Microscale Patterning of Ultrahigh‐Viscosity Metallic‐Polymer Composites via Embedded Droplet Writing

Abstract

The ability to digitally pattern metallic‐polymer composites with microscale precision would substantially expand the functionality of soft materials by enabling spatially programmed magnetic, electrical, and thermal responses within compliant architectures. However, progress in this direction has been limited by the lack of manufacturing platforms capable of processing ultrahigh‐viscosity, high‐filler‐loading pastes while maintaining microscale resolution and seamless integration with structural matrices. Here, we introduce a hybrid additive manufacturing platform that combines direct droplet writing with vat photopolymerization to fabricate heterogeneous soft structures incorporating ultrahigh‐viscosity metallic–polymer composites. The hybrid platform enables deterministic deposition of composites with filler loadings up to 87 wt% (47 vol%) and viscosities approaching 1700 Pa·s, while integrating them into photopolymerized elastomer matrices with microscale precision. This capability spatially localizes magnetic composite domains within compliant polymers, effectively decoupling magnetic functionality from the structure's overall mechanical compliance. Leveraging this material's architecture, we demonstrate programmable magnetic soft actuators with tunable deformation, pressure‐responsive magnetic microvalves exhibiting sequential shut‐off behavior, and magnetically switchable adhesives capable of controlled pick‐and‐release operations. By enabling microscale patterning and multimaterial integration of ultrahigh‐viscosity metallic composites, this strategy significantly broadens the design space for multifunctional soft materials with programmable, spatially resolved functionalities.