WO2021229432A1 - Capteur spr avec guide d'ondes et miroirs pour coupler la lumière dans le guide d'ondes et hors du guide d'ondes - Google Patents

Capteur spr avec guide d'ondes et miroirs pour coupler la lumière dans le guide d'ondes et hors du guide d'ondes Download PDF

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Publication number
WO2021229432A1
WO2021229432A1 PCT/IB2021/054001 IB2021054001W WO2021229432A1 WO 2021229432 A1 WO2021229432 A1 WO 2021229432A1 IB 2021054001 W IB2021054001 W IB 2021054001W WO 2021229432 A1 WO2021229432 A1 WO 2021229432A1
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Prior art keywords
layer
optical sensor
face
guiding
optical
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PCT/IB2021/054001
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English (en)
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WO2021229432A9 (fr
Inventor
Guido Chiaretti
Nunzio CENNAMO
Paolo CONCI
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Moresense S.R.L.
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Publication of WO2021229432A1 publication Critical patent/WO2021229432A1/fr
Publication of WO2021229432A9 publication Critical patent/WO2021229432A9/fr

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/55—Specular reflectivity
    • G01N21/552—Attenuated total reflection
    • G01N21/553—Attenuated total reflection and using surface plasmons

Definitions

  • the present invention refers to an optical sensor, to a sensor system and to a detection system to detect the presence and/or concentration of an analyte in a solution.
  • the present invention also relates to a procedure for 0 making said optical sensor.
  • waveguide optical sensors are known, for example in plastic optical fibres (POF) or planar waveguides, for monitoring the variation of refractive index of a receptor, through the physical effect of the surface plasmon resonance (SPR).
  • SPR surface plasmon resonance
  • the 0 chemical receptor is often a polymeric film in which the shape of the target molecule, or of a mixture of target molecules is imprinted when measuring a class of substances is wished, through the technology known as Molecularly Imprinted Polymer (MIP).
  • MIP Molecularly Imprinted Polymer
  • the plastic optical fibres POF used to make the above mentioned optical sensors have diameters ranging from a few hundred pm to 1 mm and have a core made of PMMA.
  • the plastic optical fibre is 0 modified, eliminating the cladding until reaching the core for at least a stretch of the length thereof, for example about 1 cm, by lapping creating a section in the shape of D. In this lapping process about 200-300 pm of core are usually removed.
  • a metallic layer is deposited on the flat portion of the modified fibre, usually gold, for example about 60 nm thick, on top of which a layer of a molecularly imprinted polymer (MIP) lower than Impi thick is deposited.
  • a photoresist layer lower than lpm thick can be deposited to modify the bandwidth or to increase the intensity of the plasmon resonance.
  • the modified plastic optical fibre as mentioned above is characterized by its own surface plasmon resonance or SPR corresponding to the frequency or to the wavelength at which the so-called surface plasmons are generated at the molecularly imprinted metal-polymeric interface.
  • the fibre is immersed in the aqueous solution to be examined for at least the stretch in which the sensor structure has been made, thus allowing the combination of the analyte with the MIP.
  • the input fibre is fed with an optical signal, for example white light, and the frequency shift of the plasmon resonance is observed. On the basis of this frequency shift it is possible to obtain information regarding the presence of the analyte in the aqueous solution.
  • Optical sensors made in this way are, for example, those described in EP3502152A1; these sensors show a very good chemical sensitivity, in the order of nanograms/litre, and a high selectivity towards the searched molecule (target).
  • these sensors are made individually of optical fibre, they require production procedures that involve rather artisanal processes, such as lapping of the cladding to realise the D-shaped section, which hinders large-scale production.
  • such sensors are instead made in planar waveguide, they require the preparation of a complex measurement setup which provides for a precise arrangement of means for coupling the light both at the input and at the output.
