Abstract
The influence of fingerprints and their curvature in tactile sensing performance is investigated by comparative analysis of different design parameters in a biomimetic artificial fingertip, having straight or curved fingerprints. The strength in the encoding of the principal spatial period of ridged tactile stimuli (gratings) is evaluated by indenting and sliding the surfaces at controlled normal contact force and tangential sliding velocity, as a function of fingertip rotation along the indentation axis. Curved fingerprints guaranteed higher directional isotropy than straight fingerprints in the encoding of the principal frequency resulting from the ratio between the sliding velocity and the spatial periodicity of the grating. In parallel, human microneurography experiments were performed and a selection of results is included in this work in order to support the significance of the biorobotic study with the artificial tactile system.
Highlights
In this work we investigate the specific role of fingerprints in artificial touch by building tactile systems, inspired to the biological model, that embed artificial fingerprints with different geometries while leaving unchanged the other design features
The presented results provide evidence that the stimulus spatial features are encoded in the spectral content of the firing pattern in human mechanoreceptors and of the outputs of the developed biomimetic artificial fingertip
The observed peak frequency values were at the expected values depending on the tested stimulus spatial period and constant sliding velocity tangential to the fingerpad, while the shape of the fingerprints was shown to have an effect on the possibility to promote and sense such vibrations, not in shifting the peak values on the frequency axis
Summary
In this work we investigate the specific role of fingerprints in artificial touch by building tactile systems, inspired to the biological model, that embed artificial fingerprints with different geometries while leaving unchanged the other design features. This comparative approach is fundamental to define design parameters in developing bioinspired sensory systems but it could be useful to provide hints and suggestions to develop experimental protocols and models in neurophysiology. In order to support the significance of the artificial touch results, in parallel we present a selection of electrophysiological studies by means of microneurographic recordings of the activity of single, identified afferent units in the fingertips of healthy human volunteers [2]. Roughness is associated to the spatial modulation of the surface (i.e., spatial coarseness) and its perception is severely degraded in case of lack of tangential motion between the fingertip and the tactile stimuli (i.e., dynamic vs. static touch) [5,6]
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