Research
Interests
Energy Scavenging for Wireless Sensor Nodes
The vast reduction in size and power consumption of CMOS circuitry has led to a large research effort based around the vision of ubiquitous networks of wireless communication nodes. As the networks, which are usually designed to run on batteries, increase in number and the devices decrease in size, the replacement of depleted batteries is not practical. Therefore, the goal of this research is to explore methods of scavenging ambient power for use by low power wireless electronic devices in an effort to make the wireless nodes and resulting wireless sensor networks indefinitely self-sustaining.
To date, most of my research in this area has centered on the development of vibration based generators that convert energy from low-level vibrations to electricity. I’ve pursued converters based on both piezoelectric and electrostatic (capacitive) coupling. I have designed, built and tested meso- and micro- scale prototypes. Current prototypes have demonstrated power densities of about 200 mW/cm3 from input vibrations of 2.25 m/s2 at 120 Hz. One of the piezoelectric converters was used to completely power a small wireless sensor device from vibrations similar to those found in common environments. See my publication list for more details on this work. Additionally, you can download a recent (well kind of recent) presentation in PowerPoint or PDF. (EnergyScavenging.ppt 11 MB) (EnergyScavenging.pdf 2.3 MB) (EnergyScavenging.zip 1.1 MB)
The goal now is to study adaptive vibration based generators that can adapt their own resonant frequency to match that of the input vibrations. Additionally, novel power electronics methods and structures are being studies to improve the power transfer to the load electronics. Finally, I’m looking at exploiting other potential power sources, such as wind, as a means to power wireless sensor nodes.
Microactuators
I’m also interested in investigating novel micro-actuators (especially Shape Memory Alloy actuators) with an eye toward applications in micro-mechatronics. Most micro-actuators use the electrostatic effect. While efficient, electrostatic actuators suffer from low force output and high sensitivity to contamination from the environment. While their efficiency is much lower, Shape Memory Alloy (SMA) actuators represent a good solution for micro-mechatronics and robotics applications because of their favorable output force and displacement characteristics. Additionally, SMA actuators are much less sensitive to environmental contamination and harsh environments. Their very limited use in MEMS is due partly to processing difficulty and partly due to a legacy of working with electrostatic actuators within the field. However, recent research has made it easier to process SMA micro-devices. Therefore, with more research on novel micro-actuator designs and control methods, SMA actuators can play a large part in the field of MEMS and micro-mechatronics.