High‐Toughness, Self‐Healing, and Conductive Waterborne Polyurethane/ MWCNT Elastomer Flexible Composite With a Dual Covalent Adaptive Network for Flexible Motion Sensing

Abstract

Waterborne polyurethane (WPU) is an attractive substrate for flexible electronics owing to its structural tunability and environmental compatibility; however, simultaneously achieving high mechanical performance, self‐healing capability, electrical conductivity, and stable sensing behavior remains challenging. Herein, a dual‐dynamic waterborne polyurethane (DWPU) matrix crosslinked by DHA/ADH was employed as a self‐healing substrate. Carboxylated multi‐walled carbon nanotubes (MWCNTs) at various loadings were incorporated to systematically investigate their effects on the mechanical, self‐healing, electrical, and sensing properties. The introduction of MWCNTs significantly enhanced the mechanical strength and electrical performance of the DWPU matrix. The composite containing 0.5 wt% MWCNTs exhibited a tensile strength of ~36 MPa, an elongation at break of ~800%, a Young's modulus of 8.6 MPa, and a toughness of 161 MJ/m 3 . All DWPU‐based samples displayed pronounced self‐healing capability under thermal stimulation. Increasing MWCNT content also enhanced the electrical conductivity and strain sensitivity, while the composites maintained stable and repeatable resistance responses during cyclic deformation. When attached to human joints, the DWPU/MWCNT flexible sensor provided rapid resistance response and reliable real‐time motion detection. This work demonstrates a feasible strategy to balance mechanical robustness, self‐healing capability, conductivity, and sensing performance in WPU‐based composites, offering potential for wearable electronics, electronic skin, and human‐machine interfaces.