From the Labs: Information Technology

Steering Microbots
Bacteria-based robots swim through blood vessels

Source: “Flagellated Bacterial Nanorobots for Medical Interventions in the Human Body”
Sylvain Martel et al.
IEEE 2008 Biorobotics Conference, October 19-22, 2008, Scottsdale, AZ

Results: Researchers have coupled swimming bacteria to 150-nanometer-wide beads, creating tiny robots that can be steered inside blood vessels using magnetic fields controlled with a modified magnetic resonance imaging (MRI) device. The MRI can also be used to track the robots.

Why it matters: The tech­nology could provide a new way to deliver drugs directly to tumors. The bacteria would swim through the bloodstream bearing drug-coated nanoparticles; doctors could use MRI to direct them to a specific site, such as a part of a tumor. At two micrometers in diameter, the bacteria are small enough to fit through the smallest blood vessels in the human body.

Methods: The researchers treated nanoscale polymer beads with an antibody that binds to the bacteria. The bacteria naturally contain magnetic particles and swim in different directions depending on the surrounding magnetic fields. The researchers tested their ability to steer the bacteria by altering magnetic fields around them with a special configuration of electromagnetic coils connected to an MRI. The coils, arranged at right angles to each other, allow the researchers to control the bacteria’s movement in three dimensions. The researchers steered the bacteria in human blood, in rat tumors, and through glass tubes that mimic human blood vessels.

Next steps: The bacteria-propelled devices can’t swim fast enough to traverse the currents in larger blood vessels. So the researchers envision ferrying the microbots through large blood vessels inside larger microparticles they have developed, whose motion can be controlled by a clinical MRI system. Those particles would release the bacteria into the small blood vessels that they are too big to enter themselves.

Source: “Flying Plasmonic Lens in the Near Field for High-Speed Nanolithography”
Xiang Zhang et al.
Nature Nanotechnology online, October 12, 2008

Results: Researchers developed, and demonstrated precise control of, a lens that converts ultraviolet light into a type of wave called a plasmon, which could be used to etch features as narrow as five to ten nanometers into semiconductor materials.

Why it matters: Photo­lithography–the technique used to manufacture microchips–is limited by the physics of conventional optical systems: it can’t produce features smaller than about 30 nanometers. The new lens produces surface plasmons, which are like waves passing through electrons on the surface of a metal. Since plasmons can concentrate light energy more narrowly than conventional optics can, the plasmonic lens could carve out ultrasmall patterns, enabling higher-capacity DVDs and faster microprocessors.

Methods: The researchers created a lens that consists of concentric circles patterned onto a thin film of silver. When the circles are illuminated with an ultraviolet laser, the electrons on their surfaces oscillate at a frequency that corresponds to the circles’ size, creating plasmons; the radiation produced by the plasmons extends about 100 nanometers from the lens. The researchers created a novel system that floats the plasmonic-­lens arrays about 20 nanometers above a substrate. The substrate spins rapidly, creating an air flow along the bottom surface of the lenses, which regulates the nanoscale gap between the lenses and the substrate.

Next steps: So far, the researchers have used their invention to produce only relatively thick, 80-­nanometer-wide lines, since they were focused on demonstrating the concept of the floating plasmonic lens. They are now conducting experiments to verify the possible resolution of the lens.