DenseTact-Mini: An Optical Tactile Sensor for Grasping Multi-Scale Objects From Flat Surfaces
Won Kyung Do, Ankush Kundan Dhawan, Mathilda Kitzmann, and Monroe Kennedy III
Abstract
Dexterous manipulation, especially of small daily objects, continues to pose complex challenges in robotics. This paper introduces the DenseTact-Mini, an optical tactile sensor with a soft, rounded, smooth gel surface and compact design equipped with a synthetic fingernail. We propose three distinct grasping strategies: tap grasping using adhesion forces such as electrostatic and van der Waals, fingernail grasping leveraging rolling/sliding contact between the object and fingernail, and fingertip grasping with two soft fingertips. Through comprehensive evaluations, the DenseTact-Mini demonstrates a lifting success rate exceeding 90.2% when grasping various objects, spanning items from 1 mm basil seeds and small paperclips to items nearly 15mm. This work demonstrates the potential of soft optical tactile sensors for dexterous manipulation and grasping.
Design of DenseTact-Mini
Exploded view of DenseTact-Mini with fingernail.
DenseTact-Mini is an optical tactile sensor with curved soft gel with fingernail, which can easily grasp and detect small daily objects. (a) shows the DenseTact-Mini with PLA fingernail, (b) represents the inner view of the sensor, (c) the fingernail is made of TPU, and (d) shows an image taken from DenseTact-Mini with fingernail.
Grasping strategy of various sizes of an object using DenseTact-Mini
Orange, green, and blue boxes represent the tap, fingernail, and fingertip strategies, respectively.
Tap Grasping
The above demonstrates the tap grasping strategy with the DenseTact-mini. Using one finger without a fingernail, we grasp the object using electrostatic and Van der Waals forces, and confirm the grasp by tapping again. After grasping, the object can be detached by scraping the sensor surface with a fingernail.
Fingernail Grasping
The gif above displays the fingernail grasping strategy. In this method, one sensor with a fingernail and another without are used to grasp the object. During the grasp, either rolling or sliding contact occurs.