Collection of Gaseous and Aerosolized Samples Using Microfluidic Devices With Gas–Liquid Interfaces

We demonstrated methods for collecting gaseous samples and aerosolized particles into microfluidic channels. Gas-liquid interfaces created by surface tension permit analytes to transfer from the environment into a microfluidic channel. In one structure of our design, hydrophobic-hydrophilic boundaries created a channel of liquid confined by gas-liquid interfaces in which analytes were collected. In another structure, circular air pillars within microfluidic channels were created by surface tension forces for analytes collection. A multileveled structure could be formed by the air pillar design with a simple process, enabling it to collect and separate multiple analytes at a time. Both structures were tested with ammonia as a gaseous sample and Kool-Aid as aerosolized particles. The sample acquisition capabilities of the devices were demonstrated by extensive testing with gaseous NH
₃
, using Nessler's reagent as the collecting fluidic stream, and with aerosolized Kool-Aid particles, using deionized (DI) water as the collecting fluidic stream. Increasing the exposed fluidic surface area to the environment effectively increased collection efficiency of the devices. This was confirmed by a resistance study between different sets of designs of both structures. Real-time analysis potential was also demonstrated through measurement of DI water resistance by collecting varying concentrations of gaseous NH
₃
.