Snail slime -- called an epiphragm -- is an incredibly strong yet reversible adhesive.
Now, University of Pennsylvania scientists have developed a new kind of glue that employs the same mechanism as the epiphragm. The new material dries like superglue but once wet, it loses its adhesion. For years, scientists have explored adhesions inspired by nature but none have been demonstrated to have the same amount of strength and reversibility. For example, the researchers report that their new adhesive "is 89 times stronger than gecko adhesion." From the University of Pennsylvania:
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The breakthrough came one day when Gaoxiang Wu was working on another project that involved a hydrogel made of a polymer called polyhydroxyethylmethacrylate (PHEMA) and noticed its unusual adhesive properties. PHEMA is rubbery when wet but rigid when dry, a quality that makes it useful for contact lenses but also, as Yang's team discovered, for adhesives.
When PHEMA is wet, it conforms to all of the small grooves on a surface, from a tree trunk's distinct ridges to the invisible microporosity of a seemingly smooth wall. This conformal contact is what allows PHEMA to stick to a surface.
To demonstrate just how durable their PHEMA adhesive is, one of Yang's lab members and co-first author, Jason Christopher Jolly, volunteered to suspend himself from a harness held up only by a postage-stamp-sized patch of their adhesive; the material easily held the weight of an entire human body. Based on the lab tests, the team determined that, although PHEMA may not be the strongest adhesive in existence, it is currently the strongest known candidate available for reversible adhesion.
Whiskers are a fantastic natural sensor that enables cats, fish, seals, and many other animals to detect not just direct contact but even air flow indicating an approaching object. In a fascinating example of biomimicry, University of Queensland engineer Pauline Pounds and her colleagues have developed tiny whisker sensors for drones. According to the researchers, the whiskers are well-suited for "navigating through dark, dusty, smoky, cramped spaces, or gusty, turbulent environments with micro-scale aircraft that cannot mount heavier sensors such as lidars." At IEEE Spectrum, Evan Ackerman writes:
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The whisker fibers themselves are easy to fabricate—they’re just blobs of ABS plastic that are heated up and then drawn out into long thin fibers like taffy. The length and thickness of the whiskers can be modulated by adjusting the temperature and draw speed. The ABS blob at the base of each whisker is glued to a 3D-printed load plate, which is in turn attached to a triangular arrangement of force pads (actually encapsulated MEMS barometers)...
It can detect forces as low as 3.33 micronewtons, meaning that the researchers had to be careful not to stand too close to the whiskers while making measurements since the force of their breathing would throw things off. This sensitivity allows the whiskers to detect the wave of air generated by objects moving towards them, perhaps not in time for the drone to actually stop, but certainly in time for it to take other steps to protect itself, like cutting power to its motors. The whiskers can also be used to measure fluid flow (a proxy for velocity through the air), and of course, at slow speeds they work as contact sensors.
New drone designs enable small UAVs to conserve battery life by taking breaks in unusual locations as opposed to landing back on the ground. Read the rest
Most aquatic animals propel themselves with a tail or fluke, so roboticists have long been interested in the remarkable speeds possible by mimicking sea lion propulsion with front flippers. Read the rest
When fire ants dig out a new nest underground, a small number are actually doing most of the work while the rest dilly-dally. Apparently this is actually an effective division of labor because it prevents the insects from getting in each other's way. Now, Georgia Tech researchers suggest this approach could be help future robot swarms be more efficient in cramped areas like collapsed buildings or construction sites. From Science News:
(Physicist Daniel) Goldman’s team created computer simulations of two ant colonies digging tunnels. In one, the virtual ants mimicked the real insects’ unequal work split; in the other, all the ants pitched in equally. The colony with fewer heavy lifters was better at keeping tunnel traffic moving; in three hours, that colony dug a tunnel that was about three times longer than the group of ants that all did their fair share.
Goldman’s team then tested the fire ants’ teamwork strategy on autonomous robots. These robots trundled back and forth along a narrow track, scooping up plastic balls at one end and dumping them at the other. Programming the robots to do equal work is “not so bad when you have two or three,” Goldman says, “but when you get four in that little narrow tunnel, forget about it.” The four-bot fleet tended to get stuck in pileups. Programming the robots to share the workload unequally helped avoid these smashups and move material 35 percent faster, the researchers found.
