"Smart Skin" optical strain sensor using single wall carbon nanotubes

Peng Sun; Ji-Hoon Kim; Sergei M. Bachilo; R. Bruce Weisman; Satish Nagarajaiah

doi:10.1117/12.2046539

10 April 2014 "Smart Skin" optical strain sensor using single wall carbon nanotubes

Peng Sun, Ji-Hoon Kim, Sergei M. Bachilo, R. Bruce Weisman, Satish Nagarajaiah

Author Affiliations +

Proceedings Volume 9061, Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems 2014; 906120 (2014) https://doi.org/10.1117/12.2046539
Event: SPIE Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring, 2014, San Diego, California, United States

Abstract

Strain measurements are essential in structural health monitoring. Traditional strain gages require physical contact between the sensor and read-out device, perturb the surface being monitored, and allow measurement only at the specific location and orientation axis of the sensor. We demonstrate a novel non-contact, multi- point, multi-directional strain sensing approach that overcomes these limitations. In our method, the surface is coated with a thin film of "smart skin" containing individualized single-walled carbon nanotubes in a polymeric host. After curing, substrate strains are transmitted through the polymer film to embedded nanotubes. This induces axial strains in the nanotubes, systematically shifting the wavelengths of their characteristic near-infrared fluorescence peaks. To measure strain, a visible laser excites nanotubes at points of interest on the surface, and the near-infrared emission is collected and spectrally analyzed. Observed spectral shifts reveal quantitative strain values. Laboratory tests show sensitivity down to ~400µm, limited by mechanical properties of the polymeric host film. We also vary excitation beam polarization to find the axis of substrate strain. Our method provides spatial resolution down to its gage length of ~100µm. Because the entire substrate is coated with nanoscale strain sensors, measurements can be made at arbitrary locations to construct a full strain map. We will describe recent smart skin refinements involving selection of polymer host, nanotube surfactant, nanotube dispersion method, and preparation protocol. Finally, we characterize the orientational distribution of nanotubes using a probabilistic model.

Citation Download Citation

Peng Sun, Ji-Hoon Kim, Sergei M. Bachilo, R. Bruce Weisman, and Satish Nagarajaiah ""Smart Skin" optical strain sensor using single wall carbon nanotubes", Proc. SPIE 9061, Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems 2014, 906120 (10 April 2014); https://doi.org/10.1117/12.2046539

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