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The Human Body as a Biomimetic Inspiration

Evolution News

As symbols of the perfection of human form, one might consider the Venus de Milo or Michelangelo’s David. But those don’t show the insides, where exceptional designs can be found. As physiologists gain deeper knowledge at smaller and smaller scales, down to the cellular and molecular levels, they find an abundance of design inspirations. Here are some of the most recent examples that have come to light.

Hair

Scientists at Queensland University have made carbon nanodots out of human hair. Carbon nanodots are “highly luminescent carbon nanomaterial from which flexible light-emitting devices” can be fabricated. To produce the carbon nanodots, “they developed a two-step process that involved breaking down the hairs and then burning them at 240 degrees Celsius.” Now isn’t that a clever way to put wasted hair to use? Think of all that hair being swept up on the floors of barber shops and beauty salons. Why not make light of it?

“Waste is a big problem,” Professor Sonar said. “Human hair derived carbon dot-based organic light-emitting devices could be used for some indoor applications such as smart packaging.

He continued, “They could also be used where a small light source is required such as in signs or in smart bands and could be used in medical devices because of the non-toxicity of the material.” [Emphasis added.]

Medusa’s hair might be toxic, but not human hair. That’s a benefit: “there could be many uses for small and cheap flexible OLED displays on Internet of Things (IoT) devices,” for instance. Milk cartons of the future might inform you of expired milk, too. And water quality engineers could use such sensors to monitor chloroform levels in treatment centers. 

But why use hair instead of other sources of carbon? Associate Professor Prashant Sonar of the QUT Centre for Materials Science answers,

Professor Sonar said the reason the researchers chose hair to extract carbon dots, rather than something else, was that hairs were a natural source of carbon and nitrogen, which are key elements to obtain light-emitting particles. Another factor was that finding a practical use for waste hair could keep it from ending up in landfill.

When burned, the keratin proteins in human hair break down into carbon and nitrogen in a molecular structure that gives it “favorable electronic properties.” If this catches on, the team says, industries could work “towards a circular economy and sustainable material technology.”

Red Blood Cells

Erythrocytes (red blood cells, or RBCs) combine flexibility, to get through narrow capillaries, with high carrying capacity, to carry oxygen in hemoglobin proteins. Health scientists would like to send medicine through the bloodstream in a similar fashion. The design of nano-vessels that can take advantage of the circulatory system is a big trend in medicine these days.

Knowing that the membranes of RBCs can squeeze and then pop back into shape, six researchers at Johns Hopkins got inspired. They published results of their work in Science Advances (an open-access journal of the American Association for the Advancement of Science, or AAAS), titled “Biomimetic anisotropic polymeric nanoparticles coated with red blood cell membranes for enhanced circulation and toxin removal.”

The design of next-generation nanobiomaterials requires precise engineering of both physical properties of the core material and chemical properties of the material’s surface to meet a biological function. A bio-inspired modular and versatile technology was developed to allow biodegradable polymeric nanoparticles to circulate through the blood for extended periods of time while also acting as a detoxification device. To mimic red blood cells, physical and chemical biomimicry are combined to enhance the biological function of nanomaterials in vitro and in vivo. The anisotropic shape and membrane coating synergize to resist cellular uptake and reduce clearance from the blood. This approach enhances the detoxification properties of nanoparticles, markedly improving survival in a mouse model of sepsis. The anisotropic membrane-coated nanoparticles have enhanced biodistribution and therapeutic efficacy. These biomimetic biodegradable nanodevices and their derivatives have promise for applications ranging from detoxification agents, to drug delivery vehicles, and to biological sensors.

It was too difficult to design RBC-like membranes from the bottom up, they found. So they tried a top-down approach: “coating particles with naturally derived cell membranes circumvented this obstacle.” Even so, it took some doing to get the right shapes and coat them with RBC membrane material. But once they did were able to mimic both the shape and the surface membrane of RBCs, they “determined that the combination of these two features achieves an enhancement of drug delivery efficacy that neither parameter can successfully attain on its own.”

