Insect Cyborgs And Rqbqflies

The U.S. military doesn't use the term "cyborgs," although this is precisely what their scientists and engineers are developing. Perhaps this sounds a bit too much like the stuff of science fiction. The Defense Advanced Research Projects Agency (DARPA) prefers to call their futuristic, insect-machine hybrids "vivi-systems."1 The goal is to merge evolution and engineering, to take insects and "turn them into war-fighting technologies." DARPA's Controlled Biological and Biomimetic Systems Program is hoping to fuse the sensory, locomotory, energetic, and orientation capacities of insects with the very best of human ingenuity. As futuristic as such ventures might appear, the notion of using insects as critical components of machines saw its first military application during the Vietnam War.

In the jungles of Southeast Asia, finding the enemy before he found you made the difference between dying in an ambush and living to fight another day. Even the most experienced soldiers were often unable to sense the presence of Viet Cong guerrillas in the dense vegetation. Our senses are unable to penetrate more than a few meters into the forest, and we are easily fooled by camouflage. Not so for blood-feeding insects. These creatures can sniff out a host from long distances, and a bouquet of other odors does not distract them from the scent of a meal. One of the most sensitive detectors of a warmblooded presence is the assassin bug (the insect that tormented victims of the Bug Pit in Uzbekistan). These insects know that they're on track when they detect a faint plume of carbon dioxide, and the bloodthirsty beasts further refine their search by honing in on a cocktail of chemicals found in mammalian breath and sweat.

Insects don't have any lips to smack in anticipation of a meal, but the bugs can make a soft buzzing sound by rubbing their sharp, elongated beaks over a series of ridges on their sternum in much the same way that we might strum the teeth of a comb. Although it seems that most assassin bugs use this sound to warn off predators or unwelcome suitors, the U.S. military found a species that sounded off when it detected a potential host. This would seem to be a peculiar behavior for a parasite, but the bug's murmur was nearly inaudible. Some entomologists speculate that the insect may live among an extended family and signal relatives of an impending feast. Whatever the creature was up to, the military had big plans for the bug that sang for its supper.

Wartime inventors developed a machine that turned assassin bugs into scouts.2 The insects were placed in special capsules that were held within a device equipped with an audio amplifier. Air was drawn into the device and passed over the encapsulated assassin bug, a design feature that presumably provided an element of directionality and prevented the insect from getting excited by the presence of the human operator. When a host or enemy— depending on whether one takes the perspective of the insect or the soldier— came within five hundred feet of the device, the bug began to buzz, the amplifier made the sound audible to the operator, and the impending ambush was defused. At least that's the way it was supposed to work. The machine with the embedded insect was tested, but there's no evidence that it was ever used in the jungles of Vietnam. This early attempt at integrating insect and machine was rather crude—the entire insect was used as the detector. It was, in a sense, the conceptual predecessor of the "Wasp Hound" used for chemical detection. Today, however, the approach is more in line with that of Dr. Frankenstein, using only those body parts of greatest value in the creation of a benevolent monster.

In an Iowa State University laboratory, entomologist Tom Baker has built a device that is a true vivisystem—an insectan cyborg for locating land mines.3 He found that the antennae of moths send neural impulses in response to volatile molecules associated with explosives. But rather than attempting to train moths, which aren't terribly clever insects to begin with, Baker simply lopped off the antennae and let technology do the thinking. The amputated antennae, which survive and function in their detached state for hours, are hooked up to microprocessors that convert the neural impulses into audible tones, such that the pitch drops as the cyborg encounters the scent of an explosive. The biggest problem is that the disembodied insect antennae respond to a wide range of stimuli, and a neurological signature unique to TNT has yet to be found. So the device works fine in the laboratory where there are few odors to compete with that of an explosive, but under field conditions the system operator is unable to distinguish the odor plume of a land mine from a plethora of other scents.

Integrating living tissues into machines is quite a challenge. After all, antennae and other body parts usually depend on being attached to the rest of the creature (see Figure 25.1). Mechanical devices aren't typically equipped with supplies of nutrients, blood, oxygen, and other conditions needed to sustain disembodied organs. So DARPA is taking the concept of entomological engineering to the next level. The ultimate goal is to dispense with the messiness of living systems entirely, transferring insect qualities into purely human creations.

Biomimetics is the most extreme version of the technological exploitation of the living world. In this field, scientists and engineers attempt to capture the essential functions of an organism in a machine. The coveted physical features are mechanically or electronically replicated without the disadvantages that come with the fickle, demanding, and unpredictable nature of living tissues.

