March 3, 2018 | David F. Coppedge

Trends in Biomimetics: Copying Irreducible Complexity

Not everything in nature can be copied effectively for human engineering. Why? Nature is sometimes too good.

Why bees soared and slime flopped as inspirations for systems engineering (Science Daily). Georgia Institute of Technology took an early lead in biomimetics, establishing an interdisciplinary Center for Biologically Inspired Design. Looking back on lessons learned, Craig Tovey found some of the center’s projects worked out better than others.

Bees? Great. Ants? Hit or miss. Slime mold amoebas? Fail. Though nature offers excellent design inspirations in some information technology systems, in other systems, it can bomb.

But is this nature’s fault? “Whether mimicking nature is prudent in a particular engineering job depends a lot on the problem to be solved,” the article says. “Often, it’s just better to use something off the shelf or adapt it.” Natural solutions are excellent for the organisms, everyone agrees. Whether they fit human needs is a different issue. For limited questions humans face, like the “traveling salesman problem” for static situations, human algorithms can perform better than ant colonies, which were studied for solutions. But ants and bees face a dynamic situation. Cities don’t move around, but insect targets do. Flowers close up at certain times of the day, for instance. For those kinds of dynamic situations, Tovey agrees that the insect solutions are superior. Even the humble slime mold he finds awe-inspiring, whether or not it led to a human application at Georgia Tech:

Though classic algorithms beat nature in simple situations, watching natural algorithms in even the simplest organisms can be awe-inspiring. Take slime mold, a non-cellular organism related to amoebas.

“If you put down lumps of food near it, the slime mold will extend to reach the lumps and connect them with each other.”

The mold makes very efficient connections that adapt well to differing constellations of food dabs.

“Some researchers placed food sources in spots corresponding to the locations of cities in Japan that were connected by rail lines, and sure enough, the slime mold eventually settled on a configuration connecting the spots that nearly perfectly matched the rail network that actually connected the cities,” Tovey said.

The rise of bioinspired microrobots (Science Daily). “Jumping robot spiders and swarms of robotic bees sounds like the stuff of science fiction, but researchers at The University of Manchester are already working on such projects and aiming to lead the world in micro robotics,” this article says, hastening to add that the projects are nothing to worry about. To make progress, they filmed a jumping spider in slow motion, analyzing its every movement.

Why jumping spiders you ask? Unlike humans, our spiders can jump up to six-times longer than their own body length from a standing start. In comparison, the maximum a human can jump is just one and half times. Dr Nabawy says if we can perfect the way spiders jump in robots they can be used for a variety of different purposes in complex engineering and manufacturing and can be deployed in unknown environments to execute different missions.

Using nature’s designs will speed up critical development of new antibiotics (Medical Xpress). This article marvels at the effectiveness of natural antibiotics over synthetic ones. “Streptomycin, chloramphenicol and tetracycline – three of the most widely used antibiotics – were all discovered in soil bacteria,” the article says. “Nature is the grand architect behind a major proportion of modern drugs.” The article begins with a quote from Alexander Fleming, discoverer of penicillin, giving credit where credit is due: “I did not invent penicillin. Nature did that. I only discovered it by accident.”

I did not invent penicillin. Nature did that. I only discovered it by accident. —Alexander Fleming

Molecule of life finds new uses in microelectronics (Science Daily). DNA has a big future in computing. At Arizona State, researchers are finding that “DNA’s remarkable properties of self-assembly and its ability to conduct electrical charge over considerable distance make it ideally suited for myriad applications, including tiny electronic circuits and computing devices, nanorobots and new advances in photonics.” And in DNA computing, researchers at Washington State made another milestone: achieving random-access memory, says Phys.org. It wasn’t a first, but set a new record for “selective retrieval of individual data files encoded in more than 13 million DNA oligonucleotides.”

Inspired by nature: Design for new electrode could boost supercapacitors’ performance (Phys.org). At UCLA, researchers looked at trees for inspiration. The branch-and-leaf design in trees maximizes surface area. At a million times smaller scale, could this produce more efficient networks of supercapacitors? Their test model was better in all respects: good news for users of battery-powered devices, like hybrid cars and household electronics.

The electrode design provides the same amount of energy storage, and delivers as much power, as similar electrodes, despite being much smaller and lighter. In experiments it produced 30 percent better capacitance—a device’s ability to store an electric charge—for its mass compared to the best available electrode made from similar carbon materials, and 30 times better capacitance per area. It also produced 10 times more power than other designs and retained 95 percent of its initial capacitance after more than 10,000 charging cycles.

Scientists create complex transmembrane proteins from scratch (Phys.org): Physicists at the University of Washington Institute for Protein Design have been busy copying nature. “Our results pave the way for the design of multispan membrane proteins that could mimic proteins found in nature or have entirely novel structure, function and uses,” they say. But even if they can traverse a membrane, can they do all that living transmembrane channels do?

In the living world, transmembrane proteins are found embedded in the membrane of all cells and cellular organelles. They are essential for them to function normally. For example, many naturally occurring transmembrane proteins act as gateways for the movement of specific substances across a biological membrane. Some transmembrane proteins receive or transmit cell signals. Because of such roles, many drugs are designed to target transmembrane proteins and alter their function.

Technomimetics vs Biomimetics

Finally, a paper in PNAS looks at two approaches for building machines at the molecular scale: technomimetics and biomimetics. The former tries to imitate what human machinery does and scale it down. The second tries to imitate what living molecular machines already do.

The widespread use of molecular-level motion in key natural processes suggests that great rewards could come from bridging the gap between the present generation of synthetic molecular machines—which by and large function as switches—and the machines of the macroscopic world, which utilize the synchronized behavior of integrated components to perform more sophisticated tasks than is possible with any individual switch. Should we try to make molecular machines of greater complexity by trying to mimic machines from the macroscopic world or instead apply unfamiliar (and no doubt have to discover or invent currently unknown) mechanisms utilized by biological machines? Here we try to answer that question by exploring some of the advances made to date using bio-inspired machine mechanisms.

The problem with technomimetics is that different physical principles operate at the nanoscopic level. In an environment where Brownian motion and quantum mechanics swamps gravity, many “simple machines” that we learned about in high school, like inclined planes, don’t work. The three authors, Zhang, Marcos and Leigh, evaluate recent successes at imitating biological switches, ratchets and rotary motors that do work at the molecular level. Recalling Richard Feynman’s famous lecture, “There’s Plenty of Room at the Bottom,” they agree that “the concept of using molecules to manipulate other molecules in robotic fashion is an intriguing one that has some precedence in biology.”

Looking to the future, they realize that technomimetic nanomachines may ‘look’ like their macro counterparts but don’t work like them. “Such issues make extrapolation of mechanical machine concepts to the molecular level fraught with difficulty.” Instead, they think the future is biomimetic:

The alternative is to design nanomachines that work in broadly the same way as biology. As with classical engineering, a route to machine complexity is to integrate the actions of several simple machine processes to generate advanced functions that cannot be achieved by the action of any of the machine parts individually. Given that most complex machine mechanisms cannot be scaled to the environments in which molecular machines operate, it may prove difficult for technomimetic designs to produce nanomachines that are significantly more advanced in terms of mechanism than the rudimentary systems made to date. However, all of biology is based on molecular machines that use (and appear to require) nontrivial mechanisms to carry out the sophisticated and useful tasks they perform. Through adopting the basic principles of how such machines work, bio-inspired mechanisms can enable the construction of molecular machines that are more than just switches, with compound mechanisms based on the integration of several simpler working parts.

Have they just described “irreducible complexity”? Read that paragraph again and look for it.

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