Experimental apparatus. (A) Indenter with load cell and von Frey monofilament attached. Three cameras around the indenter synchronously capture images for surface reconstruction via digital image correlation (DIC). (B) A von Frey monofilament (clear, buckles at force of 1 g/9.8 mN) makes contact with a speckled index finger. Randomly applied speckles (white) applied over base layer (black) create a unique pixel pattern to enable surface tracking. (C) – (D) Resultant 3D DIC tracking of skin deformation while in contact with monofilament, where point cloud shows displacement magnitude early (67 ms) and later (767 ms) into the indentation. Jagged white lines show where two overlapping 3D surfaces are stitched together. (E) First principal Lagrangian strain (767 ms). Blue color indicates negative strain, under compression, and yellow color indicates positive strain, under tension.