Cockroach Tethered Ball

Figure 25.1. A cockroach-based cyborg developed by Garnet Hertz at the University of California, Irvine, demonstrating that exciting advances in insectan robotics do not depend on DARPA funding. The device uses a living Madagascar hissing cockroach atop a modified trackball to control a three-wheeled robot. Movements of the ball beneath the insect's feet are transferred into movements by the robot. Infrared sensors provide navigation feedback to the cockroach, creating a pseudo-intelligent system with the cockroach as the CPU. (Courtesy of Garnet Hertz)

Figure 25.1. A cockroach-based cyborg developed by Garnet Hertz at the University of California, Irvine, demonstrating that exciting advances in insectan robotics do not depend on DARPA funding. The device uses a living Madagascar hissing cockroach atop a modified trackball to control a three-wheeled robot. Movements of the ball beneath the insect's feet are transferred into movements by the robot. Infrared sensors provide navigation feedback to the cockroach, creating a pseudo-intelligent system with the cockroach as the CPU. (Courtesy of Garnet Hertz)

For example, rather than trying to untangle and decipher the neural patterns generated by a moth's antenna, the goal is to build the essence of antennal neurophysiology into an electronic system. Such efforts began as early as 1968, when the Army Research Office paid the Philco Corporation to develop a "manmade nose"—a chemical sensor capable of detecting minute traces of particular odors.4 Although the project never materialized into a working prototype, the olfactory model that the scientists used was not the snout of a bloodhound but the antenna of an aphid.

In recent years, DARPA funded a project to mimic the remarkable capabilities of an obscure beetle that is the envy of weapon designers.5 Heat-seeking missiles and other "smart" bombs use infrared radiation to find their targets. The problem is that the detection systems can operate only at freezing temperatures, and sustaining these conditions requires expensive and heavy cooling systems that demand frequent maintenance. If a system could detect infrared signatures at ambient temperatures, the payoffs in terms of weight, cost, and durability would be tremendous. And that's exactly what the European jewel beetle (Melanophila accuminata) has to offer.

This beetle uses freshly burned trees as a food source for its young. The damaged trees are unable to mount a defense against the insects, so the larvae flourish beneath the charred bark. A smoldering forest triggers a mating frenzy. But the windfall of larval food occurs sporadically and the ideal conditions for egg laying don't last long, so evolution has provided the half-inch adults with an incredible capacity to locate forest fires.

The jewel beetle "feels" a distant fire by using an infrared sensor on its thorax—and the insect can sense flames from as far away as 40 miles. The beetles use a specialized organ that looks like a microscopic ear of corn within a tiny crater. Each "kernel" is a hardened dome that absorbs incoming infrared radiation. The radiation causes the dome to expand ever so slightly, with the change being sufficient to distort a sensory nerve attached to the structure. This nerve then sends a signal notifying the insect of a distant fire—and the impending orgy.

Helmut Schmitz, a zoologist at the University of Bonn in Germany, is attempting to recreate the beetle's detector using synthetic materials that absorb infrared radiation and expand enough to generate an electronic signal.6 The prototype can detect a flame that is within 12 inches. A forest fire generates a much stronger signal, but the beetle's detector functions at a distance two hundred thousand times greater than the artificial device. So the challenge is to mimic the beetle's phenomenal sensitivity to microscopic changes in its sense organs, and that means finding a component that responds when the dome expands by a millionth of an inch. Schmitz and his colleagues believe that a capacitive sensor device might do the trick. And so work continues on reconstructing an infrared sensory system using manmade parts. However, when it comes to military applications of insect anatomy and physiology the real payoff may not be in mimicking neurology.

There's a very good reason that evolution produced legged, rather than wheeled or tracked, creatures. Wheels (even with advanced suspension systems) and tracks (such as those found on tanks) lack the dynamic properties necessary to traverse extremely uneven surfaces. Thus, insects have become the standard platform for the development of robotic locomotion across random rubble and pitted pathways—the conditions invariably encountered in the course of war and other disasters.

The original motivation for putting robots on tortuous terrain was to minimize the risk to humans, and this concern drove developments in two areas. First, military commanders (not to mention soldiers) much preferred allowing machines to take the risks of finding paths through minefields or locating mines during clearing operations. Second, search-and-rescue teams saw that using robots within damaged buildings and other unstable structures would shift the danger from man to machine. Moreover, if the robots could be miniaturized, they could navigate tight spaces inaccessible to lumbering humans.

