Archive for September, 2010

It’s not easy being green

29 September, 2010 Leave a comment

Some of you may remember Kermit the Frog singing the 1970s song by Joe Raposo, “Bein’ green”. In this song, Kermit laments the fact that green is such a boring color because he blends in with leaves, so no one notices him. Interestingly, an article published today in the New York Times (Green, but Still Feeling Guilty) revives this concern, but in a different context. In fact, the article shows that indeed, it really isn’t easy to be green, especially by the modern-day definition of green.

Each of the wonderful vignettes in this article profiles an individual with a particular connection to the Green Revolution: authors, architects, a random dude who lives in a geodesic dome… yet each of these people are doing something or embracing something in their daily lives that is distinctly not green. [Just a note: the guy in the geodesic dome is practically a saint for what extremes he has gone to to be green.]

So this brings up an interesting conundrum: is it impossible, with all the technology we depend on now for anyone to be fully green? Or, approaching it from a different direction, can being green be a bit like a weight-loss program? Is there a point when we can say that we are being “green enough” so that we can have that little slice of non-green pie to keep the motivation — and our creature comforts — up?

Categories: Uncategorized Tags:

Janine Benyus at TED conference

28 September, 2010 Leave a comment

OK, so I know that some of you are a bit irked by Janine Benyus because her idealism is sometimes a bit too much (e.g., contrary to Benyus, nature really does generate waste, it is not in reality completely waste-free!). However, this TED talk still has a beautiful message that I wanted to share with you all.

Geeky dreams of an obsessed biomechanist

28 September, 2010 2 comments

There are countless stories (legends?) about dedicated faculty who conjure brilliant theories while showering, solve a major molecular roadblock while folding laundry, or dream up innovative interpretations of  complex data. Every time I hear a story like this, I have felt… so envious. But then I  would brush it off with the thought of, “Well, at least I’m not that big of a geek!”

My research strives to understand how we navigate through our complex universe with seemingly barely a thought. After all, how many of us have stood at the edge of a sidewalk in deep contemplation about how much we must flex our ankle, simultaneously activate our gastrocnemius and tibialis anterior, and then absorb the shock with the thick pad of flesh (and fat) on our heels combined with perfectly choreographed knee flexion, as we step down to the asphalt below? Should we have to go through such deep lines of thought, we would undoubtedly all go the way of the indecisive squirrel that gets 3/4 of the way across the road, just to turn around and throw itself under a tire in an effort to return to safety, rather than continue forth to the opposite side of the road a mere couple leaps away. To return to the point, we regularly move across a myriad of different surface types and barely notice it. To top it off, not only do we do it, there are tons of other organisms out there who do it better than we do. What’s going on?

To quantify movement across surfaces, my workhorse is something called kinematic analysis. This basically boils down to marking up an animal with a bunch of points (traditionally drawn on with correction fluid and a fine-tip Sharpie marker), filming with a high speed video, and then going through the record frame-by-frame clicking on each individual point across sometimes as many as 600 frames with 10-15 points per frame. Since our motion analysis is done in 3D, this means we then continue on to repeat this on a second camera (and in some instances, a third). Needless to say, this is a very time-consuming way to collect data, even when it is slightly automated with custom-written tracking software (e.g., see Ty Hedrick’s DLTdataviewer MATLAB program).

We recently purchased a super-duper auto-tracking high speed system to film our animal of choice: lizards. The system consists of six cameras that we mount in a ring, which automatically track reflective markers as the lizard runs through a calibrated filming volume. The amazing part of this system is that it literally can track up to 400+ points so accurately and quickly that we have all our tracked data the second the animal is done running through the field of view. The drawback is that we require markers covered in reflective 3M tape, which gets expensive fast, at $0.40 per mostly non-reusable marker. We are currently marking our animals up with 35-40 points, so burn through points at a rather high rate.

Chinese water dragon

A water dragon with nearly $17 worth of markers, most of which will get soaked off and destroyed in its water dish later that day.

At least one reason for the high cost of these points is that they are literally individually hand-wrapped. Yet, for us “non-professionals” in the way of sticker-wrapping beads, this can be a risky endeavor as the point is useless if it does not effectively reflect light. Additionally, wrapping beads can be extremely time intensive and mentally dull for anyone — including one of our undergraduate helpers — to do. As a result,  I have been in the midst of mental conniptions as of late, trying to figure out an inexpensive, easy way to build markers… all the while watching the dollars fall away as the lizards soak in their water bowls after a hard day’s exercise, destroying the markers so that they are unusable in future studies.

Water dragon model: lateral view

A side view of a tracked model of the lizard shown above running bipedally.

