Chip-based Sensors

The Sound of One Wing Flapping

In 1997, DARPA, the Defense Department's futuristic research program, launched a micro air vehicle (MAV) program with a goal of developing the technologies to enable a selfpowered flying machine with dimensions of 6 inches or less for reconnaissance and surveillance purposes. As time went on, DARPA shrank the package into a nano air vehicle (NAV), with dimensions less than 15 centimeters and a weight less than 20 grams, for both indoor and outdoor maneuvering capabilities. This could be thought of as hummingbird size. At Penn State, faculty in electrical and mechanical engineering and their graduate students have spent the past two years working at an even smaller scale,c called the pico air vehicle (PAV), based on insect flight.

At that size scale, everything is changed and all of the problems of fabrication, stabilization, power, and control have to be answered anew. The one thing that is already known for sure is that nature has solved the problems many times before, with dragon flies, bumble bees, and the humble house fly. In the process of creating the technologies to develop a PAV, interesting and difficult scientific questions will be answered.

"Chris and I worked for 4 ½ years on this project that was funded by the Air Force Office of Scientific Research. The idea was very simple. My group was working on micromachined PZT-based actuators, along with Prof. Rahn. We call them T-beam actuators" Tadigadapa recalled.

Srinivas Tadigadapa, an expert in the field of microelectromechanical systems, or MEMS, and Christopher Rahn a mechanical engineer with expertise in modeling, design, and control, both faculty at Penn State, call their pico air vehicle the LionFly – a name coined by their graduate student Kiron Mateti. Although it has yet to get off the ground under its own power, the Lion Fly project has made a number of contributions to the field of bio-inspired miniaturized flight.

Made from a single piece of lead zirconate titanate (PZT), a ceramic piezoelectric material, the T-beam actuator is capable of flexing in two directions, similar to the flexing of the muscles of an insect wing. "We finished with these actuators, and we got so many degrees of freedom with them, that we wondered what we could do with them," said Tadigadapa. "And the idea came to use them to actuate the wings of a nano air vehicle based on a dragon fly or butterfly." Because of Tadigadapa's experience in nano and micro fabrication, the engineers decided to try to put together the entire wing using photolithography, using photoresist as the material to build the wing and a piezoelectric actuator as the motor. This departed from other flapping wing NAVs, which run on electromechanical motors. They set themselves a lateral size limit of 5 centimeters, including wings and actuator. Then they began research.

For Further Information: Read the full article on Focus on Materials
Contact: Srinivas Tadigadapa
Professor of Electrical Engineering at Penn State and Leader of the Micro and Nanoscale Devices Group