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Updated: Jul 2, 2026

Studying Large Amplitude Oscillatory Shear Response of Soft Materials
Published on: April 25, 2019
'Seeing' Strain in Soft Materials
Zhiyong Xia1, Vanessa D Alphonse2, Doug B Trigg3
1Applied Physics Laboratory, The Johns Hopkins University, Laurel, MD 20723, USA. Zhiyong.Xia@jhuapl.edu.
Abstract:
Several technologies can be used for measuring strains of soft materials under high rate impact conditions. These technologies include high speed tensile test, split Hopkinson pressure bar test, digital image correlation and high speed X-ray imaging. However, none of these existing technologies can produce a continuous 3D spatial strain distribution in the test specimen. Here we report a novel passive strain sensor based on poly(dimethyl siloxane) (PDMS) elastomer with covalently incorporated spiropyran (SP) mechanophore to measure impact induced strains. We have shown that the incorporation of SP into PDMS at 0.25 wt% level can adequately measure impact strains via color change under a high strain rate of 1500 s-1 within a fraction of a millisecond. Further, the color change is fully reversible and thus can be used repeatedly. This technology has a high potential to be used for quantifying brain strain for traumatic brain injury applications.
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Consider a rod that is fixed at one end and subjected to an axial force at the free end. This axial force induces stress within the rod, leading to its elongation. As the axial force increases, so does the elongation of the rod, illustrating a direct relationship between the force applied and the resulting...

