David Tolfree, physicist and independent technology consultant, and Dr Alan Smith, materials scientist and independent technology consultant
Healthcare budgets are rising everywhere because new advances in medicine have raised public expectations. The increasing demand for medical products and services as well as ageing and growing populations is inevitably driving up costs. Current spending on world healthcare is about US$7,699 bn for a population of about 7.26 bn people and there was more than a 60 percent cost increase in the decade 2004–20141. The average life expectancy has been extended by about five years in the last decade, a trend that is likely to continue. These statistics demonstrate the urgent need to find more efficient and cost-effective ways of providing sustainable healthcare for the future.
Recent advances in microscopy have greatly increased visions at the nanoscale where most biochemical processes of life take place. This has enabled us to learn more about the advanced capabilities animals and plants have developed during their evolution. Over four billion years, the survivors have prototyped, market-tested, upgraded and refined what we see today. Many species have properties that are very attractive for the innovators of new products applicable to the medical and healthcare sectors.
Biomimetics or biomimicry is the study of the formation, structure and function of biologically produced substances and materials, mechanisms and processes for manufacturing similar products by artificial means. Studies in biomedical technology and engineering have already shown that our engineering cannot currently outperform many of nature’s capabilities.
Humans have evolved with larger brains but have not adapted as well to the earth’s environment as other species. We have to protect our bodies with clothing and shelters from even small changes in the climate. Our movement is limited by our physical structure, so we have built machines to compensate for that and other physical limitations. We are constantly vulnerable to life-threatening invasions from bacterial species, many of which have existed on the planet billions of years before us. By learning more about how other species survive, we are discovering more about how to protect ourselves against disease and climate change. One extreme example is a strain of bacteria known as Bacillus F that survived for 3.5 mn years beneath the ice in Antarctica and is claimed to prolong life.
Sensor-based products
One of the most exciting areas for new products in the healthcare sector is in the field of biosensors, where the objective is to detect and prevent diseases before they take hold of the body. The benefits to be achieved are reduced hospitalisation, less drugs needed to halt the disease with reduced risk to the patient and huge cost savings.
Sensors are the most ubiquitous example of products that have their origins in nature’s biosystems. All living things, including humans, are comprised of millions of biosensors. Basically, a biosensor is a device or mechanism that converts a response into an electrical signal that can be processed by the brain or a computer.
Estimates vary from different market analysts but currently biosensors are the most rapidly growing field with a 60 percent annual growth rate. The major emphasis is from the healthcare sector, in which a significant fraction of the market is for biosensors, estimated by Global Market Insights to rise to about $29 bn by 2024 2 . There is little doubt that the huge growth of medical applications for biosensors will advance the future commercialisation of medical devices. Key applications are in early cancer diagnosis, heart disease, cholesterol and blood glucose testing.
A team of researchers at the University of Leeds in the UK developed a patent-protected electronic mobility aid called UltraCane for blind and visually impaired people, taking inspiration from bats’ superior navigational abilities in the dark thanks to echolocation (figure 1) 3 . The device enables the user to detect and move around obstacles. It incorporates narrow beam ultrasonic wave emitters and two sensors that can detect obstacles 2 or 4 m ahead. The user receives tactile feedback via two vibrating buttons on the UltraCane’s handle that they rest their thumb on. The device can also be mounted on vehicles for disabled people.
Figure 1: The UltraCane electronic mobility aid for the blind and visually impaired.
EvoLogics, a company in Germany, has developed a sweep spread carrier (S2C) acoustic modem for underwater data transmission, based on dolphins’ ability to sense and recognise each others’ calls at up to 25 km apart using unique frequency-modulated whistles 4 . The device is currently employed in the tsunami early warning system throughout the Indian Ocean. Sound waves can travel over 10 times faster than tsunamis and spread out in all directions, regardless of the trajectory of the tsunami, making them easy to pick up using underwater hydrophones. Applications for the modems are being actively sought in the medical sector.
