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For the detection of chemical agents in different environments, the combination of plastic optical fibers (POFs) and molecularly imprinted polymers (MIPs) receptors has been tested as a way to obtain low cost, highly selective and sensitive optical chemical sensors based on plasmonic resonance. In this work, a novel type of optical chemical sensor able to detect the binding reactions occurring between the MIP and analyte has been designed, fabricated and applied for the selective detection of dibenzyl disulfide (DBDS) in transformer oil. This analyte is important in the control of transformer oil, since it is responsible for the corrosive properties of the oil. The new optical sensor platform is based on two plastic optical fibers that work as segmented waveguides coupled through a polymer molecularly imprinted for the analyte. The prepolymeric MIP solution was deposited by drop coating in a trench milled between the two fibers. The experimental results indicated that this new sensor can be useful for the determination of DBDS in transformer oil and it paves the way to a new approach in the optical fiber sensors for MIPs.

A low-cost plasmonic sensor based on a polymeric light diffusive optical fiber (LDF) has been designed, realized, and experimentally tested. The developed surface plasmon resonance (SPR) sensor has been realized by sputtering a gold nanofilm on the LDF. The work also presents a simple modal filter, realized by covering the LDF with an aqueous solution. Notably, this modal filter improves the signal-to-noise ratio (SNR) of the SPR sensor thanks to the filtering of the higher modes, without losing its sensitivity.

In this paper, we propose a dual wavelength scheme for the detection of liquids based on optically absorbing (Co2+-doped) optical fibers. The proposed configuration makes use of a Coherent-Optical Time Domain Reflectometer (C-OTDR) operating with standard fibers at 850 nm. Besides vibration measurements over all the sensing fiber, the proposed scheme performs liquid detection in short sections of Co2+-doped fibers, heated by a modulated optical pump at 1550 nm. We demonstrate that the proposed sensor detects the liquids surrounding the doped fiber, such as water or acetone.

A review on bio-chemical label-free sensing applications based on receptors combined with multimode plastic optical fibers (POFs) is carried out. In particular, this work focuses on different kinds of POF intrinsic sensors used in transmission mode, exploiting various types of receptors and useful in several application fields. The sensor structures and the sensing mechanisms of different simple, highly sensitive, and low-cost POF probes are reported and compared. Moreover, different kinds of chemical and biological receptors combined with POF probes, highlighting the advantages and disadvantages of each receptor, are presented in detail. More specifically, the chosen POF sensing platforms, including low-cost and simple interrogation setups, are described showing their ability to monitor specific receptors exploiting intensity variation techniques and plasmonic phenomena, as well. Finally, a prospect of future developments of biochemical sensors with multimode POFs is discussed.

Several surface plasmon resonance (SPR) sensors in optical fibers have been presented for the detection of magnetic fields. These SPR sensors measure the variation of the refractive index of a magnetic fluid in contact to the metal film, when the magnetic field changes. In this work, we have presented a different approach to monitor a magnetic field exploiting SPR optical fiber sensors and ferrofluids. More specifically, we have inserted a patch of multimode plastic optical fiber (POF) covered with ferrofluids between a light source and an SPR-POF sensor connected to a spectrometer. The magnetic field in the region near the patch covered by ferrofluids exerts a bending force on the patch changing the light in input to the SPR sensor and modifying the SPR phenomenon, in terms of resonance’s shape and wavelength.

Nowadays, the development of simple, fast, and low-cost selective sensors to detect substances of interest is of great importance in several application fields. Among this kind of sensors, those based on surface plasmon resonance (SPR) represent a promising category, since they are highly sensitive, versatile, and label-free. In this work, an SPR probe, based on a poly(methyl methacrylate) (PMMA) slab waveguide covered by a gold nanofilm, combined with a specific molecularly imprinted polymer (MIP) receptor for bovine serum albumin (BSA) protein, has been realized and experimentally characterized. The obtained experimental results have shown a limit of detection (LOD) equal to about 8.5 × 10−9 M. This value is smaller than the one achieved by another SPR probe, based on a D-shaped plastic optical fiber (POF), functionalized with the same MIP receptor; more specifically, the obtained LOD was reduced by about three orders of magnitude with respect to the POF configuration. Moreover, concerning the D-shaped POF configuration, no manufacturing process is present in the proposed sensor configuration. In addition, fibers are used only to connect the simple sensor chip with a light source and a detector, promoting a bio-chemical sensing approach based on disposable, low-cost, and removable chips.

