Friday, 23 September 2016

The Making of a Cyborg #1: Artificial Limbs

DEKA Research's "Luke Arm". (Photo by DARPA)

It's a concept straight out of science fiction. From Star Wars to Robocop to Ghost in the Shell, countless stories have imagined how man and machine can be fused into something new -- a cyborg. But the technology presented in these stories might not be as far off as people think. In this series of blog posts, I will explore the ways in which current robotic and computer technology can augment or replace parts of the human body. This week, I will start with something that will immediately spring to most people's minds when they hear the word "cyborg": artificial limbs.

Of course, it goes without saying that not all artificial limbs are robotic -- in fact, most of them aren’t. Next Step Bionics & Prosthetics, a major provider of prosthetic limbs in the northeast USA, divides current prosthetic technology into “bionic” and “non-bionic” areas [1]. But even the so-called “non-bionic” limbs make use of computers. The most common application is in microprocessor-controlled knees, the most famous being Otto Bock’s C-Leg. The microprocessor in the knee joint detects how the user is moving using sensors and adjusts the knee’s resistance accordingly, allowing for more natural movement.

As for bionic limbs, the actual mechanism for how they work is conceptually quite simple. Biosensors read signals from the user’s body (typically the nervous or muscle systems) and sends these signals to a controller. The controller then interprets or relays these signals to the device’s actuators (e.g. motors), which carry out the desired movement. The limb also contains mechanical sensors that detect the current state of the limb (e.g. position or applied force), which the controller then sends back to the user’s body as feedback [2].

One of the biggest roadblocks as far as bionic limbs are concerned comes in the materials used for construction. Most of the actuators used are either motors or wires that contract when current is passed through them. These allow for simple movement, but nothing close to what a real human hand is capable of. In this regard, the current state of the art is the Luke Arm (pictured above), created by DEKA Research for DARPA [3]. This arm makes use of additional switches on the user’s feet that wirelessly transmit signals to the arm, allowing the user to perform complex, lifelike movements. Meanwhile, researchers in Ohio have created a robotic hand with 20 different touch sensors on its fingers, back and sides, which enable the user to perform delicate actions such as removing the stem from a cherry without crushing it. The sensors can also be tuned to produce different sensations — a step up from earlier feedback technology, which only provided a “vague buzzing feeling” [4].

A robotic arm from Robohand, modelled by Esethu. (Photo from Robohand's press package)

As exciting as they are, however, devices such as these are still a long way from being widely available, let alone affordable. For something more immediately available, we can look to 3D printing technology. Companies such as South Africa's Robohand [5] offer low-cost 3D printed prosthetics in order to cater to a wider audience. While these are much less hi-tech and aesthetically pleasing than the state-of-the-art devices listed above, these prosthetics could potentially be a godsend for many amputees, particularly children who will need regular upgrades as they grow.

I've only scratched the surface here, but hopefully this post has provided an idea of the robotic limb technology currently available and what might be available in the near future. But prosthetics aren't the only way in which robotics can assist mobility, and in the next instalment of "The Making of a Cyborg" I will detail one of the alternatives.

- Sam


[1] Advancements in Technology [Internet]. Next Step Bionics Prosthetics. [cited 21 September 2016]. Available from:

[2] Freudenrich C. How Biomechatronics Work [Internet]. 2007 [cited 21 September 2016]. Available from:

[3] Guizzo E. Dean Kamen's "Luke Arm" Prosthesis Receives FDA Approval [Internet]. IEEE Spectrum. 2014 [cited 21 September 2016]. Available from:

[4] Talbot D. An Artificial Hand with Real Feelings [Internet]. MIT Technology Review. 2013 [cited 21 September 2016]. Available from:

[5] ROBOHAND – Just a South African Guy with an Idea. [Internet]. Robohand. [cited 21 September 2016]. Available from:

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