A Miniaturized Autonomous Thermomagnetic Generator

Abstract

Thermomagnetic generators (TMG) are promising devices for converting low-grade waste heat into electricity. Self-actuation using permanent magnets is the key to autonomy. Tailoring thermomagnetic materials in the form of flexible and freestanding films is a way towards high power-density through fast, and efficient heat transfer. Design optimization, and the use of micromagnets represent a unique opportunity towards miniaturization. Here the operation and performance of a TMG using a flexible freestanding Gd film as the active substance, and an array of NdFeB micromagnets as field source is presented. The Gd film self oscillates under the effect of the magnetic field gradient, entering in contact with the heat source, and the heat sink alternatively. At an operating frequency of $34$~Hz, a designed piezoelectric spring converts the mechanical oscillation into electrical energy, reaching up to 4.7 μW power-output with $20$\textdegree C temperature difference. The magnetic field gradient acting over the thermal switch, and triggering the caloric response of this 16 μm thick Gd film, is generated by an array of 50 μm thick NdFeB micromagnets, which produces a $0.2$~T variation in field strength over a 45 μm gap. The power density normalized to the combined volume of the Gd film and of the magnet reaches up to 1.46mW cm⁻³.

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Cite

BibTeX RIS

BibTeX

@article{almanza2026miniaturized,
  title = {{A Miniaturized Autonomous Thermomagnetic Generator}},
  author = {Morgan Almanza and Doan Nguyen Ba and Nesrine Belkadi and Erika Fontana and Jean‐eudes Duvauchelle and Sukhendu Sadhukhan and Loïc Becerra and Thibaut Devillers and Massimiliano Marangolo and Fabien Parrain and Nora M Dempsey and Martino Lobue},
  journal = {Advanced Functional Materials},
  year = {2026},
  month = oct,
  doi = {10.1002/adfm.78986},
  url = {https://hal.science/hal-05805684v1},
  note = {CC BY 4.0},
}

RIS

TY  - JOUR
TI  - A Miniaturized Autonomous Thermomagnetic Generator
AU  - Morgan Almanza
AU  - Doan Nguyen Ba
AU  - Nesrine Belkadi
AU  - Erika Fontana
AU  - Jean‐eudes Duvauchelle
AU  - Sukhendu Sadhukhan
AU  - Loïc Becerra
AU  - Thibaut Devillers
AU  - Massimiliano Marangolo
AU  - Fabien Parrain
AU  - Nora M Dempsey
AU  - Martino Lobue
PY  - 2026
DA  - 2026/10/15
JO  - Advanced Functional Materials
DO  - 10.1002/adfm.78986
UR  - https://hal.science/hal-05805684v1
AB  - Thermomagnetic generators (TMG) are promising devices for converting low-grade waste heat into electricity. Self-actuation using permanent magnets is the key to autonomy. Tailoring thermomagnetic materials in the form of flexible and freestanding films is a way towards high power-density through fast, and efficient heat transfer. Design optimization, and the use of micromagnets represent a unique opportunity towards miniaturization. Here the operation and performance of a TMG using a flexible freestanding Gd film as the active substance, and an array of NdFeB micromagnets as field source is presented. The Gd film self oscillates under the effect of the magnetic field gradient, entering in contact with the heat source, and the heat sink alternatively. At an operating frequency of $34$~Hz, a designed piezoelectric spring converts the mechanical oscillation into electrical energy, reaching up to 4.7 μW power-output with $20$\textdegree C temperature difference. The magnetic field gradient acting over the thermal switch, and triggering the caloric response of this 16 μm thick Gd film, is generated by an array of 50 μm thick NdFeB micromagnets, which produces a $0.2$~T variation in field strength over a 45 μm gap. The power density normalized to the combined volume of the Gd film and of the magnet reaches up to 1.46mW cm^−3.
SN  - 1616-301X
SN  - 1616-3028
ER  -

Abstract

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