Session: 01-08-02: Nondestructive Evaluation and Structural Health Monitoring 2

Paper Number: 160621

160621 - The Next-Generation Strain Sensor: Strain Sensing Smart Skin (S4) for Structural Testing and Health Monitoring 

This study reports a new strain mapping technology developed at Rice University for structural testing and health monitoring using single-wall carbon nanotubes (SWCNTs) sensors called "strain-sensing smart skin" (S4). The basis of the S4 technology is that when a SWCNT is strained by axial compression or stretching, its carbon atoms move more systematically and change the electronic band gap. This effect shifts the wavelength of the carbon nanotube's near-infrared emission peak by predictable amounts that are proportional to the strain along the nanotube axis. In this way, each nanotube can act as a tiny, optically monitored strain gauge. We dilutely disperse nanotubes in a polymer and air-brush onto the specimen to form a submicron thin sensing film that cures at ambient temperature. Subsequent strain in the structural member is transmitted through the film to those embedded SWCNTs, which then act as local strain sensors. To read out the strain values, we illuminate a region of interest with light from a red laser, capture the resulting near-infrared fluorescence, and spectrally analyze that fluorescence. Because the nanotube sensors are randomly distributed throughout the film, we can measure strain at all points of interest.

We can map strains quickly using a special hyperspectral imaging system. A custom computer program quickly analyzes the images to find the peak emission wavelength at each pixel, converts the wavelength shift into strain using a known spectral gauge factor, and compiles the results into a color-coded strain map that can show more than 100,000 independent measurements. The data acquisition and analysis are highly automated and do not require a skilled operator. The measurement results have been cross validated by digital image correlation (DIC) methods and showed advantages over DIC. A sponsored on-site demonstration was conducted at the Airbus Wing Integration Center in the UK. This technology is currently commercialized by LumiStrain, Inc. and has promising potential to provide new strain sensing solution for aerospace structural testing and health monitoring applications.

Presenting Author: Wei Meng LumiStrain, Inc.

Presenting Author Biography: Wei Meng is a co-founder and CEO of LumiStrain, a startup offering novel technology for mechanical strain mapping. Meng earned his M.S. and Ph.D. in civil engineering, co-advised by Satish Nagarajaiah and Bruce Weisman at Rice University, specializing in using carbon nanotubes as strain sensors. Passionate about leveraging microscale solutions for macro-scale challenges, Meng continued his research as a postdoctoral scholar, working to improve the safety and performance of structures through advanced testing and monitoring. Meng is also a Rice Innovation Fellow and Activate Fellow.