The program director of DARPA's Controlled Biological and Biomimetic Systems, Alan Rudolph, put the situation succinctly: "Legged robotics will likely eventually dominate because they have a greater potential to deal with obstacles . . . if we can figure out how to build them."7 And with tens of millions of dollars to entice the sharpest entomological and engineering minds, the military doesn't see failure as an option.

A menagerie of arthropods—including crabs, lobsters, and scorpions—has been used as models for locomotion. However, no creature has yielded better results to date than the lowly cockroach (order Blattodea). DARPA's golden child is a mechanical roach that owes its existence to the work of a scientist at the University of California, Berkeley, who painstakingly analyzed the dynamics of cockroach movement. Robert Full, a zoologist with a passion for biomechanics, discovered that the secret to a cockroach's ability to clamber over rough surfaces lies in an utter lack of grace.8 The creature bumbles along by using its six legs in alternating sets of three. While we two-legged animals have a single point of contact, which makes tripping all too easy, the cockroach is supported by stable tripods (the front left, middle right, and hind left alternate with the front right, middle left, and hind right). Add to this that the insect uses a sprawled posture to maintain a low center of gravity, and it's virtually impossible to build an obstacle course that would topple a cockroach. Scaled up to human proportions, a cockroach dashing along at 50 steps per second is the equivalent of a human running the high hurdles at 200 miles per hour.

Using these insights, researchers at the University of Michigan and McGill University in Canada collaborated to capture the essence of cockroach movement in a robot.9 In the late 1990s, entomological insight spawned a nightmarish machine known as RHex (short for "Robotic Hexapod"). Designed by engineering professors Martin Buehler and Dan Koditschek, the robot stumbled and thrashed its way over all sorts of debris. In the last few years, RHex metamorphosed into the Scout series, an evolving lineage of ever-improving, six-legged machines that scamper over obstacles and climb stairs. And further refinements in "roachbots" are on the horizon, thanks to work at other institutions.

As scientists come to understand how the cockroach leg performs as a limber, dynamic structure, new lines of engineering are developing. At Cleveland's Case Western University, a biologist has teamed up with an engineer to mimic a cockroach leg in excruciating detail.10 Roy Ritzmann and Roger Quinn have developed a gigantic roach, with legs 17 times larger than the real insect. This upscaling allows them to design and program every aspect of movement. Using a complex pneumatic piston system to power the behemoth, they have constructed appendages with a sophisticated network of strain gauges linked to a computer that tells the system how to compensate for changing forces by adjusting the pressure applied to the leg joints as the robot walks. But this approach might be technological overkill (see Figures 25.2 and 25.3).

While some biologists began with the assumption that mimicking insect movement would depend on developing computational feedback systems to match the insect's nervous system, recent discoveries have shown that the key might lie in the insect's musculature, rather than in its brain.11 Full has discovered that cockroach muscles don't merely move the legs but also adjust the stiffness of the individual segments and joints via a complicated but unconscious system of tugging and pulling. At least at high speeds, complex neural processing seems to fade in importance as pure, albeit staggeringly sophisticated, mechanics take over. Even without feedback from the nervous system, the 21 muscles of the cockroach leg function as elegantly reciprocating rubber bands, constantly tuning the femur, tibia, and knee to the flexibility needed to match the challenges of scurrying through kitchen cabinets, under sinks, and between walls.

Figure 25.2. BILL (Biologically-Inspired Legged Locomotion)-Ant mimics not only the movement of its namesake but also features actuated mandibles with force-sensing pincer plates. The actively compliant hexapod robot is capable of grasping and moving objects while reacting to external forces through sensors in its feet and pincers. BILL-Ant was developed in 2005 by William Lewinger at the Case Western Reserve University Center for Biologically-Inspired Robotics, directed by Roger Quinn. (Courtesy of Roger Quinn)

Figure 25.2. BILL (Biologically-Inspired Legged Locomotion)-Ant mimics not only the movement of its namesake but also features actuated mandibles with force-sensing pincer plates. The actively compliant hexapod robot is capable of grasping and moving objects while reacting to external forces through sensors in its feet and pincers. BILL-Ant was developed in 2005 by William Lewinger at the Case Western Reserve University Center for Biologically-Inspired Robotics, directed by Roger Quinn. (Courtesy of Roger Quinn)

Full's insights concerning the inner workings of the cockroach leg have led Mark Cutkosky at Stanford University to pursue development of artificial, dynamic limbs using a process called "shape deposition manufacturing."12 By incorporating solid-state structures embedded with electronics into plastic appendages, he's hoping to mimic the passive mechanical properties provided by the interacting muscles within the insect leg.

