Below is a series of projects related to the “loop closure grasping” paradigm for versatile grasping of heavy yet fragile objects,
Loop closure grasping: Topological transformations enable strong, gentle, and versatile grasps (2025)
Grasping mechanisms must both create and subsequently hold grasps that permit safe and effective object manipulation. Traditional mechanisms address the different functional requirements of grasp creation and grasp holding using a single morphology, but have yet to achieve the simultaneous strength, gentleness, and versatility needed for many applications. We present “loop closure grasping,” a method of robotic grasping that addresses these different functional requirements through topological transformations between open-loop and closed-loop morphologies. Topologically open-loop mechanisms enable versatile grasp creation via unencumbered tip movement around the object, but lack the simultaneous strength and compliance needed for holding heavy yet fragile objects. Closed-loop mechanisms (e.g., slings) can bear heavy loads in a passive cradled state with effectively infinite bending compliance, but present challenges for grasp creation because the object must somehow enter the loop. Loop closure grasping circumvents the tradeoffs of single-morphology designs by transforming the mechanism’s topology from open-loop to closed-loop between the grasp creation and holding stages. We formalize these morphologies for grasping, formulate the loop closure grasping method, and present a design architecture and implementation using soft growing inflated beams, winches, and clamps. Finally, we demonstrate grasps involving historically challenging objects, environments, and configurations.
Journal Paper: Loop closure grasping: Topological transformations enable strong, gentle, and versatile grasps
News: MIT News, Digital Trends, Interesting Engineering, National Geographic España
A High-Strength, Highly-Flexible Robotic Strap for Harnessing, Lifting, and Transferring Humans (2023)
Safely harnessing and lifting humans for transfer is a challenging unsolved problem for current robots because of the high forces and gentle interaction necessary to do so. Humans are heavy, delicate, deformable, and vary widely in shape and pose. Standard robotic manipulators and end-effectors cannot achieve sufficiently gentle human interaction while applying the high forces needed to lift the body effectively, although many high impact tasks depend on this functionality. Straps, however, are highly beneficial for manually performing this task primarily because of their simultaneously high tensile strength and high compliant bending flexibility, in that (1) the high tensile strength allows for load bearing capacities great enough to lift the full weight of the human, and (2) the high bending flexibility allows for the high passive compliance and conformity needed to safely distribute these large forces across the body.
We present the Robotic Strap, a novel concept and design for a new type of manipulator that can passively harness and lift humans safely as straps can, as well as actively articulate itself around the human into the desired harnessing configurations. The Robotic Strap manipulator is the first robot to demonstrate automatic harnessing and lifting of a human above the ground. The design is characterized by the high tensile strength and bending flexibility of straps, and its implementation consists of a hyper-articulated backbone with rolling-contact joints and embedded soft pneumatic artificial muscles. In our paper, we present the concept, framework, realization, and implementation of the Robotic Strap design, as well as model and experimentally validate the key characteristics. The prototype has a tensile load capacity of 1314.0 N, a maximum joint bending resistance of <0.1 Nm, and successfully demonstrated safe and effective harnessing and lifting of three human participants without any manual intervention. This new manipulator design paradigm unlocks significant advances in robotic handling of heavy yet gentle objects, enabling new capabilities in important applications such as elderly care, occupational therapy, emergency medical response, search and rescue.
Journal Paper: A High-Strength, Highly-Flexible Robotic Strap for Harnessing, Lifting, and Transferring Humans
Tutorial: Make a Robotic Strap: Strong yet flexible robots for lifting humans
Mechanically Programming the Cross-Sectional Shape of Soft Growing Robotic Structures for Patient Transfer (2025)
Pneumatic soft everting robotic structures have the potential to facilitate human transfer tasks due to their ability to grow underneath humans without sliding friction and their utility as a flexible sling when deflated. Tubular structures naturally yield circular cross-sections when inflated, whereas a robotic sling must be both thin enough to grow between them and their resting surface and wide enough to cradle the human. Recent works have achieved flattened cross-sections by including rigid components into the structure, but this reduces conformability to the human. We present a method of mechanically programming the cross-section of soft everting robotic structures using flexible strips that constrain radial expansion between points along the outer membrane. Our method enables simultaneously wide and thin profiles while maintaining the full multi-axis flexibility of traditional slings. We develop and validate a model relating the geometric design specifications to the fabrication parameters, and experimentally characterize their effects on growth rate. Finally, we prototype a soft growing robotic sling system and demonstrate its use for assisting a single caregiver in bed-to-chair patient transfer.
Conference Paper: Mechanically Programming the Cross-Sectional Shape of Soft Growing Robotic Structures for Patient Transfer
Tip-Clutching Winch for High Tensile Force Application with Soft Growing Robots (2024)
The navigational abilities of tip-everting soft growing robots, known as vine robots, are compromised when tip-mount devices are added to enable carrying of payloads. We present a new method for securing a vine robot to objects or its environment that exploits the unique eversion-based growth mechanism and flexibility of vine robots, while keeping the tip of the vine robot free of encumbrance. Our implementation is a tip-clutching winch, into which vine robots can insert themselves and anchor to via powerful overlapping belt friction. The device enables passive, high-strength, and reversible fastening, and can easily release the vine robot. This approach enables carrying of loads of at least 28 kg (limited by the tensile strength of the vine robot body material and winch actuator torque capacity), as well as novel material transport and locomotion capabilities.
Conference Paper: Tip-Clutching Winch for High Tensile Force Application with Soft Growing Robots