A human hand holds a stack of several plexiglass sheets with needles glued into the ends. Very faint lines can be seen in the transparent stackup.

Biomimetic Building Facades To Reduce HVAC Loads

Buildings currently consume about 50% of the world’s electricity, so finding ways to reduce the loads they place on the grid can save money and reduce carbon emissions. Scientists at the University of Toronto have developed an “optofluidic” system for tuning light coming into a building.

The researchers devised a biomimetic system inspired by the multi-layered skins of squid and chameleons for active camouflage to be able to actively control light intensity, spectrum, and scattering independently. While there are plenty of technologies that can regulate these properties, doing so independently has been too complicated a task for current window shades or electrochromic devices.

To make the prototype devices (15 × 15 × 2 cm), 3 mm PMMA sheets were stacked after millifluidic channels (1.5 mm deep and 6.35 mm wide) were CNC milled into the sheets. Fluids could be injected and removed by needles glued into the ends of the channels. By using different fluids in the channels, researchers were able to tune various aspects of the incoming light. Scaled up, one application of the system could be to keep buildings cooler on hot days without keeping out IR on colder days which is one disadvantage of static window coatings currently in use.

If you want to control some of the light going OUT of your windows, maybe you should try building this smart LED curtain instead?

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Biomimetic Surfaces: Copying Nature To Deter Bacteria And Keep Ship Hulls Smooth

You might not think that keeping a boat hull smooth in the water has anything in common with keeping a scalpel clean for surgery, but there it does: in both cases you’re trying to prevent nature — barnacles or biofilm — from growing on a surface. Science has looked to nature, and found that the micro-patterning formed by the scales of certain sharks or the leaves of lotus plants demonstrate a highly elegant way to prevent biofouling that we can copy.

In the case of marine growth attaching to and growing on a ship’s hull, the main issue is that of increased drag. This increases fuel usage and lowers overall efficiency of the vessel, requiring regular cleaning to remove this biofouling. In the context of a hospital, this layer of growth becomes even more crucial. Each year, a large number of hospital patients suffer infections, despite the use of single-use catheters and sterile packaging.

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Mapping of the displacement of a tympanum of the lesser wax moth (Achroia grisella). (Credit: Andrew Reid)

3D Printing Bio-Inspired Microphone Designs Based On Moth Ears

If many millions of years of evolution is good for anything, it is to develop microscopic structures that perform astounding tasks, such as the marvelous biology of insects. One of these structures are the ears of the lesser wax moth (Achroia grisella), whose mating behavior involves ultrasonic mating calls. These can attract the bats which hunt them, leading to these moths having evolved directional hearing that can pinpoint not only a potential mate, but also bat calling sound.

What’s most astounding about this is that these moths that only live about a week as an adult can perform auditory feats that we generally require an entire microphone array for, along with a lot of audio processing. The key that enables these moths to perform these feats lies in their eardrum, or tympanum. Rather than the taut, flat surface as with mammals, these feature intricate 3D structures along with pores that seem to perform much of the directional processing, and this is what researchers have been trying to replicate for a while, including a team of researchers at the University of Strathclyde.

To create these artificial tympanums, the researchers used a flexible hydrogel, with a piezoelectric material that converts the acoustic energy into electric signals, connected to electrical traces. The 3D features are printed on this, mixed with methanol that forms droplets inside the curing resin, before being expelled and leaving the desired pores. One limitation is that currently used printers have a limited resolution of about 200 micrometers, which doesn’t cover the full features of the insect’s tympanum.

Assuming this can be made to work, it could be used for everything from cochlear implants to anywhere else that has a great deal of audio processing that needs downsizing.

(Heading image: Mapping of the displacement of a tympanum of the lesser wax moth (Achroia grisella). (Credit: Andrew Reid) )

That Drone Up In The Sky? It Might Be Built Out Of A Dead Bird

In a lot of ways, it seems like we’re in the “plateau of productivity” part of the hype cycle when it comes to drones. UAVs have pretty much been reduced to practice and have become mostly an off-the-shelf purchase these days, with a dwindling number of experimenters pushing the envelope with custom builds, like building drones out of dead birds.

These ornithopomorphic UAVs come to us from the New Mexico Insitute of Mining and Technology, where [Mostafa Hassanalian] runs the Autonomous Flight and Aquatic Systems lab. While looking into biomimetics, [Dr. Hassanalian] hit upon the idea of using taxidermy birds as an airframe for drones. He and his team essentially reverse-engineered the birds to figure out how much payload they’d be able to handle, and added back the necessary components to make them fly again.

