We present our experiments with state-of-the-art equipment to dispense threat-representative (3 - 90 nL) freely falling droplets of viscous chemical material (< 500 cP) at room temperature and measure their time-dependent interactions with realistic surface substrates (road surfaces). A direct displacement droplet dispenser is used to generate the droplets and a goniometer/tensiometer is used to analyze the surface interaction of the free-falling droplets after surface impact. The advanced goniometer system is able to characterize the surfaces, capture images of the impact and time dependent droplet morphology after impact, and is able to calculate the average contact angle and droplet volume as a function of time. By coupling these instruments, a free-falling threat-representative droplet of viscous material can be created on demand and the behavior of the droplet on a surface can be monitored as a function of time. Knowledge of how these droplets behave on surfaces is critical in understanding an entire chemical threat scenario and directly impacts the design, testing, and success of standoff surface chemical sensor technology and modeling efforts alike. We are currently working to address this knowledge gap by recording 'cradle-to-grave' droplet dissemination and surface interaction events.

Date Published: 3 June 2011
PDF: 18 pages
Proc. SPIE 8018, Chemical, Biological, Radiological, Nuclear, and Explosives (CBRNE) Sensing XII, 80181S (3 June 2011); doi: 10.1117/12.883952

Published in SPIE Proceedings Vol. 8018:
Chemical, Biological, Radiological, Nuclear, and Explosives (CBRNE) Sensing XII
Augustus W. Fountain III; Patrick J. Gardner, Editor(s)