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John O | December 2016

Magnetically activated thermal switches developed using nanofluids

portuguese researchers from the institute of physics of materials at the university of porto and the national associate laboratory institute of nanoscience and nanotechnology have developed a new magnetically activated thermal switch that utilizes the properties of magnetic nanofluids (ferrofluids).



using magnetic fields, the device can change the magnitude and direction of heat flux. (youtube)


the device that they created, which was featured in a recent nanowerk.com article, is capable of controlling both the magnitude and direction of the heat flux by utilizing a magnetic field parallel to the temperature gradient that interacts with ferrofluids.


according to the article, “the magnetically actuated thermal switch is composed of a thermal insulator body with two thermally conductive windows at the top and bottom. this forms a closed container where the magnetic nanofluid is confined.”


when the device is in the “off” position then the nanofluids stays at the bottom of the insulator cage, which is the source of the heat. when the device is “on”, then a magnetic field moves the nanofluids from the bottom to the surface and dissipates the heat away from the surface of the insulator and through an attached heat sink.


the researchers determined that the thermal conductivity variation between the “on” and “off” settings was around 260 percent.


the process was tested on an led and proved capable of controlling the maximum temperature, which leads the engineers to believe that magnetic thermal switches could provide a new thermal management technique across a wide range of applications and electronic devices.


the research will be published in the january issue of nano energy. the abstract of the report stated:


“the exponential rise of power dissipation in electric devices has so far vastly surpassed the performance of power converter systems. new thermal management solutions are therefore in high demand to maintain devices at their optimal temperature and efficiency. here, we present an innovative magnetically actuated thermal switch (mats) based on nanofluids capable of controlling both the magnitude and direction of the heat flux.


“when in the off state (zero applied magnetic field), the nanofluid captures the heat being generated at the heat source. when an external magnetic field is applied (on state), the nanofluid is transported from the heat source to the heat sink where it releases the carried heat. this work (i) provides a detailed description of the mats operating principles, (ii) studies the effect of thickness and operation frequency in its cooling power, (iii) presents numerical simulations to forecast mats behavior and (iv) demonstrates the mats applicability in the thermal management of a 10 w light emitting diode.


“the versatility, simple design, unique operating mode and high performance of the mats suggests that the proposed approach is a promising technology to be used in a vast number of electronic devices, thermal storage systems and thermal management applications.”


to see the thermal switches in action, watch the video below:

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