Agar-based soft tactile transducer with embedded optical fiber specklegram sensor
Eric Fujiwara, Lidia Rosa
Abstract
Tactile transducers monitor physical variables like force and texture through direct contact, featuring indispensable in human–computer interaction and biomedical applications. This work proposes an optical fiber tactile sensor based on specklegram analysis. A soft matrix made of agar embeds a concatenated multimode/single-mode/multimode fiber structure. Forces exerted over the tactile surface disturb the probe mechanically, modulating the output speckle patterns for further processing through image correlation techniques. Experiments evaluated the sensor response as a function of the probe position and the agar matrix composition. Static and dynamic characterizations yielded average force and spatial resolutions of 0.006 N and 0.0008 mm, respectively, with a time response of 34.7 ms, exceeding most of the available optical fiber tactile devices. Compared with intensity and spectral approaches, the specklegram analysis provides high sensitivity (∼1.65 N−1) and relies on a straightforward interrogation system. Furthermore, as a biocompatible, degradable, and easy-to-manipulate material, the agar-based transducer shows perspectives for developing artificial skins and implantable sensors.