Figure 3.
The advantages of the increased precision and accuracy of DDE over XCOR were demonstrated by cyclically stretching a PDMS sheet with a spatial gradient in stiffness. (a–d) At a low grip-to-grip strain of 0.003, DDE was able to detect a gradient in stiffness, as evidenced by gradients in the first and second principal strains, whereas XCOR failed to detect gradients in strain above noise. (e–h) At a grip-to-grip strain of 0.03, DDE revealed a smooth gradient in first and second principle strains. XCORR also detected the spatial gradients in strain, however the detected strains were irregular and noisy. (i–l) At a large grip-to-grip strain of 0.1, DDE detected a smooth strain gradient, with local strains greater than 0.2. By contrast, XCOR failed to detect a smooth strain gradient, demonstrating its limitations at high strains. Scale bar, 2 mm. E11, strain in 11 direction.