# Regrafting submillimeter-scale ferromagnetic soft continuums

## TL;DR

Tiny magnetic soft structures can split and rejoin to adapt to confined spaces, improving biomedical navigation and manipulation.

## Contribution

Development of submillimeter-scale FSCs with active division and regrafting capabilities for enhanced biomedical adaptability.

## Key findings

- FSCs can divide and merge to navigate confined spaces and perform multiple endoscopic tasks.
- Ferromagnetic thermoplastic materials enable reversible transitions for regrafting functionality.
- Regrafting enhances flexibility and reconfigurability for biomedical applications.

## Abstract

Submillimeter-scale ferromagnetic soft continuums (FSCs) own innate skills in performing desirable and delicate bending for confined space navigation, especially in biological lumens. However, such tiny structures are difficult to endow with complex designs, thereby challenging to realize more sophisticated functions for various purposes, especially in vivo therapies and manipulations. Inspired by grafting for muscles and plants, we propose submillimeter-scale FSCs that can actively divide into pieces at any region, and conversely, the pieces can actively graft to each other to form the original structure or novel shapes. We define these functions as regrafting, comprising self-division and self-mergence. Implementing regrafting implies actively switching between two opposing characteristics: sufficient continuum structural strength for steering loads and a low fracture strength for division and mergence. Therefore, we developed ferromagnetic thermoplastic soft materials to replace the widely applied thermoset materials for continuums and shed the commonly required coating layers. Being made of the ferromagnetic material family that can undergo reversible elastomer-fluid transitions, the proposed FSCs can perform arbitrary division-mergence and navigate confined spaces for multiple endoscopic tasks in one go. Endowed with enhanced flexibility and reconfigurability in situ by regrafting, the proposed FSCs may open a multifunctional path for operating a wider range of biomedical tasks.

Ferromagnetic soft continuums (FSCs) can navigate within confined biological spaces but are limited in complex designs due to their small size. Here, authors develop submillimeter-scale FSCs that can actively divide and reconfigure into flexible shapes, enhancing in situ adaptability for biomedical applications.