Locomotion

Bioinspiration – crossing interdisciplinary borders
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Bioinspiration – crossing interdisciplinary borders

It is really going to happen! We talked about this for YEARS, and now we are finally going to see it come to fruition.

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Kate Loudon and I have known each other for a long time. It was kind of inevitable that two women who were part of the leadership of the Entomological Society of America’s Section B, now the Physiology Biochemistry and Toxicology (PBT) section, would become friends. We are actually from THAT era where female leadership in the ESA was a rarity (not anymore!).

Since we both have an interest in insect physiology (broadly) and biomechanics (specifically) we started talking about organizing a bioinspiration symposium. Fundamental insect biomechanics studies have inspired technologies for some time now. For about 5 years I have been teaching courses on bioinspiration and I use Kate’s research on bed bug-killing materials as an example of innovations that can be inspired by nature and benefit society. So the match seemed natural. Also, we really like each other and would use any excuse to collaborate on something.

It took a while but we managed to put together an awesome symposium with prestigious speakers on the biggest entomological stage ever; the 2016 XXV International Congress of Entomology to be held in Orlando, FL (Sept 25th-30th).

We are so thrilled about the line-up. There is a great variety of speakers (topics, nationality, ethnicity, gender) and we can’t wait for them to interact with each other and other interested entomologists. Some of our speakers have never been to an entomological meeting. We expect to get them hooked, or at least speak well of us entomologists once they are back at their home institutions.

We hope that as a result of this symposium new collaborations will develop, be it to delve into new research questions or to explore educational avenues.

Let me first introduce you to the speakers. Hopefully as the symposium draws closer I can share a little bit more about the topics and speakers in follow-up posts.

  • Our first speaker will be Dr. Robert Wood who is the Charles River Professor of Engineering and Applied Sciences in the Harvard John A. Paulson School of Engineering and Applied Sciences. Prof. Wood is also a founding core faculty member of the Wyss Institute for Biologically Inspired Engineering, a power-house in the field of bioinspiration.  The Wood lab is probably most famous among entomologists for their work on robobee – a miniature flying, and now also sensing, robot inspired by biology.

  • The next speaker will be Chen Li from Johns Hopkins University. Prof. Li coined his own research topic: terradynamics. Similar to how aero- and hydrodynamic principles have shaped our knowledge about animal locomotion in air and water it is Prof Li’s goal to better understand animal locomotion on complex (always shifting) terrains, thus his creation of the terradymics lab at JHU.  Cockroaches feature prominently in his research.

  • Next we switch from robotics to bioinspired materials. Kate (Dr. Catherine Loudon, University of California at Irvine) will share her work on how small structures on bean leaves kill bed bugs and how these structures (and their special characteristics) have spurred interest in the development of physical insecticidal bioinspired materials.
  • Faithful readers of this blog will know by now how enamored I am by the insect cuticle. I am therefore glad that we will have Dr. Stevin Gehrke (Fred Kurata Memorial Professor of Chemical Engineering at the University of Kansas) talk about the physical properties of beetle elytral cuticle and why this type of biomaterial may have many possible applications.
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Tenebrio molitor with characteristic elytra covering the hind wings. By gbohne from Berlin, Germany

  • Next I will discuss a relatively new project from my lab at the University of Illinois at Urbana-Champaign in collaboration with Dr. Nenad Miljkovic from Illinois’s Mechanical Science and Engineering Department and Dr. Donald Cropek who is a chemist from the U.S. Army Corps of Engineers. Over the past few months we have initiated a comparative study of native Illinois cicadas’s wings to determine physical and chemical attributes that make the wings have (super)hydrophobic, self-cleaning and maybe even antimicrobial characteristics. This collaboration has been really fun and I have learned about a lot of new techniques and I hope to share some of my excitement with the symposium’s audience (Bouncing water droplets anyone?!!!!).
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Neotibicen dorsatus at Loda Prairie, July 2016. By Marianne Alleyne

  • Another interesting biological material is, of course, spider silk. Dr. Crystal Chaw from Dr. Cheryl Hayashi‘s lab at the University of California at Riverside will explain how studies on the evolution of spider silk have helped in the engineering of artificial silk production.

