Palm beetles live on palm trees. They use the oil of the tree as a glue to keep them attached to the tree. Engineers are trying to create an artificial system that uses the same trick, and that could let humans walk on walls. But I think we’re missing the whole point.
Palm beetles harvest oil from their preferred habitat, palm trees, and use its properties of surface tension to stick to the leaves. They do it by forming over 100,000 tiny droplets of palm oil on their “feet”. Each droplet adheres to the leaf with only the tiniest force, but multiplied by all the droplets produces a significant force – enough to keep the little bug securely fixed to a leaf in almost any situation it might encounter.
If we could create a technology that simulated that, we could walk up walls just like Spiderman. Indeed, such an effort is currently being pursued by Dr. Paul Steen, a chemical and biomolecular engineer at Cornell University. Potential applications include simple switches made essentially of water and, of course, wall-walking; DARPA is funding some of this work. Reading up on his work (e.g. at this CBC web page), however, made me wonder if we’re not missing the point of the palm beetle’s sticky oil trick.
Scale and Writing
Some people might consider it counterintuitive that one could use oil to make things stick, because we usually think that oil makes things slip.
And yet, if one really understands the physics of surface tension and the properties of the materials involved, then this “neat trick” would make perfect and obvious sense. Indeed, it only seems like a “neat trick” because it runs against our intuition (which is not a particularly reliable instrument anyway).
Part of the problem is the matter of scale. Our intuition, which is largely based on our experience, is rooted in our sense of scale about the universe. Our senses work at the meso-level – not at the micro-level of atoms and molecules (where surface tension becomes a significant force) and not at the macro-level (of stars and galaxies). Our intuition only works at our meso-scale because it’s all we really know. When we’re confronted with situations that are at very different scales, the universe can act quite differently, and our intuition is usually quite useless.
This is something to which most people are totally unaccustomed, but with which most scientists and engineers are quite comfortable. Our knowledge about the meso-level is quite good – witness the myriad things we have constructed and use on a daily basis, and how most of us react with no surprise at all to meso-level events like the periodic alteration of day and night, stoplights, and the amount of rain that typically falls on a cloudy day. The connection of our intuitions to the meso-level of things is very lucidly discussed by Richard Dawkins in The Blind Watchmaker.
A long time ago, we lacked the instruments to examine the micro- and macro-levels, so we naturally focused our attention at the meso-level. And it made sense to most people because it related directly to their own experiences. This was reflected in our “science” back in the day: we could predict natural, every-day phenomena quite well because we had ready access to data through our senses alone.
But this is no longer the case. Our knowledge is now expanding rapidly at the other scales, the micro- and macro- level, where the public has little or no experience. Not only are specialized instruments needed to collect data at those scales, but the phenomena themselves are very different, largely because most relationships between things are non-linear – and the human brain really sucks at thinking in non-linear ways.
So it’s quite natural that science should seem to become ever weirder to the general public. Its apparent relevance to daily existence will seem to become less and less as it gets weirder and weirder, which makes it all seem less and less interesting, and so less and less worth knowing or pursuing.
The point is this: if science is to remain properly at centre stage as one of humanity’s most successful and important endeavours, we need to focus much more than we have done on science writing, the goal of which is to make science accessible to the general public. This is essential because science is the best, most reliable means yet devised to understand nature and to, in some small ways, control it for our benefit. It behoves every scientist and engineer, I think, to disseminate our knowledge about the nature at every scale to the broadest possible audience. Science has constantly challenged the superstitions and fables that have filled our histories, explaining those that make sense, and thoroughly demolishing those that do not.
Science works, and everyone needs to know it.
There’s another, more pragmatic reason for science writing. Scientific and engineering research happens thanks mostly to the tax dollars that are directed to it from government coffers. Dissemination (in part through science writing) is our way of explaining to the public what we’re doing with their money. It’s just the right thing to do.
This kind if dissemination becomes increasingly difficult as science pushes its boundaries because of the scale mismatch I described above. So now more than ever, we need well-educated, erudite, and enthusiastic individuals to take the time to explain science to the public.
There’s another important point in the story of the palm beetle, about sustainability and how nature works.
Nature has no intent, and no memory of the sort we have. It has no intuition. What it does have is nearly perfect information about itself. Unimpeded by the imperfections of sensory processing, the universe is a perfect rule-based system. As such, nature has no choice but to pursue avenues that are the result of only its own laws.
This is not to say that the future is pre-determined; what I mean is that the laws of nature constrain what can happen at any instant, and that nature responds to a situation in very specific ways that do not include planning, intent, and emotion.
I find the best analogy for this – at least, the one that works best for me – is thinking of nature as a state-transition system. At any instant in time, one can think of nature as described by a list of variables, each of which has a particular value. This is the state. Given a description of the state, one can calculate pretty much any other feature of the universe, at least in principle. There are some very good reasons why we can’t actually do that sort of thing for any interesting system, but just because we can’t do it doesn’t mean it’s impossible – it’s just impossible for us, now.
At any instant, there is also a list of possible events that can happen. These events are the transitions between one state and another. One of the events on that list will happen. The list of events contains only those events that obey the laws of nature and can happen with respect to the current state. When an event happens, it changes the values of some of the variables and so puts the system into a new state. Being in a new state changes the list of possible events that can happen next. Wash, rinse, and repeat, ad infinitum. That’s a state-transition system.
Some of those events are more likely than others, based on the state. But there are also random effects that change the likelihood of a particular event happening in unpredictable ways. (On large enough scales, even probabilistic events can be treated scientifically, although little can be said about such events on a case-by-case basis.)
