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Published May 2024 | Published
Journal Article Open

Permanent fluidic magnets for liquid bioelectronics

Abstract

Brownian motion allows microscopically dispersed nanoparticles to be stable in ferrofluids, as well as causes magnetization relaxation and prohibits permanent magnetism. Here we decoupled the particle Brownian motion from colloidal stability to achieve a permanent fluidic magnet with high magnetization, flowability and reconfigurability. The key to create such permanent fluidic magnets is to maintain a stable magnetic colloidal fluid by using non-Brownian magnetic particles to self-assemble a three-dimensional oriented and ramified magnetic network structure in the carrier fluid. This structure has high coercivity and permanent magnetization, with long-term magnetization stability. We establish a scaling theory model to decipher the permanent fluid magnet formation criteria and formulate a general assembly guideline. Further, we develop injectable and retrievable permanent-fluidic-magnet-based liquid bioelectronics for highly sensitive, self-powered wireless cardiovascular monitoring. Overall, our findings highlight the potential of permanent fluidic magnets as an ultrasoft material for liquid devices and systems, from bioelectronics to robotics.

Acknowledgement

We acknowledge the Henry Samueli School of Engineering & Applied Science and the Department of Bioengineering at the University of California, Los Angeles, for the startup support. J.C. acknowledges the Vernroy Makoto Watanabe Excellence in Research Award at the UCLA Samueli School of Engineering, the Office of Naval Research Young Investigator Award (award ID N00014-24-1-2065), NIH Grant (award ID R01 CA287326), the American Heart Association Innovative Project Award (award ID 23IPA1054908), the American Heart Association Transformational Project Award (award ID 23TPA1141360), the American Heart Association’s Second Century Early Faculty Independence Award (award ID 23SCEFIA1157587), the Brain & Behavior Research Foundation Young Investigator Grant (grant number 30944), and the NIH National Center for Advancing Translational Science UCLA CTSI (grant number KL2TR001882). J.C. and T.T. acknowledge the support from Caltech/UCLA joint NIH T32 Training Grant (award ID T32EB027629). S.L. acknowledges support from an NIH Grant (award ID R01 NS126918). We also acknowledge the insightful comments and careful editing from D. Di Carlo and the UCLA Writing Center for a one-on-one personalized writing consultation.

Contributions

These authors contributed equally: Xun Zhao, Yihao Zhou, Yang Song.

J.C. guided the whole research project. X.Z., Y.Z. and J.C. conceived the idea, designed the experiment, analysed the data, drew the figures and composed the paper. J.X., J.L., T.T. and G.C. assisted in device fabrication and testing. S.L., Y.S. and X.Z. performed the in vivo animal study. All authors have read the paper, agreed to its content and approved the submission.

Data Availability

Source data are provided with this paper. Other relevant information in this study is included in Supplementary Information. Further data are available from the corresponding author upon request.

Conflict of Interest

J.C., X.Z. and Y.Z. have filed a patent related to this work under the US provisional patent application no. 63/596,815 from the University of California, Los Angeles. The authors declare no competing interests.

Copyright and License

© 2024 Springer Nature Limited.

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Additional details

Created:
May 2, 2024
Modified:
May 2, 2024