In this work, we present a novel biochemical sensing approach based on a plasmonic sensor chip, combined with a specific receptor, excited and interrogated via a custom 3D-printed holder through a transmission-based experimental setup, exploiting polymer optical fibers. The setup is designed to measure a disposable plasmonic chip based on a gold nanograting fabricated on a polymethylmethacrylate substrate. The examined sensor configurations here presented are simulated, realized, and experimentally tested. More specifically, first, a numerical analysis is carried out by changing several sensor parameters, then an experimental optical characterization of different sensor configurations is reported. Finally, to test the biosensing capabilities of the proposed method, as a proof of concept, we deposit on the best sensor configuration a biomimetic receptor specific for bovine serum albumin detection. The experimental results demonstrate that the proposed sensor shows an ultra-low limit of detection, equal to about 37 pmol/L.

We have exploited a laser-based integration process of ultrathin metal-oxide (MO) films to improve the plasmonic effect in sensors based on D-shaped plastic optical fibers (POFs). More specifically, using ultrathin MO films, the performances of the surface plasmon resonance (SPR) phenomenon improve and a lossy mode resonance (LMR) can occur. Although the role of this kind of materials has been already presented, when they are deposited as overlayer (upside the thin metal film), we have used a different approach by depositing MOs, especially zirconium oxide (ZrO2) and titanium oxide (TiO2), as flexible intermediate layers between the exposed core of POFs and the gold film. The MO layer is prepared from sol-gel solution, and deep-UV laser curing allows us to densify the thin film and tune the refractive index, with a room-temperature process fully compatible with the flexible polymer substrates. In a preliminary step, we have carried out numerical results, based on transfer matrix formalism, to predict the SPR response. Subsequently, we have experimentally characterized the developed sensor configurations. Numerical and experimental results have shown above all an enhancement of the sensor performances, in terms of SPR sensitivity, with respect to a reference sensor based on a polymer instead of MOs. Moreover, in some proposed sensor configurations, together with the SPR phenomenon, an LMR phenomenon was observed. It occurred in a different wavelength range, for a typical refractive index range present when considering receptors for biochemical sensing applications. Therefore, both resonances (SPR and LMR) could be used in several application fields.

Nowadays there is an increasing request to realize green, eco-friendly, and biodegradable electronic devices for biosensor implementation. In this context, we have conceived and realized a green sensor based on localized surface plasmon resonance (LSPR) phenomenon in a thin-slab waveguide of bacterial cellulose (BC). These LSPR sensors can be obtained simply by gold sputtering on the slab BC waveguides. The performances have been studied investigating the presence of ionic liquids (ILs) inside and in absence of ILs with various thicknesses of the BC substrate. Depending of the thickness of the BC layer, the ILs effect on the LSPR can be constructive or destructive. In this work, we present a study of the sensor performances, in terms of bulk sensitivity and resolution by changing the aforementioned parameters. Analyses in terms of BC geometry are pursued in order to improve the interaction between the light and the LSPR phenomenon. The experimental setup used for this kind of extrinsic optical fiber LSPR sensor is based on two optical fibers used to connect a white light source and a spectrometer with the green LSPR sensor chip. Results evince the suitability of the proposed approach in order to realize sensors and biosensors with several intriguing properties and features. In fact, these LSPR platforms could be used to realize disposable biosensors, when a specific bioreceptor is covalently bonded to the gold.

The optical properties of multimode plastic optical fibers (POFs) could be used for both the monitoring of magnetic field and for the tuning of plasmonic phenomenon, when a magnetic fluid was deposited on its cladding and it is connected in input to a plasmonic POF sensor. In this case, a magnetic field exerts a bending force on the POF covered with magnetic fluid, thus producing a variation of light in input to the plasmonic POF sensor and changing the plasmonic phenomenon. In particular, the focus of this work is the assessment of the tuning mechanism for the plasmonic phenomenon, which has been performed through a dedicated measurement approach. Preliminary experimental results are here presented to demonstrate how this approach can be used to change several plasmonic parameters, such as the sensitivity and the signal-to-noise ratio (SNR). This approach could be used in biosensing applications, where even smaller variation of the plasmonic response can significantly improve the detection of substances.

