Abstract
This work reports on the implementation of different absorption micro-filters based on a dye-doped hybrid organic-inorganic xerogel polymeric material synthesized by the sol-gel process. Microstructures containing eight different filter widths were fabricated in polydimethylsiloxane (PDMS), bonded to glass substrates and filled with the corresponding dye doped polymeric material by a soft lithography approach. The filtering capacity as a function of dye concentration and filter width was studied and revealed a linear dependence with both parameters, as expected according to the Beer-Lambert law. Zero passband transmittance values and relatively sharp stopband regions were achieved with all the filters, also showing rejection levels between -6 dB and -55 dB. Finally, such filters were monolithically integrated into a disposable fluorescence-based photonic lab-on-a-chip (PhLoC) approach. Calibration curves carried out with a model fluorophore target analyte showed an over two-fold increase in sensitivity and a thirty-fold decrease of the limit of detection (LOD) compared with the values recorded using the same PhLoC system but without the polymeric filter structure. The results presented herein clearly indicate the feasibility of these xerogel-based absorbance filtering structures for being applied as low-cost optical components that can be easily incorporated into disposable fluorescence-based photonic lab on a chip systems.
Highlights
One of the most common approaches in photonic lab-on-a-chip (PhLoC) systems is the measurementof fluorescence as detection method [1]
In this work we present the fabrication by a soft lithography approach of simple and lowcost absorbance filters based on a dye doped hybrid organic-inorganic xerogel polymer suitable to be monolithically integrated into a PhLoC
Passband values still retain the value close to zero for all the tested filters (Tables 3-6, appendix). These results show that the dyes are homogeneously dispersed into the xerogel matrix without causing aggregates or phase separation, which may lead to scattering centers, and decrease the transmittance in the passband region, as it was the case in our previous work with ink-doped PDMS [7]
Summary
One of the most common approaches in photonic lab-on-a-chip (PhLoC) systems is the measurementof fluorescence as detection method [1]. Absorbance filters are generally fabricated with a single layer of a material containing a chromophore [4] or a band gap material [5] In both cases, they are fabricated to show high absorption at the excitation wavelength and low absorption at the fluorescence wavelength of the solution or compound being measured. They are fabricated to show high absorption at the excitation wavelength and low absorption at the fluorescence wavelength of the solution or compound being measured The performance of such absorbance filters is governed by the Beer-Lambert law and, unlike interferometric filters, their response is independent of the beam incidence angle [2]
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