Viko 2.0: A Hierarchical Gecko-inspired Adhesive Gripper with Visuotactile Sensor

Abstract

Robotic grippers with visuotactile sensors have access to rich tactile information for grasping tasks but encounter difficulty in partially encompassing large objects with sufficient grip force. While hierarchical gecko-inspired adhesives are a potential technique for bridging performance gaps, they require a large contact area for efficient usage. In this work, we present a new version of an adaptive gecko gripper called Viko 2.0 that effectively combines the advantage of adhesives and visuotactile sensors. Compared with a non-hierarchical structure, a hierarchical structure with a multimaterial design achieves approximately a 1.5 times increase in normal adhesion and double in contact area. The integrated visuotactile sensor captures a deformation image of the hierarchical structure and provides a real-time measurement of contact area, shear force, and incipient slip detection at 24 Hz. The gripper is implemented on a robotic arm to demonstrate an adaptive grasping pose based on contact area, and grasps objects with a wide range of geometries and textures.

Figures (8)

• Figure 1: Left: The Viko 2.0 adaptive gripper installed on a robotic arm and grasping an egg. Top-right: A close-up view of the hierarchical gecko-inspired adhesive adapting to the egg. Bottom-right: Real-time tracking of the hierarchical adhesive's contact area (green) and shear force (red arrow).
• Figure 2: Performance evaluation and analysis of hierarchical structures with various hardness. (a) The hierarchical adhesive's pillar structure is subjected to shear loading, demonstrating the stages of conforming to the contact surface. (b) Contact area, as measured by FTIR, plotted against displacement in shear direction for three hierarchical structures of various hardness and a non-hierarchical sample. Top: The FTIR images of the contact area at early and late stages of the shear loading test. Normal adhesion $\mathrm{f_{normal}}$(c) and shear adhesion $\mathrm{f_{shear}}$ (d) versus preload plots of the same structures, showing that hierarchical structures achieve higher adhesive performances.
• Figure 3: Hierarchical structure design and fabrication. (a) The manufacturing process of the hierarchical structure is illustrated in six simplified steps. (b) Computer-aided design (CAD)-rendered graph of the hierarchical structure in an exploded view. (c) Cross-section microscopic photo of the hierarchical structure. The white bar represents 500 $\mu m$.
• Figure 4: Mechanical design of the adaptive gecko gripper. (a) CAD-rendered side view of the gripper with an exploded view of the protective shield. (b) Cross-section view of the sensor module. The polarization filter's position and orientation are labeled to illustrate how it filters out reflected light.
• Figure 5: The F/T sensor and calibrated Viko 2.0 sensing module for shear force measurement showing a close agreement in output.