In this work, we have compared several configurations of surface plasmon resonance (SPR) sensors based on D-shaped tapered plastic optical fibers (TPOFs). Particularly, the TPOFs used to obtain the SPR sensors are made by a lab-built system based on two motorized linear positioning stages and a heating plate. Preliminarily, a comparative analysis has been carried out between two different configurations, one with and one without a thin buffer layer deposited between the core of TPOFs and the gold film. After this preliminary step, we have used the simpler configuration, obtained without the buffer layer, to realize different SPR D-shaped TPOF sensors. This study could be of interest in SPR D-shaped multimode plastic optical fiber (POF) sensors because, without the tapers, the performances decrease when the POF&rsquo, s diameter decreases, whereas the performances improve in SPR D-shaped tapered POF sensors, where the diameter decreases in the D-shaped sensing area. The performances of the SPR sensors based on different taper ratios have been analyzed and compared. The SPR-TPOF sensors have been tested using water&ndash, glycerin mixtures with refractive indices ranging from 1.332 to 1.381 RIU. According to the theory, the experimental results have demonstrated that, as the taper ratio increases, the sensitivity of the SPR sensor increases as well, while on the contrary the signal-to-noise ratio (SNR) decreases.

We have studied how the optical property of a multimode plastic optical fiber (POF) can be used to monitor a magnetic field, exploiting a Surface Plasmon Resonance (SPR) POF sensor. To realize the sensor system, we have deposited a magnetic fluid on the cladding of a multimode POF connected in input to an SPR D-shaped POF sensor platform. The target magnetic field exerts a bending force on the POF covered with magnetic fluid, thus producing a change of light in input to the SPR POF sensor and modifying the SPR phenomenon. This work presents preliminary experimental results to demonstrate that this novel principle of sensing can be used for highly sensitive measuring of the magnetic field. Preliminary results have demonstrated the viability of this approach showing the possibility to obtain higher sensitivities, compared with the state of the art on SPR optical fiber magnetic field sensors exploiting magnetic fluids.

We have used the same biomimetic receptor, a specific molecularly imprinted polymer (MIP), on two different plasmonic plastic optical fiber (POF) sensors to measure how the optical response influences the chemical response. To obtain two surface plasmon resonance (SPR) platforms, we have used two different overlayers between the core of the POF and the gold film. These overlayers, with a refractive index higher than that of the POF’s core [poly(methyl methacrylate) (PMMA)], have been used to improve the performances of the plasmonic sensor. As overlayers, we have deposited a photoresist (Microposit S1813), in two different aging conditions, namely, before and after its expiry date. In this article, we have demonstrated how the alteration in the photoresist changes the sensor’s performances and eventually the chemical response of the MIPs. More specifically, we have compared the MIPs responses of these two SPR-POF platforms in two different refractive index ranges. For this purpose, an MIP receptor already tested in the detection of perfluorinated compounds (PFAs) in water has been exploited.

Authors recall two high sensitive, small size, and low-cost surface plasmon resonance (SPR) sensors based on plastic optical fibers (POFs): the first one, a D-shaped SPR intrinsic POF sensor, the second one an SPR extrinsic POF sensor. These plasmonic POF sensors, intrinsic and extrinsic, combined with different kinds of specific receptors can be directly connected to an online platform by a software interface, allowing storing, analyzing and displaying the sensor's data, to realize low-cost biochemical sensors for several applications. The simple experimental setup, used for both these SPR POF sensor configurations, was arranged to measure the light spectrum transmitted through the plasmonic platform, exploiting a halogen lamp and a spectrometer connected to a PC.

In this work, a novel approach to realize a plasmonic sensor is presented. The proposed optical sensor device is designed, manufactured, and experimentally tested. Two photo-curable resins are used to 3D print a surface plasmon resonance (SPR) sensor. Both numerical and experimental analyses are presented in the paper. The numerical and experimental results confirm that the 3D printed SPR sensor presents performances, in term of figure of merit (FOM), very similar to other SPR sensors made using plastic optical fibers (POFs). For the 3D printed sensor, the measured FOM is 13.6 versus 13.4 for the SPR-POF configuration. The cost analysis shows that the 3D printed SPR sensor can be manufactured at low cost (∼15 €) that is competitive with traditional sensors. The approach presented here allows to realize an innovative SPR sensor showing low-cost, 3D-printing manufacturing free design and the feasibility to be integrated with other optical devices on the same plastic planar support, thus opening undisclosed future for the optical sensor systems.

