[Zurück]

C. Haiden, T. Wopelka, M. Jech, F. Keplinger, M.J. Vellekoop:
"Visualisation of single sub-micron particles by light scattering in a microflow";
Vortrag: Microfluidics 2012, Heidelberg, Deutschland; 03.12.2012 - 05.12.2012; in: "Proc. of uFLU 2012", (2012), 8 S.

We describe the fabrication and operation of microfluidic chips for optical visualization of individual sub-micron and nanoscopic particles by light scattering in a continuous flow. Particles beyond the resolution limit of an optical microscope can be directly seen and recorded as they scatter the incident laser light, which permits label-free detection of single particles. Microchannels of 120µm height structured in Ordyl dry film resist on the chips were traversed by a laser beam coupled in by a glass fiber so that particles in the flow cross the beam and scatter a portion of the incident light. At an angle of 90° to the laser beam the scattered light is observed via a microscope and recorded with a camera. 250nm particles appear as clearly visible bright spots of several micrometer diameter on the video and can individually be counted. Hydrodynamic focusing of particles with a sheath flow was performed in two ways. Vertical focusing was done in order to confine the particle containing sample liquid to the bottom of the chip so that all particles were approximately in the focal plane of the microscope and hence diffraction patterns could be avoided. By using lateral focusing the sample stream was confined to the middle of the channel, which leads to a smaller detection region and allows the use of higher microscope magnification. With the proposed sensor setup and microfluidic chips it is possible to visualize and count suspended particles.

Submicron particle detection; Light scattering; Microfluidic chip; Dry film resist

http://publik.tuwien.ac.at/files/PubDat_212661.pdf