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New Micrometer-Sized ‘Smart’ Material

Nelson Sepúlveda, assistant professor of electrical and computer engineering, is investigating a phase-changing“smart material,”looking for new ways to move things at the micro level.

Funding for the research comes from three National Science Foundation grants, totaling $860,000, to advance his work on vanadium dioxide (VO2). Sepúlveda is working to enable VO2-based technologies that can allow for the integration of this smart, multifunctional material into micrometer-sized devices.

“My research group works on very small stuff ,” Sepúlveda said. “Think about taking the motor of a car and making it fit inside a hair. You want to scale down and integrate all the individual parts so you can make the best use of the fully assembled system.

“With the help from a very talented group of graduate students, we take an actuator and make it fit within the thickness of two hairs—a device that is about 200 microns. When perfected, it could allow for very precise microsurgery and help surgeons pinpoint tissue for selective treatment,” he explained. “Other areas that are likely to be impacted by this research include RF circuits (antennas and transceivers), biomedical devices, sensors, actuators, and imagers.”

Sepúlveda said his collaboration with Xiaobo Tan, associateprofessor of electrical and computer engineering, is key in advancing the control of VO2-based devices. “Anybreakthroughs at the micro level willbe very impactful,” Sepúlveda said. An actuator is a type of device for moving or controlling a mechanism or system. It is operated by a source of energy and converts that energyinto motion. A microactuator does the same thing on a microscale.

Vanadium dioxide is a complex, strongly correlated “smart” material that experiences solid-to-solid phase transition when induced by temperature, ultrafast optical radiation, or an electric field. It is considered “smart” because it remembers its previous state.

Sepúlveda has looked at vanadium dioxide’s mechanical properties across phase transition since 2008. “A good example of a phase change is applying heat to ice. As you know, the physical properties of water are different from the properties of ice,” he said.

“The ice begins as a solid and goes through a phase change when temperature is applied and it turns to liquid. We are studying solid-to-solid phase transitions, where a solid becomes another type of solid. The change is very abrupt, fast, and it has hysteresis—which means that it has memory. The National Science Foundation is very interested in this new material.”

– Patricia Mroczek, Currents 2014

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