Data and code from: Sub-surface deformation of individual fingerprint ridges during tactile interactions

The human fingertip can detect small tactile features with a spatial
acuity roughly the width of a fingerprint ridge. However, how individual
ridges deform under contact to support accurate and high-precision tactile
feedback is currently unknown. The complex mechanical structure of the
glabrous skin, composed of multiple layers and intricate morphology within
which mechanoreceptors are embedded, makes this question challenging.
Here, we used optical coherence tomography to image and track sub-surface
deformations of hundreds of individual fingerprint ridges across ten
participants and four individual contact events at high spatial resolution
in vivo. We calculated strain patterns in both the stratum corneum and
viable epidermis in response to a variety of passively-applied tactile
stimuli, including static indentation, stick-to-slip events, sliding of a
flat surface in different directions, and interaction with small tactile
features, such as edges and grooves. We found that ridges could stretch,
compress, and undergo considerable shearing orthogonal to the skin
surface, but there was limited horizontal shear. Therefore, it appears
that the primary components of ridge deformation and, potentially, neural
responses are deformations of the ridge flanks and their relative
movement, rather than overall bending of the ridges themselves. We
conclude that the local distribution of mechanoreceptors across the ridges
might be ideally suited to extract the resulting strain gradients and that
the fingertip skin may possess a higher mechanical spatial resolution than
that of a single ridge.