Thesis defense of Thi Nhung PHAM - January 15th, 2024

Thi Nhung PHAM will defend his thesis on January 15th, 2024 at 10:00 a.m., (amphi JP. DOM – IMS Laboratory) on the subject : “Fabry-Perot interferometer based on end-of-fiber polymer microtip for chemical sensing”.
This work studies the sensor applications of a Fabry−Perot interferometer (FPI) based on a polymer tip attached to the end of an optical fiber for humidity, water, and chemical targets. The polymer tip, made of pentaerythritol triacrylate (PETA), is formed on the facet of the optical fiber by self-guiding photopolymerization. The tip acts as an optical cavity formed between the fiber-core/PETA and the PETA/environment interface, producing a clear FPI signal. The PETA structure contains hydroxyl groups, which allows the tip to strongly absorb water molecules in the ambient, causing significant swelling. This results in a shift in the FPI signal of the tip, making it suitable for sensing humidity. Moreover, when fully saturated with water, the PETA tip can be efficiently used to determine the water content in hydrophilic liquids such as glycerol and ethylene glycol. The FPI shift is linearly responsive to water content below 10 wt.%, making the tip promising for practical applications. This shift is caused by the contraction in the tip length, which results from the loss of water inside the saturated PETA structure when dipped into the hydrophilic solutions. In addition, we propose a sensor tip composed of a PETA core and a molecularly imprinted polymer (MIP) shell for detecting Dansyl-L-phenylalanine. The selective binding of Dansyl-L-phenylalanine causes a change in the refractive index of the MIP layer, resulting in a change in the FPI signal of the entire PETA/MIP tip. This method offers an affordable and straightforward approach to create FPI sensors that can detect a wide range of analytes, including both fluorescent and non-fluorescent targets.