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Detection of unlabeled particles in the low micrometer size range using light scattering and hydrodynamic 3D focusing in a microfluidic system
Author(s) -
Zhuang Guisheng,
Jensen Thomas G.,
Kutter Jörg P.
Publication year - 2012
Publication title -
electrophoresis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.666
H-Index - 158
eISSN - 1522-2683
pISSN - 0173-0835
DOI - 10.1002/elps.201100674
Subject(s) - microfluidics , polydimethylsiloxane , materials science , microchannel , micrometer , microlens , light scattering , photolithography , optics , scattering , polystyrene , lab on a chip , layer (electronics) , optoelectronics , optical fiber , lens (geology) , nanotechnology , polymer , physics , composite material
In this paper, we describe a microfluidic device composed of integrated microoptical elements and a two‐layer microchannel structure for highly sensitive light scattering detection of micro/submicrometer‐sized particles. In the two‐layer microfluidic system, a sample flow stream is first constrained in the out‐of‐plane direction into a narrow sheet, and then focused in‐plane into a small core region, obtaining on‐chip three‐dimensional (3 D ) hydrodynamic focusing. All the microoptical elements, including waveguides, microlens, and fiber‐to‐waveguide couplers, and the in‐plane focusing channels are fabricated in one SU ‐8 layer by standard photolithography. The channels for out‐of‐plane focusing are made in a polydimethylsiloxane ( PDMS ) layer by a single cast using a SU ‐8 master. Numerical and experimental results indicate that the device can realize 3 D hydrodynamic focusing reliably over a wide range of R eynolds numbers (0.5 < R e < 20). Polystyrene particles of three sizes (2, 1, and 0.5 μm) were measured in the microfluidic device with integrated optics, demonstrating the feasibility of this approach to detect particles in the low micrometer size range by light scattering detection.