Flexible and reconfigurable radio frequency electronics realized by high-throughput screen printing of vanadium dioxide switches

Abstract

Smart materials that can change their properties based on an applied stimulus are in high demand due to their suitability for reconfigurable electronics, such as tunable filters or antennas. In particular, materials that undergo a metal–insulator transition (MIT), for example, vanadium dioxide (VO2) (M), are highly attractive due to their tunable electrical and optical properties at a low transition temperature of 68 °C. Although deposition of this material on a limited scale has been demonstrated through vacuum-based fabrication methods, its scalable application for large-area and high-volume processes is still challenging. Screen printing can be a viable option because of its high-throughput fabrication process on flexible substrates. In this work, we synthesize high-purity VO2 (M) microparticles and develop a screen-printable VO2 ink, enabling the large-area and high-resolution printing of VO2 switches on various substrates. The electrical properties of screen-printed VO2 switches at the microscale are thoroughly investigated under both thermal and electrical stimuli, and the switches exhibit a low ON resistance of 1.8 ohms and an ON/OFF ratio of more than 300. The electrical performance of the printed switches does not degrade even after multiple bending cycles and for bending radii as small as 1 mm. As a proof of concept, a fully printed and mechanically flexible band-pass filter is demonstrated that utilizes these printed switches as reconfigurable elements. Based on the ON and OFF conditions of the VO2 switches, the filter can reconfigure its operating frequency from 3.95 to 3.77 GHz without any degradation in performance during bending.

Metamaterial Absorbers: From Tunable Surface to Structural Transformation

“…[ 41,121 ] Among various PCMs, vanadium dioxide (VO 2 ) has attracted tremendous interest as tunable building blocks in active MAs due to the several orders of magnitude increase in electrical conductivity at a relatively low transition temperature of 68 °C. [ 86,122–124 ] As illustrated in Figure a,b, employing VO 2 into MA design provides a simple approach to achieve reconfigurability and tunability of MAs. [ 27,118,119,125–127 ]…”

Element doping: a marvelous strategy for pioneering the smart applications of VO2

“…Besides, the large-area and high-resolution printing of VO 2 switches on various substrates has been realized by screen printing. 171 4 Smart applications of elementdoped VO 2 4.1 Energy conservation and energy storage 4.1.1 Smart window. The smart window is a special window that can dynamically and reversibly regulate undesired thermal radiation and thus maintain the sense of comfort in the room.…”

Multifunctional Flexible Vanadium Dioxide Films

“…An inkjet-printed technique has been developed to prepared flexible VO 2 switches based on VO 2 ink. − First, highly crystalline VO 2 particles were synthesized as the fundamental material; next, a mixture of terpineol and ethanol was utilized as the solvent, while ethyl cellulose (EC) was used as the organic binder, dispersing agent, and rheological modifier; then, VO 2 was added into the mixed solution with designed ratio, followed by agitation to obtain a homogeneous and stable VO 2 ink (Figure A) . This ink was directly used for screen printing to deposit VO 2 switches on various substrates.…”

“…The red and blue lines represent the switch in shapes I and II, respectively. (A)–(H) Reproduced with permission from ref , copyright 2020 Springer Nature. (I)–(L) Reproduced with permission from ref , copyright 2021 Springer Nature.…”

“…After one month, the ON resistance began to increase, which caused a sharp decrease in the ON/OFF ratio. Thus, we can find that the stability of the flexible VO 2 switches need further protection for long-term applications …”