  • From biological materials we next move to different types of flow in insects. First Hodjat Pendar from Prof Jake Socha’s lab (Virginia Tech) will be talking about how the insect’s tracheal system (which is actually linked to other physiological systems) can serve as inspiration for novel flow control. It is a fascinating topic which I have touched upon previously in a blog post.

  • Flow sensing at a small scale is definitely a topic that is of interest to engineers. And it is something that insects do very well. Dr. Jérôme Casas from the University of Tours (France) will present some of the work he has been doing with Dr. Gijs Krijnen (University of Twente, The Netherlands) on the fluid dynamics of olfaction in insects.
  • Another amazing sensor found in insects is the IR sensor in pyrophilous beetles such as in the genus Melanophila. Will we ever be able to engineer an IR sensor as sophisticated as the ones found in beetles? Dr. Helmut Schmitz (Institute of Zoology of the University of Bonn) will share his work to explain how an understanding of the active amplification mechanism seen in the beetle’s IR sensor might help bring us closer to a robust and sensitive bioinspired IR sensor.
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IR organ of Melanophila acuminata. Schmitz & Bousack (2012) PLoS ONE 7(5): e37627.

  • At this point in the symposium we are shifting gears just a little bit to talk about how to actually DO bioinspired design, and how can we best teach our students to come up with successful bioinspired designs. Most people when they first hear about bioinspiration or biomimicry they immediately think this line of thinking makes total sense. Biologists want to contribute and feel even more justified to delve into fundamental biological questions. Engineers are happy to add bioinspiration into their imaginary toolbox. But for bioinspiration to be successful, to actually have as an end result a bioinspired technology that is based on real biological data, biologists and engineers have to work together. And that is not always so straightforward (Writes the entomologist who has been married to a mechanical engineer for 20+ years. Trust me, it is not straightforward.). Prof. Ashok Goel (Georgia Tech, Co-Director of the  Center for Biologically Inspired Design. will discuss some of the cognitive challenges that he has encountered when working with collaborators and students on biologically inspired design projects. What he has learned about how engineers and biologists approach certain problems is fascinating.
  • The symposium will again switch topics somewhat by next delving into social insect behavior. First up will be Dr. Ted Pavlic (Arizona State University, Associate Director for Research at The Biomimicry Center at ASU) who will talk about how social insects make group decisions and how that knowledge can be transferred to create smart and adaptive teams of robots.
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Eciton hamatum workers on the trail, Jatun Sacha reserve, Napo Ecuador. Alexander Wild.

  • We will end the symposium with another social insect talk, this one by Dr. Deborah Gordon (Stanford University). Prof. Gordon will talk about her research on collective behavior in ants and how they have influenced engineered networks.

Kate and I hope you can join us for our symposium, either in person or virtually via Twitter or Instagram (we will use hashtag #ICE2016BioI and #ICE2016) and follow-up blog posts. Feel free to use Twitter to ask questions of the speakers (@Cotesia1).

“See” you on the 29th!

 

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Jump! Go Ahead, Jump, Little Springtail.
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Jump! Go Ahead, Jump, Little Springtail.

And here it is. Behold the best blog-banner ever – created by Nils Cordes*! 

Of course, the premiere of such a great banner also requires a blog post that explains it. So let me try.

The animal featured in this blog’s banner is a springtail from the hexapod lineage Collembola. Collembola are not insects but entomologists are an inclusive bunch so we gladly incorporate spiders and entognathous creatures into our studies and teachings.

Springtails are very likely the most abundant arthropods on earth. They occur in the soil (different species at different depths), in leaf litter, moss, under logs, etc. One of the most distinguishing features, if you can consider anything on an animal that is only 0.12 to 17 mm long distinguishing, is the forked furca at the posterior end of the animal. The furca is present in a lot of species, but not all. Those that live deeper in the soil usually lack the structure because they do not need it since its main function is for jumping.

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Generalized “elongate” (top) and “globular” (bottom) Collembola. Furca (springing mechanism) in red – the springtail at the top has the mechanism partly retracted and the springtail in the bottom picture has the furca extended. (Marianne Alleyne)

Collembola species can have varying body shapes, but generally there are those with elongated bodies and those with more globular bodies. Collembola can walk, run and climb, but the locomotory specialty that they are best known for (and which seems to be rather ancestral) is jumping.

