For wannabe thieves, nothing is more tantalizing than an empty street and a vulnerable ATM. Soon, though, they could be facing more than just failure. Taking design cues from mother nature herself, researchers are building ATMs that fend off thieves with a spray of hot, steaming foam. 
 
 The inspiration for this dastardly defense mechanism comes from none other than the bombardier beetle, which sprays near-boiling acid at any foes who coming knocking. It keeps the ingredients for its deadly concoction (hydrogen peroxide and hydroquinone) in two separate chambers in its abdomin. That way, the chemicals don't mix until they come shooting out, at which point the resulting reaction heats up and nearly vaporizes the noxious liquid. Here's our little friend in action. 
 
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 Researchers at ETH Zurich University took cues from the deadly beetle and built two chemical filled honeycomb chambers. Except this time, hydrogen peroxide was paired with manganese dioxide. Since the two are only separate by a thin sheet of lacquer, any tampering will cause the chamber to break immediately, triggering a reaction that produces water vapor, oxygen, and heat. A much less expensive—not to mention non-face melting—variation on the bomardier's own tactics. 
 
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 Even though the thief might not walk away with a half-eaten face, this is a much more effective way of rendering ATM-theft useless. The oozing foam from the reaction will be laden with dye, marking the banknotes (rendering them useless) as well as the thieves themselves. What's more, researchers say that including DNA nanoparticles will allow them to trace the cash back to the source. Thieves may be able to run, but thankfully, it's getting much harder for them to hide. 
 
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 Hopefully that barrier is thick enough to withstand the occasional (and inevitable( innocent, frustrated shake. And while this all still just being tested—no plans for immediate rollout yet—we could all use a few more acid-spitting objects in our lives. [Journal of Materials Chemistry via The Atlantic] 
 
 Image: Getty Images/Sion Touhig ||||| The bombardier beetle inspired the researchers of ETH Zurich. (Photo: jayvee18 – Fotolia) 
 
 Its head and pronotum are usually rusty red, and its abdomen blue or shiny green: the bombardier beetle is approximately one centimetre long and common to Central Europe. At first glance, it appears harmless, but it possesses what is surely the most aggressive chemical defence system in nature. When threatened, the bombardier beetle releases a caustic spray, accompanied by a popping sound. This spray can kill ants or scare off frogs. The beetle produces the explosive agent itself when needed. Two separately stored chemicals are mixed in a reaction chamber in the beetle's abdomen. An explosion is triggered with the help of catalytic enzymes. 
 
 “When you see how elegantly nature solves problems, you realise how deadlocked the world of technology often is,” says Wendelin Jan Stark, a professor from the ETH Department of Chemistry and Applied Biosciences. He and his team therefore looked to the bombardier beetle for inspiration and developed a chemical defence mechanism designed to prevent vandalism – a self-defending surface composed of several sandwich-like layers of plastic. If the surface is damaged, hot foam is sprayed in the face of the attacker. This technology could be used to prevent vandalism or protect valuable goods. “This could be used anywhere you find things that shouldn't be touched,” said Stark. In agriculture and forestry, for example, it could be used to keep animals from gnawing on trees. 
 
 Like a fuse 
 
 The researchers use plastic films with a honeycomb structure for their self-defending surface. The hollow spaces are filled with one of two chemicals: hydrogen peroxide or manganese dioxide. The two separate films are then stuck on top of each another. A layer of clear lacquer separates the two films filled with the different chemicals. When subjected to an impact, the interlayer is destroyed, causing the hydrogen peroxide and manganese dioxide to mix. This triggers a violent reaction that produces water vapour, oxygen and heat. Whereas enzymes act as catalysts in the bombardier beetle, manganese dioxide has proven to be a less expensive alternative for performing this function in the lab. 
 
 The researchers report that the product of the reaction in the film is more of a foam than a spray when compared to the beetle, as can be seen in slow motion video footage. Infrared images show that the temperature of the foam reaches 80 degrees. Just as in nature, very little mechanical energy is required in the laboratory to release a much greater amount of chemical energy – quite similar to a fuse or an electrically ignited combustion cycle in an engine. ||||| GIF 
 
 It’s a cruel world out there, and animals will do just about anything to avoid being eaten. In the case of bombardier beetles, these crafty insects are able to escape after being swallowed by toads, which they do by ejecting hot, noxious chemicals that forces the predator to barf. It ain’t pretty, but it works. 
 
