Fabrication of Miniature Surface Plasmon Resonance Sensor Chip Using Polymeric Prism

In this work, we present the development of a miniature surface plasmon resonance (SPR) sensor chip using the Kretschmann configuration. The SPR sensor chip incorporates a polymeric prism made from Norland Optical Adhesive 61 (NOA 61). By utilizing NOA 61 instead of a conventional prism, we overcome certain limitations associated with conventional SPR spectroscopy. We employed the confined sessile drop technique to fabricate the NOA 61 polymeric prism, which offers several advantages, including simplicity, low-cost fabrication, and precise control over lens parameters. A liquid NOA 61 was dropped directly onto a flat circular disk with a 6-mm diameter made of poly(dimethyl siloxane) (PDMS). The sharp edge of the PDMS circular disk facilitated controlled formation and the desired amount of the liquid NOA 61, resulting in the formation of a hemispherical prism. Subsequently, UV curing was employed to solidify the NOA 61, then obtaining the NOA 61 polymeric prism. To complete the miniature SPR sensor chip, 3 nm-thick chromium layer, and 47 nm-thick gold layer were evaporated onto the planar side of the NOA 61 polymeric prism and then mounted on a microfluidic cell fabricated using a 3D printer. The resulting SPR excitation curves were observed in the visible region and exhibited a refractive index independence sensitivity of 885.4 nm/RIU. Furthermore, we demonstrated the capability of the miniature SPR sensor chip to detect nanomaterials.