Creating a Bionic Man

In Star Wars we all see Luke Skywalker examine his new forearm and hand that was synthetically created for him.  We see pistons firing and parts moving, however we do not see what happens inside the bionic arm and what's happening on the inside is exactly what we need to figure out.  Kacy Cullen and Douglas Smith address possible approaches to creating this type of prosthetic in their article Bionic Connections.  However, before anything like Luke’s arm is made, other prosthetic designs had to be created.

In Emily Anthes Frankenstein's Cat, Keven Carroll and Dan Strzempka create an innovative tail for the dolphin Winter, who lost hers in a fishing net.  Carroll and Strzempka's dolphin tail was an impressive feat and lead to many new great ideas in prosthetic design, however it was just the beginning of what can possibly be in the future.

Winter swimming with her prosthetic tail

Continued innovation occurred in the field, leading to osseointegration, which involves "implanting one end of a prosthetic leg in an animals' stump and fastening it to whatever bone is left."  Noel Fitzpatrick and Gordon Blunn used exactly this method to create a new leg for a bulldog, Coal.  To do this, they mimicked the connection used in deer antlers.  This allowed for a soft tissue to grow into the implants creating a seal and link between the skin, metal, and bone.  The success of osseointegration has lead to one final goal in prosthetic design; the goal Kacy Cullen and Douglas Smith are striving towards.  They hope to create a way in which a prosthetic can be controlled and commanded by the person's mind and have the prosthetic send sensory information back to the brain.  

The current results in creating a product that allows a person to control an attached limb as if it were always their own are limited.  Two approaches exist that attempt to combine motor and sensory input in prosthetics.  The most common approach is to record EEG signal which is then analyzed by a computer to find the desired movement.  Although this method is advantageous in being non-invasive, it is also easily interfered with by other electronics making it difficult for computer analysis to predict the desired movement of the subject.  This leads us to a second, more invasive approach; micro-electrodes can be inserted straight into layers of the brain.  Inserting an electrode directly into the brain allows for recording of strong signal and leads to precise data that can be interpreted and translated into the correct action.  However, an obvious disadvantage to this approach is the extent to which the electrodes in a signal are responsive.  High amounts of scar tissue are formed due to the abrasiveness of the electrode and make the signal weaker and more difficult to analyze.  A drawback of both brain focused approaches is the extensive software that would always have to be present for the methods to work.  

An example of what a bionic hand may look like and how it may be connected in the future

The hand shown above represents something that may come as a result of a different approach to bionic connections to the nervous system.  This approach focuses on the peripheral nervous system, or the neurons outside of the brain and spinal cord, and attempting to connect those to the "robotic" limb.  Axons along the stump of the limb still fire, often leading to a "phantom" feeling of the limb being present.  Researchers hope to take advantage of this occurrence and use the axons to signal the new limbs.  Approaches like this one and others that adjust the axons to chest muscles are currently being looked into extensively.  The results have shown promise, however it is still early in the research process, and it remains to be seen if fine motor movements can be made using this approach.  

Overall, prosthetic design and research has come a long way.  New and exciting research is being conducted by many research facilities, and great progress is being made. Maybe one day a breakthrough will be made that will make Luke Skywalker and his robotic forearm more science than science fiction.

REFERENCES:

Anthes, Emily. (2013) Frankenstein's Cat: Cuddling Up To Biotech's Brave New Beasts. New York, NY: Scientific American/ FSG.  

Cullen, K., & Smith, D.H. (2013). Bionic Connections. Scientific American