A Brief Introduction To Bionics-The Technology Of The Future.

Have you ever wondered what it’s like to run with a prosthetic leg like Terry Fox? He developed a type of cancer called osteogenic sarcoma, which is a cancer that affects the bone. Because of this, his right leg had to be amputated and replaced with a prosthetic limb that weighed 4 kg. If you’ve seen any videos of him running, you could see him hop and skip with his left leg. This is because his prosthetic had very little shock resistance and would strain the remaining limb.

Terry Fox running in the Marathon of Hope. Image from https://montecristomagazine.com/community/terry-fox-exhibit

Generally, the prosthetic limbs in the past would make life much harder for its user. They were clunky, heavy, and had very little functionality. If Terry Fox was still alive, his right leg would’ve been fitted with amazing new technology that would ease the stress on his body. Enter the world of bionics

Bionic arm. Image from https://www.engadget.com/2016/06/08/deus-ex-open-bionics-prosthetic-arm/?guccounter=1&guce_referrer=aHR0cHM6Ly93d3cuZ29vZ2xlLmNvbS8&guce_referrer_sig=AQAAAGNO6ZGalOxqFqbMDUwMSFRdaPjKEA_guIFA-2foSP4wFAKUp2JlnWmKE2HBBDw_A9IQYFHYK8-87PUWlAyFNGGURMCc0M_xcMtoY3y2pN1mZad4qOq7NqTgvCP5rpy03GZEQcfOTg5rFjtnoeXMHfUDOJuBnH5bp_-yrfCGHgte

So… What exactly is bionics?

Bionics is a field of technology that combines the study of biology in nature and its patterns, with mechatronics, which combines mechanical, electronics and software. Bionics consists of many different subject areas, but one of the most eye-catching and popular is bionic implants. These implants aim to improve the standard of living for people who have damaged body parts such as arms, legs, eyes, or even ears.

The story of Hugh Herr (and his accomplishments).

Bionic limbs in today’s world aren’t only lighter and more durable, but some of them are being custom-built to accomplish certain tasks. Take Hugh Herr as an example, who lost both his legs due to a rock-climbing accident at the age of 17. He feared he would never be able to follow his passion for climbing again, but a few years after the accident, he became knowledgeable in the fields of bionics and built himself prosthetic legs that gave him the ability to climb again. Soon, Hugh was able to surpass his previous record with the prosthetic legs he built himself. His longer legs were specially designed to allow him to grip the mountain walls better.

Hugh Herr climbing. Image from https://nypost.com/2017/03/11/this-climber-lost-his-legs-so-he-built-robotic-replacements/

Fast forward a few years, and Hugh, who heads the biomechatronics group at MIT Media Lab is leading the innovations in bionic ankles, which are capable of closely imitating that of human legs. His product is called the BiOM system and has been clinically shown to be the first bionic implant that can help an amputee lead a normal life with the ability to walk with a normal gait (walking pattern) and speed.

Hugh Herr with his bionic limbs. Image from https://brewminate.com/human-2-0-exoskeletons-and-orthoses-with-dr-hugh-herr/

How do bionic implants really work?

To start, it’s extremely hard to mimic the actions created by regular limbs. Think about touching your nose with your hand. You need to lift your forearm, then tilt your wrist, then close all fingers except your index finger, and then move it precisely to tap your nose. While this is something we don’t think about in our day to day lives, it’s something that software and hardware engineers have a lot of trouble working with.

To solve this, pretty much all of the successful bionics systems use machine learning to mimic leg movements. Take, for example, the leg, which changes its muscle contractions and relaxations based on how fast the brain wants it to go. Because of this, the entire leg walking and running pattern changes, and engineers need to take this into account. They record the movement of the parts of the leg at different speeds and apply this to the bionic leg. The result is a bionic system that reacts based on remnant muscle contractions(more on that later) to create the effect of running, jogging or walking at different speeds. Because of this, people who suffer from an amputated limb and have to wear prosthetic limbs can now expect much higher standards of living from this smarter technology.

A reinforcement learning system is used to train bionic limbs. Image from https://www.medgadget.com/2019/01/reinforcement-learning-system-automatically-trains-prosthetic-legs.html

A closer look into the sensors used for bionics

Now that you know about the main system of creating a bionic limb, let’s take a closer look into the kind of sensors that enable such a system to function with such incredible accuracy. Myoelectric (Myo = muscles) sensors are used in bionic limbs to generate an electrical signal from muscle contractions. This is useful because it can get signals from the still functional nerve endings of the amputated limb. This means that the sensors can pick up when the user wants to move that area. In some cases, to improve the accuracy of myoelectric sensors, small incisions are made to place them closer to the muscle/nerve endings.

Target Muscle Reinnervation

Sometimes, just placing the sensors inside the body isn’t enough to receive accurate signals, especially in upper-limb amputees in which the nerves are less detectable. To improve this, targeted muscle reinnervation is sometimes used. This is a process that involves physically moving the nerves that would control the limb in upper-limb amputees and allows them to be used for bionic implants. This surgery makes these implants more accurate because the nerves are closer to the location of the sensors.

Osseointegration: its advantages and disadvantages

In most cases, bionic limbs are attached using precisely-fitted sockets, preventing them from slipping out. However, these attachments are not too healthy for the remaining bone of the amputated limb, as it is not being strained and can deteriorate very easily. To prevent this from occurring, a procedure called osseointegration (Osseo = bone) connects the bone to a titanium abutment, which is then directly connected to the bionic limb. By having this, the bone and areas around it can be strained and healthy. However, one downside to osseointegration is that there is a lengthy surgery required and the area around the abutment could become infected if it’s not cleaned properly.

Osseointegration procedure. Image from https://www.clicksafetyadapter.com/patients/osseointegration/

Non-limb bionics

Apart from arms and legs, there have also been several advancements towards bionics for other parts of the body, such as the eyes and ears. A bionic ear or cochlear implant is used when the user is partially or fully deaf, and function by bypassing the eardrums and directly stimulating the auditory nerve.

A diagram of a cochlear implant. Image from https://www.csun.edu/ncod/cochlear-implants

Bionic eyes

Bionic eyes or visual prosthetics aim to restore partial vision to those who are partially or fully blind. This is done by placing tiny light electrodes into the eye, which receives light information from a camera. These electrodes then stimulate the retina to send signals to the brain. The result is a relatively blurry view, but can still help people navigate the world.

A diagram of how visual prosthetics work. Image from https://healthcare.utah.edu/moran/news/2018/10/artificialvision.php

The field of bionics spreads far and wide, but the area of implants has a lot of potential. As an example, rather than placing a bionic implant on someone’s amputated arm, one could add an electronic exoskeleton to their bodies to improve stamina and increase their load-bearing capability. In the future, you might see the people around you walking with man-made limbs as a stronger and more efficient alternative, and you’ll have the field of bionics to thank for it!