Addition of a biomimetic fingerprint on an artificial fingertip enhances tactile spatial acuity

The fingerprint is a morphological aspect of the human fingertip that has interesting implications for our sense of touch. Previous studies focused on how the fingerprint affects the perception of stimuli that excite high temporal frequencies, such as for texture perception. These studies also only add papillary ridges to their sensors. Here, we endow a biomimetic sensor with both papillary ridges (fingerprint) and a dermal stiffness contrast (stiffer intermediate ridges), and assess the impact on localization perception accuracy. The sensor is based on a novel modular version of a three-dimensional printed tactile sensor (TacTip). Tactile data were collected with these tips on nine stimuli with varying curvature. The location perception acuity of three tips [smooth, fingerprint, and fingerprint (cores)] were compared with a probabilistic classification method, finding that both fingerprinted tips increase the perceptual acuity of small spatial scales. Interestingly, the fingerprint variant had poorer accuracy than the smooth tip for larger spatial scales; however, adding cores to enhance the dermal stiffness counteracted the degradation of accuracy. This supports the theories that the fingerprint aids the classification of edges and smaller spatial scales, and demonstrates that the addition of a fingerprint to an artificial tactile sensors improves its acuity.