Fully Inkjet‐Printed VO 2 ‐Based Radio‐Frequency Switches for Flexible Reconfigurable Components

et al. 2019

Adv Elect Materials

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phase-change temperature. In addition, VO 2 also possesses different polymorphisms, including VO 2 (A), [6] VO 2 (B), [7,8] VO 2 (D), [9] VO 2 (M), [10] VO 2 (R), [11] and VO 2 (P). [12] Among them, the VO 2 monoclinic (M) phase is the most attractive due to its MIT behavior at a relatively low temperature of 68 °C. [13] However, the simultaneous creation of polymorphs results in a mixture phase and makes it extremely difficult to achieve a pure VO 2 (M) phase. The MIT temperature of VO 2 (M) can also be further reduced by doping [14] and by varying the particle sizes. [10,12] This makes VO 2 a promising material for many practical applications, including sensors, [15] thermochromic smart windows, [16] field effect transistors, [17] radio-frequency (RF) switches, [18] terahertz nanoantennas, [19] reconfigurable antennas, [20] memory, [21] and energy. [22,23] Due to the exciting applications mentioned above, considerable effort has been devoted to producing VO 2 (M) in the form of a thin film, primarily with a dry vapor process using chemical vapor deposition, [24] sputtering, [25] metalorganic molecular beam epitaxy deposition, [26] pulsed laser deposition, [27,28] e-beam evaporation, [29] and by electric field inducing ions migration. [30] On the other hand, several bulk nanomaterials in solution processes with different shapes and sizes using sol-gel [31] and hydrothermal synthesis [32] are reported. The VO 2 thin-film deposition techniques using dry vapor processes require an ultrahigh level of vacuum conditions (10 −6 Torr) and sometimes very high processing temperatures (400-600 °C). The process also requires expensive masks and nanolithography for device prototyping. However, the solution-based VO 2 preparation processes are the simplest, require lower processing temperatures, and are highly scalable. Among the solution-based processes, hydrothermal synthesis is the most widely adopted technique due to its high-quality and purephase VO 2 nanomaterial production. [5] The only disadvantage of hydrothermal synthesis is the longer reaction time required, up to 2-4 d, to achieve pure VO 2 (M). For practical applications, VO 2 (M) nanostructures must be deposited in the form of films. Spin coating is one technique to realize VO 2 films, but large-area processing and direct patterning are not possible. [31] With the surge in inkjet printing, which is extremely low cost, completely digital, and highly suitable for rapid prototyping or large-scale manufacturing, realizing VO 2 film through inkjet The metal-insulator transition (MIT) phase change of vanadium dioxide (VO 2 ) materials has facilitated many exciting applications. Among the various crystal phases of VO 2 , the monoclinic (M) phase is the only one that demonstrates low-temperature (≈68 °C) MIT behavior. However, the synthesis of pure VO 2 (M) is challenging because various polymorphs, such as VO 2 (A), VO 2 (B), and VO 2 (D), are also typically formed during the process. Furthermore, to achieve pure crystalline VO 2 (M) phase, very long reaction times, up...

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

Development of VO₂‐Nanoparticle‐Based Metal–Insulator Transition Electronic Ink

et al. 2019

Adv Elect Materials

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“…In recent years, smart electronics have gained tremendous attention in both scientific and industrial fields 1 due to their ability to transform, change their shape or tuning, and modulate their properties in response to external stimuli, such as mechanical deformation 2 , thermal heating 3 , an electrical field 4 , or a magnetic force 5 . Creating smart electronics and exploring their versatile applications in smart energy devices 4,6 , smart skins 7,8 , smart wearables [9][10][11] , reconfigurable electronics [12][13][14] , and even smart cities 15 , has raised new requirements for functional materials that can tune their properties according to specific demands 6,13,16,17 . Despite a diverse cluster of new materials, such as carbon-based materials 2,10 , transition metal dichalcogenides 18 , and metal oxide nanocrystals 19 , metal insulator transition (MIT) materials have great promise due to their easy and reversible tunability between the metal and insulator via various external stimuli [20][21][22][23] .…”

Section: Introductionmentioning

confidence: 99%

“…Despite a diverse cluster of new materials, such as carbon-based materials 2,10 , transition metal dichalcogenides 18 , and metal oxide nanocrystals 19 , metal insulator transition (MIT) materials have great promise due to their easy and reversible tunability between the metal and insulator via various external stimuli [20][21][22][23] . For example, vanadium dioxide (VO 2 ) (M) exhibits MIT behavior by possessing an insulating state at room temperature and a metallic state at a critical temperature (~68°C) 24 and is attracting a substantial amount of interest for optical and electrical electronic applications 12,17,[25][26][27][28][29] . Currently, a variety of techniques, such as radio frequency (RF) sputtering 30,31 , pulsed laser deposition 32 , and electron beam evaporation 29 , have been evaluated to fabricate high-quality VO 2 films with an ON/OFF ratio of over 10 4 .…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2020

Microsyst Nanoeng

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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.

“…Also, these filters are The major challenge with the fully printed reconfigurable components is that the switches are difficult to print. We have recently demonstrated a vanadium dioxide (VO2) based ink and a printed switch [24]. VO2 is a metal-insulator-transition (MIT) material, which has insulating properties at room temperature and becomes conductive at the transition temperature (68 °C in this case).…”

Section: Introductionmentioning

confidence: 99%

Additively Manufactured Dual-Mode Reconfigurable Filter Employing VO₂-Based Switches

IEEE Trans. Compon., Packag. Manufact. Technol.

et al. 2020

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Modern wireless devices operate on multiple frequency bands, and thus can benefit from frequency reconfigurable Radio Frequency (RF) components, especially filters as they are typically larger in size and are required for every frequency band. In addition, many applications such as wearable electronics, desire stable performance from the devices when they are bent or flexed. However, most of the reconfigurable filters are built on rigid substrates and utilize expensive discrete RF switches, which need to be soldered to the filters. In this work, we present a fully printed filter that achieves reconfigurability through printed Vanadium Dioxide (VO2) based switches, which are extremely low cost and do not require any soldering for their attachment. The filter design is based on a dual-mode resonator which enables a second-order filter despite a single resonator, thus helping in making the filter compact. It also helps in maintaining a decent insertion loss (2.6 dB), despite relatively low conductivity of the metallic ink. The switches, when activated thermally through a printed heater at the backside, reconfigure the frequency from 4 GHz to 3.75 GHz. The filter has been realized on a flexible Kapton substrate, making the filter conformable to any surface. Measurements under various bending conditions reveal stable performance, making this filter design suitable for a number of wearable and Internet of Things applications.