Past research recognized that paper has many advantages over digital devices, such as affordability, tangibility, and flexibility. Paper, however, also lacks many of the functionalities available in digital technologies, such as access to online resources and the ability to display interactive content. Prior research therefore identified opportunities for fusing the two mediums into a combined interface. This work presents a literature review on this form of innovation - technologies that bridge the paper-digital gap. First, we synthesize an understanding of paper and its relationship with digital devices through the lens of past works. Then, we outline the state-of-the-art for paper-digital interfaces and highlight possible use cases and implementation approaches. Last, we discuss design considerations and future work for developing paper-digital interfaces. Our work may be beneficial for HCI researchers interested in the development of hybrid paper-digital interfaces, and more broadly in embedding digital functionalities in everyday objects.

In this paper, we present a series of studies on using Rubik's Twist, a type of low-cost twistable artefact, to create haptic proxies for various hand-graspable VR objects. Our pilot studies validated the feasibility and effectiveness of Rubik's-Twist-based haptic proxies. The pilot results also revealed user challenges in the physical shape creation, motivating the development of the HapTwist toolkit. The toolkit consists of the shape-generation algorithm, the software interface for shape-construction guidance and interaction authoring, and the hardware modules for constructing interactive haptic proxies. The user studies showed that HapTwist was easy to learn and use, and it significantly improved user performance in creating interactive haptic proxies with Rubik's Twist. Furthermore, HapTwist-generated haptic proxies achieved similar VR experience as the real objects.