Application of an integrated microfluidic total internal reflection (TIR)-based chip to nano-particle image velocimetry (nano-PIV)

A polymer TIR-based chip has been developed. The chip is monolithically fabricated using Si bulk micromachining and PDMS casting at very low cost. A PDMS microchannel is attached to the chip by van-der-Waals contact through a common thin glass slide to form an integrated microfluidic (TIR)-based chip. The slide-format of the microfluidic TIR-based chip can be employed with both inverted and upright fluorescent microscope. This paper reports the first application of this microfluidic TIR-based chip to study microfluidic flow by nano-PIV with an upright fluorescent microscope. Pressure-driven flows of carboxylate-modified Nile-red nanotracers are generated inside the microchannel of the microfluidic TIR-based chip. The time-sequenced fluorescent images of tracers, illuminated by evanescent field, are recorded onto a CCD camera and are cross-correlated by a PIV program to obtain the near-wall velocity field at various shear rates. Our integrated system could be an important component of a micro-total analysis system (μ-TAS) to study nanoparticles or bio-molecules transport and their near-wall interactions in a microchannel.