Mod2Hap: Two Level Modular Haptic System for Body- and Hand- Interactions using Magnetorheological Fluid

We present Mod2Hap, a two-level modular haptic system that enables both body-scale and hand-scale interactions using magnetorheological (MR) fluid. The system comprises (1) configurable frame modules for constructing spatial interaction structures, which can be flexibly assembled to suit various body postures and environments, and (2) haptic modules—rotary (e.g., for dials or pedals) and linear (e.g., for sliders or handles)—that provide customizable hand-scale feedback interfaces. Each haptic module utilizes MR fluid, whose viscosity varies with applied magnetic fields, to generate tunable resistive feedback. Our design achieves a wide feedback range (0.12–0.52 N·m torque, 41–212 N force) by optimizing the solenoid coil for power efficiency and validating magnetic field distribution via simulation. We demonstrate Mod2Hap through three interactive scenarios—cycling, kayaking, and fishing—and evaluate its performance in a user study with 12 participants. Results show high perceived realism and engagement, supporting the system's versatility, scalability, and effectiveness as an immersive haptic interaction platform.