Theoretical analysis and fabrication of PDMS-based surface plasmon resonance sensor chips

The theoretical analysis, design and fabrication of PDMS-prism-coupled Kretschmann surface plasmon resonance (SPR) sensor were presented. The optical properties of very thin metal films have been evaluated by Fresnel analysis, with optical boundary conditions pertaining to the surface plasmon resonance at the gold/water and gold/air interface. The magnitude of the resonance, reflectance, full width at half maximum and position of SPR angle are affected by the thickness of gold and chromium. The optimal thickness of the metal layer varies with different wavelength. The sharply defined gold thickness of 50 nm and chromium thickness of 2 nm are required while employing fixed incident wavelength of 650 nm, to achieve optimum SPR excitation conditions and sensor sensitivity. The refractive index (RI) of coupling prism and sample, and wavelength of incident beam affect the position of SPR angle. Bulk silicon micromachining and polymer replication were used in fabrication of the coupling prism. The experimental characteristics of PDMS SPR sensor were evaluated in the angular interrogation mode employing incident wavelength of 650 nm when the chip was applied to test samples, including air and water. The obtained SPR angles were approximately consistent with the theoretical ones.