“While 3D printing offers great design flexibility before the object is printed, it is very hard for end-users to customize a 3D-printed object to their specific needs after it is printed. We propose HotFlex: a new approach allowing precisely located parts of a 3D object to transition on demand from a solid into a deformable state and back. This approach enables intuitive hands-on remodeling, personalization, and customization of a 3D object after it is printed. We introduce the approach and present an implementation based on computer-controlled printed heating elements that are embedded within the 3D object. We present a set of functional patterns that act as building blocks and enable various forms of hands-on customization. Furthermore, we demonstrate how to integrate sensing of user input and visual output. A series of technical experiments and various application examples demonstrate the practical feasibility of the approach.”