Photobleaching‐based flow measurement in a commercial capillary electrophoresis chip instrument

Abstract

For microfluidic analytical instruments, a facile, fast, and accurate instrument test is highly demanded. The test includes the quantitative verification of the relationship between pressure drop and flow velocity for the hydrodynamic pump, between the electric voltage and electroosmotic flow (EOF) for the high-voltage supply, and the chip quality. The key point for the test is the measurement of the flow velocity. However, most currently available velocimetries cannot be directly used without any instrumental modification or adding extra instruments. We applied a recently developed Laser Induced Fluorescence Photobleaching Anemometer (LIFPA) for the instrument test through measuring fluid flow velocity in a microfluidic instrument with optical measurement without any modification and extra instrument. We have successfully used the method to test Caliper HTS 250 System from Caliper Life Sciences (Hopkinton, MA) with its own light source and detector. The experimental result demonstrates that this single-point method of measuring flow velocity can be easily used for accurate test of a microfluidic instrument in less than 10 min at extremely low cost without any modification and extra instrument.

Measuring flow velocity distribution in microchannels using molecular tracers

“…The present measurement method is based on photobleaching and the stronger the photobleaching, the higher the sensitivity (Wang 2005;Wang et al 2008). A neutrally charged dye coumarine 102 (Sigma-Aldrich Corp.) is used, which has a relatively high quantum efficiency of photobeaching and has a high absorption coefficient at about 400 nm wavelength and emission around 460 nm wavelength (Eggeling et al 1998).…”

“…The dye was diluted with pure methanol solution to a concentration of 100 lM with a HEPES 20 mM buffer solution. The measurement principle is based on LIFPA (Wang 2005;Wang et al 2008). While the earlier work can measure the bulk velocity, it cannot measure the velocity profile of the microchannels.…”

“…Although this method is subtle and relatively simple, it has lower temporal resolution and cannot measure velocity profile. Recently, Wang et al (Wang 2005;Wang et al 2008) proposed another molecular tracer method for measuring the velocity in microchannel based on laser induced fluorescence photobleaching anemometer (LIFPA), but the presented system cannot measure the velocity profile of the microchannels. The goal of the present work is to develop a single point measuring method based on LIFPA and epi-fluorescence structure, which could easily measure flow velocity profile with high spatial resolution and potentially high temporal resolution (Kuang et al 2008).…”

Thermal Effect on Microchannel Electro-osmotic Flow With Consideration of Thermodiffusion

“…The fundamental fluid mechanics aspects in terms of the effects of inertial forces, pressure forces, and nonuniform wall charge on EOF were discussed [21]. Experimentally, measurements of EOF have been carried out by using several techniques for steady [22][23][24][25][26][27][28][29][30][31] and transient conditions [32][33][34][35][36]. It should be pointed that these theoretical and experimental works only deal with EOF under isothermal conditions.…”

A novel far-field nanoscopic velocimetry for nanofluidics

“…[40][41][42][43] In LIFPA, a molecular tracer of fluorescence dye and the photobleaching effect are applied as a transducer to measure the flow velocity. The velocity is calculated by measuring fluorescence with a calibration relationship between the velocity and fluorescence.…”