Microfabricated Passive Preconcentrator/Injector for Personal VOC Exposure Monitoring

Research Trainee: Jung Hwan Seo, MS, PhD Student in Mechanical Engineering at the University of Michigan

Faculty Researcher: Katsuo Kurabayashi, PhD, Associate Professor of Mechanical Engineering at the University of Michigan

The adaptation and testing of a recently invented (in-house) microfabricated passive preconcentrator/injector (µPPI) as a lapel-mountable badge with integrated heater to monitor breathing zone exposures to volatile organic compounds (VOC) are proposed. The µPPI chip measures 8 × 8 mm. It contains a small adsorbent-packed Si cavity with integrated thin-film heater, capped with a precision-etched Si grid on its top surface and inlet/outlet ports/capillaries for fluidic interconnections. The sampling rate is governed by Fickian diffusion, as with commercial passive samplers. The device is designed to be interfaced with a properly configured field-portable (possibly microfabricated) gas chromatograph (GC) to permit field analyses in a matter of minutes. Following sample collection, the device could be connected to the GC inlet port, rapidly heated to thermally desorb the captured VOCs, removed, and then re-used immediately. During desorption, carrier gas is passed through the ancillary fluidic ports of the device to transfer captured VOCs to a downstream column and detector for separation and quantification. This approach to exposure monitoring is new and could potentially decrease costs and increase the number and quality of breathing-zone personal exposure measurements of workers. Preliminary studies have established that the µPPI operates as expected, but only one vapor has been tested, with one adsorbent, under one set of exposure and desorption conditions, and the sampling rate is constant for only ~30 minutes. This project will: 1) document the performance of the µPPI for short-term sampling (and desorption) of other individual vapors at relevant concentrations; 2) test simple VOC mixtures to assess whether competition for adsorption sites will decrease the sampling rate or capacity; and 3) fabricate and test a secondgeneration (Gen-2) µPPI design optimized for long-term (i.e., 8-hr), low-rate sampling. The project will provide critical project management experience for the doctoral-student lead investigator and gather preliminary data illustrating the utility of this new device for worker exposure assessment to support an R01 proposal to NIOSH.

Publications resulting from this project:
Seo JH, Liu J, Fan X, Kurabayashi K. Fabry-Pérot cavity sensor-based optofluidic gas chromatography using a microfabricated passive preconcentrator/injector. Lab Chip. 2013;13(5):851-859. doi:10.1039/c2lc41119a.

Seo JH, Liu J, Fan X, Kurabayashi K. Effect of thermal desorption kinetics on vapor injection peak irregularities by a microscale gas chromatography preconcentrator. Anal Chem. 2012;84(15):6336-6340. doi:10.1021/ac300755d.

 

Research trainee’s current position:
Jung Hwan Seo completed his PhD in 2012 and is currently an Assistant Professor of Mechanical and System Design Engineering at Hongik University in South Korea.