A new technology for revealing the flow profile in integrated lab-on-a-chip.

Purpose: Recently, greater attention has been paid to interactions between biomolecules particularly at the single-molecular level. Due to their novel properties, integrated lab-on-a-chip (LOC) devices and fluorescence correlation spectroscopy (FCS) are in high demand.

Methods: The LOC was manufactured using the technique of proton beam writing. The biomolecule fluorescein was used to probe flow profiles in the micro∕nanochannels on the LOC by FCS. The FCS optical system was based on a confocal microscopy setup. At different locations on the LOC, the numbers and traveling time of the fluorescein fluidic solution were investigated.

Results: From calibrations, ω(0) and τ(D) were 217 nm and 2.2 × 10(-5) s, respectively. Particle number and duration in passing through the detect volume, τ(F), were investigated. Results indicated that particle number was proportional to the size of micro∕nanochannels in the LOC. The particle number distribution and speed of the flow were mirror-symmetric in the two parallel (inlet∕outlet) microchannels. The distribution of the fluidic particles remained stable and the speed of the flow was nearly symmetrical when being transferred in the nanochannels.

Conclusions: The results were realistic and in line with the hydromechanics, indicating that in multidisciplinary areas measurements of flow profiles by FCS are possible inside the LOC channels. This study paves the way to investigate biomolecular interactions at the single-molecular level.