I woke up early this morning — too early by anyone’s standards at 4.30AM — and my brain started whirring. Perhaps it was due to the various discussions we have had in this course, or possibly it was due to one of our recent chapters from Janine Benyus’s book on Biomimetics, but I started seeing bubbles in my half-dream, half-awake state, and gradually began to realize (to my growing horror) that I had become a bona fide geek. These “bubbles” were actually phospholipid balls that were oriented with hydrophobic tails facing inwards and hydrophillic heads facing outwards. It was as if I had returned to Intro Bio my freshman year, only this time, it had really gotten in my head.

Liposome and micelle

When exposed to water, phospholipids will orient the hydrophobic fatty acyl side chains (tails) inwards, away from water, and their hydrophilic heads outwards, forming globules, or balls. Image by Mariana Ruiz Villarreal

As I was lying there confused, disturbed, and exhausted but still determined to stay asleep enough to continue this thought process while awake enough to remember it, I realized that if there were some way to attach reflective glass beads to the hydrophobic heads, I could drop this solution into water to form balls that I could use as quick and easy, highly-reflective markers. Of course, I would also need to find a way to make them solidify so they maintain their shape in air… but that’s just my cynical, awake inner voice talking.

Wispy weeping willows

23 September, 2010 1 comment

I consider myself to be among the lucky few in Philadelphia that get to both live in the city and also live on a large plot of land. My home is built on a 0.6 acre lot that is flanked on three sides by dense “forests” (i.e., unmaintained growth). This forest consists of quite the diverse flora, including introduced maples, pines, black walnut, cherry, and sycamore, as well as an understory dominated by a nearly equal mix of matted wild rose briars and poison ivy.

A gorgeous weeping willow tree that holds very little resemblance to our skinny backyard companion.

The centerpiece of our yard, and Rob’s pride and joy, is a rather Sideshow Bob-like weeping willow tree. Last winter, the unusual amounts of heavy, wet snow broke one of its primary branches off the main trunk, such that what used to be the crown of the tree draped over our lawn for easily 5-6 months before we finally managed to remove it. The lanky trunk and wispy branches that make the willow “weep”, combined with the thin halo of leaves form a deceivingly delicate facade on an incredibly tenacious plant. This enormous, 2 foot diameter branch actually began to heal itself during the course of the 5-6 months it braced itself against the ground! By the time we chopped the branch off in the spring, as it threatened to take down the rest of the tree in its fight to survive, it was sending out new branches and had actually even tried to root a section of itself to the ground!

The aggressive roots of willows are one of their most simultaneously beloved and hated traits. Those who hate the willow tree roots complain about the nearly magical ability for the roots to detect the presence of water, even through metal pipes, and will gradually bore their way through, repeatedly clogging pipes. In fact, there is even a blog dedicated to one such incident of a swamp willow that clogged water intake pipes, and continued to clog them even after the trees were chopped down!

swamp willow roots in pipe

An intake pipe clogged full with swamp willow tree roots.

Those who love the root’s determined hydrophilic nature plant these trees close to rivers, streams, and lakes, to control erosion on embankments. The complex root system wraps the soil, holding it in place, while presenting a zen-like tree above ground for all to admire.

The properties of roots are highly complex. They are very weak resisting compressive and bending forces, excelling in their tensile strength. In other words, roots are strongest when you are trying to play tug-of-war with them, which is precisely why they can be hard to pull out of the ground!

It turns out that the way the roots hold the soil in, is through a process known as edaphoecotropism — quite the mouthful to simply say “stress-avoidance”. In effect, wherever there are particularly high resistive or sheer forces, roots will turn and move down the path of least resistance. In short, what this means is that wherever there is a sheer plane in soil (i.e., one layer of soil moving relative to another), when the root reaches this layer of sheer, it will turn and orient itself parallel to the direction of sheer. Interestingly, what this does is transfer the sheer forces of the soil to tension in the roots, by means of friction of the soil along the entire length of the root. This tension causes the root to lengthen and deform, further increasing the surface area exposed to friction and making the pull out even more difficult.

A potential fruitful area of continued study would be to examine the precise mechanisms of edaphoecotrophism. We already utilize ideas of tensile reinforcement in many familiar materials such as clothing and fibreglass plates. However, I suspect that if we can harness the means of edaphoecotrophism from its sensory or even mechanistic perspectives, we may have some potential innovations for the fields of robotics or artificial growth of stronger construction materials.

Want to read more on soil reinforcement? Check out Simon and Bennett. 2004. Riparian Vegetation and Fluvial Geomorphology. American Geophysical Union.

A tent like a leaf

14 September, 2010 1 comment

Sketches for a biomimetic tent by Ondrej Vaclavik

I happened to come across these sketches tonight for a biomimetic tent designed by Ondrej Vaclavik, a graduate from Prague’s Academy of Arts, Architecture, and Design.

