Microfluidic condensation nanoparticle counter using water as the condensing liquid for assessing individual exposure to airborne nanoparticles

Hong Beom Kwon, Seong Jae Yoo, Yong Jun Kim

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)


We present a compact and inexpensive detection system that can accurately measure the number concentration of nanoparticles (NPs; particles smaller than 100 nm) in real-time for assessing individual exposure to airborne NPs in various environments. Our system is based on the condensation nucleation light scattering technique and uses water as the condensing liquid, which solves the self-contamination issues that affect most portable NP detection systems. Our system comprises two units: a microfluidic condensation chip for growing NPs into water droplets and a miniature optical detector for singly counting grown droplets. To effectively minimize the size and cost of our system, droplets are grown on a single chip according to the semiconductor manufacturing process. To use water as the condensing liquid, a super-hydrophilic wick (i.e., Cu micropillar array coated with CuO nanowires) is monolithically integrated into the chip. Simulations were performed to verify the method of generating supersaturated water vapor. Quantitative experiments using NaCl and Ag NPs revealed that our system grew NPs larger than 9.3 nm into 2.25 μm diameter water droplets and could count individual droplets over an extremely wide concentration range (0.021-105 N cm-3) with high accuracy. This outstanding performance allowed our system to resolve the daily pattern of the NP concentration along a metropolitan commuting street with strong agreement compared to the reference instrument. Because our system uses water, it can accurately monitor individual exposure to NPs in various kinds of environments, including multiuse facilities such as elementary schools and hospitals.

Original languageEnglish
Pages (from-to)1092-1102
Number of pages11
JournalLab on a chip
Issue number6
Publication statusPublished - 2020 Mar 21

Bibliographical note

Funding Information:
This work was supported by Samsung Research Funding & Incubation Center of Samsung Electronics under Project Number SRFC-TA1803-05.

Publisher Copyright:
This journal is © The Royal Society of Chemistry.

All Science Journal Classification (ASJC) codes

  • Bioengineering
  • Biochemistry
  • Chemistry(all)
  • Biomedical Engineering


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