CoFe nanowires for remote heating using an alternating magnetic field

A nanowire material for remote, rapid and uniform heating of biological samples.
Technology No. 2019-122
IP Status: Pending US Patent; Application #: 16/852,850


  • Cryopreservation
  • Hyperthermia treatment of cancers
  • Remote heating
  • Medical imaging

Key Benefits & Differentiators

  • Rapid and uniform heating even in non-uniform magnetic field
  • Alignment on-demand for faster heating due to magnetic anisotropy of nanowires
  • Suitable for biological uses because of its low cellular toxicity
  • Cryopreservation material can be perfused or suspended
  • Tunable heating rate based on alignment, nanowire dimensions and applied field strength

Magnetic nanowires for rapid heating

Researchers at the University of Minnesota have developed a CoFe-based magnetic nanowire material that generates heat when placed in an alternating magnetic field. High saturation magnetization and magnetic anisotropy of this material makes it ideal for applications that require remote, rapid and uniform heating. Additionally, on-demand alignment of these nanowires offers higher heating rates (up to 1000°C/min). Furthermore, these nanowires can be coated with chemical agents to improve shelf life, buoyancy, dispersibility and biocompatibility. Low cellular toxicity makes this material suitable for applications in thawing of cryopreserved tissues and organs, medical hyperthermia treatments for ablation of diseased tissues, and medical imaging.

Thawing without devitrification

Vitrification, or ice-free cryopreservation, of tissues and organs is performed by the cooling of biomaterials in the presence of cryoprotective agents. Successful rewarming of these cryogenically stored samples requires 1) rapid heating rates to avoid crystallization (devitrification), and 2) uniform heating of the entire volume to avoid fracture or damage. Currently, there are no biocompatible, cryoprotective materials that can facilitate rapid and uniform heating of volumes larger than droplets or thin films. The CoFe magnetic nanowires fabricated by Prof. Stadler and Prof. Bischof, when mixed with a common cryoprotective agent (VS55), shows promising results. Vitrified glycerol and VS55 solutions containing nanowire-cryoprotective agent combination can be heated at rates up to 1000°C/min. With rapid, uniform heating, and minimal cell toxicity, this nanowire material presents an excellent potential for nanowarming cryopreserved biomaterials.

Phase of Development

Proof of Concept. The researchers have fabricated nanowires in 1-2 gram batches. The material has been evaluated for heating rates in cryoprotectants and tested for cytotoxicity in vitro in the presence of alternating magnetic fields.

Bethanie Stadler, PhD
Professor and Associate Head, Electrical and Computer Engineering
External Link (
John C. Bischof, PhD
Professor, Mechanical Engineering Director, Institute for Engineering in Medicine
External Link (

Nanowarming using Au-tipped Co 35 Fe 65 ferromagnetic nanowires.
Nanoscale 11.31 (2019): 14607-14615.,
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