New on/off functionality for fast, sensitive, ultra-small technologies
- Date:
- September 15, 2020
- Source:
- Osaka University
- Summary:
- Researchers have developed an ultra-small actuator that can be turned on and off in a fraction of a millisecond and exhibits nanometer-scale position control. This actuator is unparalleled in modern technologies, and will be useful in robotics, medicine, and many other advanced applications.
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How do you turn on and off an ultra-small component in advanced technologies? You need an actuator, a device that transmits an input such as electricity into physical motion. However, actuators in small-scale technologies to date have critical limitations. For example, if it's difficult to integrate the actuator into semiconductor electronics, real-world applications of the technology will be limited. An actuator design that operates quickly, has precise on/off control, and is compatible with modern electronics would be immensely useful.
In a study recently published in Nano Letters, a team including researchers from Osaka University has developed such an actuator. Its sensitivity, fast on/off response, and nanometer-scale precision are unparalleled.
The researchers' actuator is based on vanadium oxide crystals. Many current technologies use a property of vanadium oxide known as the phase transition to cause out-of-plane bending motions within small-scale devices. For example, such actuators are useful in ultra-small mirrors. Using the phase transition to cause in-plane bending is far more difficult, but would be useful, for example, in ultra-small grippers in medicine.
"At 68°C, vanadium oxide undergoes a sharp monoclinic to rutile phase transition that's useful in microscale technologies," explains co-author Teruo Kanki. "We used a chevron-type (sawtooth) device geometry to amplify in-plane bending of the crystal, and open up new applications."
Using a two-step protocol, the researchers fabricated a fifteen-micrometer-long vanadium oxide crystal attached by a series of ten-micrometer arms to a fixed frame. By means of a phase transition caused by a readily attainable stimulus -- a 10°C temperature change -- the crystal moves 225 nanometers in-plane. The expansion behavior is highly reproducible, over thousands of cycles and several months.
"We also moved the actuator in-plane in response to a laser beam," says Nicola Manca and Luca Pelligrino, co-authors. "The on/off response time was a fraction of a millisecond near the phase transition temperature, with little change at other temperatures, which makes our actuators the most advanced in the world."
Small-scale technologies such as advanced implanted drug delivery devices wouldn't work without the ability to rapidly turn them on and off. The underlying principle of the researchers' actuator -- a reversible phase transition for on/off, in-plane motion -- will dramatically expand the utility of many modern technologies. The researchers expect that the accuracy and speed of their actuator will be especially useful to micro-robotics.
Story Source:
Materials provided by Osaka University. Note: Content may be edited for style and length.
Journal Reference:
- Nicola Manca, Teruo Kanki, Fumiya Endo, Daniele Marré, Luca Pellegrino. Planar Nanoactuators Based on VO2 Phase Transition. Nano Letters, 2020; DOI: 10.1021/acs.nanolett.0c02638
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