Abstract
Haptic feedback is required for medical palpation; however, conventional force display devices face limitations in miniaturization and localized stiffness presentation. This paper introduces magnetorheological (MR) fluid as an effective dynamic actuator, utilizing changes in its viscosity to present stiffness. Two developed devices are described, both employing an MR fluid cell sealed in fingertip-sized silicone resin. These devices generate a reaction force when the finger presses against them. The first device, a fingertip-mounted type, demonstrated the feasibility of presenting a stiffness distribution through fingertip contact with a magnetic stage featuring a prearranged permanent magnetic field. The second device employs an electro-permanent magnet (EPM) to instantly switch the magnetic flux density applied to an MR fluid cell. Sensory evaluation using this device confirmed the perception of stiffness differences through magnetic switching, verifying the potential for biological stiffness presentation using MR fluid. Future work will focus on EPM miniaturization, magnetic flux density enhancement, and establishing control methods to realize a real-time stiffness display system applicable to telemedicine, surgical training, and virtual-reality technology.