Globular Springtail Dicyrtomina saundersi. Body length = 1.7mm. Picture by Lord V. Used with permission.

Globular springtail Dicyrtomina saundersi. Body length = 1.7mm. Picture by Lord V. (Used with permission.)

Picture by Lord V. Used with permission.

Elongate springtail. Body length = 2.3 mm. Picture by Lord V. (Used with permission.)

This excellent picture by Lord V is of a picture walking over a glass slide. Clearly visible is the forked furca that can prope the springtail into the air.

This excellent picture is of a springtail’s underbelly. The picture was taken by Lord V as a springtail walked over a glass slide. Clearly visible is the forked furca that can propel the animal into the air. (Used with permission.)

Collembola can jump multiple times in a row, those with globular bodies and more advanced tracheal systems more often (1). In general, springtails tire easily so that jumping is usually only used as an escape mechanism. The jump can take the animal in any direction. Since the furca is located at the extremity of the body, directly beneath the center of gravity, the dynamics of the jump cause the body to rotate head over end. Some Collembola species can jump very high, others take a shallower trajectory but land far away from point of takeoff.

This jumping escape response is quite successful but it does require modifications of the entire body plan. The cuticle, the (hydrostatic) endoskeleton, tendons, and muscles all work together to manipulate the body in such a way that the propulsion is optimal.  How exactly this happens is not very well understood, yet this system holds inspirational lessons for passively compliant locomotory structures.

At rest the furca is held within a ventral groove of the abdomen. At the time of the jump the furca moves from this resting (retracted) position to the extended position. Based on morphological and kinematic observations (there is no direct experimental evidence) it appears that as the furca moves it compresses a “spring”. After it passes a critical point of extension the spring releases all the energy, which in turn causes the springing organ to snap out at high speed. If this happens as the springing organ hits a substrate a force is created that propels the animal upward.

The springing mechanism of a generalized springtail; partially retracted (left) and extended (right).

The springing mechanism of a generalized springtail; partially retracted (left) and extended (right). (Marianne Alleyne)

What exactly comprises this “spring” is not clear. Earliest experiments done by Manton (2) in the early 1970s concluded that to evert the springing organ the body’s hydraulics (pressure on the fluid that makes up most of inside of the body = hemocoel) was important. However, later in the 1970s, Christian (3) concluded that direct muscle action, and not necessarily hydraulics, was the main force inducer. In the 1990s, when high-speed photography had advanced greatly, Brackenbury and Hunt (4) concluded from their experiments that hydraulic forces created by pressurizing the hemocoel increases tension on abdominal sclerites (the exoskeletal plates) that results in a click mechanism that propels the animal into the air. All these studies do agree that elastic elements within the base of the springing organ and within the exoskeleton, as well as the body as whole, are important too. To what extent is not known.

Click mechanism model of the furca. The furca, at rest, is retracted into an abdominal ventral groove. A pair of "basal rods" (springs) are embedded in ventral and lateral parts of the abdominal sclerites 4 & 5, these springs also attach to the apex of the furca. The spring/click mechanism gets help from muscle and active dorsiflexion of the body, which both help release to spring organ from the groove)

Click mechanism model of the furca (red) and distal end of abdomen. The furca, at rest, is retracted into an abdominal ventral groove. A pair of “basal rods” (springs, in blue) are embedded in ventral and lateral parts of the abdominal sclerites 4 & 5, these springs also attach to the apex of the furca. The spring/click mechanism gets help from muscle and active dorsiflexion of the body (in orange), to release the spring organ from the groove. After the furca passes a critical point of extension the spring releases all the energy. (Drawing by Marianne Alleyne based on Brackenbury & Hunt, 1993)

Imagine a beam or a chopstick that’s flexible transversally but somewhat stiff longitudinally. If you compress it, it doesn’t change…up to a point. Then it ‘snaps’ out and buckles. You get a rapid displacement as all the strain energy is released. The exoskeleton of the springtail does a similar thing. It stores the strain energy and then goes through a snap-through buckling phenomenon to produce large strain motion which is then amplified by the tail and presto…springtail in motion.

