The history of prosthesis begins several hundred years ago, more precisely in the 1500’s when the first copies of human limbs were made using iron, steel, copper and wood. Robotic artificial limbs have as ancestors prosthetics which were used to replace disability of a human body.
The science that deals with prosthesis control by reading activity of biological components is called Biomecatronics. Scientists who are activating in this area have made significant improvements in device performance and design, so that nowadays these prosthetic limbs can be used almost as well as their biological counterparts. Nowadays materials like carbon fiber or plastic are used to create these robotic prosthesis, in order to achieve low weight and high strength and durability characteristics.
Can we name a human with a robotic arm controlled by the nervous system a cyborg? Yes, we can, because a cybernetic organism includes both biological and artificial parts. Most common human body parts replaced by artificial limbs are arms and legs. The control of artificial limbs can be done in many ways, from directly reading brain impulses and up to connecting the robotic prosthesis directly to the muscle fibers. But this system only allows open communication between the brain and the artificial prosthesis.
Connecting an artificial system to the human nervous system is a difficult task due to the sensitivity of the human body to external components. Muscle contraction generates a weak electric signal which can be read by using electrodes mounted on the body’s tissues. This type of operation is called a myoelectric prosthesis.
The project, funded by DARPA, solves the problem of compatibility between electrodes and body tissues. So far metals were used to read the electrical signals of muscles.
Another disadvantage is the amount of information processed by this system which is very little. For an accurate and timely handling of the limbic artificial system, a large amount of information and fast processing is required.
In 2005 the first step was made in using infrared light to read nerve signals. The next step, within a long period of time, was the development of a sensor that can read the very weak signal from the nervous system using optical cables. This sensor was developed at the SMU Micro-Sensor Laboratory and is very small in diameter so that it can be installed in an optical fiber. For a better reading of the electrical signal of the nervous system, hundreds of these micro-sensors are installed in a single optical line.
This sensor is not rejected by the human body and the amount of information read even from a single neuron is superior in every way compared with technologies used so far. The speed at which data moves from the biological organism to the robotic device is also an advantage of using this optical fiber based solution.
As a conclusion, using optical fiber and micro sensors for artificial limbs resolves compatibility issues with the human body and elevates the speed at which nerve signals are read and processed. The reaction speed of the prosthesis must be consistent with the speed at which the brain sends and receives signals to and from the artificial sensor. For instance, touching a cup makes artificial sensors to react, in turn these sensors send stimulus to the nervous system which has the role to carry information to the brain.Resources
- SMU research program for robotic limbs and human brain interfacing, Southern Methodist University research blog
- Laser powered artificial limbs, Wired