ORIGINAL ARTICLE Temperature-dependent electrical resistance of conductive polylactic acid filament for fused deposition modeling Fraser Daniel 1 & Naim Hossain Patoary 1 & Arden L. Moore 1,2 & Leland Weiss 1,2 & Adarsh D. Radadia 1,3,4 Received: 20 April 2018 /Accepted: 17 July 2018 # Springer-Verlag London Ltd., part of Springer Nature 2018 Abstract This study characterizes the microstructure and temperature dependence of resistance of two commercially available electrically conductive polylactic acid (PLA) composites for fused deposition modeling (FDM): PLA-carbon black and PLA-graphene. No microstructural changes were observed between the filament and the printed parts; however, the resistivity of the filament was found to drop by four to six times upon FDM. Also, compared to the resistivity of individual extruded wire, the resistivity of the printed parts was found to be up to 1500 times higher for PLA-graphene and up to 300 times higher for PLA-carbon black. The raw PLA-carbon black filament and printed wire showed a positive temperature coefficient of resistance (α) value between ~ 0.03 and 0.01 °C -1 , which makes them more suitable for sensor development. The raw PLA-graphene filament and printed wire did not exhibit a significant α, which makes them more suitable for printing wires. However, the parts made with multilayer FDM exhibited a negative or a negligible α up to a certain temperature prior to exhibiting a positive α; further, these α values were significantly lower than those obtained for the filaments before or after extrusion. These findings enable proper selection of commercial conductive FDM filaments for enabling quicker prototyping of electronics and sensors. Keywords Fused deposition modeling . 3D printing . PLA-carbon black . PLA-graphene . Temperature coefficient of resistance 1 Introduction Over the last decade, fused deposition modeling (FDM) or more commonly referred to as 3D printing has been revolu- tionizing the way we prototype and fabricate parts. These scale from a few centimeters to a meter [1–3]. FDM is finding application in electronics [4–9], RF applications [10–12], microfluidics [ 13–17], medical [ 18–23], and robotics [24–26]. The expansion of FDM has been possible because it is cost-effective for prototyping or producing parts in low number, and most importantly, a wide range of thermoplastic filaments with different textures, colors, and mechanical prop- erties are available commercially. Our research group is inves- tigating fabrication of a variety of sensors via FDM; specifi- cally, sensors that leverage outstanding temperature- dependent electrical properties, like resistance thermometers, thermal conductivity detectors, and flow meters. We report our findings on the temperature-dependent resistance of com- mercially available conductive thermoplastic filaments for FDM. Conductive plastic composites of a wide variety have been reported previously; however, very few have been translated for application to FDM. Thus, lately there have been some efforts to prepare conductive plastic composites specifically for FDM to print electrical circuits and sensors. Wei et al. (2015) prepared and characterized electrical properties of con- ductive acrylonitrile butadiene styrene filament doped with varying amounts of graphene and its application to FDM; their work presented a best conductivity of ~ 10 5 Ω·cm at 5.6 wt% graphene content [27]. To make an economically viable con- ductive filament, Wai et al. (2017) prepared and characterized electrical properties of conductive polypropylene filaments doped with varying concentration of carbon black and * Adarsh D. Radadia radadia@latech.edu 1 Institute for Micromanufacturing, Louisiana Tech University, 911 Hergot Avenue, Ruston, LA 71272, USA 2 Mechanical Engineering, Louisiana Tech University, Ruston, LA 71272, USA 3 Chemical Engineering, Louisiana Tech University, Ruston, LA 71272, USA 4 Center for Biomedical Engineering and Rehabilitation Sciences, Louisiana Tech University, Ruston, LA 71272, USA The International Journal of Advanced Manufacturing Technology https://doi.org/10.1007/s00170-018-2490-z