Design and microfabrication of a miniature fiber optic probe with integrated lenses and mirrors for Raman and fluorescence measurements


Fiber optics coupled to components such as lenses and mirrors have seen extensive use as probes for Raman and fluorescence measurements. Probes can be placed directly on or into a sample to allow for simplified and remote application of these optical techniques. The size and complexity of such probes however limits their application. We have used microfabrication in polydimethylsiloxane (PDMS) to create compact probes that are 0.5 mm thick by 1 mm wide. The miniature probes incorporate pre-aligned mirrors, lenses, and two fiber optic guides to allow separate input and output optical paths suitable for Raman and fluorescence spectroscopy measurements. The fabricated probe has 70 % unidirectional optical throughput and generates no spectral artifacts in the wavelength range of 200 to 800 nm. The probe is demonstrated for measurement of fluorescence within microfluidic devices and collection of Raman spectra from a pharmaceutical tablet. The fluorescence limit of detection was 6 nM when using the probe to measure resorufin inside a 150-μm inner diameter glass capillary, 100 nM for resorufin in a 60-μm-deep × 100-μm-wide PDMS channel, and 11 nM for fluorescein in a 25-μm-deep × 80-μm-wide glass channel. It is demonstrated that the same probe can be used on different sample types, e.g., microfluidic chips and tablets. Compared to existing Raman and fluorescence probes, the microfabricated probes enable measurement in smaller spaces and have lower fabrication cost.

A microfabricated spectroscopic probe with integrated optics was developed for chemical detection in small spaces and in remote applications

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We acknowledge Professor Fred Terry (EECS, UMich) for measuring the refractive index of PDMS, Brian Johnson (CHE, UMich) for the assistance with multilayer mask alignment, Jim Tedesco (Kaiser Optical Systems) for the help with Zemax modelling, and Rafal Pawluczyk (Fiber Tech Optical) for the advice and donation of various supplies in support of this project. This work was supported by NIH R37DK46960 & R37EB003320 (R.T.K.) and R01AR056646 (M.D.M.).

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Correspondence to Robert T. Kennedy.

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Thitaphat Ngernsutivorakul and Cynthia M. Cipolla contributed equally to this work.

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Ngernsutivorakul, T., Cipolla, C.M., Dugan, C.E. et al. Design and microfabrication of a miniature fiber optic probe with integrated lenses and mirrors for Raman and fluorescence measurements. Anal Bioanal Chem 409, 275–285 (2017).

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  • Microfabrication/microfluidics
  • Miniaturized optical probe
  • Spectroscopy
  • Remote application
  • Diagnostics