Artificial limbs strong enough to crush human bone. Wireless neural implants. Robotic “sleeves” that keep the heart pumping. And synthetic skin that can “feel”. Sound like ideas from a sci-fi novel? If you answered “yes”, then it might be surprising to know that all of the above are either in the midst of being developed or are, even more amazingly, already being used by patients around the globe. From wood and leather to titanium and carbon fiber, colossal advances have been made in the world of prosthetic design but researchers are still in the pursuit of crafting gear capable of fully mimicking their human counterparts.
Let’s start with the brain and signal transmission. In the past, wires were connected from the neural implant to an apparatus external of the body in order to send signals to the artificial limb. This not only limits mobility but increases the risk of infection at the implant insertion site. At Nanyang Technological University (NTU) in Singapore, a wireless neural implant the size of a five-cent coin is currently in the works. In addition to having a reported brain signal transmission accuracy of 95%, the chip is also extremely energy efficient. Compared to other neural implants which need to be recharged every couple of hours, the NTU smart chip can perform for days before a recharge—wirelessly, of course—is required.
Normally, neural implants require a great deal of energy due the thousands of channels that are used to transmit the large amount of raw data that is produced by the brain. Since a larger battery would take up space that could otherwise be used for hardware, Professor Arindam Basu and his team at NTU designed the chip to first analyze the data received from the brain for patterns before condensing and transmitting only the necessary signals to the receiver.
Excitingly, the uses of the NTU chip extend farther than just prosthetics. Since the chip functions to analyze data and identify peculiar patterns, the team at NTU hopes to incorporate the device into improving home and commercial security sensors. Moreover, the chip could also help patients with neurodegenerative diseases such as Parkinson’s in alleviating symptoms, such as tremors and muscle rigidity, that perturb daily life.
South of the brain resides one of the most fascinating organ of the human body (although I have to say I am a teensy bit biased)—the heart. Defined as the inability of the heart to distribute the necessary amount of blood to the body, heart failure is the leading cause of death in the world. Patients in more advanced stages of disease will usually be directed towards transplantation but donor hearts are often not readily available.
Ventricular assist devices (VADs) currently being used are in direct contact with circulating blood which can promote clotting, risk of stroke, and the use of blood thinners. Harvard’s School of Engineering and Applied Sciences, the Wyss Institute for Biologically Inspired Engineering, and Boston Children’s Hospital are in pursuit of a safer alternative. They have designed a sleeve made of Ecoflex 00-30 silicone, chosen for its softness and capacity to withstand strain, that fits around the heart and simulates its natural contractions. Since this sleeve is not in immediate contact with the blood, anti-coagulants can be avoided making it a safer option than VADs.
To mimic the natural movements of a heart, the sleeve receives signals from a pacemaker which can impressively provide instruction on when, where, and how to contract or twist depending on the heart’s conditions. Powered by pressurized air, the sleeve requires an external pump that scientists are trying to convert into a portable apparatus for better maneuverability. Though this device is not meant to be a permanent installation within the patient, it could provide for a safer “bridge” to transplantation.
The sleeve has already shown a staggering restoration of ~45% to ~97% in cardiac output in pigs with induced acute heart failure. If further testing is approved, such a device could benefit the lives of people living with heart failure—an affliction that causes 31% of all global deaths.
From buttoning your shirt to pipetting that microliter of reagent into an Eppendorf tube, the human hand performs the most diverse array of tasks. As such, one can only imagine the extensive list of challenges that comes with generating a well-designed bionic hand. While huge strides have been made in prosthetic limb design, the most advanced developments are not yet feasible for everyone. Nigel Ackland, one of the few hundred people fortunate enough to wear a bebionic 3 hand, understands just what one must go through in order to acquire such a piece of technology.
After losing his right forearm in an industrial accident in 2006, Nigel was given a passive limb that served no other purpose other than to look like a hand. Next, Nigel was fitted with a body-powered system in which a harness around his body controlled the opening and closing of a hook. Though he now had a prosthetic that served some practical function, the harness was uncomfortable and looked like a contraption out of the 1800’s. In 2012, Nigel reached stage 3—an electronic claw-like device called a greifer that can only be worn for a couple of hours a day. Finally, Nigel saved enough money—because his company’s insurance did not cover it and bionic arms can cost up to $50 000—to buy a custom-made bebionic 3.
Initially owned by Steeper and now by Ottobock, the bebionic 3 is believed to be one of the most advanced bionic arms in the world. Controlled by electrical changes on the skin, it can perform over 14 grip patterns, lift over 40 kilograms and operate for 22 hours at a time. When asked if his new arm could crush a hand, Nigel replies: “I’m not allowed to”. Today, he is a public speaker who advocates for affordability in prosthetics to maximize availability for amputees so that they too can complete everyday tasks, such as driving, typing, shopping, and shaking somebody’s hand. In other words, Nigel hopes to help as many people as he can to feel “human again”.
Artificial skin that can feel. Researchers at Caltech and ETH Zurich are currently trying to turn this bold idea into a reality. While trying to create a synthetic wood in the lab, researchers generated a material capable of detecting changes in temperature to as little as one hundredth of a degree (human skin is sensitive to temperature changes of about two-hundredths of a degree). Even more impressive is the range at which this electronic skin can function. From 5° to 50°, this new skin can recognize minute changes over a full 45-degree range.
The key component to this “artificial skin”? Pectin. A polysaccharide found in the cell wall of plants which is also used as the jellifying agent in many of our favourite jams. Combined with water, a flexible film of just 20 micrometres thick—the diameter of a human hair—can be made. Remarkably, the mechanism through which these films function is inspired by snakes.
Pit vipers are known to possess one of the most sensitive heat detectors in the animal kingdom—the pit organ—that permits them to locate and pinpoint prey even in complete darkness. In these organs is a membrane, like the pectin film, that contains ion channels that expand upon an increase in temperature. As the temperature goes up, the channels open, releasing positively charged calcium ions. The change in electrical resistance can then be measured by electrodes planted within the films.
The film maintains its functionality even when shaped into various shapes and forms, making it suitable for use in prosthetics. If successful, this innovative creation could help alert individuals with prosthetics of potential dangers as well as restore the ability to feel the world around us.
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