In this study the influence of the surface roughness on the transmission capacities of D-shaped plastic optical fibers (POFs) and sensors performance was investigated. Five D-shaped POF sensors were produced and characterized for refractive index sensing between 1.33 and 1.41. The sensors were characterized using a low-cost optical sensing system based on the variation of the transmitted light though the POF with refractive index changes (RI). Higher surface roughness increases the scattering losses through the POF and influences the sensors&rsquo, performance, therefore, a balance must be attained. Generally, the best performance was achieved when the sensing region was polished with P600 sandpaper as a final polishing step. Polishing with sandpapers of lower grit size resulted in lower scattering, higher linearity of the sensor response and generally lower performance for RI sensing. A sensor resolution of 10&minus, 3&ndash, 10&minus, 4 RIU, dependent on the value of the external refractive index, was obtained through simple and low-cost manufacturing procedures. The obtained results show the importance of surface roughness in the development of POF sensors which can be used in several applications, such as for water quality assessment.

We have investigated, in a numerical and experimental way, a refractive index (RI) sensor based on surface plasmon resonance (SPR) in a silver-coated light-diffusing fiber (LDF). The experimental tests were conducted using water-glycerine mixtures with refractive indices ranging from 1.332 to 1.388. In the considered refractive index range, the experimental results show a sensitivity of the SPR wavelength to the outer medium’s RI ranging from 2600 to 4700 nm/RIU, which is larger than the sensitivity recently reported for a gold-coated LDF sensor (1200 to 4000nm/RIU). The silver-coated sensor is also shown to ensure a higher signal-to-noise ratio (SNR) compared to the gold-coated sensor.

In this work we want to compare performances of different plasmonic sensors, obtained by different polishing processes of D-shaped Plastic optical fibers (POFs). Three D-shaped POF plasmonic sensor configurations, obtained by three different polishing processes, have been created and experimentally tested. The proposed devices are based on the excitation of surface plasmons at the interface between the under test medium and a thin gold layer directly deposited on plastic fiber core (D-shaped area). The experimental results have shown that the performances are influenced by surface roughness variations in the D-shaped POF region.

As a proof of principle, we have developed a novel surface plasmon resonance (SPR) sensor used to monitor the interaction between a molecularly imprinted polymer (MIP) and a small molecule as the substrate. This plasmonic platform is based on a removable polymethyl methacrylate (PMMA) chip with a thin gold film on the top, two PMMA plastic optical fibers (POFs) and a special holder, designed to obtain the plasmonic phenomenon. We have experimentally tested whether the optical sensitivity is sufficient for monitoring an MIP receptor. The advantage of MIPs is that they can be directly deposited on a flat gold surface by a spin coater machine, without modifying the surface, as needed for the bio-receptors. With this new sensor, it is possible to achieve remote sensing capabilities, by POFs, and also to realize an engineered platform with a removable chip sensor.

An optical sensor for transformer oil monitoring is reported. It has been implemented in a plastic optical fiber which acts as optical platform for the sensing element, that is, a Molecular Imprinted Polymer layer, which is a robust, reproducible and low-price receptor for chemical marker in the insulating oil matrix. This optical sensor has been assessed on the detection of a chemical byproduct of transformers’ paper degradation, the furfuraldehyde (2-FAL). The optical sensor performances have been tested on used insulating oil samples spilled from ex-serviced instrument transformers and compared with results of standard methods applied to the same samples. The achieved good agreement emerging by comparative analysis confirms the ability of the optical sensor of detecting low 2-FAL contents directly in mineral oil, without any treatment or dilution of the oil.

A novel optical platform has been used to monitor the interaction between a molecularly imprinted polymer (MIP) and a small molecule. The new optical sensor is made of a polyethylene terephthalate substrate with a pattern of silver nanoparticles, printed on it by inkjet technology, and two plastic optical fibers (POFs). The POFs connect the optical sensor, later covered by the MIP layer, with a light source and with a spectrometer. The detection of furfural (furan-2-carbaldehyde, 2-FAL) in aqueous media was investigated exploiting a selective MIP receptor. The experimental results show that this novel approach presents a limit of detection of about 0.03 ppm, comparable to that of plasmonic sensors combined with the same MIP, but with the advantage of an easier preparation procedure.

