Continuous cytometric bead processing within a microfluidic device for bead based sensing platforms

Sung Yang, Akif Ündar, Jeffrey D. Zahn

Research output: Contribution to journalArticlepeer-review

31 Scopus citations


A microfluidic device for continuous biosensing based on analyte binding with cytometric beads is introduced. The operating principle of the continuous biosensing is based on a novel concept named the "particle cross over" mechanism in microfluidic channels. By carefully designing the microfluidic network the beads are able to "cross-over" from a carrier fluid stream into a recipient fluid stream without mixing of the two streams and analyte dilution. After crossing over into the recipient stream, bead processing such as analyte-bead binding may occur. The microfluidic device is composed of a bead solution inlet, an analyte solution inlet, two washing solution inlets, and a fluorescence detection window. To achieve continuous particle cross over in microfluidic channels, each microfluidic channel is precisely designed to allow the particle cross over to occur by conducting a series of studies including an analogous electrical circuit study to find optimal fluidic resistances, an analytical determination of device dimensions, and a numerical simulation to verify microflow structures within the microfluidic channels. The functionality of the device was experimentally demonstrated using a commercially available fluorescent biotinylated fluorescein isothiocyanate (FITC) dye and streptavidin coated 8 μm-diameter beads. After, demonstrating particle cross over and biotin-streptavidin binding, the fluorescence intensity of the 8 μm-diameter beads was measured at the detection window and linearly depends on the concentration of the analyte (biotinylated FITC) at the inlet. The detection limit of the device was a concentration of 50 ng ml-1 of biotinylated FITC.

Original languageEnglish (US)
Pages (from-to)588-595
Number of pages8
JournalLab on a Chip
Issue number5
StatePublished - 2007

All Science Journal Classification (ASJC) codes

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


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