Lensfree Air-Quality Monitoring of Fine and Ultrafine Particulate Matter Using Vapor-Condensed Nanolenses

Current commercial air-quality monitoring devices lacka largedynamic range, especially at the small, ultrafine size scale. Furthermore,there is a low density of air-quality monitoring stations, reducingthe precision with which local particulate matter hazards can be tracked.Here, we show a low-cost, lensfree, and portable air-quality monitoringdevice (LPAQD) that can detect and measure micron-sized particlesdown to 100 nm-sized particles, with the capability to track and measureparticles in real time throughout a day and the ability to accuratelymeasure particulate matter densities as low as 3 mu g m(-3). A vapor-condensed film is deposited onto the coverslip used tocollect particles before the LPAQD is deployed at outdoor monitoringsites. The vapor-condensed film increases the scattering cross sectionof particles smaller than the pixel size, enabling the sub-pixel andsub-diffraction-limit-sized particles to be detected. The high dynamicrange, low cost, and portability of this device can enable citizensto monitor their own air quality to hopefully impact user decisionsthat reduce the risk for particulate matter-related diseases.