Highly sensitive plasmonic optical fiber platforms combined with receptors have been recently used to obtain selective sensors. A low-cost configuration can be obtained exploiting a D-shaped plastic optical fiber covered with a multilayer sensing surface. The multilayer consists of a gold film, functionalized with a specific receptor, where the surface plasmon resonance (SPR) occurs. The signal is produced by the refractive index variation occurring as a consequence of the receptor-to analyte binding. In this work, a selective sensor for copper(II) detection in drinking water, exploiting a self-assembled monolayer (SAM) of d,l-penicillamine as the sensing layer, has been developed and tested. Different concentrations of copper(II) in NaCl 0.1 M solutions at different pH values and in a real matrix (drinking water) have been considered. The results show that the sensor is able to sense copper(II) at concentrations ranging from 4 &times, 10-6 M to 2 &times, 10-4 M. The use of this optical chemical sensor is a very attractive perspective for fast, in situ and low-cost detection of Cu(II) in drinking water for human health concerns. Furthermore, the possibility of remote control is feasible as well, because optical fibers are employed.

In several application fields, plasmonic sensor platforms combined with bio-receptors are intensively used to obtain biosensors. Most of these commercial devices are based on a disposable chip. Usually a gold chip, functionalized with a specific bio-receptor, inside a costly sensor system, is used. In this work, we propose a low-cost and small-size sensor system, used for monitoring a disposable plasmonic chip, based on an innovative optical waveguide made of bacterial cellulose (BC). In particular, we have sputtered gold on the green slab waveguide that is able to excite localized surface plasmon resonance (LSPR). Experimental results are presented on the capabilities of using the BC-based composite as an eco-friendly plasmonic sensor platform, which could be exploited for realizing disposable biosensors. The sensor has been used with optical fibers and simple equipment. More specifically, the fibers connect the green disposable LSPR sensor with a light source and with a spectrometer. The novel plasmonic sensing approach has been tested using two different optical waveguide configurations of BC, with and without ions inside BC.

In the present investigation a new intensity-based sensor platform for refractive index sensing is presented. It is based on a special holder, a slab waveguide and two Plastic optical fibers (POFs). In particular, we present a comparison between two different configurations: the slab waveguide with and without a buffer layer. Advantages of this new approach are the possibility of sensing with a removable chip, the easy production of an engineered platform and the use of a special holder, which is also suitable for thermo-stabilized flow cells implementation.

Optical chemosensors offer a decisive solution to monitor critical parameters in power transformers, as they can operate safely on electrical equipment. Surface Plasmon Resonance (SPR) is widely used as a detection principle for many sensors operating in different fields, such as bio and chemical sensing. Its use with optical fibers makes the remote SPR sensing straightforward and suitable for applications also in presence of high electromagnetic interferences, as in the case of power transformers. Additionally, a low-cost sensing device is achieved when an SPR chemical sensor is implemented in a plastic optical fiber (POF) in which an artificial receptor of chemical agents in different liquid environments is exploited. In this work, we report an overview on the main results about the feasibility of application of a developed SPR-POF sensor for the detection, in oil matrix, of two markers of the paper-oil insulating system degradation in oil-filled transformer.

A simple approach to low-cost plasmonic sensing is obtained exploiting Plastic Optical Fibers (POFs). POFs are especially advantageous for their properties and, when receptors are used for bio/chemicals detection, are suitable for different application fields.

A new approach for the selective detection of the Perfluorinated compounds in water is presented. The low-cost sensor system is based on a Molecular Imprinted Polymer deposited on a D-shaped Plastic Optical Fiber platform.

A novel sensing platform based on a SPR-cell, implemented with side-emitting plastic optical fiber has been design and optimized to work in the 1.36-1.40 refractive index range. The SPR-cell was integrated into a low-cost hybrid platform capable of complementary and sensitive detection of analyte refractive index variation, using electrochemical and optical approach.

A low cost and simple to realize optical temperature sensor is proposed. The sensor is fabricated on the fiber end by removing, near the fiber tip, the cladding of a multimode plastic optical fiber (POF) with a polishing process, to deposit, by dip coating, a silicone layer around the fiber tip. We have experimentally tested the sensor by measuring, at different wavelengths, the temperature of a water bath. The best sensor's performances were obtained at a wavelength of 625 nm. The novel polymer optical fiber sensor exhibits a good linear response in the temperature range from 24°C to 46°C. This temperature range is interesting for hyperthermia in cancer treatment.

