Microchannel integrated tapered and tapered-bend waveguides, for proficient, evanescent-field absorbance based, on-chip, chemical and biological sensing operations

Abstract

In our preceding-approaches, we had investigated (theoretically/experimentally) diverse single/multiple-bend-waveguides i.e. U-shaped/C-shaped/S-shaped/Spiral-polymer-waveguides coupled with the microchannel-network, for chemical/biological-sensing functions. In the current-approach, we aimed to additionally explore the enhanced efficiency of different designs of embedded-tapered-waveguide-probe, compared to U-bend-waveguides of similar length, which was crucial for utilizing it in several realistic evanescent wave absorption oriented chemical/biological-sensing operations. Earlier reported single-step production-process (with SU-8 photoresist), was performed to fabricate: tapered-waveguide-probes coupled with two-microchannels (interfacing at both of the waveguide side surfaces), and tapered-bend-waveguide coupled with single-microchannel (interfacing only at waveguide's outer-bend side surface); collectively with coupler formations for fiber-to-waveguide. Via the proper experiments, the evanescent-field-absorbance sensitivity of embedded-tapered-waveguides was realized ∼11 % superior, in comparison to that of embedded-tapered-bend-waveguides of analogous waveguide-length, although both side-surfaces of the tapered-waveguide were interacting with the analyte-solution. Contrast to our former reported embedded-U-bend-waveguides [33,34], the general evanescent-field-absorption oriented detection-sensitivity of embedded-tapered, and embedded-tapered-bend-waveguides were realized improved respectively by ∼2 times and ∼1.85 times. The devices were observed to be perfectly appropriate for further responsive Biological/Chemical-sensing purpose, on condition that proper waveguide-surface-modification procedure is executed. Additionally, the microdevices possess all potential-competence for a simple-uninterrupted concurrent-investigation, a preset analyte-quantity interface, and the restraint for samples-analyte-evaporation placed inside microdevice.