Abstract
A novel microfluidic optical cell is presented that enables simultaneous measurement of both light absorbance and fluorescence on microlitre volumes of fluid. The chip design is based on an inlaid fabrication technique using clear and opaque poly(methyl methacrylate) or PMMA to create a 20.2 mm long optical cell. The inlaid approach allows fluid interrogation with minimal interference from external light over centimeter long path lengths. The performance of the optical cell is evaluated using a stable fluorescent dye: rhodamine B. Excellent linear relationships (R2 > 0.99) are found for both absorbance and fluorescence over a 0.1–10 µM concentration range. Furthermore, the molar attenuation spectrum is accurately measured over the range 460–550 nm. The approach presented here is applicable to numerous colorimetric- or fluorescence-based assays and presents an important step in the development of multipurpose lab-on-chip sensors.
Highlights
We have developed a microfluidic optical system capable of simultaneous detection of absorption and fluorescence signals in liquid samples, without physically attaching optic components to the chip
By spatially separating excitation and fluorescence optical paths and using absorptive filters, backgrounds and scattered signals are minimized in our fluorescence detection. This microfluidic cell is characterized using a rhodamine B dye, and we find high sensitivity and low detection limits in both absorbance and fluorescence detection
A microfluidic chip was successfully fabricated to validate a novel inlaid optical cell could be used in conjunction with numerous assays and a wide range of other lab-on-chip that simultaneously measures the light absorbance and fluorescence of injected fluids
Summary
Lab-on-chip (LOC) sensors have emerged as a promising technology to reduce costs in environmental and diagnostic sampling [1]. By consolidating the chemistry and instrumentation from analytical laboratory techniques onto a network of microfluidic channels, expensive and time-consuming steps can be automated and streamlined. LOC further allows the collection of real-time data in remote settings by non-technical personnel. Current colorimetric LOC technologies have led to sensitive platforms for in situ measurement of nitrate/nitrite [2,3], phosphate [4,5,6], E. coli [7], and various heavy metals [8,9,10]. There are LOC technologies which use electrochemical techniques, often used to monitor biological cell death and protein/DNA separation/purifications [11]
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