A new study digs into how Fused Filament Fabrication (FFF) changes the performance of carbon-loaded plastics used as 3D printed electrodes.
This work comes from Manchester Metropolitan University, where researchers evaluated conductive polymer composites (CPC) based on PLA and ABS, filled with graphene, nano-graphite and Super P carbon black. The goal was straightforward: measure what FFF does to electrochemical behavior compared with the same material before printing.
The team compared three forms from the same mixes: bulk filament straight from a mini twin-screw, compression-molded thin films, and 3D printed electrodes. They used cyclic voltammetry with a well-behaved outer-sphere redox probe to estimate the heterogeneous electron transfer rate constant (often written k0) and tracked peak separation as a proxy for kinetics and resistance.
Inside The Experiments
Two results stand out. First, bulk filament consistently showed faster electron transfer than its 3D printed counterpart. For example, a 20 percent Super P carbon black in PLA measured roughly 8.28e-4 cm/s in one filament segment versus 2.39e-4 cm/s after printing. The printed parts also showed larger peak-to-peak separations, signaling added polarization and resistance.
Second, uniformity was a problem — even before printing. Different segments from the very same filament spool (tail, middle, other tail) returned noticeably different k0 values. In one case with 20 percent SP/PLA, measured values ranged from 2.824e-4 to 8.28e-4 cm/s across the spool. At 15 percent filler, some printed electrodes showed no appreciable response at all. In other words, dispersion and percolation varied along the filament length, and printing made that variability more visible.
Material choices seemed to make a difference. Higher filler loading helped, as expected from percolation theory. Single-polymer matrices performed better than immiscible blends: ABS plus Super P outperformed ABS-PC plus the same filler in electrochemical area and peak currents, even though immiscible blends can reduce percolation thresholds. The team’s explanation is pragmatic — the added phase can localize filler at interfaces and shrink the active electrochemical area.
The researchers looked at shear, pressure and thermal history in the extruder and print head. Printing likely breaks conductive clusters into smaller groups and redistributes particles, nudging the network away from the sweet spot of connected pathways and tunneling gaps. That aligns with other reports that print orientation and post-processing (for example, solvent exposure to reveal conductive phases) can swing performance.
The Catch: Uniformity And Processing
This sounds promising, but there’s one issue: reproducibility. The work used small-batch compounding and a desktop FFF system, so industrial twin-screw compounding and full-scale filament lines could reduce the variability. But the printing step changes the conductive network, and the changes are not always good for electrochemistry.
How do these plastics compare to traditional electrodes? Screen-printed carbon and edge-plane pyrolytic graphite still lead, with k0 values around 1.19e-3 and 7.0e-3 cm/s respectively. The best bulk filaments landed in the 3e-4 cm/s range, which is within an order of magnitude in some cases but generally lower. For many sensing tasks that may be fine; for high-rate energy storage, probably not without further processing.
The commercial result is pretty clear here. Control the compounding, specify higher filler loadings where printability allows, consider single-matrix systems before jumping to blends, and expect the print path and post-processing to matter as much as the formulation. Inline monitoring of filament resistivity, tighter lot control, and on-printer process sensing could pay off quickly.
