PillCam SB2 PillCam SB3
Normal villi Normal villi
PHOTONICS APPLIED: ROBOTICS
Microrobots slide, crawl, and
swarm into new applications
GAIL OVERTON
Loosely defined as miniature robots
on the order of 1 mm to a few centimeters in size, microrobots or microbots are being developed for a host
of new applications that only ul-trasmall devices can tackle. For example, 2-mm-long oxygen-sensing
microbots injected into the eye can
deliver real-time oxygenation information to surgeons; the decades-old
pill camera and other robotic capsule
endoscope designs have improved vision capabilities and are gaining traction with robotic articulation for improved gastrointestinal analysis; and
centimeter-scale crawling and flying
microbots could seek signs of life in
collapsed buildings or mines.
Microrobotics should be distinguished from nanorobotics.
Nanorobots or nanobots are at least
an order of magnitude smaller (nanometer-scale) than microrobots and lack the more
complex, system-based imag-ing/actuation/sensing capabilities of microbots. Nanoscale
molecular machines are also
classified in the nanorobotics
category. This article will focus on microrobots only—the
nanorobots will have to wait
their turn.
Inside the eye
Researchers at the
Institute of Robotics
and Intelligent Systems at ETH Zurich
(Zurich, Switzerland)
recognize that for in
vivo biomedical tissue diagnostics,
smaller and much-less-invasive microrobotic systems can have marked
advantages over bulky external equipment such as optical fiber probes and
standoff imaging/microscopy systems.
“Due to the invasive nature of available methods, the number of studies
on humans is limited regarding the effects of inadequate oxygen supply [ret-inal hypoxia] that is correlated with
major eye diseases such as diabetic retinopathy, glaucoma, and age-related macular degeneration,” says
ETH Zurich scientist Olgaç Ergeneman. “Our intraocular microrobots
are tackling this deficiency through
real-time oxygen sensing.” 1
Consisting of magnetically sensi-
tive 2-mm-long oval or cylindrical-
shaped platforms coated with an ox-
ygen-sensitive fluorescent dye, the
microrobots—which luminesce when
illuminated—are magnetically posi-
tioned within an aqueous environ-
ment. For the specific dye used, lu-
minescence quenching as a function
of oxygen level decreases the emission
lifetime; a custom-made optical read-
out system measures this quenching
to reveal location-specific oxygen lev-
els within the eye. Ergeneman adds
that ETH Zurich has developed and
tested magnetically actuated helical
micromachines roughly 9 µm long
and 2 µm wide capable of controlled
swimming and small cargo trans-
port. 2 These helical swimmers could
eventually become wirelessly con-
trolled platforms for in vivo diagnos-
tics and/or drug delivery in a variety
of biological environments.
Along the GI tract
As I researched the capabilities
of these retinal microrobots, visions from the 1966 science fiction film Fantastic Voyage come
to mind. Essentially, a diagnos-
Whether diagnosing poor oxygen supply
in eyes, sensing diseases in the GI tract,
or cleaning up dangerous situations,
microbots are becoming more mobile,
better communicators, and more precise.
