title: Design and microfabrication of a miniature fiber optic probe with integrated lenses and mirrors for Raman and fluorescence measurements.
abstract: 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. Graphical abstract A microfabricated spectroscopic probe with integrated optics was developed for chemical detection in small spaces and in remote applications.
authors.affiliation: Department of Chemistry, University of Michigan, 930 N. University Ave, Ann Arbor, MI, 48109, USA.
authors.forename: Thitaphat
authors.initials: T
authors.lastname: Ngernsutivorakul
authors.affiliation: Department of Chemistry, University of Michigan, 930 N. University Ave, Ann Arbor, MI, 48109, USA.
authors.forename: Cynthia M
authors.initials: CM
authors.lastname: Cipolla
authors.affiliation: Department of Chemistry, University of Michigan, 930 N. University Ave, Ann Arbor, MI, 48109, USA.
authors.forename: Colleen E
authors.initials: CE
authors.lastname: Dugan
authors.affiliation: Department of Chemistry, University of Michigan, 930 N. University Ave, Ann Arbor, MI, 48109, USA.
authors.forename: Shi
authors.initials: S
authors.lastname: Jin
authors.affiliation: Department of Chemistry, University of Michigan, 930 N. University Ave, Ann Arbor, MI, 48109, USA.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Morris
authors.affiliation: Department of Chemistry, University of Michigan, 930 N. University Ave, Ann Arbor, MI, 48109, USA. rtkenn@umich.edu.|Department of Pharmacology, University of Michigan, 1150 W. Medical Center Drive, Ann Arbor, MI, 48109, USA. rtkenn@umich.edu.
authors.forename: Robert T
authors.initials: RT
authors.lastname: Kennedy
authors.affiliation: Department of Chemistry, University of Michigan, 930 N. University Ave, Ann Arbor, MI, 48109, USA.|Kaiser Optical Systems Inc, 371 Parkland Plaza, Ann Arbor, MI, 48103, USA.
authors.forename: Francis W L
authors.initials: FW
authors.lastname: Esmonde-White
keywords: Diagnostics; Microfabrication/microfluidics; Miniaturized optical probe; Remote application; Spectroscopy