All About the Water Strider

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You’ve probably been out by the water on a warm summer day when you noticed something skimming across the top of the nearby lake. Upon closer inspection you see that it’s indeed a small insect that is able to effortlessly glide across water. Personally, this fascinates me, so I dug a little deeper to better understand how the water strider is capable of this biblical feat.

Water striders are of the family Gerridae, are only about half an inch long, and possess six legs. These six legs have a number of hairy projections called setae that are hydrophobic (2).Up until this point, scientists had believed that the water strider’s ability to glide on water was due to a was it secreted by the cuticle, however recent research by Xuefang Gao and Lei Jiang has indicated that this is not the case. These researchers believe the ability to effortlessly walk on water is the result of the heirarchial structure of many small microsetae on the insect’s legs that give it a sort of “superhydrophobicity.” They found that the water strider is able to withstand a force of up to 15x its body weight before drowning. Gao and Jiang hope that this knowledge can be used in the future to create water-resistant, drag reducing materials (1).

While there are currently a number of rain repellant products, many pale in comparison to the superhydrophobicity of a water strider leg. Maybe in the future a water resistant coating could be added to cars? Or maybe something as simple as super-water resistant umbrellas will be a commonality? Only time will tell.

Sources:

(1) Gao X, Jiang L. Biophysics: Water-repellent legs of water striders. Nature [serial online]. November 4, 2004;432(7013):36. Available from: Academic Search Premier, Ipswich, MA. Accessed November 18, 2013.

(2) Water Strider: National Wildlife Federation http://www.nwf.org/Wildlife/Wildlife-Library/Invertebrates/Water-Strider.aspx

(3) Walking on Water: Insect’s Secrets Revealed http://www.livescience.com/62-walking-water-insect-secret-revealed.html

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Submarine Sensors Based on Fish Lateral Lines

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Modern submarines rely on sonar and vision for navigation, however these systems have limitations. Blind spots and dark, murky water can make them useless. It is because of this that Douglas Jones of the University of Illinois at Urbana-Champaign and Chang Liu of Northwestern University have developed sensors based on the lateral lines of fish.

Fish lateral lines are clusters of hair cells called neuromasts that run along the length of a fish. These hairs allow fish to detect changes in water pressure and are what allow them to swim in closely grouped schools without running into each other and swim through darkened waters blindly.

Jones and Liu have developed artificial lateral lines using silicon fibers and have tested them attached to a metal tube submerged in water. They found that the fibers were able to detect movement in the surrounding water and they were then able to analyze the data and calculate the distance to various objects.

By placing these sensors on submarines, the hope is to make nautical travel more safe and efficient in the areas that current sonar and vision systems are lacking. A true example of biomimicry, these artifical lateral lines would indeed be a societal win by improving upon a modern, somewhat inefficient system by incorporating mechanics of nature.

Sources:

Scientists create sensors for subs based on fish anatomy: http://www.gizmag.com/researchers-create-lateral-line-sensors/14141/

Giving Robots a sixth sense to see in the murky depths: http://www.gizmag.com/snookie-underwater-robot-lateral-line/14657/

Marks, Paul. “Fishy Sensors Could Keep Submersibles Out Of Trouble.” New Scientist 205.2745 (2010): 19. Academic Search Premier. Web. 14 Nov. 2013.

Distant touch hydrodynamic imaging with an artificial lateral line: http://www.pnas.org.proxy2.library.illinois.edu/content/103/50/18891.full#cited-by

Insect Sensory Systems

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The sensory organ of insects is called the sensilla. These specialized cells are capable of detecting a variety of sensory stimuli and are located beneath the cuticle – the hard outer covering of insects.

Generalized insect

Diagram of Insect Sensillum. Source: Marianne Alleyne

Among the possibilities are:

  • Mechanical
  • Thermal
  • Chemical
  • Visual

Mechanical Stimuli

Mechanical stimuli can be caused by the environment, the insect’s interaction with the environment, or the internal workings of the insect. It includes touch, position, gravity, etc. Three examples are:

  • Tactile Mechanoreception – Accomplished via the trichoid sensilla which deforms when receiving stimuli and sends an electrochemical signal.
  • Proprioception – This is the ability to sense the body’s relative position in relation to its surroundings. This can be accomplished by hair beds or setae, stretch receptors, and the campaniform sensillum.
  • Sound Perception – Waves of air pressure cause movement of an organ used in hearing.

