MICRORING RESONATOR PLATFORM BASED ON FLOW-THROUGH APPROACH

Microring resonators are emerging as promising building blocks of integrated optics thanks to their versatility in different research fields, such as telecommunication, biosensing and environmental protection and monitoring [1-3]. The small device sizes and the easy of fabrication, with conventional lithographic techniques, make them ideal for large scale integration. A novel fabrication approach include the employment of polymeric materials, for both the substrate and the sensing element, instead of the traditional silicon. The low costs, the high flexibility and ease structuring with micromilling machines makes the polymer materials very attractive for the fabrication of sensing platforms [4-5]. Many efforts were made to optimize the transport kinetic of the analyte under test to the sensing area in order to reduce both detection time and limit of detection. The most interesting method, investigated mainly for suspended nanohole arrays, is based onto "flow through" approach. In that case, the analyte is flowing orthogonally to the sensor surface, so ensuring higher transfer rate respect to standard "flow-over" approach, in which the analyte flows along the surface [6]. In the present work, we developed a novel microring architecture based onto flow-through approach with a fully integrated microfluidic. Su-8 based microring resonators were fabricated on to PMMA substrate with a direct laser writing technique. A drilled hole is realized in the center of the microring resonators by means of a micromilling machine. The biomolecule sensing capability is studied by employing bovine serum albumin (BSA) protein. The sensor response time is evaluated in both in flow-over and flow-through approach, as reported in figure 1. An improvement of about four times of the sensor response time is observed for flow-through approach respect to flow-over, so indicating a better transport kinetic for a real- time detection