A thin and soft optical tactile sensor for highly sensitive object perception

TL;DR

This paper introduces a thin, soft, and alignment-free optical tactile sensor that uses speckle pattern deformation in silicone to achieve high sensitivity in force measurement and texture recognition, suitable for soft robotics.

Contribution

The study presents a novel, compact, and easy-to-fabricate optical tactile sensor that operates without complex optical assemblies, enabling precise sensing in flexible and wearable applications.

Findings

Root-mean-square force error of 40 mN

Texture classification accuracy of 93.33%

Alignment-free, speckle-based sensing approach

Abstract

Tactile sensing is crucial in robotics and wearable devices for safe perception and interaction with the environment. Optical tactile sensors have emerged as promising solutions, as they are immune to electromagnetic interference and have high spatial resolution. However, existing optical approaches, particularly vision-based tactile sensors, rely on complex optical assemblies that involve lenses and cameras, resulting in bulky, rigid, and alignment-sensitive designs. In this study, we present a thin, compact, and soft optical tactile sensor featuring an alignment-free configuration. The soft optical sensor operates by capturing deformation-induced changes in speckle patterns generated within a soft silicone material, thereby enabling precise force measurements and texture recognition via machine learning. The experimental results show a root-mean-square error of 40 mN in the force measurement and a classification accuracy of 93.33% over nine classes of textured surfaces, including Mahjong tiles. The proposed speckle-based approach provides a compact, easily fabricated, and mechanically compliant platform that bridges optical sensing with flexible shape-adaptive architectures, thereby demonstrating its potential as a novel tactile-sensing paradigm for soft robotics and wearable haptic interfaces.