Characterization of a 3D-Printed Conductive PLA Material With Electrically Controlled Stiffness

In this paper, we present characterization results for thermal, mechanical, and electrical properties of a 3D-printed conductive polylactic acid (PLA) composite material. The material exhibits electrically controllable stiffness, allowing for the fabrication of novel robotic and biomedical devices. In particular, an applied voltage induces a Joule heating effect, which modulates the material stiffness. Dumbbell samples are 3D-printed and loaded into a universal testing machine (UTM) to measure their Young’s moduli at different temperatures. The conductive PLA composite shows 98.6% reduction of Young’s modulus, from 1 GPa at room temperature to 13.6 MPa at 80 °C, which is fully recovered when cooled down to its initial temperature. Measurements with differential scanning calorimeter (DSC) and thermal diffusivity analyzer are conducted to investigate the thermal behavior of this material. Electrical conductivity of the material is measured under different temperatures, where the resistivity increases about 60% from 30 °C to 100 °C and hysteresis between the resistivity and the temperature is observed. These tests have shown that the conductive PLA composite has a glass transition temperature (Tg) of 56.7 °C, melting point (Tm) of 153.8 °C, and thermal conductivity of 0.366 W/(mK). The obtained results can be used as design parameters in finite element models and computational tools to rapidly simulate multi-material components for several applications such as object manipulation, grasping, and flow sensing.