Development of VO2 -Nanoparticle-Based Metal-Insulator Transition Electronic Ink

The metal–insulator transition (MIT) phase change of vanadium dioxide (VO2) materials has facilitated many exciting applications. Among the various crystal phases of VO2, the monoclinic (M) phase is the only one that demonstrates low-temperature (≈68 °C) MIT behavior. However, the synthesis of pure VO2 (M) is challenging because various polymorphs, such as VO2 (A), VO2 (B), and VO2 (D), are also typically formed during the process. Furthermore, to achieve pure crystalline VO2 (M) phase, very long reaction times, up to 2–4 days, are typically required. In this work, an additional annealing step is introduced post nanoparticle preparation, which not only reduces the complete synthesis time from days to only 6 h but also removes the impure phases and helps in achieving the desired pure VO2 (M) phase. This work covers the complete synthesis and characterization details of such as-prepared nanoparticles. A VO2 (M)-nanoparticle-based ink is formulated for the inkjet printing of films with controlled thicknesses. The inkjet-printed films are investigated for their electrical conductivity with external stimuli such as temperature and electrical current. Finally, a fully printed antenna is devised that can change its frequency based on the different states of the VO2 film.