Disposable grating-integrated surface plasmon resonance sensor chips for biomolecule detection

Abstract

In this study, two different types of disposable sensor chips are presented for simple and inexpensive SPR (surface plasmon resonance) biomolecule detection: a convex single-grating SPR sensor chip and a flat multi-grating SPR sensor chip. In the convex single-grating SPR sensor chip, the incident angle of the incident light on the sensor chip is modulated by the curved surface of the convex grating for a simple and inexpensive incident-angle-modulated SPR sensing system. On the other hand, for a simple and inexpensive wavelength-modulated multi-channel SPR sensing system, a flat multi-grating SPR sensor chip generates two SPR dips in the reflected light spectrum by using an external mirror. The proposed SPR sensor chips offer a simple and inexpensive SPR sensing system without precise movable elements or expensive optical elements. The grating pitch in the proposed sensor chips was designed as 833 nm for biomolecule detection in buffer solutions. The convex single-grating SPR sensor chip is 9 mm x 9 mm in size, and the convex grating integrated in the sensor chip has a 40-mm radius of curvature. The flat multi-grating SPR sensor chip has two fluidic channels in which a 9 mm x 9 mm grating is integrated. The distance between the two fluidic channels is 30 mm. To reduce the fabrication cost of the proposed SPR sensor chips for disposable applications, a micromolding process for the nano pitch gratings that utilizes using a commercialized master grating and PDMS was developed. Using the fabricated convex single-grating SPR sensor chip with a 633-nm laser source, the SPR angle of water was measured with an angular resolution of 0.31 °. To improve the angular resolution for biomolecule detection, the surface roughness of the convex grating as well as the spatial resolution of the detection elements should be improved. A polychromatic light source is illuminated on the flat multi-grating SPR sensor chip. The incident angle of the light is controlled by an...