Untethered soft machines and robots enabled by hard-magnetic soft materials

We introduce our recent works on advanced fabrication and mechanics of hard-magnetic soft materials towards the development of untethered soft machines and robots actuated and controlled by magnetic fields. 

- Abstract

Soft active materials capable of transforming into programmed shapes in a remotely controllable manner can bring promising applications in diverse fields such as soft robotics and biomedicine. Several types of shape-programmable soft matter have been proposed but often limited to simple geometries and thus with limited functionalities. Moreoever, such transformations are often slow, with the shape changes taking sometimes a few minutes to complete. Existing soft robots are fast but often heavily tethered because they need to be pneumatically actuated and thus practically limited for biomedical applications.

In the first paper (link) attached, we introduced a method of printing ferromagnetic domains in soft materials to realize highly responsive and fully programmable soft active materials that quickly transform into multiple desired shapes in applied magnetic fields as shown in the figure below.

In the second paper (link), we also discussed the mechanics of this new class of materials, so-called hard-magnetic soft materials, for which we developed a simple nonlinear field theory to describe the coupling of finite deformation and magnetic fields that results from the intricate patterns of programmed magnetic domains. The model-based simulation also enabled us to quantitatively predict the complex shape changes, thereby guiding the optimal design of our magnetic soft robots and actuators. 

We believe the emerging field of research from this new class of soft active materials would offer new possibilities in practical applications, especially in biomedicine, such as targeted drug delivery or minimally invasive surgery, where such untethered soft machines and robots remotely controlled by magnetic fields can be useful. To open this new venue, we are trying to further expand our materials and fabrication platform as well as a fundamental understanding of our magnetic soft active materials. 

1. Y. Kim, H. Yuk, R. Zhao, S. A. Chester, X. Zhao, "Printing Ferromagnetic Domains for Untethered Fast-transforming Soft Materials," Nature 558, 274-279 (2018). [Link]
2. R. Zhao, Y. Kim, S. A. Chester, P. Sharma, X. Zhao, "Mechanics of Hard-magnetic Soft Materials," Journal of the Mechanics and Physics of Solids 124, 244-263 (2018). [Link]

- What's more?

Another article (link) may also be worth reading if you find this posting interesting.
If interested, please also check our research videos (link) which are not only interesting but also help better understand our works. 
For more detailed information, please refer to the attached papers.

- Acknowledgement

Last but not least, I need to mention that I am posting these works on behalf of my wonderful collaborators which include:
Mr. Hyunwoo Yuk (MIT), Prof. Ruike Zhao (OSU), Prof. Shawn Chester (NJIT), Prof. Pradeep Sharma (Univ. of Houston), and Prof. Xuanhe Zhao (MIT), all of who greatly contributed to those works. 

Thank you for reading this post!