Thermoreception

Some insects are able to detect infrared radiation. This allows some species of beetle to locate forest fires which provide them with burned wood critical for their mating ritual. They are able to do so by using infrared sensors located underneath their wings to absorb heat, which through a poorly understood process converts this IR heat into a mechanoreceptive signal.

Chemoreception

Two types of chemoreceptors are found in insects: gustatory and olfactory sensors. Gustatory sensors can be considered “taste” sensors and are located in the mouths and on the legs of insects. Olfactory is to be considered “smell” and is found on insect antennae and certain parts of the mouth.

These chemoreceptors are further categorized into uniporous and multiporous.

Vision

Most insects possess a compound eye, which consists of a varying number of units called ommatidia. The number of ommatidia can be anywhere from a few to tens of thousands. Compound eyes allow a very large visual field and also let the insect focus on objects near and far away simultaneously.

 

In addition to compound eyes, insects often also have dorsal ocelli and stemmata.

 

A Trip to the Indianapolis Zoo

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So this past week, I drove my girlfriend to the Indy airport. Before we went, we decided to stop by the zoo. In this blog post I wanted to share some of the pictures we took. Unfortunately, this late in the year many animals weren’t available and the reptile area was closed for construction. Still, we had a pretty good time. Enjoy, and maybe you can find inspiration from something in this gallery!

An Addition to My Mars Rover

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In a previous blog post, I designed a robot that I believe could replace the current series of Mars rovers created by NASA. This robot would incorporate many biomechanical aspects from nature, among them:

  • Walking/Running: Inspired by the cockroach and its ability to navigate very rough terrain without sacrificing speed.
  • Digging: Inspired by the specialized forelimbs of the mole cricket which allow it to burrow.
  • Jumping: Inspired by the powerful hind legs of the grasshopper, which allow it to manipulate potential energy and leap tall buildings in a single bound.

Together, these three natural implements would allow my mars rover to more easily and efficiently navigate the foreign terrain of Mars and possibly other planets in the future.

But why stop there? This week we learned about insects and biological sensors. By adding sensors to my robot, I feel it could be made even more efficient and effective. These are the ideas I have:

Vision: The first sensor I would add would be based on the insect eye. Insect eyes consist of hundreds of individual units known as ommatidia. Each ommatidium is able to focus on a particular image and then send that info to the brain to form one whole, coherent image. What this means is the insect eye is able to focus on objects both near and far at the same time and at the same resolution. Furthermore, the compound eye also possesses a 180o viewing angle. These characteristics would make navigation that much more efficient.  I would like to add something similar to the insect-eye camera currently being developed by our very own John Rogers (2):

 

Proprioceptive Sensors: Proprioception is the ability to sense the relative position of a body part and its relation to gravity. Insects can do so in the following ways:

  • Hair beds – Small hairs called setae are located where two appendages of an insect meet. When the setae touch the cuticle due to bending of an appendage, a nerve impulse is sent and information regarding bodily position is transmitted.
  • Stretch receptors. – These are associated with muscles and are sensitive to such things as gut distension, egg maturation, and muscle fiber stretching. They basically prevent the insect from exploding in many cases.
  • Campaniform sensillum

In my opinion, something similar to the setae of insects would be best suited to my Mars rover. It obviously is very important that the robot know its leg position relative to the terrain, so perhaps it would be possible to develop some sort of mechanism mimicking setae that alert the robot to its position periodically.

Echolocation – By bouncing soundwaves off walls and other objects, bats are able to “see” where they’re going. This could prove useful if implemented in my robot.

As far as actually implementing these sensors into a robot, we have quite a ways to go. For the most part we have still been unable to replicate completely many of the structures found in insects. Once we have a better understanding of the mechanisms behind insect sensor modalities we should be able to develop these sensors into a reality.

Sources:

(1) Mars Rover, Brandon Nelson https://learn.illinois.edu/mod/forum/discuss.php?d=168826

(2) Insect Eye Digital Camera Sees What You Just Did http://phenomena.nationalgeographic.com/2013/05/02/insect-eye-digital-camera-sees-what-you-just-did/

(3) Mechanical Stimulus https://learn.illinois.edu/mod/lesson/view.php?id=195373&pageid=53404

Modular Snake Robots

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Created by Howie Choset and his colleagues at Carnegie Mellon University, Modular Snake Robots are proving to be a big up and comer in the world of robotics. Consisting of 16 joined modular segments connected via hinge joints, these snakes are capable of a variety of natural movements such as climbing, rolling, and even swimming.

