In this schematic, a micrometer-sized polymer particle is coated with a nanoelectric circuit. Source: Michael StranoIf you wanted to probe the human gut for disease, or search the environment for pollutants, you might employ the services of a tiny, floating robot.
That’s the thesis of researchers led by the Massachusetts Institute of Technology’s Dr. Michael Strano, whose team is presenting their work today at the 255th National Meeting & Exposition of the American Chemical Society (ACS). The meeting runs March 18-22, 2018, in New Orleans, and features more than 13,000 presentations on a wide range of science topics.
Strano’s group outlines the creation of aerosolizable, microscopic machines through a combination of ultrathin 2D electronic circuits no more than a single atom thick and colloidal particles that can float in the air like a speck of dust. “You can bring these new electronics to environments they otherwise could not access," Strano explains. "Think of these as proto-robots.”
Creating the Devices
In order to form a closed autonomous circuit, the researchers needed to develop a set of electronic components compatible with the particle’s coating. After a number of different configurations were tried, the team settled on a biocompatible material, the micrometer-sized SU-8, to be lithographically etched to create a closed circuit. That circuit consisted of a power source, a detector and a memory device.
The power source, a p-n heterojunction of semiconductors MoS2 and WSe2, could convert light into electric current. The detector was a chemiresistor, a distinct single layer of MoS2 designed to change its electrical resistance in response to an environmental agent. And the memory device, which could store electrical output, consisted of a separate layer of MoS2 flakes sandwiched between gold and silver electrodes.
The next step in developing the devices was to test whether the particles could travel; to this end, the researchers aerosolized them and propelled them toward a target. Testing in a simulated gas pipeline was successful in detecting the presence of carbon particulates or volatile organic compounds — information that was stored in the devices’ memory.
Possibilities Abound
"We put small retroreflectors on the particles — like you have on your bicycles — so they reflect light and allow us to rapidly find the particles," says Dr. Volodymyr Koman, a research fellow in Strano’s group. After capture, information can be downloaded from the particles. The memory can also be wiped so the miniature machines can be reused.
The researchers envision a range of uses for their aerosolizable electronic device, which would greatly lessen the resources required for tasks such as monitoring large areas for bacteria, spores, smoke, dust or toxic fumes. Next, the team plans to develop particles for additional applications, such as monitoring the human digestive system.
