft mechanics within an HCI context, and describe a soft mechanical alphabet that provides the kinetic foundation for the design of four design probes: Surflex, SpeakCup, Sprout I/O, and Shutters. These probes explore how individual soft mechanical elements can be combined to create large-scale transformable surfaces, which can alter their topology, texture, and permeability. We conclude by providing application themes for shape-changing materials in HCI and directions for future work. Keywords Form transformation Á Shape change Á Kinetic Á Morph Á Tangible interface Á Transitive materials Á Shape...