1, University of Michigan, Ann Arbor, Michigan, United States
With the advent of massive telecommunications networks and the expansive development of wireless electronics operating in the gigahertz range, “electromagnetic pollution” has risen to unprecedented levels. To mitigate the effects of electromagnetic interference (EMI) from spurious radiation, improved EMI shields are needed. Shields composed of solid metals or metal-based coatings oftentimes exhibit high shielding efficiency (SE) but have issues such as poor wear and corrosion resistance and high rigidity. This has led researchers to pursue next generation polymer composites for EMI shielding. Foaming of these materials has demonstrated higher broadband EMI absorption as compared to the non-foamed material due to minimization of the air-to-shield impedance mismatch. However, the pore morphology which is difficult to control using physical or chemical foaming can drastically affect EMI shielding efficiency. To mitigate the lack of design control, we are using Digital Light Processing (DLP) to print magnetically functionalized graphene composites with a periodic pore morphology optimized by modeling. Cobalt ferrite nanoparticles prepared by co-precipitation are attached to graphene platelets and then dispersed in Formlabs UV resin via ultra-sonication. Finite element method-based optimization using experimentally determined constitutive electromagnetic properties of the bulk composite was used establish the preferred periodic geometry with high EMI shielding. The shielding efficiency was measured for samples printed using a B9 Creator with different pore geometries and graphene loading. The measured values are compared with the model predictions.