Research on forming and application of U-form glass micro-nanofluidic chip with long nanochannels

Microfluidics and Nanofluidics (Impact Factor: 2.67). 09/2009; 7(3):423-429. DOI: 10.1007/s10404-009-0407-8

ABSTRACT The forming process of U-form glass micro-nanofluidic chip with long nanochannels is presented in this paper, in which the
fabrication of channels and the assembly of plates are included. The micro-nanofluidic chip is composed of two glass plates
in which there are microchannels and nanochannels, respectively. This chip can be used for trace sample enrichment, molecule
filtration, and sample separation, etc. In fabrication process, the two-step photolithograph on one wafer is often required
in early papers, as nano and micro structure designed in one plate have different depths. In this paper, the channels in micro-nanofluidic
chip are designed in two glass plates instead of in one wafer. The nanochannels and microchannels are, respectively, formed
on plates using wet etching and two-step photolithograph on one wafer is not required. Since the channels are formed, the
upper plate and the bottom plate are assembled together by alignment, preconnection and thermal bonding orderly. Firstly these
plates are aligned with the cross-marks on an inverted microscope. The aqueous film between plates is controlled to decrease
the static friction force for accurate adjustment. Then the adhesion strength of connection is enhanced with semi-dry status
for limiting movement from slight inclining and shaking. At last, the bottom plate and the upper one are irreversibly linked
together with thermal bonding. The heating period and max temperature of thermal bonding are optimized to eliminate thermal
stress gradient and the size shrinking. With the micro-nanofluidic chip, the 1μM fluorescein isothiocyanate in 10mM PBS
buffer is concentrated successfully. The sample concentrating factor of light intensity varies from 2.2 to 8.4 with applied
voltages between 300 and 2,000V. The switch effect and the instability effect in concentrating process are described and
analyzed too.

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