Video Extensometer Marking Techniques for Soft Tissue Testing
Extensometers are often used to accurately measure the deformation of a material under mechanical loading. Due to the fragile nature of biological soft tissues, such as fascia, skin and intestinal lining, a non-contacting extensometer is the ideal solution for measuring tensile strain in these specimens.
Our video extesnometers use a high-resolution digital camera and advanced real-time image processing to make precise axial and transverse (optional) strain measurements on test specimens. Because these biological specimens are soft, moist and vary in color, the challenge in acquiring strain data lies in the marking technique. We conducted a study to find the best methods for marking biological specimens The results showed that there are a wide variety of marks that can be used depending on the coloring of your sample, whether or not you need to test in a bath or the surface characteristics of your specimen. The following examples are used to demonstrate.
- For ambient testing of soft, compliant and moist tissue specimens, we recommend paper dots or graphite powder. The absorbancy of both allow for enough adhesion to test the specimen through failure. White dots usually work best, but if not, try black dots.
- For in-vivo testing of soft, compliant and moist tissue specimens, we recommend either of the following: black magic marker, cyanoacrylate (superglue), or a mixture of graphite powder and cyanoacrylate (superglue). In all cases, the mark should be applied in the shape of a line or dot. Although superglue is clear, it is actually very reflective and is most often recommended.
- For in-vivo testing of rigid, flat materials, we recommend magic marker dots or lines. Paint can also work, but you need to look for a water-resistant paint.
- For in-vivo testing of rigid, round materials or wire, we recommend adhesive putty. The putty should be wrapped around the specimen and molded into a round shape.
The Instron Standard Video Extensometer(SVE)is a non-contacting extensometer that meets most testing standards for accuracy. The SVE can be used to measure axial strain in a wide variety of materials through failure and provides many advantages over traditional contacting extensometers.
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