Bionic Human/ Discover the Bionic Technology
Bionics experts attempt to build mechanical and electronic devices to mimic biological functions. With the exception of the brain, the human body can essentially be broken down and rebuilt using a combination of mechanical, electronic and biological technologies.
A bionic limb strips human biology back to its constituent parts. Tough materials like aluminum and carbon ﬁbre replace the skeleton, motors and hydraulics move the limb, while springs replace the tendons that store and release elastic energy. A computer controls motion and wires relay electrical signals, as nerves would have done in a real limb. Users are now even able to control these limbs with their minds (see ‘The power of thought’).
Technology is also in development to replace individual muscles and tendons following injury. The synthetic muscles are made from a polymer gel, which expands and contracts in response to electrical currents, much like human muscle. The tendons are made from ﬁne synthetic ﬁbres designed to imitate the behavior of connective tissue.
The mechanical nature of limbs makes them excellent candidates for building robotic counterparts, and the same applies to the human heart. The two ventricles, which supply blood to the body and lungs, are replaced with hydraulically powered chambers. However, it’s not just the mechanical components of the human body that can be replaced; as time goes on, even parts of the complex sensory system can be re-created with technology.
Cochlear implants, for example, use a microphone to replace the ear, while retinal implants use a video camera to stand in for the human eye. The data that they capture is then processed and transformed into electrical impulses, which are delivered to the auditory or optic nerve, respectively, and then on to the brain. Bionic touch sensors are also in development. For example, the University of California, Berkeley, is developing ‘eSkin’ – a network of pressure sensors in a plastic web. This could even allow people to sense touch through their bionic limbs.
Replacing entire organs is one of the ongoing goals of bionic research. However, breaking each organ down and re-creating all of its specialized biological functions is challenging. If only part of an organ is damaged, it’s simpler to replace the loss of function using bionics. In type 1 diabetes, the insulin producing beta cells of the pancreas are destroyed by the immune system. Some patients are now ﬁtted with an artiﬁcial pancreas: a computer worn externally, which monitors blood sugar and administers the correct dose of insulin as required.
Entire organ replacements are much more complicated, and scientists are turning back to biology to manufacture artiﬁcial organs. By combining 3D printing with stem cell research, we are now able to print cells layer by layer and build up tissues. In the future, this could lead to customized organ transplants made from the recipient’s very own cells.
Advances in bionics mean that already limbs are emerging that exceed human capabilities for weight bearing and speed. That said, the sheer complexity of our internal organs and how they interact means that it is not yet possible to fully replace man with machine. But maybe it’s just a matter of time.
Material used in Bionic Technology
One of the most important factors in biomedical engineering is biocompatibility – the interaction of different materials with biological tissues. Implanted materials are often chosen because they are ‘biologically inert’ and as a result they don’t provoke an immune response. These can include titanium, silicone and plastics like PTFE. Artiﬁ ial heart valves are often coated in a layer of mesh-like fabric made from the same plastic used for soft drink bottles – Dacron. In a biological context, the plastic mesh serves as an inert scaffold, allowing the tissue to grow over the valve, securing it in place. Some scaffolds used in implants are even biodegradable, providing temporary support to the growing tissue, before harmlessly dissolving into the body.
Bionic limbs are worn externally, so their materials are chosen for strength and ﬂexibility as opposed to biocompatibility. Aluminum, carbon ﬁbre and titanium are all used as structural components, providing huge mechanical strength
The Power of Thought
Cutting-edge bionic limbs currently in development allow the user to control movements with their own thoughts. Technically called ‘targeted muscle reinnervation’ it’s a groundbreaking surgical technique that rewires the nerves in an amputated limb. The remaining nerves that would have fed the missing arm and hand are rerouted into existing muscles. When the user thinks about moving their ﬁngers, the muscles contract, and these contractions generate tiny electrical signals that can be picked up by the prosthetic.
The prosthetic is then programmed to respond to these muscle movements, taking each combination of signals and translating it into mechanical movement of the arm. Some of the most sophisticated have 100 sensors, 26 movable joints and 17 motors, all co-ordinated by a computer built into the prosthetic hand.
Building a Bionic Human/ Fiction or Reality
Advances in technology make it possible to build limbs with components that mimic the function of the skeleton, musculature, tendons and nerves of the human body. Meanwhile, the sensory system can be replicated with microphones, cameras, pressure sensors and electrodes. Even that most vital organ, the heart, can be replaced with a hydraulic pump. Some of the newest technologies are so advanced that the components actually outperform their biological counterparts.
Plastic hearts can be implanted to replace the two ventricles of the heart. Plastic tubing is inserted to replace the valves, and two artiﬁcial chambers are also attached. The heart is then connected to a pneumatic pump worn in a backpack, which sends bursts of air to the chambers, generating the pressure that’s required to pump blood around the body. Unlike donor organs, artiﬁ cial hearts are available for implantation immediately so patients don’t face long waits.
Prosthetic limbs have come on leaps and bounds in the past couple of decades. They still retain characteristic features, such as an internal skeleton for structural support and a socket to attach to the amputation site, however the most innovative models are now able to reproduce, or even exceed, biological movements. Motors are used in place of muscles, springs instead of tendons and wires instead of nerves.
The movement of many prosthetics is controlled externally, using cables attached to other parts of the body, or using a series of buttons and switches. New technology is emerging to allow the user to move the limb using their mind (see ‘The power of thought’). The next logical step in this process is developing technology that enables the prosthetic limb to sense touch, and relay the information back to the user.
DARPA-funded researchers have developed FINE, a ﬂ at interface nerve electrode (see below left) which brings nerves into close contact with electrodes, allowing sensory data to pass to the brain.
Bionic History Timeline
The first known mention of wooden prosthetic limb, worn by a prisoner after his foot was amputated.
The first cochlear implant is created. Sounds are unprocessed but it does help with lip reading.
The first successful artificial heart implant operation is performed at the University of Utah.
The first artificial trachea transplant takes place in Sweden, using a synthetic scaffold coated in stem cells.
The Argus II retinal implant is licensed, enabling patients with retinitis pigmentosa to see again.