 Small prey animals have evolved all sorts of physical defenses, including thorns, hairs, and highly unpleasant toxic substances. Back in May 2016, Kobe University researcher Takuya Sato and his colleagues were studying the defensive behaviors and chemical attacks utilized by a species of bombardier beetle known as Pheropsophus jessoensis, an insect common to Korea and Japan. In one experiment, the researchers fed a bombardier beetle to a toad under lab conditions to see what would happen. 
 
 “The toad readily swallowed the beetle,” wrote the researchers in a follow-up study, published yesterday in Biology Letters. “However, it vomited the beetle 44 minutes after swallowing it. The vomited beetle was still alive and active.” 
 
 The scientists had never seen a toad or frog do this before, prompting further investigation. The follow-up study was an effort to clarify the ecological factors involved, and determine how the beetles are able to survive for so long in the belly of their predators. 
 
 There are nearly 650 known species of bombardier beetles, all of which produce noxious chemicals in their guts. When threatened, they mix these chemicals together and eject a hot spray from the tips of their abdomens (that is, their behinds) with tremendous force. This typically happens during a predatory attack, dissuading the enemy from eating the bug. In some cases, these chemicals can reach an astounding 100 degrees Celsius (212 degrees Fahrenheit). In Pheropsophus jessoensis, the resulting chemical reactions produce hydrogen peroxide and a class of compounds known as benzoquinones—irritants that are known to damage tissue, such as skins and lungs. 
 
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 In the new experiment, Sato fed the live bombardier beetles to two different toad species, Bufo japonicus and B. torrenticola, to see if the hot chemical brew might force the amphibians to regurgitate. To test various conditions, some beetles were depleted of their chemical defenses prior to being eaten (which the scientists did by poking and prodding the bombardier beetles before they were exposed to the toads), and by testing beetles and toads of various sizes. 
 
 All beetles depleted of their chemical defenses were killed and fully digested in the stomachs of the toads. So there’s that. 
 
 But those who retained their defenses fared considerably better: 43 percent of toads puked out the beetles anywhere from 12 to 107 minutes after they swallowed them. Incredibly, all vomited beetles were alive and well following the ordeal. 
 
 
 
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 Importantly, large beetles did better than small beetles, escaping more frequently, while small toads vomited the beetles more often than large toads. “Our results demonstrate the importance of the prey–predator size relationship in the successful escape of prey from inside a predator,” wrote the researchers in the study. 
 
 This experiment also tells us something about bombardier beetle durability. The digestive system of toads contain digestive juices in the form of acidic chemicals. Incredibly, the upchucked beetles were able to withstand this tortuous environment for nearly two hours. The researchers say the beetles have evolved a hardy, defensive shell, which allows the beetles to remain intact and stay alive until their hot butt stuff forces the toad to vomit. 
 
 Isn’t nature lovely? 
 
 [Biology Letters]
– The ATM is getting a lesson in self-defense—from a bug. Researchers in Switzerland were inspired by the bombardier beetle, which shoots out a gas that can burn skin, the Atlantic reports. The beetle's mechanism works by mixing two chemicals normally kept separate in its abdomen. When under attack, the beetle combines the hydrogen peroxide and hydroquinone to spray its attack gas. The researchers copied this system by putting hydrogen peroxide and manganese dioxide side-by-side, separated by only a lacquer. Break that lacquer, and you get the reaction. ATM makers could employ the principle in their machines by rigging them to ooze foam if someone begins tampering, say the researchers. Instead of burning acid, the ATMs could cover bills with dye and DNA, making the cash hard to use and easy to track. "Thieves may be able to run," notes Gizmodo, but "it's getting much harder for them to hide." In fact, the mechanism "could be used anywhere you find things that shouldn't be touched," a researcher tells ETH Zurich—whether to fight vandalism or keep animals off crops. (Click to read about another odd method of self-defense in the animal kingdom.)