Potential applications derived from observations
Charcoal beetles—found in Central America, North America and Oceania—are ultra-sensitive to temperature changes. After a wildfire, they appear in vast numbers, and the females lay their eggs in the charred wood. The larvae burrow into the wood and feast, safe from the defences that a healthy tree might rely on to get rid of them. The beetle has a unique set of sensors mounted on its thorax that can detect infrared radiation. Every sensor array contains about 70 individual organs called sensilla, each of which contains a small pocket of water that expands when heated, pushing against a receptor at the base of the pocket—a relatively simple pressure sensor. Their biological infrared receptors are more sensitive than infrared sensors currently on the market. An application where the sensitivity of such sensors could be of value is infrared thermography for the early diagnosis of skin and breast cancer.
Similar ultra-sensitive heat sensors have been found in the wings of some butterflies. Morpho butterfly wings are iridescent, thanks to rows of tiny tree-like structures on their surfaces. Light reflecting off each micrometre-long branch and trunk interferes, producing shimmering colours. Researchers at the University of Albany and General Electric (GE) Global Research Center in the US have found that the tree-like structures make excellent heat sensors. 5 As heat or infrared radiation hits these trees, the chitin that they are made from expands. This increases the distance between the branches and trunks, perceptibly shifting the wavelength of light they reflect. To boost the wings’ sensitivity, the researchers coated samples with a layer of heat-absorbing carbon nanotubes. The coated wings were able to reveal temperature differences of just 0.018˚C. Applications are envisaged in thermal imaging sensors.
A research team led by Brigham and Women’s Hospital in the US has been inspired by jellyfish using their tentacles to grab miniscule food floating by to develop a microchip that could have broad diagnostic and therapeutic uses in the capture of rare cell types, for example, cancer and fetal cells. 6 The microchip has a microfluidic surface made up of numerous, long DNA aptamer strands that can be programmed to detect and capture certain cell types. The researchers first of all took short strands of DNA aptamers that bind to the targeted cell surface, copied these hundreds of times and then joined them together to form strands tens of microns long. At one end, the strands are connected to the microchip, and at the other, they float freely in the bloodstream, grabbing the required cells floating by, much like the jellyfish. A potential application studied by the researchers is the isolation of cells that break away from solid tumours and travel through the bloodstream.
General healthcare applications
Bombardier beetles repel attacking insects by using catalysts to decompose hydrogen peroxide rapidly and produce a very fine spray of near boiling liquid. Swedish Biomimetics 3000, a company in Sweden, has been inspired by the beetle’s defence mechanism to develop a micro mist spray technology called μMIST that has a lower carbon impact than aerosol sprays. There are many different commercial techniques for spray generation, but this is believed to be the only one that does not require a a propellant to spray highly viscous formulations. Possible applications are in new types of nebulisers.
There is a continuing trend for less invasive medical procedures. Studies of mosquito bites have enabled a team of micro engineers at Kansai University in Japan to develop a method of giving pain-free injections 7 . The team replicated the mosquito’s proboscis in the design of a needle to enable doctors to painlessly and more safely extract blood and inject drugs. Mosquitos inject painlessly by vibrating their proboscis to help their maxillae (serrated sections) ease down through skin painlessly. They then inject anticoagulant saliva to stop blood clotting during feeding. We feel discomfort afterwards because they inject bacteria that cause irritation and pain. We do not feel the bite however, because the proboscis is highly serrated and so leaves only small points in contact with the skin tissue, thus reducing friction and therefore nerve stimulation. By contrast, conventional hypodermic steel needles are smooth, leaving a lot of metal in contact with skin tissue. Deep penetration results in contact with the maximum number of nerves and therefore causes pain. Hypodermic needles designed around the mosquito’s proboscis can eliminate this pain (figure 2).
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Figure 2 and 2b: Painless injections inspired by mosquitos.
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Figure 2 and 2b: Painless injections inspired by mosquitos.