Since transitions depend on states and vice versa, the way things are now is the result of all the state transitions and all the states that led to the current state. In this way, there is a kind of memory built into nature, but it’s a strictly structured and implicit one and not like the far more malleable and error-prone (but also more “enjoyable”) memory that humans have. You can think of the-way-things-are right now as a kind of running total of everything that has come before.
In this kind of existence, using the surface tension of an oil to create stickiness at the microscopic level is not only normal, it’s pretty much inevitable. Here’s what I mean.
One of the reasons the palm beetle developed its trick is that over a very long time the kinds of forces that try to dislodge the beetle were less than the sticking force afforded by the palm oil. So beetles that could use this trick had an advantage over other beetles that could not. Over time, the sticky-footed beetles took over because they survived better and could pass on their genes for stickiness. If the forces that try to dislodge the beetle had been much more than what those ancestor beetles could handle, then the sticky oil trick would not have given the beetle an evolutionary advantage and, all else being equal, beetles who could perform that trick would not have survived. So, that the beetle can do the sticky oil trick implicitly includes a “memory” that the external forces were never large enough to overcome the sticky forces.
There may be have been other ways that the palm beetle could have stuck to the tree – but for some reason lost in the mist of time, the sticky oil trick won out. It could have also just been a random effect.
I think that the reason we find it so surprising and even awesome that these kinds of things happen in nature is just because our minds don’t work like nature does. It’s not that nature is “better” than the human mind at doing things. Granted, it has had a bit longer to experiment with things than we have – a few billion years longer. And granted, nature isn’t afraid to wipe out whole species, let alone planets and even galaxies as part of it’s process. We’re a bit more timid to engage in such experimentation. Nature is just works differently than we do.
And while we might choose to be not as heartless as nature, we can still learn many valuable lessons from it. Indeed, we’re only now starting to understand how puny our greatest accomplishments are, largely thanks to disciplines like systems science, biomimetics, cosmology, complex dynamics, chaos theory, and others.
Of course, adapting our own inventions to be more “natural” is a huge challenge because of the burden of historical and cultural baggage that informs us – wrongly, I think – that humanity’s role is to tame nature. This implies that humanity and nature are two different things, which is just not true. This is a problem that will take a long time to address. But the longest journey begins with a single step; if we don’t start, we won’t get anywhere. So projects like Dr. Steen’s are a good start, even though I have serious reservations about it.
My main concern with Dr. Steen’s approach is that it lacks any sense of symbiosis. That is, the palm beetle harvests oil from the palm tree, whereas the fluids being used by Dr. Steen’s team are supplied separately. The beetle’s “equipment” for delivering and using the palm oil is organic, imperfect, and highly variable. The artificial system is carefully made to tolerances no natural system can ever achieve, out of materials that generally don’t exist in nature. The palm beetle uses materials that are readily available on site. As such, it exists in a symbiotic relationship with the palm tree on which it lives. This is not the case with the artificial system. This is a hallmark of sustainability – making use of what’s available. In the case of the artificial system based on the palm beetle, we are not using what’s available. So while the artificial system is biomimetic, I really don’t think it’s sustainable. It may be a technical marvel, but it isn’t especially natural.
I believe that this is one of the biggest problems facing product development. We can’t just copy how nature does one specific thing and claim that it’s sustainable. Nature always does things in a context. As soon as we copy it in a different context, we’ve lost the one fundamental characteristic of any natural system – that it’s strictly responsive to the current state, something that humans tend not to do, especially in modern, “developed” societies.
Not that I’m saying we have to stop thinking and just follow the laws of nature. If we did that, we’d have to give up many things that I’m not sure society is willing to give up, including a significantly lengthened lifespan, an essentially disease-free existence, food, water, and heat on demand, and diversions like Twitter.
What I’m saying is that we need to revisit how we do things and make things, and look more deeply at how we can find a better balance between what we need and how we can satisfy those needs in as natural a way as possible.
The most obvious way in which we do not balance our society with respect to nature is in waste creation. We great more waste than the Earth knows what to do with. The facile answer is to stop consuming so much, because waste generation is a function of consumption. And this is certainly a good start. Humans are the only animals on Earth that use resources for what are essentially frivolous reasons. Cutting back on such frivolity would be good, in principle and in practise.
But that won’t prevent some very nasty waste from being generated anyways. What we need is to think in more ecological terms about the waste we produce. For instance, there’s some talk of literally mining landfills for exotic materials commonly used in electronics. We’re thrown away so much high-tech stuff that some landfills may have a higher concentration of these materials than any naturally occurring deposit. So why do we bother throwing the stuff away to begin with?
There’s another idea that’s been floating around for decades – industrial ecologies – that leverage this notion. These entities are groups of industries that depend on one another, each using the waste of one of the others as raw materials. There are a few such ecologies in the world, and they seem to be doing quite well.
I don’t know why they haven’t caught on more than they have. I think it has to do with the admittedly large costs of relocating factories and other facilities to be closer to their ecological partners. But I find such explanations facile and superficial. Some day, sooner than we probably think, we may be confronted with the eminent destruction of the biosphere. That is something that we really ought to avoid, regardless of the cost. There must be some combination of regulation, incentive and subsidy, and economy of scale, that can help this all move along. Indeed, it annoys me tremendously that with all the talk about climate change, virtually no one on the political stage has been pushing industrial ecologies.
In any case, we need to work harder to understand more deeply the kinds of relationships that has let the biosphere thrive for these billions of years since life began. There’s too much at stake to drop this ball.
…And all this from a palm beetle.
This post was inspired by a story on CBC Quirks and Quarks, 27 Feb 2010.