The notion of tiny machines that could move through the human body, performing microsurgery to alleviate a range of disease processes, has been a topic of speculative fiction and serious scientific consideration for the past 50 years. Although linked with nanotechnology in the minds of the public, the size of these hypothetical microrobots would be much larger than the scale of a nanometer. Although scientists such as Richard Feynman and science fiction writers including Isaac Asimov anticipated this concept, until recently no working proposal existed for how such devices might be constructed, designed, guided, and controlled.
The repair of lesions within the eye lends itself naturally to speculations on the role of microrobotic surgery. Because the eye is relatively accessible to surgical intervention, the fluid within the chamber of the eye is transparent, and many ophthalmologic interventions demand exquisitely sophisticated surgery, all make this a prime target. The challenge to microengineers is how to compress all the necessary components into a space so small that it could be injected into the eye to perform re-establishment of detached retinas, obliteration of tumors, and removal of abnormal blood vessels.
A research team headed by Doug Adkins, PhD, and Ed Heller, PhD, at Sandia National Laboratory in Albuquerque, NM, has designed a robot about the size of a dime with cavities for batteries, electronics, axles, tiny motors, switches, and wheels that allow a limited degree of mobility. In the future it may be possible to miniaturize these devices even more, but they are still too large to fit into the tiny spaces of the body where they would carry out their repair functions. Although such devices are a striking microengineering tour de force, to perform actual surgery within the eye, it would be necessary to add to the mini-robots wireless two-way communication capability, as well as miniature video cameras. Of course, the surgical instrumentation is necessary to execute their targeted function. With currently available technology, it is not possible to miniaturize all of these entities to a manageable size.
An alternative approach to the miniaturization predicament circumvents the need for elaborate power generation and communications accessories. Scientists at the Technical University of Zürich, Switzerland, have attacked the problem from another angle. Bradley Nelson, PhD, and his colleagues at the Institute of Robotics and Intelligent Systems are investigating wireless microrobots, guided by external magnetic fields, thus eliminating the need for internal power.
His team is designing untethered medical microrobots that are steered through the human eye by external magnetic fields. These tiny vehicles can be injected into the chamber of the eye filled with vitreous humor, achieving a noninvasive access to the retina and posterior part of the eye without damaging sensitive internal structures. Established technologies such as micro-needles, micropumps, and sensors could be carried on-board for ophthalmologic surgery and diagnosis.