In this paper, we propose a novel vertical SU-8 waveguide for evanescent analyte sensing. The waveguide is designed to possess a vertical and narrow structure to generate evanescent waves on both sides of the waveguide's surface, aimed at increasing the sensitivity by enlarging the sensing areas. We performed simulations to monitor the influence of different parameters on the waveguide's performance, including its height and width. E-beam lithography was used to fabricate the structure, as this one-step direct writing process enables easy, fast, and high-resolution fabrication. Furthermore, it reduces the sidewall roughness and decreases the induced scattering loss, which is a major source of waveguide loss. Couplers were added to improve the coupling efficiency and alignment tolerance, and will contribute to the feasibility of a plug-and-play optical system. Optical measurements show that the transmission loss is 1.03 ± 0.19 dB/cm. The absorption sensitivity was measured to be 4.8 dB per refractive index unit (dB/RIU) for saline solutions with various concentrations.

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Outbreaks of bacteria have caused many problems over the last few years and are a major public health concern. Bacteria are now affecting our lives in many ways to a more severe extent, from contaminated food in markets to polluted water. There are some devices available which detect bacteria, however, all of them can only be used in the lab condition and are very expensive. This research is aimed at the development of a biomedical sensor which is capable of monitoring bacteria, especially focusing on diagnosing colorectal anastomotic leakage (AL) in patients at an early stage by detecting the existence of E. coli in the drain fluid. The occurrence of AL in patients after colon surgery is high and is cause for concern as it can lead to severe consequences, such as morbidity or even mortality. Therefore, there is a vital need for an efficient, on-line bedside tool to monitor the bacteria in the leakage: a diagnostic on-line device that is accurate, cost-effective, and ideally operates in an easy plug-and-play fashion which is beneficial for practical application. @en

For optical waveguide sensing, the challenging problems lie in the coupling efficiency and alignment tolerance [1]. This paper presents two different types of waveguides with tapers for evanescent sensing to relieve these problems. The first waveguide is SiC waveguide with 3D tapered coupler and the other is SU8 standing waveguide with horizontal tapered coupler. The design, simulation and fabrication of both structures will be illustrated.@en

In this paper, a novel vertical waveguide made from SU8 photoresist is proposed for the first time to be used in an evanescent bio-medical optical sensor. The vertical structure increases the sensing area and can be fabricated in a one-step lithography step enabling easy and high-resolution fabrication and making this waveguide attractive in optical sensing. Tapers were added to the system improving the alignment tolerance and enabling the manufacturing of plug-and-play optical system.@en