Direct ink writing of 3D conductive polyaniline structures and rheological modelling

Abstract

The intractable nature of conjugated polymers(CP) leads to practical limitations in the fabrication of CP-based transducers having complex three-dimensional geometries. Conventional CP device fabrication processes have focused primarily on thin-film deposition techniques; this study explores novel additive manufacturing processes specifically developed for CP with the ultimate goal of increasing the functionality of CP sensors and actuators. Herein we employ automated polymer paste extrusion processes for the direct ink writing of 3D conductive polyaniline(PANI) structures. Realization of these structures was enabled through a modified fused filament fabrication delta robot equipped with an integrated polymer paste extruder to fabricate high-resolution 3D conductive PANI structures. The required processability of PANI was achieved by means of a counterioninduced thermal doping method. The effect of thermal doping on the PANI-DBSA paste by means of a constitutive relationship to describe the paste flow as a function of the thermal doping time is explored. This relationship is incorporated within a flow model to predict the extruded track width as a function of various process parameters including: print speed, gauge pressure, nozzle diameter, and pre-extrusion thermal doping time.

Assessment of Embedded Conjugated Polymer Sensor Arrays for Potential Load Transmission Measurement in Orthopaedic Implants

“…The model of the flexible polymeric substrate was 3D-printed using Cheetah filament, a thermoplastic elastomer (TPE) filament in the shore hardness 95A (Ninjatek, Manheim, PA, USA) and PANI doped by the use of dodecylbenzene sulfonic acid (DBSA) prepared according to the protocols described by Holness et al [ 25 ]. To this end, a specialized multi-material 3D printing technique has been developed at the Organic Mechatronics and Smart Materials Laboratory for direct-ink writing processes using a modified fused filament fabrication delta robot equipped with an integrated polymer paste extruder, which has been discussed in detail elsewhere [ 12 , 25 , 26 ]. In accordance with this technique, PANI was dispensed using a 22 Gauge stainless steel tip (Nordson EFD, East Providence, RI, USA), in a rectilinear fill pattern, and without a perimeter wall.…”

Extrusion 3D printing of conjugated polymers

“…However, due to strong π-π stacking interactions, CPs are typically hydrophobic, brittle, and insoluble. To make CPs processible in solvents or as solventless inks, side chains 75,76 or dopants 77,78 can be added. The most common CPs that have been used in biointerfaces, actuators, and energy storage are poly(ethylene dioxythiophene) (PEDOT), polypyrrole (PPy), and polyaniline (PAni) (Figure 1A).…”

“…This solventless ink was used to print 3D structures (Figure 6C). 78 Del Agua et al developed ion gels that used PEDOT to provide electronic conductivity. EDOT monomers were polymerized in the presence of guar gum that acted as a dopant and dispersing agent.…”

3D printing of conjugated polymers

“…As stated previously, suitable rheological properties are of paramount importance when developing a DIW platform. Work carried out at the University of Western Ontario under the direction of Prof. Aaron D. Price tackled this problem directly for the case of polyaniline (PANI) . PANI is a prototypical conducting polymer and can exist as three distinct oxidation states, of which only one displays good electrical conductivity upon acid doping, referred to as the emeralidine salt .…”

“…Work carried out at the University of Western Ontario under the direction of Prof. Aaron D. Price tackled this problem directly for the case of polyaniline (PANI). 37 PANI is a prototypical conducting polymer and can exist as three distinct oxidation states, of which only one displays good electrical conductivity upon acid doping, referred to as the emeralidine salt. 38 The emeralidine salt is formed by reversible protonation of the partially oxidized form (emeralidine base) with strong protic acids (mineral acids, sulfonic acids, etc.).…”