From the brief video in the tweet embedded below, it’s clear that they’ve come up with a huge variety of feathered drones. Some are clearly intended for testing the aerodynamics of taxidermy wings in makeshift wind tunnels, while others are designed to actually fly. Propulsion seems to run the gamut from bird-shaped RC airplanes with a propeller mounted in the beak to true ornithopters. Some of the drones clearly have a conventional fuselage with feathers added, which makes sense for testing various subsystems, like wings and tails.

It’s easy to mock something like this, and the jokes practically write themselves. But when you think about it, the argument for a flying bird-shaped robot is pretty easy to make from an animal behavior standpoint. If you want to study how birds up close while they’re flying, what better way than to send in a robot that looks similar to the other members of the flock? And besides, evolution figured out avian flight about 150 million years ago, so studying how birds do it is probably going to teach us something.

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Miles The Spider Robot

Who doesn’t love robotic spiders? Today’s biomimetic robot comes in the form of Miles, the quadruped spider robot from [_Robox].

Miles uses twelve servos to control its motion, three on each of its legs, and also includes a standard HC-SR04 ultrasonic distance sensor for some obstacle avoidance capabilities. Twelve servos can use quite a bit of power, so [_Robox_] had to power Miles with six LM7805 ICs to get sufficient current. [_Robox_] laser cut acrylic sheets for Miles’s body but mentions that 3D printing would work as well.

Miles uses inverse kinematics to get around, which we’ve seen in a previous project and is a pretty popular technique for controlling robotic motion. The Instructable is a little light on the details, but the source code is something to take a look at. In addition to simply moving around [_Robox_] developed code to make Miles dance, wave, and take a bow. That’s sure to be a hit at your next virtual show-and-tell.

By now you’re saying “wait, spiders have eight legs”, and of course you’re right. But that’s an awful lot of servos. Anyway, if you’d rather 3D print your four-legged spider, we have a suggestion.

Little Jumping Bot Can Now Stick The Perfect Landing

Sticking the perfect landing can take years of practice for a human gymnast, and it seems the same is true for little monopedal jumping robots. Salto-1P, an old acquaintance here on Hackaday, always needed to keep jumping to stay upright. With some clever control software improvements, it can now land reliably on an area the size of a coin, and then stay there. (Video after the break)

[Justin Yim] from the UC Berkeley’s Biomimetics Lab has been working on Salto for the past four years, and we’ve covered it twice before. Attitude control is handles by a combination of propeller thrusters for roll and yaw, and a reaction wheel for pitch.While it was already impressive before, it had a predictable landing area about the size of a dinner plate.

The trick to the perfect landing is a combination of landing angle, angular velocity and angular momentum. Salto can only correct for ±2.3° of landing angle error, because it doesn’t have a second foot to catch itself when something goes wrong. Ideally the robot’s angular velocity and momentum should be as close as possible to 0 at takeoff, which gives the reaction wheel maximum control authority in flight, as well as on landing.  Basically a well executed takeoff directly influences the chances of a good landing.  [Justin] does an excellent job explaining all this and more on the project’s presentation video. Continue reading “Little Jumping Bot Can Now Stick The Perfect Landing”

Slipping Sheets Map Multiple Bends In This Ingenious Flex Sensor

When thoughts turn to measuring the degree to which something bends, it’s pretty likely that strain gauges or some kind of encoders on a linkage come to mind. Things could be much simpler in the world of flex measurement, though, if [Fereshteh Shahmiri] and [Paul H. Dietz]’s capacitive multi-bend flex sensor catches on.

This is one of those ideas that seems so obvious that you don’t know why it hasn’t been tried before. The basic idea is to leverage the geometry of layered materials that slip past each other when bent. Think of the way the pages of a hardbound book feather out when you open it, and you’ll get the idea. In the case of the ShArc (“Shift Arc”) sensor, the front and back covers of the book are flexible PCBs with a series of overlapping pads. Between these PCBs are a number of plain polyimide spacer strips. All the strips of the sensor are anchored at one end, and everything is held together with an elastic sleeve. As the ShArc is bent, the positions of the electrodes on the top and bottom layers shift relative to each other, changing the capacitance across them. From the capacitance measurements and the known position of each pad, a microcontroller can easily calculate the bend radius at each point and infer the curvature of the whole strip.

The video below shows how the ShArc works, as well as several applications for the technology. The obvious use as a flex sensor for the human hand is most impressive — it could vastly simplify [Will Cogley]’s biomimetic hand controller — but such sensors could be put to work in any system that bends. And as a bonus, it looks pretty simple to build one at home.

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