According to Choset’s webpage, the robots are capable of the following gaits:

LINEAR PROGRESSION

SIDEWINDING

CORKSCREWING

ROLLING

SWIMMING

CHANNEL CLIMBING

PIPE/TUBE CLIMBING

POLE CLIMBING

CORNERING

PIPE ROLLING

Many of these movements have been adapted from the ways in which actual snakes move, making modular snake robots a prime example of biomimicry.

Due to its ability to perform various “gaits,” these snake robots are able to traverse terrain that other robots may not be capable of. As such, Choset and his associates hope to eventually put them to use for cave rescue missions and possibly even on Mars. This is indeed a societal win, and could potentially save many lives in the future.

 

Sources:

http://biorobotics.ri.cmu.edu/projects/modsnake/gaits.html

http://www.popularmechanics.com/science/4285289

Mars Rovers of the Future?

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My “Mars Rover.” Hey, I’m no artist…

Since conquering the moon in the early 70’s, we’ve since set our sights further out into the universe. Our primary focus in the last couple decades has been exploring Mars and the potential for discovering water. To aid in our research, scientist have created many robots that allow us to remotely collect samples and learn about the red planet without sending actual human beings. Scientists could (and have) taken a page from the biomechanics of nature in creating this robots.

So how exactly can we mimic nature in order to further our knowledge of Mars (and potentially other planets in the future)? I propose a robot incorporating the various aspects of biomechanics we have studied in this week’s module: primarily digging, walking, jumping, and possibly flying.

As of this posting, NASA has utilized four Mars rovers in their endeavors: Sojourner (inactive), Opportunity, Spirit (inactive), and Curiosity. (1) These high-tech robots must successfully navigate the rocky, foreign terrain of Mars. This means keeping the rover well-balanced and generally allowing it to navigate far and wide without impediments. This, I believe, is where biomechanics come into play. By incorporating some of the unique ways insects move, maybe we could in the future create a more efficient Mars Rover. Let’s break it down according to some of the characteristics I believe are most crucial:

Walking/Running: As learned in this week’s lesson on biomechanics and robotics, insects are statically stable thanks to their six legs which provide a sort of stability along with a mechanism for movement. One of the insects discussed was the cockroach, which is able to scurry very quickly and stably and, as seen in a Module 1 during Robert Full’s TED talk, is able to traverse rough terrain without losing a step. Also inspired by cockroach movement is the robot RHex, which is capable of navigating very rough terrain and has been suggested for use on Mars missions as well. Attempting to implement these mechanics into future rovers is critical.

Digging: Another critical addition in my opinion, is an insect like ability to burrow and dig. Insects such as the mole cricket have specially adapted limbs for this. This allows us to take soil samples and further our quest to discover water and prove that life once existed on the red marble. While very little is currently understood about the mechanics behind this, I believe it is well worth the time and effort to research and implement this in the future.

 

                                                                          

Jumping: Another wonder of biomechanics I could see proving useful in this robot would be the ability to jump akin to the way a grasshopper does so. By storing up energy and then releasing it via muscular contractions in its powerful hindlegs, grasshoppers are able to jump great distances. The ability of a mars rover to jump over rougher terrain that might not be as easily walked across could prove invaluable.


So, is this idea of mine reasonable whatsoever? I think so. Implementing these aspects of insect biomechanics seems like a worthy pursuit. However, there could be some potential drawbacks. As mentioned by another student in IB 411, cost could be an issue. Furthermore, it could take quite some time to develop adequate machinery to replicate the biomechanics seen in a previous blog post. This in itself could cost a lot of money. At least for the time being, it seems NASA might be better off sticking with their current tried and true version of Mars rovers.

Sources:

(1) Mars Rover http://en.wikipedia.org/wiki/Mars_rover

(2) http://mars.nasa.gov/msl/mission/rover/

(3) http://marsrover.nasa.gov/mission/tl_surface_nav.html

(4) IB 411 Course Blackboard Site, M. Alleyne