How butterflies can detect deadly chemical weapon agents
Every spring caterpillars shed their cocoons, emerging as butterflies. This timeless symbol of change is now being applied to enhanced chemical detection for our nation's warfighters. Researchers from the military service academies, funded by the Defense Threat Reduction Agency's Chemical and Biological Technologies Department, are using butterflies to detect trace amounts of chemical warfare agents with increased precision and speed.
Managed by DTRA CB's Brian Pate, Ph.D., researchers at the U.S. Air Force Academy demonstrated that analyzing light reflected from the scales of a butterfly wing may fill a critical capability gap for our service members. Currently, only expensive, non-portable instrumentation exists for the required sensitivity of certain CWA. Other tools, such as colorimetric and nanomaterial methods show promise, however, they pose challenges for long-term field use such as inadequate sensitivity or sensor poisoning.
Highlighted in the ACS Omega article, "Sensing Chemical Warfare Agent Simulants via Photonic Crystals of the Morpho didius Butterfly," researchers tested both naturally occurring and synthetic photonic crystals for CWA vapor detection. Using the reflective properties of the butterfly wings, researchers were able to identify changes in the refractive index or distance between structure layers.
Notional image illustrating how light reflected from butterfly wing scales results in unique data when in the presence of different vapors. Experimental data is shown for dichloropentane (orange), a mustard gas simulant, and dimethyl methylphosphonate (blue), a sarin simulant.
When exposed to water, methanol, ethanol and simulants for mustard gas, researchers found that vapors could be detected at parts per million concentrations in under one minute. Offering an innovative, low-cost and rapid means of threat agent detection, this sensing technique may offer significant advantages for deployed warfighters. The portable technique only requires a small photonic crystal, a visible light source and a fiber optic cable. Further, this method could potentially be used as a long-term, continuous, passive sensor.
While promising, these sensing agents present some challenges such as generating a synthetic butterfly wing to increase vapor sensitivity and selectivity towards chemical agents. Ongoing efforts are underway at the Air Force Academy to address this issue.
Collectively, these efforts highlight the capability of the service academies to contribute to the chemical and biological defense enterprise's mission of protecting our force from threat agents, while fostering critical thinking and technical excellence in the next generation of military leaders.