High-Aspect-Ratio SU-8-Based Optofluidic Device for Ammonia Detection in Cell Culture Media

Miniaturization of sensing technology has led to the development of multifunctional micro total analysis systems (μTAS) that benefit from microfluidic technology. Optical sensing is one of the most commonly used sensing approaches integrated into μTAS devices and features high sensitivity and low detection limits. Different materials have been used for the fabrication of μTAS devices, each having their advantages and disadvantages. Herein, a high-aspect-ratio optofluidic waveguide fabricated from SU-8 is presented for the first time. The suitable optical properties and chemical inertness of SU-8 provide a durable device made by a flexible and cost-efficient fabrication process. The optofluidic device was used for colorimetric ammonia (NH₃) sensing with a dynamic range of 3-70 μM, a detection limit of 2.5 μM, a response time of 8 min, and close to 10 times better analytical performance compared to using a standard microplate reader. The μTAS device was capable of monitoring NH₃ accumulating in the cell culture media of prostatic epithelial cell (BPH-1) culture.