4D printing with the assistance of electrical stimulation on polylactic acid coated with carbon nanotubes

Purpose This paper aims to present an innovative approach to fabricating an electrically responsive shape memory polymer (SMP). Design/methodology/approach Polymers that change shape over time when a stimulus is applied are known as SMPs. It uses polylactic acid (PLA) as the base material and carbon nanotubes (CNTs) as conductive additives. Instead of blending CNT with PLA, they were coated on the surface of the samples. The coating consisted of a mixture of CNT/ polycaprolactone. The samples were made using fused deposition modeling, an additive manufacturing method and the shape memory properties of the samples were analyzed under various parameters, including infill angle, coating layers and applied voltage. The voltage generates the Joule heating effect and results in the recovery of SMP to the original shape. Findings The highest conductivity of samples belongs to three coating layers, whose conductivity is equal to 0.51 S/cm. Under different parameter settings, the highest recorded shape recovery ratio reached 71.47% at voltage 60, infill angle 0 / 90 and two coating layers. This value emphasizes the remarkable ability of the developed material to return to its original shape. Furthermore, the maximum shape recovery speed observed was 0.3593 degree/s, providing valuable information about shape recovery speed under optimal conditions. Originality/value This paper presents the surface coating method and the effects of process parameters for activating shape memory using electric current. Compared to previous techniques, this method offers higher speed and requires less material, making it suitable for use in various industries.