Thesis Defence: High-Resolution Additive Manufacturing of Highly Electrically Conductive Inks for 3D-Printed Electromagnetic Interference Shielding Applications

Saeed Ghaderi, supervised by Dr. Mohammad Arjmand, will defend their thesis titled “High-Resolution Additive Manufacturing of Highly Electrically Conductive Inks for 3D-Printed Electromagnetic Interference Shielding Applications” in partial fulfillment of the requirements for the degree of Master of Applied Science in Mechanical Engineering.

An abstract for Saeed’s thesis is included below.

Defences are open to all members of the campus community as well as the general public.

To access a zoom link to attend this defence please contact the supervisor at mohammad.arjmand@ubc.ca.

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ABSTRACT

A wide range of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS)-based 3D printable inks are formulated for additive manufacturing (AM) of multifunctional highly electrically conductive printed electromagnetic interference (EMI) shields using a direct ink writing (DIW) technique. The doping effects of different types of high-boiling-point co-solvents (e.g., dimethyl sulfoxide (DMSO), ethylene glycol (EG), and dimethyl formamide (DMF)) on rheological properties and, thus, printability of the inks as well as tuning the electrical conductivity were explored. The printed structures were based on 6 wt.% PEDOT:PSS doped with 7 vol/vol % DMSO in water showed the highest electrical conductivity (858.1 ± 60.8 S cm-1), comparable with solvent-post-treatment values. Appropriate viscoelastic properties, continuous uniform filament formation, high-resolution printing (line width and thickness variations less than 20 % from average values), high aspect ratio 3D printing (≥ 25 layers), shape fidelity, and simple dry-annealing technique of the formulated inks give rise to manufacturing of high-performance micro- and macro-scale printed electronics and EMI shields. By engineering the micro- and macro-scale design of the EMI shield using the DIW technique and drying method, the shielding mechanism shifts from reflection to absorption. The maximum EMI SE of 39.36 dB for dry annealed and 50.16 dB for freeze-dried were achieved for 10 layers of printed DMSO-doped PEDOT:PSS grid-infilled patterns at the X-band range of the electromagnetic waves (8.2-12.4 GHz). The effects of printing parameters such as the number of printed layers and infill density along with the impact of the drying technique were evaluated on the EMI SE of the printed architectures. The DIW of PEDOT:PSS-based inks allow for fabricating unique flexible, self-standing, and geometry-friendly EMI shields, which can be wet-transferred on unusual sharp edges and uneven substrates. The comprehensive experimental data demonstrated that the strong electrostatic interactions between undoped free PSS chains and solvent molecules account for the removal of the non-conductive PSS-rich matrices from the conductive PEDOT-rich cores.