In this article, we demonstrate the application of digital image correlation (DIC) in evaluating the strainsand Poisson ratio of a range of soft materials in terms of their spatial and temporal resolutions. Four samplesof Polydimethylsiloxane (PDMS) were used as control substances and were measured to have Poisson ratiosof 0.498, 0.503, 0.500, and 0.499, in agreement with the reported incompressible value of 0.50 [1]. Twocarbon nanotube (CNT) elastomers of identical composition, but one of a homogeneous and the other of aninhomogeneous CNT distribution, were used to determine the spatial resolution with good results (Fig. 2and Fig. 4). The relaxation of a 3D polydomain liquid crystal elastomer (3D-LCE), a cholesteric liquidcrystal elastomer (CLCE), and a polyacrylamide gel (PAAm) in water, were used to determine the temporalresolution. A 10min video short at 25fps was used to evaluate the time dependence of the 3D-LCE overwhich time an increase in the Poisson ratio was observed. The 3D-LCE relaxes from its initial state at 0.42to 0.50, converging towards incompressibility. The CLCE was found to have a similar initial value of 0.44but converged to0:60, a consequence of its anisotropic nature. PAAm gel relaxation in water was studiedover a time period of 7 hours with digital images taken periodically every minute. Its Poisson ratio wasfound to decrease smoothly from 0.50 to 0.26, with an accompanying reduction in force. The equilibriumresult compares well to the 0.25 value predicted by theories of the strain induced swelling of dilute gels. Insummary, we nd DIC to be a powerful and easy to implement method of accurately measuring local strainsin a range of soft materials
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