When designing an electronic system, the influence of the surrounding environment can be considered either a nuisance (and hence something to be suppressed) or a convenient knob that can be turned to affect the material properties. In the latter view, an ideal scenario would be to have the system designed in such a way that the external effect could be amplified and not only the local material characteristics but also the collective device property can be drastically manipulated with environmental stimuli
In a study [1] in collaboration with the Groups led by Yuki Sato and Shriram Ramanathan (Harvard University), we demonstrated for the first time a metamaterial electric circuit integrated onto a silicon wafer that can dynamically reconfigure the preferred conduction paths. This is enabled by introducing a correlated electron oxide thin film that undergoes a sharp thermally-induced insulator-metal transition in the circuit.
The tunable metamaterial is designed with the aid of two interwoven coordinate-transformation equations and implemented with a network of thin-film resistors and vanadium dioxide (\(VO_2\)), as shown in the figure top panels. The strong temperature dependence of \(VO_2\) electrical conductivity results in a significant modification of the resistor network behavior, and we provided experimental evidence for a reconfigurable metamaterial electric circuit that not only mimics a continuous medium, but is also capable of responding to thermal stimulation through dynamic variation of its spatial anisotropy.
As shown in the figure bottom panels, upon external temperature change, the overall effective functionality of the material switches between a “truncated cloak” and a “concentrator” for electric currents.
These results suggest that the metamaterial paradigm may be used to provide solutions for tangible compact electronics using thin-film technologies. Traditionally, electronic systems comprise several blocks, each designed to play a specific role. A smarter design approach could rely on a single unit capable of handling multiple functions, such as carrying electric current and heat simultaneously but independently. A potential first step in this direction has been shown recently, by using metamaterial structures designed with the framework of multiphysics transformations. The same goal may be approached through a different path of utilizing phase-change materials that have varying responses in different physical domains.
Moreover, our demonstration paves the way for future high performance chips that can be environmentally responsive, for instance moving heat away from hot spots in circuits to colder regions by simply being aware of local temperature. This can overcome significant constraints that limit innovation in information processing today where heat dissipation is the primary bottleneck.
We demonstrate an innovative multifunctional artificial material that combines exotic metamaterial properties and the environmentally responsive nature of phase-change media. The tunable metamaterial is designed with the aid of two interwoven coordinate-transformation equations and implemented with a network of thin-film resistors and vanadium dioxide (\(VO_2\)). The strong temperature dependence of \(VO_2\)electrical conductivity results in a significant modification of the resistor network behavior, and we provide experimental evidence for a reconfigurable metamaterial electric circuit that not only mimics a continuous medium, but is also capable of responding to thermal stimulation through dynamic variation of its spatial anisotropy. Upon external temperature change, the overall effective functionality of the material switches between a “truncated cloak” and a “concentrator” for electric currents. Possible applications may include adaptive matching resistor networks, multifunctional electronic devices, and equivalent artificial materials in the magnetic domain. Additionally, the proposed technology could also be relevant for thermal management of integrated circuits.
@article{IJ115_PRB_91_134105_2015, title = {Reconfigurable anisotropy and functional transformations with \(VO_2\)-based metamaterial electric circuits}, author = {Savo, Salvatore and Zhou, You and Castaldi, Giuseppe and Moccia, Massimo and Galdi, Vincenzo and Ramanathan, Shriram and Sato, Yuki}, journal = {Physical Review B}, volume = {91}, issue = {13}, pages = {134105}, numpages = {10}, year = {2015}, month = apr, publisher = {American Physical Society}, doi = {10.1103/PhysRevB.91.134105}, url = {http://link.aps.org/doi/10.1103/PhysRevB.91.134105} }