  • the object of the present invention is to obviate the aforementioned drawbacks and in particular to devise an optical sensor which can be made by means of a production procedure suitable for large-scale production and which is simple and easy to couple to optical sources and detectors.
  • Another object of the present invention is to provide a detection system comprising such an optical sensor which is simple to assemble.
  • a further object of the present invention is to provide a procedure for making the optical sensor according to the invention which is suitable for large-scale production.
  • optical sensor of the sensor system, of the detection system and of the procedure for making the optical sensor are the subject of the dependent claims.
  • FIG. la is a perspective view of a first embodiment of an optical sensor according to the present invention.
  • FIG. lb is a perspective view of a second embodiment of an optical sensor according to the present invention.
  • Figure lc is a sectional view of the optical sensor of Figure la or Figure lb along the plane Ic-Ic;
  • FIG. 2a is a perspective view of a third embodiment of an optical sensor according to the present invention.
  • Figure 2b is a sectional view of the optical sensor of Figure 2a along the plane Ilb-IIb;
  • FIG. 3a is a plan view of a fourth embodiment of an optical sensor according to the present invention.
  • Figure 3b is a sectional view of the optical sensor of Figure 3a along the plane Illb-IIIb;
  • FIG. 4 is a perspective view of a fifth embodiment of an optical sensor according to the present invention.
  • FIG. 5a, 5b and 5c are three perspective views of three possible embodiments of a sensor system according to the present invention
  • - Figures 6a, 6b, 6c, 6d, 6e, 6f are six sectional views of six possible embodiments of a sensor system according to the present invention
  • FIG. 7a, 7b and 7c are respectively a perspective view, a top view and a side view of a possible embodiment of a detection system according to the present invention.
  • Figures 8a, 8b, 8c, 8d, 8e, 8f, 8g, 8h illustrate successive steps of two alternative embodiments of a procedure for making at least one optical sensor according to the present invention; in particular, the initial step of Figure 8a is common to all the embodiments of the procedure, while the steps of Figure 8b-8d are alternatives to the steps of Figures 8e-8h;
  • FIG. 9a is a graph showing the intensity of the optical signal transmitted through the guiding layer of the optical sensor of Figure la as the refractive index of the layer of molecularly imprinted polymeric material varies;
  • FIG. 9b is a graph showing the intensity of the optical signal transmitted through the guiding layer of the optical sensor of Figure 2a as the refractive index of the layer of molecularly imprinted polymeric material varies
  • FIG. 10a is a schematic perspective view of a sixth embodiment of an optical sensor according to the present invention.
  • Figure 10b is a side view of the optical sensor of Figure 10a.
  • an optical sensor to detect the presence and/or concentration of an analyte in a solution, indicated as a whole with 10, is shown.
  • the terms "upper”, “lower”, “lateral” refer to the configurations of the optical sensor 10 as illustrated.
  • Said optical sensor 10 comprises a base layer 20 lying on a lying plane XY and consisting of a material with a first refractive index.
  • the base layer 20 may be made up of an adhesive material for example of a silicone or epoxy type having the first refractive index around 1.4 at visible light wavelengths.
  • the thickness of the base layer 20 is ranging between 5 pm and 50 pm.
  • the optical sensor 10 further comprises, at least one guiding layer 21 developing in length in a longitudinal direction X between two longitudinal ends 22, 23 and that is made up of a material having a second refractive index greater than the first refractive index.
  • the at least one guiding layer 21 is made up of PMMA having the second refractive index around 1.49 at visible light wavelengths.
  • the at least one guiding layer 21 has a thickness ranging between 100 pm and 1000 pm.
  • the at least one guiding layer 21 has a first face 24 in direct contact with the base layer 20 and a second face 25 that are opposite to each other and parallel to the lying plane XY, a third face 26 and a fourth face 27 that are opposite to each other developing along the longitudinal direction X,
  • the at least one guiding layer 21 and the base layer 20 realize a planar dielectric waveguide.
