Planar Chalcogenide Glass Based Biochemical Sensors
Juejun Hu, Vladimir Tarasov, Nathan Carlie, Laeticia Petit, Kathleen Richardson, Anuradha Agarwal and Lionel C. Kimerling
Sponsor: Department of Energy
The aim of the project is to develop a novel, highly sensitive and specific, integrated sensor system used for advanced biochemical detection and intelligent sensing applications, using chalcogenide materials. To address the robustness and sensitivity of current chemical sensor technologies, the proposed work will explore the development of a chalcogenide-based optical sensor system that is monolithically integrated onto a silicon platform, and is capable of parallel task processing with detection specificity and sensitivity. The specialty properties of chalcogenide glasses which make the materials an ideal candidate for sensing include high refractive index, wide infrared transmission window, low processing temperature and high optical transparency. The device configurations under investigation include evanescent waveguide absorption sensor, interferometers and optical resonators.
We have recently demonstrated, for the first time, the fabrication and characterization of a microfluidic sensor device integrated with planar chalcogenide waveguides (Fig. 1). We also demonstrate the feasibility of using this sensor to detect N-methylaniline. Sensor performance was tested by monitoring the optical output while injecting a solution of N-methylaniline mixed with a solution of carbon tetrachloride into the microfluidic channel. The N-H bond in N-methylaniline is known to exhibit an absorption peak near 1500 nm, which was used as the characteristic fingerprint for chemical identification in our test. The absorption (in dB), aL, induced by N-methylaniline in our microfluidic channel was calculated by taking the ratio of light intensity transmitted through a microfluidic channel filled with pure carbon tetrachloride (Isolvent) and through a channel filled with N-methylaniline solution in carbon tetrachloride (Ianalyte) (0.33, volumeric concentration). The resultant absorption spectrum shown in Fig. 2a exhibits a well-defined absorption peak at 1496 nm, which is in excellent agreement with a traditional absorption measurement carried out on a Cary 5E UV-Vis-NIR dual-beam spectrophotometer as seen in Fig. 2b. As seen in Fig. 2b, carbon tetrachloride has no absorption band in this range. Since carbon tetrachloride is transparent in the wavelength range investigated, this spectral peak is unambiguously assigned to N-H bond vibrational absorption. The peak absorption in dB at 1496nm was measured for different concentrations of N-methylaniline solution in carbon tetrachloride and the result is shown in Fig. 3. The excellent linear fit suggests that the sensor exhibits linear response when varying analyte concentrations. Given the small size, high robustness, low-cost fabrication and good sensitivity, the sensor can find applications in environmental monitoring, explosive detection, or biomedical diagnostics.
Fig. 1: Photo of the assembled microfluidic chip with fluid inlet and outlet tubing.
Fig. 2(a) Absorption spectrum showing the N-H bond absorption at 1496 nm wavelength in N-methylaniline measured using our integrated evanescent sensor. The absorption is defined by taking the ratio of light transmission in the case of a microfluidic channel filled with pure carbon tetrachloride against the case when the channel is filled with N-methylaniline solution in carbon tetrachloride (0.33, volumetric concentration).
Fig. 2(b) Transmission spectra of pure N-methylaniline and carbon tetrachloride (CCl4) measured using traditional UV-Vis spectroscopy. The absorption spectrum of N-methylaniline shows the same N-H absorption peak near 1496 nm while carbon tetrachloride is transparent in the wavelength range of interest.
Fig. 3: Peak absorption of N-methylaniline solution in carbon tetrachloride at 1496 nm wavelength measured using the waveguide evanescent sensor as a function of N-methylaniline volume concentration, indicating good linearity of the sensor response.
