The Science in Science Fiction's Artificial Men

October 2006 A Luke Skywalker’s hand seems trivial compared to the technology used for Lieutenant Commander Data and Darth Vader, compared to modern technology, it emulates our current efforts to create a synthetic, symbiotic robotic arm. Figure 1 depicts an overview of the components necessary to make up an artificial limb such as the one used to replace Skywalker’s hand. At the heart of this system are the voluntary and autonomous control components, generally encapsulated in a coordinated digital signal processing (DSP) microcontroller and capable of real-time processing. These two components control the functional branches of the system as shown by the black and gray arrows. The first branch, indicated in black, allows the user control over basic motions required of the limb, for example, grabbing an object. The second branch, indicated in gray, allows the limb to autonomously fine-tune its activities based on sensory feedback made available to the system through sensors within the limb itself. This functionality is more subtle than voluntary control because it usually goes unnoticed when we do it with a natural limb. For instance, when we grab an egg, we do not think about how hard we should grasp. Instead, our nervous system automatically takes care of that for us so that we can grab the egg without breaking or dropping it. The dashed gray arrows indicate a sub-branch of this function, allowing users to be made aware of the sensory feedback provided by the hand. For instance, we can feel when our grasp is slipping in a natural hand, and a fully functional artificial hand should provide a similar function. Modern developments in microcontroller, micromotor, and microsensor technologies yield promising avenues for continued development of the front-end actuation and fine-tuning efforts necessary for a fully functional artificial limb. The real challenge for bioengineers pioneering this technology is the back-end voluntary control and sensory perception function. Moreover, the challenge becomes even more daunting as the degrees of freedom for the artificial limb increase, yet the solution becomes more essential for the user.