# A Microwave-Assisted, Rapidly Self-Healing, FFF-Printed TPU and Its Application in Supercritical Foaming

## TL;DR

This paper introduces a microwave-assisted method to improve the strength and performance of 3D-printed thermoplastic polyurethane by enhancing interlayer bonding.

## Contribution

A novel microwave-assisted healing strategy using aminated helical carbon nanotubes to improve interlayer adhesion in 3D-printed and foamed TPU.

## Key findings

- Microwave irradiation with AS-MWCNTs enhances interlayer bonding and mechanical performance of TPU.
- The method preserves the cellular structure while improving energy absorption and strength.
- Optimized AS-MWCNT loading leads to significant improvements in bonding and material integrity.

## Abstract

To mitigate the interlayer defects and weak interfacial adhesion inherent in FFF-printed parts, thereby facilitating subsequent supercritical foaming applications, a microwave-assisted interlayer healing strategy is developed for FFF-printed, supercritical CO2-foamed thermoplastic polyurethane (TPU) by incorporating aminated helical multi-walled carbon nanotubes (AS-MWCNTs). Owing to their unique helical morphology, AS-MWCNTs exhibit enhanced microwave absorption and localized heating capability, enabling selective thermal activation at interlayer regions within the foamed architecture. Microwave irradiation induces localized softening of the TPU matrix and promotes polymer chain mobility and interdiffusion across layer interfaces, while preserving the cellular morphology and bulk foamed structure. By optimizing AS-MWCNT loading, substantial improvements in interlayer bonding strength, energy absorption, and overall mechanical performance are achieved. This work provides an effective strategy to restore interlayer integrity in supercritical CO2-foamed, additive manufactured elastomers and offers insights into the design of microwave-responsive, self-healing cellular materials.