"Collective clog control: Optimizing traffic flow in confined biological and robophysical excavation" (Science)
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Earwigs can fly but they mostly live underground, intricately folding their wings into a surface area that's 10 times smaller than when they're opened up. According to new research, the folds "cannot be sufficiently described by current origami models." The earwigs manage the marvelous by incorporating a bit of stretch into the joints where the creases occur, leading to a new design for a robotic gripper. From Science News:
(The earwig's wings are) an example of a bistable structure — something like the slap bracelets, popular in the 1980s and 1990s, which switch from a flat conformation to a curved one when whacked against a wrist, says study coauthor André Studart, a materials scientist at ETH Zürich. When locked open, earwig wings store energy in the springy resilin joints. When that strain is released, the wings rapidly crumple back to their folded position.
Such constructions can inform robotics design. Inspired by the wings, the researchers created a prototype gripper. Its rigid pieces are held together by rubbery, strategically placed joints. Within fractions of a second, the structure can snap from its mostly flat conformation to one that can grip a small object and hold it without constant external force.
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The millimeter-scale RoboBee can fly, dive into water, swim around, and then take off into the air again. At just 175 milligrams, it's 1,000 times lighter than any other aerial-to-aquatic robot. Designed at Harvard's microrobotics laboratory, the RoboBee is outfitted with four tiny "floaties" and a chamber that converts water into oxyhydrogen, fuel that combusts to propel the robot out of the water.
“The RoboBee represents a platform where forces are different than what we – at human scale – are used to experiencing,” says researcher Robert Wood. “While flying the robot feels as if it is treading water; while swimming it feels like it is surrounded by molasses. The force from surface tension feels like an impenetrable wall. These small robots give us the opportunity to explore these non-intuitive phenomena in a very rich way.”
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The gas increases the robot’s buoyancy, pushing the wings out of the water and the floaties stabilize the RoboBee on the water’s surface. From there, a tiny, novel sparker inside the chamber ignites the gas, propelling the RoboBee out of the water. The robot is designed to passively stabilize in air, so that it always lands on its feet.
“By modifying the vehicle design, we are now able to lift more than three times the payload of the previous RoboBee,” said (researcher Yufeng) Chen. “This additional payload capacity allowed us to carry the additional devices including the gas chamber, the electrolytic plates, sparker, and buoyant outriggers, bringing the total weight of the hybrid robot to 175 miligrams, about 90mg heavier than previous designs.
Surgeons close internal incisions with stitches and staples but they, and their patients, would benefit from a glue that stays stuck even to wet tissue and organs. Researchers from McGill University in Montreal are making progress with a powerful new glue inspired by the the sticky slime secreted by scared slugs. Science News surveys the state-of-the-art in adhesives that take inspiration from marine worms, mussels, and geckos:
Using the (slug-inspired) glue to plug a hole in the pig heart worked so well that the heart still held in liquid after being inflated and deflated tens of thousands of times. (McGill University's Jianyu) Li, who did the research while at Harvard University, and colleagues also tested the glue in live rats with liver lacerations. It stopped the rats’ bleeding, and the animals didn’t appear to suffer any bad reaction from the adhesive...
One layer of the material is a polymer, a type of material made from long molecules built from many repeated subunits, like a string of beads. Positively charged appendages dangling off the polymers are drawn to wet tissue surfaces by the same forces underlying static electricity. This first layer weaves into another layer, a water-based gel. The gel layer acts like a shock absorber in a car, Li says. It soaks up energy that might otherwise dislodge or snap the adhesive.
Despite being 90 percent water, the material is both sticky and tough, Li says. The fact that it’s mostly water makes it more likely to be nontoxic to humans. Read the rest
Diphylleia grayi, the "skeleton flower" is normally opaque white but when it rains, the petals become transparent until the flower dries. Nanotechnologists are developing new materials inspired by the flower's structure that could lead to the likes of new underwater goggles that repel oil. From Mother Nature Network:
Skeleton flowers are native to wooded mountainsides in the colder regions of Japan, and they bloom from mid-spring to early-summer in shady conditions. The plant might be easier to spot if you look for its large, umbrella-shaped leaves. The pearly white (or clear, if it's raining) blossoms top the leaves in small clusters...
A related species, Diphylleia cymosa, can be found in the deciduous forests of the Appalachian Mountains here in the United States.
(via Daily Grail)
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Slug mucus sticks well to wet tissues, which appeals to surgeons. David J. Mooney of Harvard University made a glue similar to slug snot, and "tested the adhesive on pig skin, liver, heart, and cartilage and found that it was stronger than both cyanoacrylate (superglue) and a surgical sealant called CoSeal," reports Chemical and Engineering News.