A comparative analysis of two optical fiber sensing platforms is presented. The sensors are based on surface plasmon resonance (SPR) in a D-shaped plastic optical fiber (POF) with a photoresist buffer layer between the exposed POF core and the thin gold film. We show how the sensor's performances change when the photoresist layer changes. The photoresist layers proposed in this analysis are SU-8 3005 and S1813. The experimental results are congruent with the numerical studies and it is instrumental for chemical and bio-chemical applications. Usually, the photoresist layer is required in order to increase the performance of the SPR-POF sensor.

A novel sensing platform based on thin metal bilayer for surface plasmon resonance (SPR) in a D-shaped plastic optical fiber (POF) has been designed, implemented and tested. The experimental results are congruent with the numerical studies. This platform has been properly optimized to work in the 1.38 -1.42 refractive index range and it exhibits excellent sensitivity. This refractive index range is very interesting for bio-chemical applications, where the polymer layer are used as receptors (e.g. molecularly imprinted polymer) or to immobilize the bio-receptor on the metal surface. The proposed metallic bilayer is based on palladium and gold films and replaces the traditional gold by exhibiting higher performances. Furthermore, the deposition of the thin bilayer is a single process and no further manufacturing step is required. In fact, in this case the photoresist buffer layer between the POF core and the metal layer, usually required to increase the refractive index range, is no longer necessary.

For the detection of chemical agents in different environments, the combination of a D-shaped plastic optical fibre (POF) and a molecularly imprinted polymer (MIP) layer resulted as an effective way to obtain a low cost, highly selective and sensitive surface plasmon resonance (SPR) optical platform. In this work a deeper investigation on the dependence of performance of this optical platform on the gold film thickness is reported, aiming to the improvement of the signal to noise ratio. Preliminary results have been obtained on a specially developed SPR optical platform with a 30 nm gold layer and a new molecularly imprinted polymer as a receptor for the selective detection of dibenzyl disulfide (DBDS) in transformer oil. The experimental measurements confirm that a good compromise between high signal to noise ratio and high sensitivity of the developed optical chemical platform can be obtained by decreasing the gold layer thickness down to 30 nm.

A new augmented workplace (eSPR) approach for a simple, low cost, easy to use and portable experimental platform was implemented, to integrate a multispectral Surface Plasmon Resonance-Plastic Optical Fiber (SPR-POF) sensor. The eSPR has a dedicated user-friendly software Spectraberry interface. Surface Plasmon Resonance in plastic optical fibers (POF-SPR) is a low cost and sensitive label-free technique for selective detection of refractive index variations of the liquid sample that contains the analyte, at the interface between a metallic layer and a dielectric medium. SPR is widely used as a detection principle for bio and chemical sensing applications.

The experimental investigations of the performance of a D-shaped Plastic Optical Fiber (POF) sensor are presented. The phenomenon behind this optical fiber sensor based platform is the variation of the transmitted light at the output of the POF with the external refractive index. The resolution of the optical sensing platform is strongly dependent on the length of the sensing region, decreasing from 10 -1 to 10 -3 RIU with length varying from 1cm to 5cm. The sensor production procedure is very easy, fast and low-cost. The obtained resolution allows further development for chemical and biochemical sensing by chemical receptor, e.g. molecularly imprinted polymer. A good resolution was obtained using sensing area length of 5cm.

The first example of an optical sensor platform based on surface plasmon resonance (SPR) in a plastic optical fiber (POF) integrated into a thermo-stabilized flow cell for biochemical sensing applications is proposed. In this work, an IgG/anti-IgG assay was implemented as model bioassay, with the IgG biolayer deposited on the sensor gold surface and the biological target, anti-IgG, transported through a new thermo-stabilized flow cell. The experimental results show that the proposed device can be successfully used for label-free biochemical sensing. This complete optical sensor system can be used for the future reduction of the device cost and dimension, with the possibility of integrating the POF-SPR sensing platform with microfluidic and optoelectronic devices. © (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

