Magnetorheological elastomers (MREs) are in demand in the field of high-tech microindustries and nanoindustries such as biomedical applications and soft robotics due to their exquisite magneto-sensitive response. Among various MRE applications, programmable actuators are emerging as promising soft robots because of their combined advantages of excellent flexibility and precise controllability in a magnetic system. Here, we present the development of magnetically programmable soft magnetic microarray actuators through field-induced injection molding using MREs, which consist of styrene-ethylene/butylene styrene (SEBS) elastomer and carbonyl iron powder (CIP). The ratio of the CIP/SEBS matrix was designed to maximize the CIP fraction based on a critical solids loading. Further, as part of the design of the magnetization distribution in micropillar arrays, the magnetorheological response of the molten composites was analyzed using the static and dynamic viscosity results for both the on and off magnetic states, which reflected the particle dipole interaction and subsequent particle alignment during the field-induced injection molding process. To develop a high-aspect-ratio soft magnetic microarray, X-ray lithography was applied to prepare the sacrificial molds with a height-to-width ratio of 10. The alignment of the CIP was designed to achieve a parallel magnetic direction along the micropillar columns, and consequently, the micropillar arrays successfully achieved the uniform and large bending actuation of up to approximately 81° with an applied magnetic field. This study suggests that the injection molding process offers a promising manufacturing approach to build a programmable soft magnetic microarray actuator.

Metal–polymer hybrid joining has attracted increasing attention for lightweight, compact, and multifunctional components; however, reliable joining of copper-based alloys to nonpolar polypropylene remains challenging because strong interfaces require both effective polymer anchoring and chemically robust interfacial bonding. In this study, a multi-step chemical/electrochemical surface treatment combined with triazine-based activation was developed for injection-molded direct joining of UNS C26800 Cu–Zn alloy and 30 wt% glass-fiber-reinforced polypropylene. Sequential pretreatment, etching, chemical oxidation, and anodic oxidation generated a hierarchical micro-/nano-porous CuOₓ/ZnO surface, in which the multiscale porous and hydroxylated oxide layer increased the surface area and provided reactive sites for subsequent triazine/silane/disulfide activation. Subsequent triazine activation formed a chemically integrated organic–inorganic interphase on the anodized brass surface. XPS and fracture-surface analyses indicated that triazine-derived species were immobilized through Cu–S/Zn–S anchoring and Si–O–Cu/Zn linkages, while silane-mediated Si–O–Si coupling with glass fiber/sizing and possible azide-derived C–N type interactions with the PP backbone additionally contribute to polymer composite-side interfacial bridging. The joint strength increased with increasing anodization voltage, reaching an average tensile-shear strength of 28.3 MPa and a maximum strength of 29.4 MPa at 25 V in 0.15 M KOH. Fracture-surface analyses revealed residual PP-GF30 and interfacial species on the fractured surfaces, indicating mixed interphase/cohesive failure rather than clean adhesive delamination. These results demonstrate that the synergistic combination of hierarchical mechanical interlocking and triazine-mediated chemical interfacial bridging is an effective strategy for high-strength Cu–Zn alloy/polymer hybrid composite joining in electrical, electronic, and electrified-vehicle applications.

Magnetorheological elastomers (MREs) are in demand in the field of high-tech micro- and nano-industries such as biomedical applications and soft robotics due to their exquisite magneto-sensitive response. Among various MRE applications, programmable actuators are emerging as promising soft robots because of their combined advantages of excellent flexibility and precise controllability in a magnetic system. Here, we present the development of a magnetically programmable soft magnetic microarray actuators through field-induced injection molding using MREs, which consist of styrene-ethylene/butylene styrene (SEBS) elastomer and carbonyl iron powder (CIP). The ratio of the CIP/SEBS matrix is designed to maximize the CIP fraction based on a critical solids loading. Further, as part of the design of the magnetization distribution in micropillar arrays, the magnetorheological response of the molten composites is analyzed using the static and dynamic viscosity results for both the on- and off- magnetic states, which reflect the particle dipole interaction and subsequent particle alignment during field-induced injection molding process. To develop high aspect ratio soft magnetic microarray, X-ray lithography is applied to prepare the sacrificial molds with a height-to-width ratio of 10. The alignment of CIP is designed to achieve a parallel magnetic direction along the micropillar columns, and consequently, the micropillar arrays successfully achieve the uniform and large bending actuation of up to approximately 81˚ with an applied magnetic field. This study suggests that the injection molding process offers a promising manufacturing approach to build a programmable soft magnetic microarray actuator.