A microfluidics-based on-chip impinger for airborne particle collection

Abstract

Capturing airborne particles from air into a liquid is a critical process for the development of many sensors and analytical systems. A miniaturized airborne particle sampling device (microimpinger) has been developed in this research. The microimpinger relies on a controlled bubble generation process produced by driving air through microchannel arrays. The particles confined in the microscale bubbles are captured in the sampling liquid while the bubbles form, are released and travel in a millimetre-scale sealed liquid reservoir. The microchannel arrays in the impinger are fabricated using a soft-lithography method with polydimethylsiloxane (PDMS) as the structural material. To prevent air leakage at the connections, a PDMS-only sealing technique is successfully developed. The hydrophobicity of the microchannel surface is found to be critical for generating continuous and stable bubbles in the bubbling process. A Teflon layer is coated on the walls of a microchannel array by vapor deposition which effectively increases the hydrophobicity of the PDMS. The collection efficiency of the microimpinger is measured by counting different sizes of fluorescent polystyrene latex particles on polycarbonate membrane filters. Collection efficiencies above 90% are achieved. Furthermore, the particle capturing mechanisms during the injection, formation and rise of a single microbubble are investigated by a computational fluid dynamics (CFD) model. The Navier-Stokes equations are solved along with the use of the volume-of-fluid (VOF) method to capture the bubble deformations and the particles are tracked using a Lagrangian equation of motion. The model is also employed to study the effect of bubble size on the collection efficiency of the microimpinger.

The study of atmospheric ice-nucleating particles via microfluidically generated droplets

“…This would increase the simplicity for the end-user who wishes to use the platform as a monitoring tool, and efforts could be made to establish a “standard design” that could be used by multiple research groups. Looking to the future, further optimisation and integration of the microfluidic set-up will be explored based on the findings and experiences associated with the current set-up and method, in order to combine the droplet generation and freezing steps, as will the potential for direct aerosol sampling into the microfluidic devices (Noblitt et al 2009 ; Liu et al 2016 ; Mirzaee et al 2016 ; Damit 2017 ). Given the low signals obtained via the aerosol sampling studies presented here, the study of many more droplets would be beneficial to obtain a larger number of INP-containing droplets analysed, for which a continuous flow device such as that of Stan et al ( 2009 , 2011 ) may be more suitable for the high-throughput study of 100–1000s of droplets per second.…”

On-chip analysis of atmospheric ice-nucleating particles in continuous flow

“…The LOC-NIPI could then run alongside aerosol particle sizing instruments in order to estimate the particle numbers and surface areas in the collected aerosol samples, such that important INP parameters like n s IJT) could be calculated alongside [INP] T . Microfluidic methods could also potentially be employed rather than conventional impingers for directly sampling aerosol into a chip, [178][179][180] such as a microfluidic microimpinger, 181,182 a condensational growth tube collector, 183 an aerodynamic lens connected to a microfluidic droplet system, 184 electrostatic sampling, 185 or an electrostatic precipitator combined with an electrowetting-ondielectric (EWOD) concentrator. 186 However, due to the relative rarity of INPs in the atmosphere that can vary widely with location, higher flow rate sampling methods are likely required and so an impinger-based system, such as the Coriolis® Micro used in this study, may be the better option for future development of the platform.…”

The role of computational fluid dynamics tools on investigation of pathogen transmission: Prevention and control

“… Yang et al (2016a) ANSYS 12.0 Investigation of mass diffusion and species transport of suspensions in turbulence. VOF model Mirzaee et al (2016) Ansys 14.0 Analysis of capturing airborne particles from the air into the liquid. Li et al (2020a) Ansys-Fluent 19.2 Investigation of the virus transmission through the siphon toilet.…”