title: Mid-infrared spectrometer using opto-nanofluidic slot-waveguide for label-free on-chip chemical sensing.
abstract: A mid-infrared (mid-IR) spectrometer for label-free on-chip chemical sensing was developed using an engineered nanofluidic channel consisting of a Si-liquid-Si slot-structure. Utilizing the large refractive index contrast (Δn ∼ 2) between the liquid core of the waveguide and the Si cladding, a broadband mid-IR lightwave can be efficiently guided and confined within a nanofluidic capillary (≤100 nm wide). The optical-field enhancement, together with the direct interaction between the probe light and the analyte, increased the sensitivity for chemical detection by 50 times when compared to evanescent-wave sensing. This spectrometer distinguished several common organic liquids (e.g., n-bromohexane, toluene, isopropanol) accurately and could determine the ratio of chemical species (e.g., acetonitrile and ethanol) at low concentration (<5 μL/mL) in a mixture through spectral scanning over their characteristic absorption peaks in the mid-IR regime. The combination of CMOS-compatible planar mid-IR microphotonics, and a high-throughput nanofluidic sensor system, provides a unique platform for chemical detection.
authors: Microphotonics Center, Massachusetts Institute of Technology , 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States.
authors: Pao Tai
authors: PT
authors: Lin
authors: Sen Wai
authors: SW
authors: Kwok
authors: Hao-Yu Greg
authors: HY
authors: Lin
authors: Vivek
authors: V
authors: Singh
authors: Lionel C
authors: LC
authors: Kimerling
authors: George M
authors: GM
authors: Whitesides
authors: Anu
authors: A
authors: Agarwal
mesh_terms: D002623:Chemistry Techniques, Analytical / Q000295:instrumentation*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D046228:Microarray Analysis / Q000295:instrumentation*; D008832:Microchemistry / Q000295:instrumentation*; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation*; D036103:Nanotechnology / Q000295:instrumentation*; D013055:Spectrophotometry, Infrared / Q000295:instrumentation*; D013194:Staining and Labeling; D020349:Surface Plasmon Resonance / Q000295:instrumentation*