We have developed a simple-to-manufacture microfabricated gas preconcentrator for MEMS-based chemical sensing applications. Cavities and microfluidic channels were created using a wet etch process with hydrofluoric acid, portions of which can be performed outside of a cleanroom, instead of the more common deep reactive ion etch process. The integrated heater and resistance temperature detectors (RTDs) were created with a photolithography-free technique enabled by laser etching. With only 28 V DC (0.1 A), a maximum heating rate of 17.6 °C/s was observed. Adsorption and desorption flow parameters were optimized to be 90 SCCM and 25 SCCM, respectively, for a multicomponent gas mixture. Under testing conditions using Tenax TA sorbent, the device was capable of measuring analytes down to 22 ppb with only a 2 min sample loading time using a gas chromatograph with a flame ionization detector. Two separate devices were compared by measuring the same chemical mixture; both devices yielded similar peak areas and widths (fwhm: 0.032-0.033 min), suggesting reproducibility between devices.

Air pollution can cause acute and chronic health problems. It has many components, and one component of interest is volatile organic compounds (VOCs). While the outdoor environment may have regulations regarding exposure limits, the indoor environment is often unregulated and VOCs often appear in greater concentrations in the indoor environment. Therefore, it is equally critical to monitor both the indoor and outdoor environments for ambient chemical levels that an individual person is exposed to. While a number of different chemical detectors exist, most lack the ability to provide portable monitoring. We have developed a portable and wearable sampler that collects environmental VOCs in a person's immediate "exposure envelope" onto custom micro preconcentrator chips for later benchtop analysis. The system also records ambient temperature and humidity and the GPS location during sampling, and the chip cartridges can be used in sequence over time to complete a profile of individual chemical exposure over the course of hours/ days/weeks/months. The system can be programmed to accumulate sample for various times with varying periodicity. We first tested our sampler in the laboratory by completing calibration curves and testing saturation times for various common chemicals. The sampler was also tested in the field by collecting both indoor and outdoor personal exposure samples. Additionally under IRB approval, a teenaged volunteer wore the sampler for 5 days during which it sampled periodically throughout a 12 hour period each day and the volunteer replaced the micro preconcentrator chip each day.

Asthma affects over 300 million people worldwide. Asthmatics experience difficulty breathing and airflow obstruction caused by inflammation and constriction of the airways. Home monitoring of lung function is the preferred course of action to give physicians and asthma patients a chance to control the disease jointly. Thus, it is important to develop accurate and efficient asthma monitoring devices that are easy for patients to use.While classic spirometry is currently the best way to capture a complete picture of airflow obstruction and lung function, the machines are bulky and generally require supervision. Portable peak flow meters are available but are inconvenient to use. There also exist no portable inexpensive exhaled breath biomarker devices commercially available to simultaneously measure concentrations of multiple chemical biomarkers.We have created a user-friendly, accurate, and portable external mobile device accessory that collects spirometry, peak expiratory flow (PEF), exhaled nitric oxide (NO), carbon monoxide (CO), and oxygen (O 2 ) concentration information from patients after two breath maneuvers. We have also developed a software application that records and stores the gathered test information and e-mails the results to a physician. Telemetric capabilities help physicians track asthma symptoms and lung function over time, which allows physicians the opportunity to make appropriate changes in a patient's medication regimen more quickly.

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