  • the at least one guiding layer 21 comprises a portion 30 sensitive to the analyte to be detected extending for a stretch of length of the at least one guiding layer 21.
  • the sensitive portion 30 comprises above the second face 25 in succession to each other along the vertical direction Z orthogonal to the lying plane XY a first metallic layer 31 and a layer of molecularly imprinted polymeric material or MIP 32.
  • the layer of molecularly imprinted polymeric material 32 comprises a plurality of reception sites arranged to capture the molecules of the analyte to be detected.
  • the dimensions along the directions X and Y of the sensitive portion 30 substantially coincide with those of the layer of molecularly imprinted polymeric material 32.
  • the layer of molecularly imprinted polymeric material 32 and the first metallic layer 31 have optical properties, dimensions, and shape such that, when the optical signal propagating in the at least one guiding layer 21 impinges on the first metallic layer 31, a surface plasmon is excited at the interface between the first metallic layer 31 and the molecularly imprinted polymeric layer 32 in correspondence of a certain wavelength.
  • This determined wavelength corresponds to the wavelength of the surface plasmon resonance or SPR.
  • the first metallic layer 31 is made up of gold, but it can also be made of silver or other metals.
  • the first metallic layer 31 has a thickness ranging between 40 nm and 70 nm.
  • the layer of molecularly imprinted polymeric material 32 can be made up of EGDMA, or DVB and has a thickness lower than 1 pm.
  • the layer of molecularly imprinted polymeric material 32 is preferably in direct contact with the first metallic layer 31.
  • the layer of molecularly imprinted polymeric material 32 may be in indirect contact with the first metallic layer 31; in this case a nanometre oxide film (not illustrated), for example graphene oxide, is interposed between the layer of molecularly imprinted polymeric material 32 and the first metallic layer 31.
  • a nanometre oxide film (not illustrated), for example graphene oxide
  • the first metallic layer 31 may be, in particular, in direct contact or indirect contact with the second face 25 of the at least one guiding layer 21.
  • a photoresist layer 33 is interposed between said second face 25 and the first metallic layer 31 and is in direct contact with the second face 25.
  • photoresist is defined as a polymeric or other photosensitive material having a refractive index higher than that of the guiding layer 21, for example around 1.5 at visible light wavelengths; the photoresist layer 33 is used to increase the interaction between the plasmonic excitation and the analyte. In fact, the photoresist layer 33 increases the number of photons coming out from the at least one guiding layer 21 towards the first metallic layer 31 consequently increasing the surface plasmon resonance phenomenon.
  • the effectiveness of the action of the photoresist layer 33 decreases with the thickness of said layer, which can range from a few tens of nanometres to a few hundreds of nanometres.
  • the photoresist layer 33 has a thickness lower than 1 pm.
  • the photoresist layer 33 serves to create a layer of adequate roughness to promote adhesion of the first metallic layer 31.
  • the optical sensor 10 has on the base layer 20 two reflective portions 34, 35 opposed to the longitudinal ends 22, 23 of the at least one guiding layer 21; said reflective portions 34, 35 have respective reflective faces defining with the lying plane XY an angle greater than 90° and are at least partially covered by respective second metallic layers 36, 37.
  • the second metallic layers 36, 37 are made up of gold but can also be made of silver or other metals.
  • the first metallic layer 31 and the second metallic layers are made up of the same material.
  • the second metallic layers have a surface roughness ranging between 2 nm and 1000 nm.
  • the second metallic layer 36 of the first reflective portion 34 has, preferably, a roughness ranging between lOOnm and lOOOnm, while the second metallic layer 37 of the second reflective portion 35 has, preferably, a roughness ranging between 2 and 50nm.
  • the reflective faces define with the lying plane XY an angle ranging between 130° and 140°.
  • the reflective faces define with the lying plane XY an angle of about 135°.
  • the reflective portions 34, 35 are made up of the same material as the base layer 20.
  • the reflective portions 34, 35 are made up of the same material as the at least one guiding layer 21.
