Distinct from this approach is a screw shaped microbot with
embedded magnetic material that physicians could some
day drive through tissue wirelessly. This approach can
enable moving through soft tissue and not just inside veins.
This approach requires the helix to make only one full
rotation to move the length of the microbot through
human tissue. The other helix-propelled bots must turn the
helix several times to move through human fluid.
Another propulsion method for microbots is the
traveling wave. Traveling wave propulsion looks like a fish
tail swimming behind the microbot. Traveling waves are
more efficient at propulsion than propellers, assuming the
efficiency of the actuation is equal to that of the propeller
system. However, there are fabrication, power, and control
issues related to creating distributed actuation for the
traveling wave method. Methods that create traveling
waves without distributed actuation are more feasible but
Mini Medical Robots
In another approach to microbots, researchers are
adding active locomotion and telemetry to capsule
endoscopy technology. According to IRIS, the size of the
capsule cannot be larger than what a person can swallow.
In this new method, the larger robot would be swallowed
in individual pieces that would assemble themselves inside
the gastrointestinal tract. Self-assembly is the biggest
challenge to this approach.
By using magnets on the faces of the modules that
Institute of Robotics and Intelligent Systems
Research of Professor Bradley J. Nelson
12 SERVO 07.2011
This is an image of the Octomag. In the background,
you can see an image as viewed through an ophthalmic
must connect to one another, researchers hope to solve the
self-assembly problem. The results are promising for a
snaking robot that can assemble itself and make its way
through the small intestine.
The self-assembling robot would have sensors on its
front end to detect pathologies that would wirelessly
communicate to the surgeon or physician. A module
designed for specific tasks would execute commands to
accomplish the task once an actuation module moves the
robot into the right place. Sensors and actuators that work
on individual pill sized devices are already being developed.
Each sensor or actuator could eventually constitute a
module in the larger robot discussed here.
Eye See the Robot
One application of microbots is retinal therapies where
the robot could help the surgeon operate inside the human
eye. The primary challenge to this approach is localization.
Because researchers and clinicians can easily see what is in
the eye, they can look through the eyeball to localize the
robot. Using high quality imaging of the rear of the human
eye, they can develop algorithms to track and localize the
microbots. However, there is no existing research that
explains what the effects of this will be.
IRIS researchers have developed a mechatronic
vitreoretinal ophthalmoscope that can take an image of the
entire retina despite the obstruction of view created by the
other parts of the eye. They can use this device to image
and follow objects in the retina. There is on-going research
to discover how much illumination will be necessary to
follow objects in the human eye.
The imaging device must be able to differentiate the
microbot from the rest of the retina. The mechatronic
device must use several lenses to see beyond the other
components of the eye to keep the retina in view. Images
are still blurry much of the time. The light that reaches the
eye’s interior can decrease the quality of the images taken
due to uneven brightness. The microbot has no distinctive
colors to distinguish it from the rest of the eye.
IRIS researchers have surmounted many of these
obstacles by using trained color histograms, colorspace
evaluation, and maximum separability thresholding.
According to IRIS, a real time color tracker in the right color
space assures that the microbot can be separated from the
rest of the eye.
Production-quality microbots are on the horizon. Soon,
a variety of surgeries will be possible using these
magnificent miniaturized microbots. SV