Publications

The jamming transition—marked by dramatic changes in mechanical properties, such as stiffness and damping—enables programmable and adaptive structures for robotic applications. This phenomenon, driven by changes in the coupling between individual subunits of an aggregate, can be controlled through external actuation sources. Existing jamming actuation methods, such as applying a vacuum with an airtight envelope, pose significant limitations, as they require the structures to be tethered, limiting reconfigurability and scalability. Here, we introduce an untethered jamming mechanism based on magnetic interactions between soft-ferromagnetic composites. We establish composite design principles to program the magnetization of the subunits, demonstrate linear, planar, and volumetric jamming and shape-locking, and model the magneto-mechanical behavior. This approach contributes to the development of jamming-based materials in which the jamming directions and transition points can be tuned on-the-fly by adjusting the external magnetic field orientation and strength, respectively.

Perception by touch is fundamentally linked to the motor system. A hallmark of this linkage takes the form of stereotyped haptic “exploratory procedures” [1], movement patterns that emerge when people set a perceptual goal such as judging the roughness of a textured surface. This paper expands the study of touch-directed movements by asking what patterns emerge when people encounter and interact with novel objects without explicitly specified goals. Participants were invited to freely interact with an art installation containing novel objects with distinct design features, intended to vary familiarity, structural affordance, and aesthetic response. Objects’ affordances were additionally varied over time by utilizing jamming, a physical mechanism that induces changes in stiffness and plasticity. From video recordings, four categories of spontaneous “interactive procedures” differentiated by underlying goals were reliably identified: passive observational, active perceptual, constructive, and hedonic. Perceptual actions were most frequent, indicating an overriding goal of acquiring information about physical properties. The prevalence of other interactive procedures varied across objects, demonstrating the influence of perceptual affordances and prior knowledge. Changes in state further moderated interactions, such that interactions were longer in the stiff/jammed state, and the occurrence of a state change during an interactive procedure lengthened its duration. These findings extend our understanding of haptic exploration beyond explicitly goal-directed contexts, revealing how spontaneous responses in complex and dynamic environments are linked to perceptual outcomes and prior knowledge.