Fused filament fabrication of commercial conductive filaments: experimental study on the process parameters aimed at the minimization, repeatability and thermal characterization of electrical resistance

Abstract

Nowadays, a challenging scenario involving additive manufacturing (AM), or 3D printing, relates to concerns on the manufacturing of electronic devices. In particular, the possibility of using fused filament fabrication (FFF) technology, which is well known for being very widespread and inexpensive, to fabricate structures with embedded sensing elements, is really appealing. Several researchers in this field have highlighted the high electrical resistance values and variability in 3D-printed strain sensors made via FFF. It is important to find a way to minimize the electrical resistance and variability among strain sensors printed under the same conditions for several reasons, such as reducing the measurement noise and better balancing four 3D-printed strain gauges connected to form a Wheatstone bridge to obtain better measurements. In this study, a design of experiment (DoE) on 3D-printed strain gauges, studying the relevance of printing and design parameters, was performed. Three different commercial conductive materials were analyzed, including a total of 105 printed samples. The output of this study is a combination of parameters which allow both the electrical resistance and variability to be minimized; in particular, it was discovered that the “welding effect” due to the layer height and printing orientation is responsible for high values of resistance and variability. After the optimization of printing and design parameters, further experiments were performed to characterize the sensitivity of each specimen to mechanical and thermal stresses, highlighting an interesting aspect. A sensible variation of the electrical resistance at room temperature was observed, even if no stress was applied to the specimen, suggesting the potential of exploiting these materials for the 3D printing of highly sensitive temperature sensors.

Fabrication of High-Performance CNT Reinforced Polymer Composite for Additive Manufacturing by Phase Inversion Technique

“…Ultrasonic dispersion [34], surface treatment by surfactants [35], chemical modifications [36], and grafting improve the CNTs-polymer matrices compatibility [26]. Lately, filled polymers with electrically conductive nanowires or particles have been 3D printed to produce electronic devices on several substrates [37]. In addition, utilizing the 3D printing approach to design pressure sensors is another application in recent articles [38].…”

Additive manufacturing for capacitive liquid level sensors

“…Several studies have been performed to reduce the gap of knowledge in the field of MeX-manufactured sensors: Arh et al [5] proposed an experimental method to identify the dynamic piezo resistivity of unidirectionally printed structures providing coefficients needful for the building of analytical and numerical models; Cardenas et al [6,7] used high-intensity pulsed light to increase of two orders of magnitude the conductance of the tracks made up of commercial conductive filaments; Stano et al [8], exploiting the Design of Experiment (DoE) approach, found out a relationship between process parameters (layer height and printing orientation) and electrical resistance (and variability) minimization; Maurel et al [9] defined a novel framework to direct 3D print ion-lithium battery.…”

Modelling of Anisotropic Electrical Conduction in Layered Structures 3D-Printed with Fused Deposition Modelling

“…The anisotropy in the electrical properties can be explained by means of interfacial and inter-layer contact resistance, which is believed to originate from imperfect bonding conditions (e.g. the presence of voids) [ 35 , 36 , 37 , 38 ] and the inhomogeneous distribution of the conductive particles (especially in between traxels and layers) [ 27 , 39 , 40 , 41 ]. For low numbers of layers, the thickness variation is also of importance, as Gnanasekaran et al showed for a varying layer thickness with a factor of due to ridges [ 27 ].…”