Next Article in Journal
Hierarchical MEC Servers Deployment and User-MEC Server Association in C-RANs over WDM Ring Networks
Next Article in Special Issue
Miniaturized Continuous-Flow Digital PCR for Clinical-Level Serum Sample Based on the 3D Microfluidics and CMOS Imaging Device
Previous Article in Journal
A Self-Calibrating Probabilistic Framework for 3D Environment Perception Using Monocular Vision
Previous Article in Special Issue
A Hybrid Lab-on-a-Chip Injector System for Autonomous Carbofuran Screening
Open AccessArticle

Digital Microfluidics for the Detection of Selected Inorganic Ions in Aerosols

1
Department of Electrical and Computer Engineering, Duke University, Durham, NC 27708, USA
2
Division of Atmospheric Sciences, Desert Research Institute, Reno, NV 89512, USA
*
Author to whom correspondence should be addressed.
Sensors 2020, 20(5), 1281; https://doi.org/10.3390/s20051281
Received: 10 January 2020 / Revised: 20 February 2020 / Accepted: 23 February 2020 / Published: 27 February 2020
(This article belongs to the Special Issue Lab-on-a-Chip and Microfluidic Sensors)
A prototype aerosol detection system is presented that is designed to accurately and quickly measure the concentration of selected inorganic ions in the atmosphere. The aerosol detection system combines digital microfluidics technology, aerosol impaction and chemical detection integrated on the same chip. Target compounds are the major inorganic aerosol constituents: sulfate, nitrate and ammonium. The digital microfluidic system consists of top and bottom plates that sandwich a fluid layer. Nozzles for an inertial impactor are built into the top plate according to known, scaling principles. The deposited air particles are densely concentrated in well-defined deposits on the bottom plate containing droplet actuation electrodes of the chip in fixed areas. The aerosol collection efficiency for particles larger than 100 nm in diameter was higher than 95%. After a collection phase, deposits are dissolved into a scanning droplet. Due to a sub-microliter droplet size, the obtained extract is highly concentrated. Droplets then pass through an air/oil interface on chip for colorimetric analysis by spectrophotometry using optical fibers placed between the two plates of the chip. To create a standard curve for each analyte, six different concentrations of liquid standards were chosen for each assay and dispensed from on-chip reservoirs. The droplet mixing was completed in a few seconds and the final droplet was transported to the detection position as soon as the mixing was finished. Limits of detection (LOD) in the final droplet were determined to be 11 ppm for sulfate and 0.26 ppm for ammonium. For nitrate, it was impossible to get stable measurements. The LOD of the on-chip measurements for sulfate was close to that obtained by an off-chip method using a Tecan spectrometer. LOD of the on-chip method for ammonium was about five times larger than what was obtained with the off-chip method. For the current impactor collection air flow (1 L/min) and 1 h collection time, the converted LODs in air were: 0.275 μg/m3 for sulfate, 6.5 ng/m3 for ammonium, sufficient for most ambient air monitoring applications. View Full-Text
Keywords: digital microfluidics; aerosol impaction; droplets; sulfate sensing; ammonium sensing digital microfluidics; aerosol impaction; droplets; sulfate sensing; ammonium sensing
Show Figures

Figure 1

MDPI and ACS Style

Huang, S.; Connolly, J.; Khlystov, A.; Fair, R.B. Digital Microfluidics for the Detection of Selected Inorganic Ions in Aerosols. Sensors 2020, 20, 1281.

AMA Style

Huang S, Connolly J, Khlystov A, Fair RB. Digital Microfluidics for the Detection of Selected Inorganic Ions in Aerosols. Sensors. 2020; 20(5):1281.

Chicago/Turabian Style

Huang, Shuquan; Connolly, Jessica; Khlystov, Andrei; Fair, Richard B. 2020. "Digital Microfluidics for the Detection of Selected Inorganic Ions in Aerosols" Sensors 20, no. 5: 1281.

Find Other Styles
Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.

Article Access Map by Country/Region

1
Search more from Scilit
 
Search
Back to TopTop