Diego Lopez-Torres

Micro and Nanostructured Materials for the Development of Optical Fibre Sensors

The measurement of chemical and biomedical parameters can take advantage of the features exclusively offered by optical fibre: passive nature, electromagnetic immunity and chemical stability are some of the most relevant ones. The small dimensions of the fibre generally require that the sensing material be loaded into a supporting matrix whose morphology is adjusted at a nanometric scale. Thanks to the advances in nanotechnology new deposition methods have been developed: they allow reagents from different chemical nature to be embedded into films with a thickness always below a few microns that also show a relevant aspect ratio to ensure a high transduction interface. This review reveals some of the main techniques that are currently been employed to develop this kind of sensors, describing in detail both the resulting supporting matrices as well as the sensing materials used. The main objective is to offer a general view of the state of the art to expose the main challenges and chances that this technology is facing currently.

Sensitivity enhancement of a humidity sensor based on poly(sodium phosphate) and poly(allylamine hydrochloride)

The particular behavior of poly(sodium phosphate) (PSP) when it is deposited by means of the spraying layer-by-layer (LbL) technique has been used here to enhance the response of optical fiber humidity sensors. The roughness of the PSP films varies depending on the concentration of the polymeric solutions. In this work, it is demonstrated that this special feature of PSP allows the fabrication of optical fiber humidity sensors with different responses. Particularly, multilayer thin-films made of 10-3 and 10-4 M PSP and poly(allylamine hydrochloride) (PAH) solutions have been studied and used for the fabrication of optical fiber interferometers sensitive to humidity. To our knowledge this is the first time that the spray-assisted LbL technique has been used for the fabrication of optical fiber sensors.

Comparison between Different Structures of Suspended-Core Microstructured Optical Fibers for Volatiles Sensing

In this paper, different core structures of microstructured optical fibers (MOFs) for low-finesse Fabry–Pérot (FP) sensors are experimentally compared to get the highest sensitivity. These devices are designed for volatile organic compounds (VOCs) measurements. Indium tin oxide (ITO) thin films were deposited by sputtering on the MOFs and different optical fast Fourier transform (FFT) phase responses from the FP were measured for saturated atmospheres of ethanol. It has been demonstrated that the sensitivities of the developed sensors depend strongly on the geometry and the dimensions of the MOF-cores. The sensors show recovery times shorter than 100 s and the baselines are fully recovered after every exposure to ethanol vapors.