Chamorro, with Northwestern's Rogers, develops colorimetric fliers for environmental monitoring

New work on novel flying microchips that includes the use of environmentally degradable materials and colorimetric chemical reagents, combined with the aerodynamics of the 3D fliers, represents a major breakthrough in the development of distributed monitoring technology.

The work was a synergistic collaboration of an international team led by Professor John Rogers at Northwestern University, MechSE Professor Leonardo Chamorro as a corresponding author, and former MechSE doctoral student Jin-Tae (Jimmy) Kim (now a postdoc in Rogers’ lab) as co-first author. The same team made significant design improvements to the flying microchips in 2021.

The researchers have now incorporated bioresorbable materials and colorimetric assays for various environmental parameters, including pH, heavy metal concentrations, ultraviolet exposure, humidity, and temperature. The “microfliers” are modeled after wind-dispersed Tristellateia seeds or “helicopter seeds” and have wireless, electronic components for sensing.

“These fliers can be used for remote sensing of multiple environmental parameters and can also be deployed in regions difficult to access, such as complex terrain or bodies of water, allowing for more comprehensive monitoring of environmental conditions,” Chamorro said.

About the size of a grain of sand, the microfliers are formed using mechanically induced buckling methods that eliminate the need for bonding to a supporting substrate, enabling release into free-standing forms. They can be deployed in large quantities and remotely sensed via drones and digital image capture analysis.

Chamorro’s group used advanced fluid experimental techniques such as particle tracking velocimetry and particle image velocimetry to optimize the aerodynamic performance of the fliers and enhance their flight capabilities. Their research incorporated lift/drag estimation, Euler’s rotation equations, and pitch stability to achieve low, stable terminal velocity.

Chamorro’s contributions to previous collaborative work on winged microelectronic systems resulted in a dispersal strategy that he believed could be adapted for environmental monitoring, population surveillance, pathogen tracking, and other related applications.

“The insights gained from our collaborative research were critical to informing the design and development of the fliers,” he said. “Specifically, the team drew upon our prior experience developing aerodynamically optimized weight distribution strategies and using responsive materials to create structures that could passively fly in the environment.”

The paper, “Biodegradable, three-dimensional colorimetric fliers for environmental monitoring,” was published in Science Advances.