Mechanically Programming the Cross-Sectional Shape of Soft Growing Robotic Structures for Patient Transfer

TL;DR

This paper introduces a mechanical programming method for soft growing robotic structures that allows for customizable cross-sectional shapes, enabling effective patient transfer without rigid components.

Contribution

It presents a novel technique using flexible strips to control the cross-section of soft robots, maintaining flexibility while achieving desired shapes.

Findings

The model accurately predicts geometric design outcomes.

Flexible strips enable wide and thin profiles simultaneously.

The robotic sling successfully assisted patient transfer.

Abstract

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.