MobileSPR App and Case: A Combined Logical and Mechanical Solution for Surface Plasmon Resonance Sensors Based on Smartphone

This paper proposes a mechanical structure (MobileSPR Case) combined with mobile application (MobileSPR App) to provide a complete solution for surface plasmon resonance (SPR) sensor based on smartphones. The mechanical structure was specially designed to hold all optical elements on the smartphone to archive the surface plasmon excitation. Manufactured in a 3D printer, the case fit from the top, and is adjustable for several frontal camera dispositions. Composed of two parts, makes the smartphone replacement process easier, as well enable thin- and thicker- biochips for surface plasmon excitation. The embedded application controls light source, camera, data process, information displayed and results storage, avoid an extra components to create a portable SPR solution. The App manipulate the light beams provided by the smartphone screen, varying the color between 380 nm to 780 nm, allowing the usage with biochips of different materials, metal layer and configurations. To demonstrates the solution feasibility a Xiaomi MI 9 Lite smartphone was used. Both a flat (thin) and trapezoidal (thicker) biochips operating in the angular interrogation were attached in the MobileSPR Case & App solution, and aqueous substances were exploited experimentally.