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Robotic Insects

May 8, 2013

If you show a nickel and a dime to a child too young to understand their monetary value and ask him to choose which one he wanted, he would choose the nickel, simply because it's bigger. Larger things and larger quantities obviously have more value than the smaller. This principle doesn't vanish when the child becomes an adult. He wants the larger automobile when a smaller one would suit his needs and benefit the environment.

A pile of United States Coins

When I was a child, you could buy "penny candy" at the corner store. These were quite large chunks of confection sold for just a penny.

Sales tax had not been invented, and there were still many corner stores.

(Via Wikimedia Commons.)

Fictional robots of the past were huge, also. Gort, the robot in the classic science fiction film, "The Day the Earth Stood Still," (1951, Robert Wise, Director), was eight feet tall.[1] As I wrote in the article Teen Scientists (February 1, 2013), Tom Swift had a large robot, a fact that can be gleaned from the 1954 book title, "Tom Swift and His Giant Robot."

Nowadays, consumers prefer their technology to be small. Smaller tablet computers have superseded desktop computers for many applications, and there are personal music players replacing the bulky stereo systems of the past. The trend to the smaller-can-be-better mentality has extended to robotics. As I wrote in a previous article (Pop-Up Robots, February 23, 2012), governments would like to procure the proverbial "fly-on-the-wall," a minuscule flying robot for surveillance.

First a disclaimer of sorts. I'm a long time member of the Electronic Frontier Foundation, and I oppose unwarranted government surveillance of its citizens. However, appropriate intelligence gathering to preserve public safety has become increasingly important in today's world. Somewhere there's a middle ground, but I'm not skilled enough to know where to draw the line.

There have been some impressive demonstrations of small-sized flying robots. Engineers at the General Robotics, Automation, Sensing and Perception (GRASP) Laboratory of the University of Pennsylvania have demonstrated "nano quadrotors," which are helicopter-type objects, about the size of a human hand.[2] There's a YouTube video showing the nano quadrotors doing synchronized flying.[3]

Engineers at Harvard University's School of Engineering and Applied Sciences and Wyss Institute for Biologically Inspired Engineering have decided to pursue an insect model for robotic flight. Their coin-sized device, which is quite a bit smaller than the nano quadrotors, is called a "Mobee," for monolithic bee (see photograph).

Harvard University Mobee

Are coins a subliminal subtopic of this article?

The 2012 version of the Mobee was 2.4 millimeters tall, and it had about 2% the mass (90 mg) of a US quarter.

(Screen capture from a YouTube video).[4)]

As can be seen, the Mobee uses flapping wings instead of rotating airfoils for flight. One unique feature of the Mobee is its fabrication. It's built as a lamination of many layers of dissimilar material, including carbon fiber, titanium, brass, ceramic, adhesive, and Kapton for the hinges (see figure). The 2012 version had eighteen laser-cut laminations which "popped-up" from the plane to form the robot. Harvard Mobee hinge

Making a micro hinge.

Kapton is used as the hinge layer in the Harvard Mobee.

(Screen capture from a YouTube video)[4]

The Harvard Mobee work is part of a National Science Foundation funded RoboBee project led by Robert J. Wood, an Associate Professor of Electrical Engineering. The present version of the Mobee has a reduced weight of 80 milligrams. Its wings flap 120 times per second, powered by piezoelectric "muscles."[5-7] The Harvard team has demonstrated stable hovering and basic flight maneuvers for a tethered, but unconstrained, Mobee.[5]

For flight control, each wing is controlled independently in real time.[6] As for real insects, airflow effects have a big effect on flight dynamics. The control system needs to react quickly to maintain stability.[6] The control is effected by use of an external computer through signals provided by the tether. The tether is essential, since there are no suitably small and lightweight power supplies which could be integrated into the robot.[6]

Figure caption

Sessile and flying robotic insects. (Still images from a Harvard University video; background of right image modified to reduce clutter.)

The Mobee pop-up fabrication technique facilitated development. Says Kevin Y. Ma, a coauthor of the report on the device recently published in Science,[5] "We can now very rapidly build reliable prototypes, which allows us to be more aggressive in how we test them." The research team has tested twenty prototypes in just six months.[6]

Among the non-surveillance applications of this technology are environmental monitoring, search-and-rescue operations, and crop pollination, just like real bees.[6] However, none of these applications are possible without smaller batteries, integrated control systems, and stronger, more lightweight materials. At this time, the principal failure mechanism is failure of the wing hinges.[5,7]


  1. The Day the Earth Stood Still, 1951, Robert Wise, Director, on the Internet Movie Database. I prefer that version over the 2008 version (The Day the Earth Stood Still, 2008, Scott Derrickson, Director), since the later version is too violent for my taste.
  2. Evan Ackerman, "Swarming Quadrotors Get Nano-ized," IEEE Spectrum, February 1, 2012.
  3. A Swarm of Nano Quadrotors, YouTube video, January 31, 2012.
  4. Caroline Perry, "In new mass-production technique, robotic insects spring to life," Harvard School of Engineering and Applied Sciences Press Release, February 15, 2012.
  5. Kevin Y. Ma, Pakpong Chirarattananon, Sawyer B. Fuller and Robert J. Wood, "Controlled Flight of a Biologically Inspired, Insect-Scale Robot," Science, vol. 340, no. 6132 (May 3, 2013), pp. 603-607.
  6. Caroline Perry, "Robotic insects make first controlled flight," Harvard School of Engineering and Applied Sciences Press Release, May 2, 2013.
  7. Elizabeth Pennisi, "Robotic Fly Takes to the Air, Briefly," Science Now, May 2, 2013.

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