Top view of tent

A top view rendering of the biomimetic tent. Note the clear leaf-like veins!

The structures for this tent are modeled after a leaf, with the veins forming the primary support structures for the tent. Despite the obvious beauty of this structure, it nonetheless is not immediately clear if this offers any added functionality. For example, is it lighter or stiffer? Does it shed water more effectively or deal with wind storms? Alternatively, is this a tent simply constructed for its beauty and to invoke emotions of oneness with the surrounding environment?

Irrespective of this, the design reminded me of tent caterpillars (and other similar insects) that actually will stick two or more leaves together to form a shelter while they pupate. My best guess is that the leaves provide more camouflage than protection, although I could imagine that there could be additional environmental advantages conferred from being wrapped in live, respiring leaves, possibly for temperature or humidity control.

Tent caterpillar cocoon wrapped in leaves (from

Can this design be taken a step further: Are there certain repeatable patterns to the way the leaves or folded and stuck together that can be predictable based on the structural properties of the leaves? Are there any properties to the cell structure and their patterns relative to the veins that can be adapted for addressing construction challenges or for increasing the efficiency/organization of transport?

Interestingly, Mr. Vaclavik also has designed other rather slick looking products inspired by biological shapes, for example, this “cactus juicer”, shown below.

Cactus juicer

A juicer shaped like a cactus. The edges of the ellipses extract the juice, which is then funneled into the cup below.

Hairy feet and scuttling cockroaches… oh my!

7 September, 2010 Leave a comment

As an undergraduate at Berkeley, I found myself dumbfounded and awestruck by the awesome adhesive powers of gecko toepads. For months, I poured hour after hour into removing single toe pad hairs (setae), sticking them to a filed down insect pin, and pressing them against a thin filament of silver wire. I had already stuck a dead gecko on a smooth door and seen it dangling by a single toe with a heavy metal stapler tied to its hips, so I knew there was something spectacular about its adhesive powers (Note: no animals were injured or tormented to discover this!). Yet, each time I pressed a seta to the wire, absolutely nothing would happen. It took countless late night hours of pushing setae to wires with (an arguably) stupidly optimistic outlook, until suddenly, the seta began to stick!

Much of this motivation and inspiration for continuing onwards in this quest was in no small part due to a particularly spectacular advisor, Dr. Robert Full. In the hopes of having him also inspire all of you with his big dreams and creativity, I’ve posted one of his TED conference talks below. I hope you enjoy this as much as I do!

Why daddy long-legs are so cool

2 September, 2010 1 comment

A daddy long leg. Image from

I started catching creepy crawlies before I could walk — or at least that’s what my parents insist I did. When I was two, I caught a spider in my preschool sandbox by cupping it with a baby food jar. I remember that spider just barely fit into the mouth of the jar because it was HUGE; or at least I certainly thought it was. With this in mind, it’s probably not hard to believe that there are few things that make me squirm… except daddy long legs.

To be totally clear, contrary to popular notion, daddy long legs are not spiders. They arise from an entirely different order and lack many of the segmentation and life history patterns observed in spiders.

Daddy long legs are characterized by having eight, long, spindly legs surrounding a bulbous body (although there are some short-legged forms). Their legs can sometimes be so thin that their much heavier body seems to float through the air as they gallump about their daily chores. When they have eyes, they only have one pair, which are placed sideways rather than facing forward. These eyes do not functionally project a usable image; so they have modified their second set of legs to effectively act as antennae to help them tap their way around as they either quietly ambush or actively chase down their prey. Unlike most other arachnids, which live off a liquid diet, daddy long legs consume their prey in chunks.

All these characteristics make daddy long legs rather sinister; yet, whenever my hair stood on end as a daddy long leg made an appearance in the room, I found myself inexplicably drawn to the same question over and over and over again: How do these animals support such a heavy body on such skinny legs?

Photo by Will Cook,

I started looking in to this question several years ago and was stunned by what I found. Despite having such skinny legs, Schultz (2000) showed that the muscles are both numerous and complex. While the bulk of the muscle lies close to the hard, carapacial body, long tendons extend all the way to the tippy tips of the legs (often 50+ segments away!!), enabling fine, prehensile motion. This prehensile motion is used to help them climb thin structures such as grass blades, enabling them to wrap their leg completely around a single blade! More detailed studies by Guffey and colleagues (2000) on the microscopic morphology of these leg tips showed that there indeed is only a single tendon that extends to the toe tip, enabling prehensile motion. I couldn’t help but wonder how such a complex, prehensile motion across so many segments could be possible by means of a single tendon, and how this type of design could be applied industrially for highly mobile, exploratory devices… Thoughts? Does anyone know if something like this already exists in true mechanical models?

%d bloggers like this: