Aligned Nanofibers Cool Down Hot Electronic Devices

Market competitions force the engineers to design electronic devices more powerful but importantly smaller in size. Such smaller size electronic devices face the problem of heat generated from the process cycle, thus experience poor reliability. Efficient thermal interface materials that are able to remove heat from electronic devices have been in great demand.

 While many have been in search of novel materials with higher thermal conductivityProf. Baratunde Cola from theGeorgia Institute of TechnologyUniversity of Texas at Austin thought in the other way, which resulted in the development of innovative thermal material. Prof Cola primarily had the goal of identifying suitable material and improving the contact as poor contact fails to relax out the stress developed from thermal cycling. His team and collaborators from and the Raytheon Company realized that even many of the best thermal materials in today market were actually making poor contact at the interface.  As known, polymeric nanofiberous structure is one of the most preferable choices to have better contact, thanks to its large surface area and cost effectiveness. The team chose conjugated polymer (polythiophene) that is used in solar cells and electronic devices owing to its high temperature stability despite the fact that it is a poor heat conductor because of its amorphous structure.

Through an innovative way, the group of researchers include Dr. Virendra Singh and Thomas Bougher and led by Prof. Cola demonstrated that the conjugated polymers can work as an efficient thermal material. They produced arrays of aligned polymer nanofibers using electropolymerization process that facilitated the transfer of phonons efficiently. In fact, it was a multi-step process that required an alumina template containing tiny pores covered by an electrolyte containing precursors (monomers). By applying an electrical potential to the template, the team guided electrodes at the base of each pore to attract the monomers and form hollow nanofibers. After formation, the nanofibers were cross-linked, and the template was removed.

Thomas Bougher, Virendra Singh and Prof. Baratunde Cola
Thomas Bougher, Virendra Singh and Prof. Baratunde Cola, Photo courtesy:  Candler Hobbs, Georgia Tech 

Using the template assisted process, the polymer chains of polythiophene were highly aligned – about 40 %. Aligning not only helped the nanofibers to transfer the heat-conducting phonons effectively, but also prevented the brittleness, which in turn facilitated to expand and contract during heating and cooling cycles. The team also found that the aligned polymer nanofibers have a higher thermal stability because the bonding was stronger than in typical polymers. The aligned polymeric nanofibers was able to operate up to 200°C through 80 thermal cycles without any noticeable change in performance, and also shown to conduct heat 20 times better than the original polymer.

As developed aligned nanofiberous material could reduce the need for larger thickness (conventional materials are in thickness of 50 to 75 μm), also work as reliable thermal interface material just with μm thickness. Owing to its great benefits to draw heat away from electronic devices in servers, automobiles, high-brightness LEDs and mobile devices, Prof Cola’s team believe that it could be scaled up for commercialization.

This research work was published in the top ranked journal “Nature Nanotechnology

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