Magnetorheological ultraviolet-curable resin and its mechanical properties for additive manufacturing

Driven by labor shortages caused by aging population, the deployment of robots in fields such as food, agriculture, and medicine is expanding, increasing the demand for soft grippers capable of handling flexible and delicate objects. While additive manufacturing facilitates the creation of complex shapes, the resulting mechanical complexity poses challenges for control. Although magnetorheological fluids (MRFs) and elastomers (MREs) offer potential solutions with magnetic-field-responsive properties, conventional methods struggle to balance controllability with manufacturability. To address this, we propose a magnetorheological ultraviolet-curable resin (MRUVR) capable of selectively functioning as an MRF in uncured state and as an MRE after ultraviolet (UV) curing. This approach enables the monolithic fabrication of grippers possessing regions with distinct magnetic properties using a single material and process. This paper presents the material design and characterization of MRUVR and examines the mechanical property variations of both cured and uncured MRUVR. The MRUVR was prepared using soft resin and two types of magnetic particles. Experimental results confirmed that the MR effect is present in both the uncured and cured states of the MRUVR. The optimal conditions for MRE fabrication involve using 74 μm particles at a mixing ratio of 5 vol% and a curing time of approximately 1 min. These findings suggest that the mechanical behavior of the device is governed by a synergistic mechanism involving both MRF and MRE characteristics. Furthermore, the feasibility of fabricating such devices and their magnetic controllability are demonstrated. Future work will focus on improving the MRUVR using finer iron particles to suppress sedimentation and enhance the MR properties.