Standoff infrared spectroscopy on energetic materials using hydrogel microcantilevers

A standoff trace-chemical sensing system for the detection of highly energetic materials is developed by using infrared (IR) sensitive hydrogel microcantilever. Low cost, hydrogel microcantilevers having rectangular cross-section are simply fabricated by ultraviolet curing of polyethyleneglycol diacrylate (PEGDA) introduced into a polydimethylsiloxane (PDMS) mold. For the first time, we are demonstrating that PEGDA microcantilevers exhibit significant shifts of resonance frequency upon heating and IR. The IR absorption by target chemical weapons at specific IR wavelengths decreases the resonance frequency shift of the PEGDA microcantilever which provides a foundation for photothermal cantilever resonance spectroscopy (PCRS). Using this, we detect four different chemical weapons located four meters away from the PEGDA microcantilevers with a limit of detection of 40 ng/cm2.