Whiskers (vibrissae) are functional hairs connected to a mechanically sensitive base and devoted to tactile surveillance by contact or approximation. Nowadays, bioinspired robots equipped with electronic, piezoelectric, or magnetic whisker-like transducers are available for 3D localization, texture recognition, and shape retrieval. However, these sensors demand a multi-axis response for decoding the magnitude and direction of applied stimuli, making the interrogation hardware intricate with excessive measurement channels. Therefore, we propose a biocompatible whisker device based on an optical fiber specklegram sensor, wherein the transducer comprises a flexible, conical structure made of glycerol-agar gel. The whisker foundation embeds a short single-mode fiber section spliced between multimode waveguides to create a hetero-core structure responsive to the vibrissa bending. Thus, we excite the optical fiber with a 633 nm laser and analyze the output speckle field through image correlation techniques. Stimulation with transverse displacements revealed sensitivity and resolution of 0.09 mm−1 and 0.62 mm, respectively. Furthermore, one may calibrate the correlation algorithm with additional reference speckle images to retrieve the bending magnitude and direction with a single optical channel, avoiding wavelength-based demodulation schemes. We anticipate applications of such compact, biocompatible whisker probes in tactile surveillance regarding biomedical and human-robot interaction setups.
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