Biosignal, a company in Australia, has found a way to control bacteria rather than kill them so that bacterial resistance is avoided at the same time as preventing infection. The company has developed synthetic furanones based on the natural ones produced by the eastern Australian seaweed Delisea pulchra because of their ability to prevent bacteria from communicating. This means that colonies of bacteria cannot then form and cause infection, yet the bacteria are not killed and do not form a resistant strain. Most bacterial infections in humans result from the formation of bacterial colonies, or biofilms, on surfaces. Potential applications for the synthetic furanones include avoidance of dental plaque and biofilms on membranes or medical devices.
Ophthalmic implants
A group of engineers at the California Institute of Technology set out to help alleviate the onset of glaucoma, the second leading cause of blindness globally. They have developed a synthetic analogue for eye implants that is more effective and longer-lasting, taking inspiration from tiny nanostructures on the transparent sections of longtail glasswing butterfly wings (figure 3) 8 . These sections are almost perfectly transparent because they are coated in tiny pillars, each about 100 nm in diameter and spaced about 150 nm apart, giving them unusual optical properties. The pillars redirect the light as it strikes the wings so that the rays pass through regardless of the original angle at which they hit the wings, an effect known as angle-independent antireflection. As a result, there is almost no reflection of the light from the wings’ surface and they are clearer than plain glass. The engineers produced an eye implant with pillars about the same size and shape as those on the butterfly’s wings made from silicon nitride, an inert compound often used in medical implants. These pillars have improved the performance of eye implants.
Figure 3: A longtail glasswing butterfly.
A team of researchers at Stanford University in the UK has developed a biomimetic material called Duoptix for use in artificial corneas 9 . Corneas shield the eye from dust and germs, acting as the eye’s outermost lens and contributing up to 75 percent of its focusing power. More than 10 mn people globally are blind due to damaged or diseased corneas and many millions more are near-sighted or far-sighted due to misshapen corneas. The material created by the researchers is a hydrogel that can swell to a water content of 80 percent; a similar figure is possible with biological tissues. The pores built into the artificial material enable cells that need to to infiltrate the artificial lens and integrate it with surrounding natural tissue.
Robotic engineering
Robotics has been growing rapidly during the last fifty years and is now recognised as an interdisciplinary area of engineering. More recently, biological science has seen new breakthroughs in robotics science and technology, and many have been influenced by biomimetics. Some leading universities in the US have departments devoted to the subject. For example, the Berkeley Robotics and Human Engineering Laboratory—at the University of California, Berkeley in the US—has a number of different research areas under investigation, some of which are listed below 10 .
•Biomimetic fish with actuated tail fins for propulsion and actuated pectoral fins for dynamic lift and turning.
•Four-legged biomimetic insects using mechanical linkages combined with a centralised actuation mechanism.
•Robots that explore vibrational locomotion using three high-frequency solenoid pulses to propel and rotate.
•Biomimetic gecko exhibiting incline climbing behaviour.
•Biomimetic snake using two segment linear-drive actuators.
•Biomimetic frog with solenoid driven project exploring symmetric and asymmetric rear propulsion.
•Exploratory project where wheels are equipped with compliant leg-like spokes to help cars move easier over uneven terrain.
The focus is now moving to biotensegrity; taking inspiration from the complementary arrangement of bones and tendons in biology, where we use separate elements for compressive and tensile loads to create lightweight structures capable of supporting large loads.
Prosthetics
Prosthetics is a field that is receiving a great deal of attention. A group of researchers at the University of Washington in the US has developed a real-time, user-controlled antropomorphic robotic hand that mimics the movement of a human hand down to exact muscular and tendon action 11 . This technologically advanced robotic hand incorporates 40 tendons, 24 joints and more than 130 sensors. It not only exhibits a high level of dexterity but is capable of learning from experience and so is able to become progressively more adept at performing tasks. An ongoing project, the ultimate objective is to make the robotic hand as like a human hand as possible and allow amputees to regain freedom of movement.