Many insects, and other animals, use musculoskeletal springs that are incorporated into the complete body plan.  These springs help achieve a high rate of acceleration, or a further jumping distance, and help save metabolic energy. Based on these findings compliant structures and materials have been incorporated into bioinspired legged robots (5). Compliant legged robots achieve a few important things: increased energy efficiency, increased speed, ability to avoid obstacles (in case of jumping robots), and the ability to use more simplified controls to enable enhanced gait control and shock absorption. Springs in bioinspired robots have used elements such as airsprings (e.g. compressed air) and compliant materials, but improvement is still possible. Airsprings, for instance, are not very efficient because they end up converting much of the energy they store into heat. In addition, some of the compliant materials are better than others. Rubbery materials, like elastomers, tend to have a fair bit of viscosity in them and so some (maybe lots) of the energy that it stores is lost to heat as well. For high efficiency, most robotic-type systems currently use mechanical springs (i.e. metals). Bioinspired robots also incorporate series elastic actuators that have linear springs intentionally placed in series between the motor and actuator output, which results in the actuator being bulky.

The variety of jumping mechanisms among insects is great (think: click beetle, flea, grasshoppers, treehoppers, etc.). The intriguing aspect of the jumping mechanism in springtails is that it operates so efficiently at a very small scale, much smaller than any bioinspired robot that has been developed. In the future we will be able to manufacture almost microscopic devices incorporating different characteristics into small structures using “springs” and compliant materials.

Maybe we can incorporate locomotory mechanisms that propel the object, using very little energy. Inspiration for what materials to use and how to construct the object can be found through further study of the springtail’s click mechanism. Somewhat surprisingly not much research has been published on this system since the 1990s. Yet with help from today’s high-speed cameras and microscopy techniques we should be better able to understand how the springtail propels itself. Advanced computer aided engineering (CAE) tools, like finite element analysis (FEA), could be used to augment the visual data and elicit some fundamental internal characteristics that are not visibly detectable.

By researching this topic I thought of a few applications for technologies based on the Collembola’s spring mechanisms. Click mechanisms at the scale of a springtail’s springing mechanism could possibly aid stent design or inspire development of other deployable structures that snap open or closed based on certain environmental conditions. Maybe small springing mechanisms can be incorporated in groups and serve as strain sensors on bigger structures. And who wouldn’t welcome millimeter-sized robots that can perform in a futuristic “flea circus”?

PLEASE LEAVE A COMMENT (OR CONTACT ME VIA TWITTER @COTESIA1) IF YOU HAVE ANY NOVEL IDEAS FOR A SPRINGTAIL INSPIRED JUMPING MECHANISM. JUST IMAGINE.

REFERENCES:

(1) B. Ruhfus and D. Zinkler, Investigations on the sources utilized for the energy supply fueling the jump of springtails, Journal of Insect Physiology, Volume 41, Issue 4, April 1995, Pages 297-301, ISSN 0022-1910, 10.1016/0022-1910(94)00122-W.

(2) S. M. Manton. The Arthropoda: Habits, functional morphology, and evolution. Clarendon Press, Oxford, 1977. ISBN: 019857391X

(3) E. Christian. The jump of the springtails. Naturwissenschaften, Volume 65, Issue 9, 1978, Pages 495-496, 10.1007/BF00702849

(4) J. Brackenbury and H. Hunt. Jumping in springtails: mechanism and dynamics. Journal of Zoology, Volume 229, Issue 2, 1993, Pages 217-236, ISSN 1469-7998, 10.1111/j.1469-7998.1993.tb02632.x

(5) Z. Zhou and S. Bi. A survey of bio-inspired compliant legged robot designs. Bioinspiration and Biomimetics,Volume 7, Issue 4, 2012, 20 pages 10.1088/1748-3182/7/4/041001

SPRINGTAIL RESOURCES:

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*My friends can attest to the fact that I have been talking for a long, long time about starting a blog about how we can use insects to inspire new technologies. One of these friends who had to humor me for so long is Nils Cordes. I met Nils when he was a student at Illinois, but he is currently finishing up his PhD at the University of Bielefeld in Germany. Nils is a great scientist, and a great communicator. He is also a wonderful artist. He offered, those many years ago, to create some art work for this (then still imaginary) blog that I was going to use to communicate my love of insects. And he did…behold the best blog banner EVAH!