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Mooney and his colleagues came across a paper analyzing the material properties of mucus from a type of slug (Arion subfuscus). The sticky mucus has two components: polycations that help the mucus adhere to surfaces through electrostatic interactions and covalent bonding, and a tough matrix that absorbs and dissipates stress. This combination allows the slug to stick strongly to a surface by resisting forces—such as those from wind, rain, or the beak of a hungry bird—that could dislodge it.
Biomimicry continues to make amazing strides. Festo just released footage of their OctopusGripper being put through the paces. Read the rest
Poking a golden tortoise beetle ("goldbug") triggers the insect's color to change from gold to a red-orange. Inspired by the natural system underlying that insectoid superpower, MIT researchers have developed flexible sensors circuits that can be 3-D printed. Eventually, the technology could lead to sensor-laden skin for robots. From MIT News:
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“In nature, networks of sensors and interconnects are called sensorimotor pathways,” says Subramanian Sundaram, an MIT graduate student in electrical engineering and computer science (EECS), who led the project. “We were trying to see whether we could replicate sensorimotor pathways inside a 3-D-printed object. So we considered the simplest organism we could find...."
The MIT researchers’ new device is approximately T-shaped, but with a wide, squat base and an elongated crossbar. The crossbar is made from an elastic plastic, with a strip of silver running its length; in the researchers’ experiments, electrodes were connected to the crossbar’s ends. The base of the T is made from a more rigid plastic. It includes two printed transistors and what the researchers call a “pixel,” a circle of semiconducting polymer whose color changes when the crossbars stretch, modifying the electrical resistance of the silver strip.
In fact, the transistors and the pixel are made from the same material; the transistors also change color slightly when the crossbars stretch. The effect is more dramatic in the pixel, however, because the transistors amplify the electrical signal from the crossbar. Demonstrating working transistors was essential, Sundaram says, because large, dense sensor arrays require some capacity for onboard signal processing.
A team of roboticists from Caltech and Urbana-Champaign have built a biomimetic "bat bot" that uses nine joints to deform a foot-wide wing membrane to achieve breathtaking aerial maneuvers. Read the rest
Biomimicry in robotics has led to robots that can climb, fly, and swim better. Now researchers have developed hair-like filaments for robots that allow them to have more fine-grained senses of touch, sensing even forces as delicate as coming in contact with a piece of tissue. Read the rest
Biomimickry continues to improve and refine specialized drones and flying robots. Mindy Weisberger at LiveScience dives into an issue of The Royal Society's journal Interface Focus on coevolving advances in animal flight and aerial robotics. Read the rest
Penn State researchers funded by the Army Research Office and the Office of Naval Research have posted video showing their progress on "self-healing" textiles that use proteins similar to those found in human hair and squid teeth to allow fibers to coated in polyelectrolytes so that they can be set and bonded using safe solvents under ambient conditions. Read the rest
Aerospace corporation Airbus's Light Rider concept motorbike looks a bit like something HR Giger would draw (although his, of course, would be much cooler). In reality, the 3D-printed frame was inspired by skeletal structures that enable its bare-metal frame to weigh just 13 pounds but support a 220 pound rider. From the BBC News:
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To design the bike's frame and swingarm rear section, (Airbus's) APWorks team collaborated with Altair Engineering, a US-based consulting company whose structural-design software works through the principle of "morphogenesis" — which in biology refers to process of environmental forces defining a natural organism's form and structure. Morphorgenetic software is written to create forms that achieve maximum strength with minimal mass, and Altair's system has contributed to the designs of such boundary-pushing machines as the Boeing 787 Dreamliner, the Volvo Ocean 70 racing yacht, and the jet-powered Bloodhound SSC, which next year will attempt to break the land speed record...
The 3D-printing process employed to produce the Light Rider's frame is a marvel unto itself. The system uses a laser to melt powdered aluminium alloy in thousands of layers, each only 60 microns thick — about the width of a human hair. Airbus Group Innovations, the company’s research arm, developed the frame's aircraft-grade alloy, called Scalmalloy, which it claims matches the specific strength of titanium. The fabrication process — and the strength of the material — allows the morphogenetic software to specify finer and thinner structures than traditional tooling or moulding methods of manufacturing can produce. In fact, notes Gruenewald, the Light Rider’s frame even features hollow branches that hide cables and other components.