Kau, as a former BA industrial design student at the University of Washington, designed an octopus-inspired, motor-driven prosthetic (figure 4). The device is intended to complement the user’s existing damaged or partially impaired arm, mimicking octopus tentacles aesthetically as well as in terms of their flexibility and adaptability. The user is able to control the amount that the arm curls and its strength of grip to accommodate a variety of tasks.
Figure 4: A prosthetic arm inspired by octopus tentacles.
Van Phillips, a former athlete and himself an amputee, invented the prosthetic running blades known as Flex-Foot Cheetah, aptly named since they are designed to enable users to replicate the running movements of the cheetah’s hind legs (figure 5). Cheetahs are the fastest land animal, being able to reach speeds of 45–70 mph.
The aforementioned applications are just a few of many demonstrating the use of biomimicry to advance prosthetics.
Future opportunities
Tooth loss in humans continues to be a concern, but a study by researchers from the Natural History Museum and University of Sheffield in the UK and the University of Tokyo has revealed that the pufferfish has remarkably similar tooth growth to other vertebrates, including humans 12 . Pufferfish overcome dental problems by re-growing their characteristic beak-like teeth. Over 450 mn years ago, we had common ancestors, so it may be possible to awaken dormant genes to re-grow our teeth.
Similarly, stags’ ability to grow their antlers at a rate of up to 4 cm per day by redirecting calcium from body bones to their antlers might offer clues to more rapid bone repair.
Nova Laboratories, a UK company, has developed the Hypodermic Rehydration Injection System (HydRIS) for preserving vaccines without refrigeration, which is crucial for developing countries where vaccines are a matter of life or death and electricity supplies are unreliable. The company was inspired by a species of tiny creatures about 1 mm long called tardigrades that can survive and even reproduce in the harsh environment of space after being frozen or heated up to 150˚C. There are 900 known species of tardigrades that have adapted to various extreme environments 13 . They can be dried out and exposed to high levels of radiation; both are damaging to their DNA, but they possess the ability to repair it. These remarkable creatures can live in suspended animation for years by replacing water in their cells with a sugar called trehalose.
The biochemistries that enable tardigrades and many other creatures to go into long periods of hibernation to survive harsh environments are being actively studied since the results could pave the way to humans similarly surviving these environments. If the biochemicals possessed by such creatures could be synthesised into drugs, this might allow humans to extend and protect their lives by the same means animals do and thus achieve the previously impossible. One use of such drugs could be hibernation in long-term space travel.
Another discovery that is having an impact on human gene therapy is the application of a process known as clustered regularly interspaced short palindromic repeats (CRISPR), a naturally occurring, ancient defence mechanism discovered in a wide range of bacteria for using against viruses that prey on them and destroy their genes. CRISPA is described in David Tolfree’s article CRISPR—A life changing editing tool, published in the February 2017 issue of CMM 14 . It has applications in DNA editing for the repair or replacement of damaged genes.
Many of the applications summarised in this article are reliant on an ability to copy different surface nanostructures that are found in nature. There is perhaps a lot to learn here for the electronics industry. Future advances in 3D printing are already providing rapid methods for surface engineering. In the healthcare sector, diagnostic monitors with sensors could be printed on human skin to extend and enhance natural sensory systems. Many animals and plants already have such sensors on their skins and surfaces, so again we would be mimicking nature.
This article highlights how observations and studies of animals and plants are enabling, or have the potential to enable, solutions to be found for certain medical conditions as well as how some healthcare products could be more efficiently manufactured. Many of the applications are still at the research stage and await innovative entrepreneurs to invest in their development. Advances in the emergent technologies have greatly benefitted medical practice, but there is still much to learn from the natural world, including ourselves, since we are one of its most successful end-products. We need and depend on plants and animals for our existence and critically on the chemical balance of gases in the atmosphere in which we live.
David Tolfree, physicist and independent technology consultant
Dr Alan Smith, materials scientist and independent technology consultant
References
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