Unraveling the complexities and overturning the assumptions of the insect leg have proved critical to embedding the evolutionary brilliance of living organisms into the engineering of robots. But as unexpected as the process of insect walking has turned out to be, the real surprises came with ventures into insect flight—a phenomenon that DARPA has spent $50 million trying to capture and copy for military applications.

The U.S. Department of Defense has been salivating at the possibility of building tiny aircraft for reconnaissance and espionage.13 Imagine a microspy the size of a house fly peeking into enemy strongholds, eavesdropping on

Figure 25.3. This is the first version (2005) of an articulated hexapod robot under development by Dr. Alejandro Ramirez-Serrano and his research team at the Autonomous Reconfigurable Robotics Systems Laboratory at the University of Calgary, Alberta, Canada. The hexapod and its control mechanisms are being developed to overcome obstacles five times the height of the robot. The robot features pan-tilt cameras for eyes, ultrasonic and infrared sensors, 20 servo motors, and four computers. (Courtesy of Alejandro Ramirez-Serrano)

Figure 25.3. This is the first version (2005) of an articulated hexapod robot under development by Dr. Alejandro Ramirez-Serrano and his research team at the Autonomous Reconfigurable Robotics Systems Laboratory at the University of Calgary, Alberta, Canada. The hexapod and its control mechanisms are being developed to overcome obstacles five times the height of the robot. The robot features pan-tilt cameras for eyes, ultrasonic and infrared sensors, 20 servo motors, and four computers. (Courtesy of Alejandro Ramirez-Serrano)

conversations, or sniffing out stores of chemical weapons. Such possibilities led DARPA to lure aeronautical engineers (generous funding is effective bait for grant-starved academics) into directing their formidable intellects toward the development of "micro air vehicles," or MAVs—self-powered, aerodynam-ically stable flying machines no more than six inches long. The early ventures consisted of simply shrinking conventional aircraft, but it soon became evident that the principles that accounted for fixed-wing flight became irrelevant at this scale. For a Lilliputian plane to stay aloft it would need to fly at a phenomenal speed to attain the necessary lift, and generating such speeds—let alone controlling the thing as it screamed along—was deemed to be technically impossible.

Thinking in terms of biomimicry was the first crucial step in solving the problem. Robert Michelson of Georgia Institute of Technology's Aerospace Laboratory put the situation in simple terms: "Nothing in nature achieves sustained flight with fixed wings or with propellers. . . . All tiny creatures flap their wings."14 Not unexpectedly, the engineers tried to mimic birds. But attempts to build diminutive ornithopters—bird-like flying machines—were quickly scrapped when scientists realized that the physics underlying flight in these animals is no different from that which accounts for the lift of airplane wings. What engineers needed was a whole new conceptualization of flight, a novel set of principles that would allow MAVs to generate lift. And then came the conceptual breakthrough: build an entomopter.

An insect is not just a small version of a bird when it comes to flight. Indeed, the old yarn about physicists being able to prove that a bumblebee can't fly— despite its evident ability to do so—is not entirely apocryphal. If the analysis is limited to large-scale aerodynamic forces, such as those that provide an airplane or bird wing with lift, no insect should be able to stay aloft. But as the scale decreases, entirely new properties emerge: small is different. The essence of flight is beautifully captured in a single mathematical term called the Reynolds number. The value of this parameter for any particular structure is a function of three components: speed, wing dimension, and density of the fluid.15 When thinking of conventional flight, the air density plays a role at high altitudes where the atmosphere is thin. With insects, air density at the earth's surface is extremely relevant. When you're tiny, normal air becomes thick.

We don't usually think of air as a fluid, but a gas behaves like a very diffuse liquid. As an animal's body size decreases, the effective density of air increases. For a gnat (suborder Nematocera), air has the same resistance as oil does to us. This explains why you can drop an ant from a height of 10 feet—which would be like our falling from a mile above the earth—and it lands without injury. The little fella is dropping through the air the way we'd be sinking into a tank of honey. Insects don't so much fly through the air as they swim through it.

At the scale of an insect, it makes more sense to call those flapping structures oars rather than wings. Everything that engineers had learned about design in terms of airfoil properties, wingspan factors, and surface smoothness had no bearing on insects. Thrips can "fly" using a structure composed of hairs sticking out along a shaft; try flying an airplane using palm fronds for wings. With a scientific understanding of insect aerodynamics, the challenge became building a machine that would fly like a fly flies.

