Surface deformation tracking and modeling of soft materials

Characterizing the mechanical properties of skin may lead to improvements in surgical scarring, burns treatments, artificial skin science, and disease detection. We present a method of validating a phase-based crosscorrelation method of material point tracking, used to measure surface deformations in soft tissues, using a silicone gel phantom. Tracking of a high spatial-resolution speckle pattern was validated using independent fluorescent microsphere markers. A finite element mesh was deformed according to the tracked speckle pattern, and used to predict the location of the markers. Predictions of microsphere location were compared to stereo-reconstructions. Under a 2900 μm indentation, markers under rms displacements of 125 μm produced a discrepancy between prediction and reconstruction of 23 μm. The same deformation conditions were used to illustrate the use of surface tracking for identifying mechanical properties. A force-driven finite element mesh, using a Neo-Hookean constitutive model, reproduced the surface deformation with an rms error of 172 μm.