The coated nano-vessels retained the flexibility that makes RBCs able to squeeze through the tiniest capillaries. And by mimicking the anisotropic shapes of RBCs, the team was able to avoid the problem facing spherical vessels, that of elimination from the bloodstream. The team’s RBC-mimicking vessels thus had three advantages: flexibility, non-toxicity, and longevity. The result is “a more favorable pharmacokinetic profile and greater therapeutic efficacy.”

Synapses

It may seem odd that neural signals, being electrical, must pass repeatedly through chemical signals across gaps, called synapses. The proof of the pudding is in the efficiency of the system. A lizard can skitter across a sidewalk several body lengths per second, moving its limbs like a blur, and then climb a brick wall without a break. Elite athletes can run the high hurdles like a locomotive, making split-second decisions about limb movement from brain to toes, while keeping their eyes steady. Remember the ID maxim, “If it works, it’s not happening by accident.”

Two teams are researching the mimicry of synapses, using electronic switches called memristors instead of traditional transistors. Massachusetts Institute of Technology “Engineers put tens of thousands of artificial brain synapses on a single chip,” they boast:

MIT engineers have designed a “brain-on-a-chip,” smaller than a piece of confetti, that is made from tens of thousands of artificial brain synapses known as memristors — silicon-based components that mimic the information-transmitting synapses in the human brain.

The team is translating synapses from a software concept to a hardware reality. Memristors imitate synapses by moving strictly digital technology a bit back toward analog, combining the benefits of both:

A transistor in a conventional circuit transmits information by switching between one of only two values, 0 and 1, and doing so only when the signal it receives, in the form of an electric current, is of a particular strength. In contrast, a memristor would work along a gradient, much like a synapse in the brain. The signal it produces would vary depending on the strength of the signal that it receives. This would enable a single memristor to have many values, and therefore carry out a far wider range of operations than binary transistors.

Like synapses, memristors can “remember” prior states. How can this be applied? MIT envisions artificial intelligence on the move. “Such brain-inspired circuits could be built into small, portable devices, and would carry out complex computational tasks that only today’s supercomputers can handle.” 

Another group working on memristors as artificial synapses is the Jülich Aachen Research Alliance (JARA) and the German technology group Heraeus. They also see gold in biomimicry:

The researchers’ design directions could help to increase variety, efficiency, selectivity and reliability for memristive technology-based applications, for example for energy-efficient, non-volatile storage devices or neuro-inspired computers.

A diagram shows a comparison between a synapse and a memristor. The caption explains one reason for biological synapses:

Synapses, the connections between neurons, have the ability to transmit signals with varying degrees of strength when they are excited by a quick succession of electrical impulses. One effect of this repeated activity is to increase the concentration of calcium ions, with the result that more neurotransmitters are emitted. Depending on the activity, other effects cause long-term structural changes, which impact the strength of the transmission for several hours, or potentially even for the rest of the person’s life.

Memristors achieve a similar effect by allowing “the strength of the electrical transmission to be changed in a similar way to synaptic connections, by applying a voltage.”

Cartilage

One more human body design that garnered imitators recently is described by the University of Colorado, Denver

Biological tissues have evolved over millennia to be perfectly optimized for their specific functions. Take cartilage as an example. It’s a compliant, elastic tissue that’s soft enough to cushion joints, but strong enough to resist compression and withstand the substantial load bearing of our bodies: key for running, jumping, and our daily wear and tear.

Creating synthetic replacements which truly match the properties and behaviors of biological tissues hasn’t been easy. But University of Colorado Denver scientists, led by mechanical engineer professor Chris Yakacki, PhD, are the first to 3D print a complex, porous lattice structure using liquid crystal elastomers (LCEs) creating devices that can finally mimic cartilage and other biological tissues.

The evolution-talk is forgettable, contributing nothing. Skipping on to the meat of the article, they mention “layers of complexity” the researchers had to traverse in order to mimic some of the properties of cartilage. With a 3-D printer, they succeeded partially by printing honeycomb-like lattice structures with a honey-like resin that cures under UV light. As they learn more, they think they can produce shock-absorbing material for football helmets, and — even more valuable — customized biomedical implants for the spine.

These examples — and there are many more — should help us take a moment to reflect on the ingenuity of our earthly habitations, both inside and out, and use them for good.

Photo: Venus de Milo, by Livioandronico2013 / CC BY-SA.