When one thinks of advanced materials, they probably think of some new, high-tech aerospace composite, nanomaterial or some other fancy, expensive or exotic material. However, by only looking at the newest processing and characterization techniques, one overlooks an important source of inspiration: nature.

This article is not about worshiping dirt, or becoming one with the forest, but rather turning to biology to find inspirations for design. Every living organism on this planet does something unique; something that its nearest genetic neighbors do not, which is why conservation efforts and biodiversity are about saving all species.

Engineers who look to biology for design inspiration often look at these differences and figure out how to reverse engineer them. Once the feature has been reverse-engineered, it can be redesigned and developed for a modern, industrial use.

While there are many instances of bioinspired materials, this article will focus on a few unique topics, including robotic grippers, solid materials transport and epoxy. Once the pattern is established, the reader is encouraged to look for more such designs not covered in this article.

Robotic grippers

Robots are used in most aspects of manufacturing. In particular, they are good at gripping, holding and transporting raw materials and products in a consistent, sanitary, safe and stable manner. One of the challenges to this operation is figuring out how to make grippers that can handle all of the items that need to be gripped.

Metallic claws and fingers are perhaps the first grippers most people think about for this purpose. They work great for handling heavy and hard items. However, consider instead the design requirements for handling a glass sheet, a tomato or foam padding. Perhaps a metallic set of fingers is not the best gripper.

Enter bioinspired materials design. Research and development (R&D) engineers turned to nature to see how various creatures maintain their grips when climbing, catching prey and navigating. Geckos, starfish, squid, octopi and many other animals have small, soft suction cups they use for these purposes. One such system gripper was developed at Stanford University.

An octopus uses suction cups to capture prey and to climb. Source: Victor Micallef/CC BY-SA 4.0 DEEDAn octopus uses suction cups to capture prey and to climb. Source: Victor Micallef/CC BY-SA 4.0 DEED

Suction cups made from polymers instead of metal fingers can be used to lift glass sheets, produce and other fragile items. Furthermore, their design can be modified to include a vacuum system to draw a stronger vacuum on the object that needs to be lifted. This vacuum system can operate more quickly and reliably than an animal’s muscles can contract, leading to quick gripping and unwrapping of objects.

Abrasive material transport

Another engineering challenge is dealing with the constant erosive effects of transporting abrasive materials, such as sand, gravel and cement. Depending on the specific application, these materials may be embedded in a slurry or moved pneumatically. The force of the fluid (liquid or gas) pushing the particles causes them to slowly erode away at the piping, valves and other hardware along the path.

Erosion of this kind can lead to all sorts of headaches. For the pneumatically driven system, pinhole leaks mean an air leak. The compressor must work harder and more often to deliver the same results. If it does not maintain the pressure drop across the piping, some of the particles will fall out of suspension, leading to clogging. In a slurry, pinholes will leak, dripping out the product. Ultimately, erosion leads to wasted energy.

The design of this system requires a hard, abrasion-resistant material. However, glass or ceramic lined pipes are often too fragile for the concrete manufacturing and mining industries. A solution that is simultaneously abrasion-resistant yet will not crack from thermal stresses as it sits in the hot sun, or shatter on an occasional bump by construction equipment is necessary.

Instead, engineers turned to studying snakes. Snakes crawl on the ground, rubbing past sand all day. Their secret is a two-layer system; a series of relatively hard plates that can rub freely past each other that rest on top of softer, flexible tissue. Mimicking this, engineers are experimenting with coating the inside of the pipes with a polymeric material that has a series of ceramic plates attached to them. The polymer allows the plates to move around a little, making them less susceptible to damage from thermal stresses, impact and other mechanical damage as compared to glass or ceramic lined pipes. Then, the ceramic plates are hard enough that they have high abrasion resistance. Parker Hannifin developed the first pipes of this design.

Snakeskin is made of hard plates on a soft medium. Source: Public domainSnakeskin is made of hard plates on a soft medium. Source: Public domain

Biological epoxy

Hip replacements do not last forever. The body never seems to fully accept the addition of titanium replacements. At best, the body tries to keep to itself and avoid the implant, and at worst, the implant is fully rejected, which can be a life-threatening problem. The surgery itself is risky and painful, and so long-lasting, biocompatible alternative solutions are highly desirable.

Titanium alloys have high strength to weight ratio, are resistant to corrosion and are generally biocompatible. Researchers turned to finding a way to improve the bond between the bone and the titanium implant to extend the lifetime of the hip replacement. Through their research, they discovered that barnacles may help.

Barnacles are typically a nuisance as they slow down ships, but perhaps they will help make hip replacements last longer. Source: James St. John/CC BY 2.0 DEEDBarnacles are typically a nuisance as they slow down ships, but perhaps they will help make hip replacements last longer. Source: James St. John/CC BY 2.0 DEED

Barnacles develop a natural epoxy that allows them to stick to the bottom of ships, along wharves and docks and other nuisance locations. The researchers at Fraunhofer found that they could mimic this epoxy for bonding bone. With the proper additives, the epoxy would actually encourage bone growth, which led to even stronger bonding to the hip replacement.

Final thoughts

These are just a sampling of the many projects that use bioinspired materials and bioinspired design. All of these projects and many others start with a problem statement. From there, the engineers look to both the natural and the human-made world for solutions. When a solution from the biological world is discovered, it is distilled to its most important, fundamental parts and improved to meet the design criteria. Using this process, bioinspired design will continue to play an important role in the development of new technology.