# Scalable Self-Sensing Mechanical Metamaterials by Conformal Coating of 3D-Printed Lattices with Nanocomposites

## TL;DR

Researchers developed a scalable method to create self-sensing materials by coating 3D-printed lattices with nanocomposites, enabling stable strain sensing for large-scale applications.

## Contribution

A scalable fabrication strategy for self-sensing metamaterials using conformal dip-coating of 3D-printed lattices with CNT–SEBS nanocomposites.

## Key findings

- Coating 3D-printed lattices with CNT–SEBS nanocomposites yields stable and repeatable piezoresistive responses under cyclic compression.
- Auxetic unit cells showed the highest strain sensitivity, up to four times that of Octet cells.
- Scaling to eight-cell auxetic lattices retained high sensitivity and consistent electromechanical performance.

## Abstract

What are the main findings?
An efficient fabrication process conformally integrates CNT–SEBS nanocomposites onto 3D-printed flexible lattices, yielding stable and repeatable piezoresistive response under 0–40% quasi-static cyclic compression.Lattice topology strongly governs the strain sensing performance, where the auxetic unit cell achieved the highest sensitivity, and scaling to 8-cell auxetic lattices retained the high sensitivity.

An efficient fabrication process conformally integrates CNT–SEBS nanocomposites onto 3D-printed flexible lattices, yielding stable and repeatable piezoresistive response under 0–40% quasi-static cyclic compression.

Lattice topology strongly governs the strain sensing performance, where the auxetic unit cell achieved the highest sensitivity, and scaling to 8-cell auxetic lattices retained the high sensitivity.

What are the implications of the main findings?
Strain sensing metamaterials can be scaled from unit cells to larger lattices while maintaining repeatable electromechanical readout, supporting large-scale and conformal sensing applications.A desired strain sensitivity could be engineered by tailoring the cell type using the same coating formulation and fabrication process, enabling design-driven tuning without reformulating the nanocomposites.

Strain sensing metamaterials can be scaled from unit cells to larger lattices while maintaining repeatable electromechanical readout, supporting large-scale and conformal sensing applications.

A desired strain sensitivity could be engineered by tailoring the cell type using the same coating formulation and fabrication process, enabling design-driven tuning without reformulating the nanocomposites.

Metamaterials possess unique and desirable multiphysical behaviors derived from deliberately arranging conventional materials into designed structural topologies. Multifunctional mechanical metamaterials that can both carry load and provide in situ state awareness are increasingly needed for applications such as structural health monitoring and soft robotic systems. To address the demand for multifunctional metamaterials, this study reports a scalable fabrication strategy for self-sensing lattice metamaterials by conformally dip-coating 3D-printed flexible cells with a carbon nanotube (CNT)–styrene–ethylene–butylene–styrene (SEBS) nanocomposite. Scanning electron microscopy shows that the coating conforms closely to the printed struts with well-dispersed CNT networks. The electromechanical behavior of coated Octet, Kelvin, and auxetic unit cells was characterized under quasi-static cyclic uniaxial compression (0–40% strain). All the coated structures exhibited highly stable, reversible, and repeatable piezoresistive response, with a near-linear relationship between resistance change and strain. Among the tested geometries, the auxetic unit cell achieved the highest strain sensitivity that was approximately four times that of the Octet cell and six times that of the Kelvin cell. To evaluate scalability, auxetic lattices containing eight scaled auxetic unit cells were shown to retain high sensitivity and remained statistically similar to the unit cell. This study demonstrates that the strain sensing performance of nanocomposites can be engineered through lattice topology using a simple dip-coating functionalization approach, enabling scalable self-sensing metamaterials for large-scale and conformal sensing applications.