4D Printing of Electroactive Triple-Shape Composites

Abstract

Triple-shape polymers can memorize two independent shapes during a controlled recovery process. This work reports the 4D printing of electro-active triple-shape composites based on thermoplastic blends. Composite blends comprising polyester urethane (PEU), polylactic acid (PLA), and multiwall carbon nanotubes (MWCNTs) as conductive fillers were prepared by conventional melt processing methods. Morphological analysis of the composites revealed a phase separated morphology with aggregates of MWCNTs uniformly dispersed in the blend. Thermal analysis showed two different transition temperatures based on the melting point of the crystallizable switching domain of the PEU (Tm~50 ± 1 °C) and the glass transition temperature of amorphous PLA (Tg~61 ± 1 °C). The composites were suitable for 3D printing by fused filament fabrication (FFF). 3D models based on single or multiple materials were printed to demonstrate and quantify the triple-shape effect. The resulting parts were subjected to resistive heating by passing electric current at different voltages. The printed demonstrators were programmed by a thermo-mechanical programming procedure and the triple-shape effect was realized by increasing the voltage in a stepwise fashion. The 3D printing of such electroactive composites paves the way for more complex shapes with defined geometries and novel methods for triggering shape memory, with potential applications in space, robotics, and actuation technologies.

Advances in Functional Rubber and Elastomer Composites

“…Ahmed A. Bakhsh [ 20 ] explored the mechanical and thermal properties of polyolefin–hydroxyapatite nanocomposites using HDPE and LDPE matrices, finding significant enhancements with minor decreases at the 40% level of hydroxyapatite loading. Razzaq et al [ 21 ] reported the 4D printing of electro-active, triple-shape composites made from polyester urethane (PEU), polylactic acid (PLA), and multiwall carbon nanotubes (MWCNTs). These composites, suitable for fused filament fabrication, demonstrated the triple-shape effect through resistive heating, offering potential applications in space, robotics, and actuation technologies.…”

4D Printing: The Development of Responsive Materials Using 3D-Printing Technology

“…The development of electroactive materials requires the inclusion of conductive components such as CNTs, carbon fibers, carbon black, graphene or gold, silver, nickel, copper nanoparticles, conducting polymers, etc. For example, the 4D printing of electro-responsive composites based on thermoplastic polyester urethane (PEU), PLA, and multiwall CNTs (MWCNTs) [ 162 ], wherein the MWCNTs act as fillers to make the polymeric material electroactive and induce Joule heating to trigger shape change after applying an electric current. Four different structures were printed with electro-active filaments and the triple-shape effect (TSE) was studied, demonstrating that after applying a low voltage to a U-shape composite containing 14% of MWCNTs, the temperature increased to 50 °C and the original form was partially recovered.…”

“…Composite materials comprising polyester urethane, PLA, and MWCNTs as conductive fillers were printed employing the fused filament fabrication method. The composites displayed a stepwise, tunable shape change process that may be triggered remotely on demand [ 162 ]. Alternatively, hydrogel precursors offering 3D-printability were prepared with a combination of pyrrole with a high-gelatin-content oxidized alginate–gelatin (ADA-GEL).…”