Electrically and Thermally Functional Nano/Micron Materials for Additive Manufacturing: Conductivity, ESD, EMI Shielding, Percolation, Interfaces, Anisotropy and Qualification

Nano-and micron-scale carbon, metal, conducting-polymer and ceramic phases can provide electrical conduction, controlled electrostatic dissipation, electromagnetic shielding or heat transport in additively manufactured components. The same constituent can also increase viscosity, cure attenuation, sedimentation, nozzle wear, agglomeration, porosity, contact resistance, anisotropy and occupational-control burden. This qualitative engineering review separates four functions that are frequently collapsed under the word conductive: direct-and alternating-current transport; electrostatic-discharge control; electromagnetic-interference shielding; and thermal conduction or diffusivity. For each function it identifies the measurable quantity, specimen and electrode or fixture, direction, conditioning, geometry, frequency or temperature domain, uncertainty and product-level evidence required for qualification. The review explains electrical percolation, tunnelling and contact-limited networks; distinguishes a dispersed filler population from a connected transport network; and examines how shear, toolpath, layer interfaces, cure shrinkage, porosity and post-processing change the as-tested state. Retained composites based on carbon black, carbon nanotubes, graphene-related materials, graphite, conducting polymers, metallic particles or nanowires, conductive oxides and thermally conductive ceramics are compared with printed metal inks, selective metallization, infiltration and conversion routes. Process sections address material extrusion, direct ink writing, inkjet and material jetting, vat photopolymerisation and powder-bed composites. Primary studies are used as bounded demonstrations of mechanisms rather than transferable recipes. An applied example compares three routes for an electronics fixture that requires grounded electrostatic dissipation, local electrical insulation and heat removal, and shows why the functions should be allocated to different material zones when a single composite cannot close all requirements. The review concludes that functional qualification must preserve the causal chain from lot and formulation through local network, printed direction, contact architecture, ageing and the accepted device. No loading, conductivity, surface resistance, shielding effectiveness or thermal conductivity is universal outside that chain.