3D sketch (left) of the thermo-stabilized home-made flow cell developed to house the SPR-based plastic optical fibre biosensor. Exemplary response curve (shift of the SPR wavelength versus time) of the proposed biosensor (right) for the detection of C-reactive protein in serum. A plastic optical fibre biosensor based on surface plasmon resonance for the detection of C-reactive protein (CRP) in serum is proposed. The biosensor was integrated into a home-made thermo-stabilized microfluidic system that allows avoiding any thermal and/or mechanical fluctuation and maintaining the best stable conditions during the measurements. A working range of 0.006–70 mg L–1 and a limit of detection of 0.009 mg L–1 were achieved. These results are among the best compared to other SPR-based biosensors for CRP detection, especially considering that they were achieved in a real and complex medium, i.e. serum. In addition, since the sensor performances satisfy those requested in physiologically-relevant clinical applications, the whole biosensing platform could well address high sensitive, easy to realize, real-time, label-free, portable and low cost diagnosis of CRP for future lab-on-a-chip applications.

For the detection of chemical agents in different environments, the combination of plastic optical fibers (POFs) and molecularly imprinted polymer (MIP) layers has been tested as a way to obtain a low cost, highly selective and sensitive surface plasmon resonance (SPR) chemical sensor. A novel type of optical chemical sensor based on POF-MIP has been designed and fabricated, and in this work it has been applied for the selective detection of dibenzyl disulfide (DBDS) in transformer oil. This analyte is important in the control of transformer oil, since it is responsible for the corrosive properties of the oil. The new optical sensor platform is based on two plastic optical fibers coupled through a polymer molecularly imprinted for DBDS. The new sensor has been found to be useful for the determination of DBDS in transformer oil.

We have realized a plasmonic sensor based on Au/Pd metal bilayer in a multimode plastic optical fiber. This metal bilayer, based on a metal with high imaginary part of the refractive index and gold, shows interesting properties in terms of sensitivity and performances, in different refractive index ranges. The development of highly sensitive platforms for high refractive index detection (higher than 1.38) is interesting for chemical applications based on molecularly imprinted polymer as receptors, while the aqueous medium is the refractive index range of biosensors based on bio-receptors. In this work we have presented an Au/Pd metal bilayer optimized for 1.38-1.42 refractive index range.

The experimental results obtained with two different Plastic Optical Fiber (POF) geometries, tapered and not-tapered, for a sensor based on Surface Plasmon Resonance (SPR) are presented. SPR is used for determining the refractive index variations at the interface between a gold layer and a dielectric medium (aqueous medium). In this work SPR sensors in POF configurations, useful for bio-sensing applications, have been realized for the optimization of the sensitivity and experimentally tested. The results show as the sensitivity increases with the tapered POF configuration, when the refractive index of aqueous medium increases.

In this work an innovative, miniaturized and low cost optical chemical sensor (POF-MIP platform), based on a molecular imprinted polymer (MIP) and surface plasmon resonance in a plastic optical fiber (POF), is presented and preliminarily tested for monitoring of furfural (furan-2-carbaldehyde) in transformer oil. To this end, the optical platform was coupled to an MIP layer, highly selective for furfural. The ability of the developed sensor to directly detect furfural in the insulating oil was investigated. The detection limit of the sensor has been found to be 9 ppb, with a linear response up to about 30 ppb. However there is a sensible response up to 0.15 ppm. Because of the small linearity range, the Hill equation is suggested for the quantification. The sensor has been effectively tested in real oil samples collected from aged electrical equipment removed from service. The assessed concentration of furfural is in good agreement with that evaluated by a high pressure liquid chromatography (HLPC) method, confirming the good selectivity of the proposed sensor.

An SPR sensor in POF, with possible implementation as bio/chemical sensor, is presented. This SPR-POF platform can be used in different application fields: industrial, medical diagnostics, environmental monitoring, food safety and security. © 2015 OSA.

In this work, a simple and low cost experimental setup (based on Arduino) for an optical sensor platform based on Surface Plasmon Resonance (SPR) in a Plastic Optical Fiber (POF), is presented. Surface Plasmon Resonance in plastic optical fibers is a very low cost and sensitive technique for determining refractive index variations at the interface between a metallic layer and a dielectric medium. SPR is widely used as a detection principle for many sensors operating in different application fields, such as bio and chemical sensing.

