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A gripper for flap separation and opening of sealed bags

Sergi Foix, Jaume Oriol, Carme Torras, Júlia Borràs

TL;DR

This work presents a novel gripper design and opening strategy that enables reliable flap separation and robust seal opening in a high-volume repetitive hospital procedure in which nurses manually open up to 240 bags per shift, a physically demanding task linked to musculoskeletal injuries.

Abstract

Separating thin, flexible layers that must be individually grasped is a common but challenging manipulation primitive for most off-the-shelf grippers. A prominent example arises in clinical settings: the opening of sterile flat pouches for the preparation of the operating room, where the first step is to separate and grasp the flaps. We present a novel gripper design and opening strategy that enables reliable flap separation and robust seal opening. This capability addresses a high-volume repetitive hospital procedure in which nurses manually open up to 240 bags per shift, a physically demanding task linked to musculoskeletal injuries. Our design combines an active dented-roller fingertip with compliant fingers that exploit environmental constraints to robustly grasp thin flexible flaps. Experiments demonstrate that the proposed gripper reliably grasps and separates sealed bag flaps and other thin-layered materials from the hospital, the most sensitive variable affecting performance being the normal force applied. When two copies of the gripper grasp both flaps, the system withstands the forces needed to open the seals robustly. To our knowledge, this is one of the first demonstrations of robotic assistance to automate this repetitive, low-value, but critical hospital task.

A gripper for flap separation and opening of sealed bags

TL;DR

This work presents a novel gripper design and opening strategy that enables reliable flap separation and robust seal opening in a high-volume repetitive hospital procedure in which nurses manually open up to 240 bags per shift, a physically demanding task linked to musculoskeletal injuries.

Abstract

Separating thin, flexible layers that must be individually grasped is a common but challenging manipulation primitive for most off-the-shelf grippers. A prominent example arises in clinical settings: the opening of sterile flat pouches for the preparation of the operating room, where the first step is to separate and grasp the flaps. We present a novel gripper design and opening strategy that enables reliable flap separation and robust seal opening. This capability addresses a high-volume repetitive hospital procedure in which nurses manually open up to 240 bags per shift, a physically demanding task linked to musculoskeletal injuries. Our design combines an active dented-roller fingertip with compliant fingers that exploit environmental constraints to robustly grasp thin flexible flaps. Experiments demonstrate that the proposed gripper reliably grasps and separates sealed bag flaps and other thin-layered materials from the hospital, the most sensitive variable affecting performance being the normal force applied. When two copies of the gripper grasp both flaps, the system withstands the forces needed to open the seals robustly. To our knowledge, this is one of the first demonstrations of robotic assistance to automate this repetitive, low-value, but critical hospital task.
Paper Structure (11 sections, 5 equations, 9 figures, 1 table)

This paper contains 11 sections, 5 equations, 9 figures, 1 table.

Table of Contents

  1. Introduction
  2. Related work
  3. Problem statement
  4. Mathematical description of the problem
  5. Gripper design
  6. Evaluation
  7. Buckling force and finger design
  8. Dented-roller
  9. Grasp holding force evaluation
  10. Opening sealed bags
  11. Discussion and Conclusions

Figures (9)

  • Figure 1: (Top) A nurse opening a sealed bag for the operating room preparation. (Bottom) A bi-manual robotic system, based on two UR5E manipulators, performing the same task. First grasping from the table (left) and then opening (right).
  • Figure 2: Schematic drawing of the physical elements involved in the problem: two layers of material laying on a table and a roller in contact with the upper one.
  • Figure 3: Examples of a human manipulating a two layer flat pouch for layer separation: a) Rubbing against each other: grasping on both sides of the layers, moving the finger contact points one against the other to drag away one of the layers and grasp the other. b) Edge discovery: while on a table or in the air, positioning one of the fingers over the edge so that only one of the layers moves. c) Pinch-like manipulation: on a table, one of the fingers holds the layers against the table, to prevent them from moving, and the other finger performs the right amount of pressure to only drag the top layer.
  • Figure 4: Our gripper can be mounted on the RobotiQ Hand-e gripper. The actuated roller structure is fixed, and the couple of holding flexible fingers can be closed against the roller using the Hand-e actuator. For reproducibility purposes, here there are some details of the main parts of the gripper: part 6 is a Dynamixel XM430-W350, part 11 is a Contitech 10/T5/150 SS polyurethane synchronous timing belt, parts 4 and 5 are made of Dragon Skin 30 silicone, as well as the tip of the fingers (part 1).
  • Figure 5: Phases of the layer separation. In each phase we describe the interactions following the taxonomy introduced in blanco2025TDOM.
  • ...and 4 more figures