Shape-Change as a Haptic Modality: A Taxonomy and Survey of Hand-Contacting Shape-Changing Haptic Interfaces (SCHIs)

Shape-Changing Haptic Interfaces (SCHIs) are haptic devices whose principal output is the deliberate reconfiguration of user-contacting geometry, such that shape or shape-change itself is what the user perceives. Although SCHIs have been widely used for virtual reality, tangible interaction, tactile displays, navigation assistance, accessibility, telerobotics, and affective haptics, they remain less clearly defined than interfaces based on established haptic modalities such as vibrotactile, force, thermal, or skin-stretch feedback. Without a shared definition or taxonomy, many SCHIs are treated as isolated, application-specific systems, making it difficult to compare designs, identify recurring patterns, or build reusable perceptual knowledge. This review positions SCHIs within the broader haptic landscape and organizes them along three axes: shape-change morphology, interaction mode, and shape-information carrier (MIC taxonomy). The first two axes are derived from existing taxonomies, while the carrier axis was developed and refined through a survey of 123 hand-contacting SCHIs. Classifying these devices along the three axes reveals how they populate the design space and identifies several recurring design groups. Reviewing the perceptual evidence for the carrier classes then shows that SCHI perception remains under-characterized. We identify open challenges in boundary-setting, design-space exploration, and systematic perceptual characterization. Taken together, this review provides a foundation for treating shape change as a deliberate and comparable haptic modality.