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Ghaderi, Saeed

University of British Columbia

3D printing of conducting polymers has been achieved very recently by direct ink writing of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS)-based inks. This field is in its infancy, calling for further research to broaden the application horizon of 3D-printed conductive polymers by fine-tuning their inherent properties. Indeed, engineering PEDOT:PSS inks with customizable electrical properties while keeping their rheological fingerprint within the proper range for high-fidelity 3D printing is an arduous challenge, yet to be achieved. Herein, a range of PEDOT:PSS-based inks were formulated by molecular engineering via co-solvent doping and solvent post-treatment with various solvents for high-resolution (line width and thickness variations less than 20 % from average values) and high-aspect-ratio ( ≥ 25 layers) 3D printing. Dimethyl sulfoxide (DMSO), ethylene glycol (EG), and N,N-dimethylformamide (DMF) were used for co-solvent doping, and DMSO, EG, DMF, methanol, and ethanol were used for solvent post-treatment. The effects of co-solvent doping of high-boiling-point co-solvents on rheological properties and, thus, printability of the inks were explored. Inks’ 3D printability range was defined based on shear viscosity, storage modulus, and yield stress values as a function of PEDOT:PSS concentration. Experimental analyses demonstrated that the strong interactions between solvent molecules and free PSS chains account for the partial removal of non-conductive PSS-rich shells from conductive PEDOT-rich cores. Via coupling solvent treatment and a simple dry-annealing technique, samples featured a wide range of conductivity, i.e., from 0.6 to 858.1 ± 60.8 S cm-1. Taking advantage of solvent treatment, the 3D-printed geometries were wet-transferred onto uneven substrates and complex objects with sharp edges. By exploiting their tunable molecular-scale chemistry and macro-scale geometric features, the 3D-printed parts were used to create electromagnetic interference (EMI) shields with controlled mechanisms. 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 3D printing parameters such as the number of printed layers, infill density, and drying technique were evaluated on the EMI shielding effectiveness (EMI SE), specific SE, and absolute SE of the 3D-printed EMI shields.

Text

2023-02-27

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/83860

Mechanical Engineering

University of British Columbia

UBCO

http://creativecommons.org/licenses/by-nc-nd/4.0/