Performance Limits of Microactuation with Vanadium Dioxide as a Solid Engine

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• 作者：Kevin Wang ; Chun Cheng ; Edy Cardona ; Jingyang Guan ; Kai Liu ; Junqiao Wu
• 刊名：ACS Nano
• 出版年：2013
• 出版时间：March 26, 2013
• 年：2013
• 卷：7
• 期：3
• 页码：2266-2272
• 全文大小：421K
• 年卷期：v.7,no.3(March 26, 2013)
• ISSN：1936-086X

文摘

Miniaturization of the steam engine to the microscale is hampered by severe technical challenges. Microscale mechanical motion is typically actuated with other mechanisms ranging from electrostatic interaction, thermal expansion, and piezoelectricity to more exotic types including shape memory, electrochemical reaction, and thermal responsivity of polymers. These mechanisms typically offer either large-amplitude or high-speed actuation, but not both. In this work we demonstrate the working principle of a microscale solid engine (渭SE) based on the phase transition of VO₂ at 68 掳C with large transformation strain (up to 2%), analogous to the steam engine invoking large volume change in a liquid鈥搗apor phase transition. Compared to polycrystal thin films, single-crystal VO₂ nanobeam-based bimorphs deliver higher performance of actuation both with high amplitude (greater than bimorph length) and at high speed (greater than 4 kHz in air and greater than 60 Hz in water). The energy efficiency of the devices is calculated to be equivalent to thermoelectrics with figure of merit ZT = 2 at the working temperatures, and much higher than other bimorph actuators. The bimorph 渭SE can be easily scaled down to the nanoscale, and operates with high stability in near-room-temperature, ambient, or aqueous conditions. On the basis of the 渭SE, we demonstrate a macroscopic smart composite of VO₂ bimorphs embedded in a polymer, producing high-amplitude actuation at the millimeter scale.

Keywords:

bimorph actuator; single-crystal; vanadium dioxide nanobeam; phase transition; microscale engine