Optimization of planar waveguides for fluorescence biosensing is presented in this paper. In particular, the authors show that optical (refractive index) and geometrical parameters have a strong influence on the efficiency of excitation and collection of fluorescent signals. Numerical analyses show that a single-mode slab waveguide, operating at its fundamental transverse magnetic mode and near its cutoff point, results in an efficient fluorescence excitation when employed as evanescent wave biosensor. A high-refractive index contrast is demonstrated to be the key parameter for an efficient fluorescence collection. Other geometries that are an alternative to the classical slab waveguide may result in an improvement of the fluorescence excitation and collection efficiencies

In this work we present a new low cost SPR (Surface Plasmon Resonance) sensor configuration based on efficient higher-order mode filtering in plastic multimode fibers, using a tapered POF (Plastic Optical Fiber) after the sensor system, without decreasing the sensitivity of the sensor. In particular, we present the experimental results obtained with this new configuration. The experimental results have shown as the tapered POF after the sensor system influences the performances in terms of refractive index range and Signal-to-Noise Ratio (SNR). © 2014 SPIE.

This paper analyses the temperature behaviour of an optical trigger sensor, based on a low-cost transparent electro-optic ceramic. The knowledge of the temperature behaviour is important for assessing the feasibility of this sensor as a means for accurate and safety measurements of electric parameters in Medium Voltage (MV) equipment, in addition to the previously proved its suitability for the continuous monitoring of the phase of the voltage in MV electric boards. Results of thermal tests, carried out with the optical device inserted in a climate chamber, for simulating typical thermal excursion in MV equipment, evidenced a significant sensitivity reduction of the sensor response. Nevertheless it does not affect the phase sensitivity of the sensor, this measured temperature dependence limits an accurate measure of the voltage amplitude. A linear behaviour of the characteristic parameter of the ceramic material with temperature confirms the possibility of an active temperature compensation of the sensor response. © 2014 AEIT.

Preliminary results of feasibility assessment of an optical Surface Plasmon Resonance (SPR) based sensor, exploiting a Plastic Optical Fiber (POF) platform, for an early and high sensitivity detection of chemical agents of interest are reported. In this investigation, a Molecularly Imprinted Polymer (MIP) has been used as an artificial receptor in connection with SPR transduction in POF for the selective detection of small molecules in oil-filled power transformer. The proposed device has been experimentally tested for the detection of furfural (furan-2-carbaldehyde), so that the MIP is specific for this substance. This particular kind of synthetic receptor has been used instead of the most usual bio-receptors, in view of the fact that the sample matrix here considered is the transformer oil. Actually, it is widely recognized that bio-receptors poorly perform in non aqueous media. © 2014 AEIT.

The paper reports the numerical analysis and some experimental results relative to an optical sensor system based on Surface Plasmon Resonance (SPR) at the interface of a liquid sample and a sandwiched structures realized starting from the exposed core of a Plastic Optical Fiber (POF). The advantages of POF sensors is that they are simpler to manufacture than those based on silica optical fibers. In the scientific literature there are only simple POF sensors based on laterally polished bent structures prepared along a plastic optical fiber [1]. In this paper different POF sensor configurations are simulated and experimentally tested. The classical geometry of sensors based on SPR in silica optical fiber is adapted and borrowed for Plastic Optical Fibers [2], so representing a simple approach to low cost plasmonic sensing. © 2014 Springer Science+Business Media.

A novel waveguide geometry for an integrated optics bio-sensor suitable for fluorescence detection is presented. In particular, we propose a polymeric waveguide realized on a glass substrate. This new geometry is aimed to an efficient evanescent-wave excitation of the fluorophores and subsequent collection of the fluorescence emission with no need of optical filters. The absence of any optical filters simplifies the device operation and permits to avoid the losses resulting from the use of the filter itself.

This work presents how the altering in the photoresist (Microposit S1813) changes the performances of D-shaped plastic optical fiber (POF) plasmonic sensors. In particular, this photoresist has been used to obtain a buffer layer, deposited on the exposed core in the D-shaped POF region before sputtering the gold film, to improve the performances of the sensor. We have studied how the optical property of the photoresist layer changes when the photoresist is used after the expiry date. In particular, we have compared the performances of two surface plasmon resonance (SPR) sensors realized exploiting two Microposit S1813 photoresists, one before and the other after the expiry date. When the refractive index of the medium of interest (aqueous medium) is minor than 1.36, the sensitivity improves with the use of S1813 after the expiry date, vice versa when the refractive index is major than 1.36.