Additive Manufacturing Engineering for Electrochemistry: Conductive High-Density Polyethylene Filament Expands the Materials Landscape.

Additive manufactured electrochemical platforms produced using bespoke conductive filaments are becoming increasingly established within modern electrochemical research; however, the latest developments within the field of additive manufacturing electrochemistry using fused filament fabrication technology have shown that it is constrained by the available material pool. Here, we introduce the first conductive high-density poly(ethylene) (HDPE) filament engineered for additive manufacturing implementation as a new alternative for conductive, chemically resilient filaments which is paramount to unlocking new applications. Using a thermal compounding process that avoids environmentally harmful chemical solvents, 40 wt% carbon black (CB) was incorporated into HDPE and extruded into a flexible, plasticizer-free filament with a low bulk resistivity of 16.4 (±1.0) Ω cm‒ 1. Following printing, electrochemical activation was required to expose the conductive carbon black phase and generate the functional electrode surface, particularly for inner-sphere electron transfer. Optimized additive manufacturing produced electrochemical platforms with reproducible performance and heterogeneous electron transfer kinetics corresponding to 2.93 (±0.19) × 10-3 cm s-1. Electrochemical stability testing revealed that the CB/HDPE additive manufactured electrodes exhibited consistent voltammetric responses for over 60 scans, representing an improvement compared to other conductive polymer feedstocks. Over a 70-day period, the CB/HDPE electrodes also maintained chemical stability following immersion in six different solvents. The material's versatility was demonstrated through proof of concept for the electrosynthetic oxidation of chlorpromazine-to-chlorpromazine sulfoxide and the electroanalytical determination of caffeine in commercial energy and coffee beverages, which was validated against liquid chromatography mass spectroscopy, both in aqueous and organic media. This work establishes conductive HDPE as a new entrant to the additive manufacturing electrochemistry toolkit, expanding the material landscape and enabling applications previously inaccessible with existing polymers.