Flies, rather than bees, became the model for MAVs (probably because the former are both safe and easy to raise). A creature that can take off backward, hover in place, dart sideways, and land upside down had to be the epitome of flight for an aeronautical engineer with a penchant for grand challenges. Studies showed that blow flies—disgusting insects all in all, but easily observed and mass-produced—created eddies by flapping and twisting their wings in a manner not unlike how one sculls while treading water. These microscopic whirlwinds provided the insect with lift, stability, and maneuverability. But constructing an entomopter the size of a fly was asking a lot, so the goal was phrased in slightly more realistic terms: develop a machine with flexible, 1-inch wings that could sustain autonomous flight.

With support from DARPA and the Office of Naval Research, Ron Fearing and his team at the University of California, Berkeley, have been working toward a "micromechanical flying insect."16 Although there are no "roboflies" zipping down the corridors of Cory Hall, there has been substantial progress since they began in 1998. At least Fearing's group has shown that an entomopter with a tiny motor powered by lithium batteries, set into a carbon fiber "thorax," could flap a polyester wing fast enough (150 beats per second) to generate lift comparable to that of a blow fly. Other research teams at California Institute of Technology and Vanderbilt University have also made strides. Engineers at Harvard University recently launched a flylike robot that weighed a little more than the plastic head of a pushpin, but the entomopter was tethered to its power supply.17

In addition to a lightweight power supply, stability and maneuverability remain challenges, not to mention getting a flying robotic insect to navigate its way through a complex environment and carry a payload. But if everything continues to play out as hoped, the engineers could soon have a bitty device that zips along at a respectable seven miles per hour. Or maybe they've already succeeded.

A Washington Post article in October 2007 reported that people gathered at political rallies have been describing the appearance of insectlike flying devices since as early as 2004. One individual at the Republican National Convention in New York described "a jet-black dragonfly hovering about 10 feet off the ground, precisely in the middle of 7th Avenue."18 Perhaps the person was paranoid (black helicopters giving way to black insects) or simply saw an actual dragonfly. However, several people at an antiwar rally in Washington, D.C., independently described large dragonflies trailing strings of small berrylike spheres and flying in formation. Not surprisingly, government agencies have declined to discuss the topic. If the CIA (the agency reportedly developed a gasoline-powered "insectothopter" in the 1970s, but scrapped the project because the dragonfly-like device was unstable) or other defense and security agencies have such a device, then mission creep has begun to change the tenor of the venture.

The military began its biomimetic project with the most altruistic of intentions, or so one is led to believe.19 The goals included activities such as locating land mines and wounded soldiers. Finding injured people in bombed-out buildings is laudable, but it is a small step from search-and-rescue to a bit of harmless snooping and then to seek-and-destroy. Rather than mounting a tiny video camera on a robotic insect, one could arm it with a poisoned needle—a mechanical bee with a lethal sting. Just a milligram or two (about the weight of a grain of sand) of the right venom would be deadly, and this warhead would be much lighter than any other payload of military interest. The increasingly creepy game of "what if?" did not stop at pinpoint assassinations. As scientists have come to understand more about swarming behavior, another tactic mastered by insects becomes plausible—coordinated, collective attacks by MAVs. A swarm of entomopters sucked into a jet engine could quickly bring down enemy aircraft or disable a hijacked plane.

Such futuristic weapon systems would require enormous, but not at all inconceivable, engineering advances. And we can be sure that wealthy industrial nations will be the ones making the technological breakthroughs and deploying the entomechanical armaments. However, the most frightening and likely uses of insects as weapons in the modern world do not require sophisticated science. In the fast-changing, high-tech world of warfare, some of the most effective tactics are ironically the most primitive. Consider that in the Middle East, American smart bombs have given way to "improvised explosive devices," and Islamic suicide bombers function as cheap—if human life is perceived as having little value—guided missiles.

To engineer an MAV is well beyond the ability of today's terrorist organizations. Even carrying out germ warfare requires sophisticated technology such as autoclaves, incubators, sterile media, and other accoutrements. But insects could become the terrorists' six-legged box-cutters, their biological weapon of choice. These creatures are abundant, available, safe to handle, easy to transport, self-dispersing, self-perpetuating, and—if properly selected—phenomenally effective. The newest liquid explosives are surely cause for concern, but an insect net and a Ziploc bag could be sufficient to wreak environmental and economic havoc. One might wonder whether the U.S. government is able to protect the nation from the possible range of entomological attacks.

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