Quantitative 3-dimensional profiling of channel networks within transparent ‘lab-on-a-chip’ microreactors using a digital imaging method

Abstract

We have developed a method for the quantitative 3-dimensional profiling of micron sized channel networks within optically transparent "lab-on-a-chip" microreactor devices. The method involves capturing digitised microscope images of the channel network filled with an optically absorbing dye. The microscope is operated in transmission mode using light filtered through a narrow bandpass filter with a maximum transmission wavelength matching the wavelength of the absorbance maximum of the dye solution. Digitised images of a chip filled with solvent and dye solution are analysed pixel by pixel to yield a spatially resolved array of absorbance values. This array is then converted to optical path length values using the Beer-Lambert law, thereby providing the 3D profile of the channel network. The method is capable of measuring channel depths from 10 to 500 microm (and probably even smaller depths) with an accuracy of a few percent. Lateral spatial resolution of less than 1 microm is achievable. It has been established that distortion of the measured profiles resulting from a mismatch in refractive index between the dye solution and the glass of the microreactors is insignificant. The method has been successfully used here to investigate the effects of thermal bonding and etch time on channel profiles. The technique provides a convenient, accurate and non-destructive method required to determine channel profiles; information which is essential to enable optimisation of the operating characteristics of microreactor devices for particular applications.

A Microfluidic System for Testing the Responses of Head and Neck Squamous Cell Carcinoma Tissue Biopsies to Treatment with Chemotherapy Drugs

“…The final device was generated in glass using standard photolithography and wet-etching techniques. 4 Access holes and a central chamber (diameter 3 mm) were drilled in the top plate and was then thermally bonded with the etched bottom plate in a furnace at 590°C for 3 h. The channel network was etched into the bottom 1-mm glass layer to produce channels of 190-lm width and 70-lm depth, which diverged into two channels as shown in Fig. 1.…”

“…4,23 AutoCAD LT software, a computer-assisted design package, was used to design the microdevice from which a photomask was generated. The final device was generated in glass using standard photolithography and wet-etching techniques.…”

Micro reactors: principles and applications in organic synthesis

“…These disadvantages can be overcome by using a newly-developed method based on digital microscopic imaging of a dye solution-®lled channel network. 30 As shown in Fig. 4, the chip is mounted on a transmission microscope operating with monochromatic light at a wavelength corresponding to the maximum absorbance of a dye solution within the channel network.…”

Monitoring of chemical reactions within microreactors using an inverted Raman microscopic spectrometer

“…It was observed that the cross sectional shape of the channel etched by powder blasting consisted of a trapezoidal shape in which the bottom of the channel was slightly rounded. This shape was markedly different from the cross sectional shape obtained for a channel produced by isotropic wet etching of glass which consists of a rectangle flanked by quarter circles [14]. By fitting the channel profile (Fig.…”

“…To determine the average liquid linear velocity in the channel, it was necessary to profile the channel cross section. An optical microscope absorbance imaging technique [14] of the channel network filled with dye solution was used to obtain the quantitative 3-D profile of the T-junction region (see Fig. 2).…”