Thermally elongated thermoplastic nozzles unlock micro-scale multimaterial direct ink writing

In additive manufacturing, micron-scale nozzles are critical for direct ink writing to regulate micro-interconnect structures in electronics and heterogeneous interfaces in biomedical devices. Existing techniques (glass capillary thermal forming, precision machining, and micromachining) struggle to fabricate complex core-shell or multilayer nozzles due to material incompatibility, limited geometric flexibility, or high costs. This work introduces a high-throughput strategy combining fused deposition modeling and thermal stretching to fabricate core-shell nozzles with feature sizes that are reduced by ~5 times, achieving an inner diameter less than 170 µm. The extrusion process is enabled by the use of polyethylene terephthalate because of its suitability for thermal elongation at high speeds. The thermally elongated nozzles, characterized by slender extended tips and small outlet diameters, can be manipulated by a robotic arm under remote center-of-motion control to enable material delivery through a small access port, highlighting the potential of this technology for minimally invasive surgery. This approach paves the way for miniaturized, multimaterial devices in electronics and precision medicine.