  • the air acts as a confinement layer around the guiding layer 21 in correspondence of the second face 25, of the third face 26 and of the fourth face 27.
  • the sensitive portion 30 extends in width along the transverse direction Y only for a stretch of the width of the guiding layer 21 leaving a portion of the guiding layer 21 without the sensitive portion 30 i.e. without the multilayer structure included in said sensitive portion 30.
  • the reflective portions 34, 35 extend along the transverse direction Y for at least the same width as the guiding layer 21.
  • the optical sensor 10 comprises a first confinement layer 28 and a second confinement layer 29 which extend starting from the base layer 20 in direct contact respectively of the third face 26 and the fourth face 27 of the at least one guiding layer 21 along their entire longitudinal length, like for example in the embodiment illustrated in Figure la.
  • the air acts as a confinement layer around the guiding layer 21 in correspondence of the second face 25.
  • the first confinement layer 28 and the second confinement layer 29 are made up of the same material as the base layer 20.
  • the optical sensor 10 comprises the first confinement layer 28 which extends starting from the base layer 20 in direct contact with the third face and in correspondence of the sensitive portion 30 the fourth face 27 is inclined defining with the lying plane XY an angle greater than 90°.
  • the first metallic layer 31 and the layer of molecularly imprinted polymeric material 32 also at least partially overlie the fourth face 27.
  • the at least one guiding layer 21 has at least one curvilinear stretch 38 upstream and/or downstream of the sensitive portion 30.
  • the sensitive portion 30 remains rectilinear.
  • the function of the at least one curvilinear stretch 38 upstream of the sensitive portion 30 is to naturally deflect the optical beam guided by the at least one guiding layer 21 towards the fourth inclined face 27, increasing photon extraction towards the first metallic layer 31 and the layer of molecularly imprinted polymeric material 32, thus being able to avoid using the photoresist layer 33.
  • the curvilinear stretches 38 may be asymmetrical to improve the sensitivity and signal-to-noise ratio of the optical sensor 10.
  • Asymmetrical means that the curvilinear stretches 38 may have different radii of curvature.
  • the optical sensor 10 comprises a third confinement layer 39 which extends in direct contact with the second face 25 along its entire longitudinal length except in correspondence with the sensitive portion 30, like for example in the embodiment illustrated in Figure lb.
  • the optical sensor 10 comprises a substrate 80 in direct contact with the base layer 20 on the side opposite to the at least one guiding layer 21.
  • the reflective portions 34, 35 are realized in correspondence of the two longitudinal ends of the base layer 20 in the form of raised portions of the substrate 80 covered by cover layers 46, 47 of the same material as the base layer 20.
  • the third face 26 and the fourth face 27 of the at least one guiding layer 21 may be made substantially perpendicular to the lying plane XY or alternatively may be inclined with respect to the lying plane XY like for example illustrated in Figure 10a.
  • the optical sensor 10 comprises the first confinement layer 28 and the second confinement layer 29 which extend starting from the base layer 20 in direct contact respectively of the third face 26 and the fourth face 27 of the at least one guiding layer 21 along their entire longitudinal length; the first confinement layer 28 and the second confinement layer 29 being made so as to have the same inclination with respect to the lying plane XY as the third face 26 and the fourth face 27.
  • the first confinement layer 28 and the second confinement layer 29 are in turn in direct contact with side walls of the substrate 80 on the side opposite to the side in direct contact with the at least one guiding layer 21.
  • the first confinement layer 28 and the second confinement layer 29 are made up of the same material as the base layer 20.
  • the at least one guiding layer 21 and the confinement layers 28, 29 result recessed in the substrate 80.
  • the optical sensor 10 preferably comprises two of the guiding layers 21 placed side by side and spaced apart along a transverse direction Y, like for example in the embodiment illustrated in Figure 4.
  • the reflective portions 34, 35 extend along the transverse direction Y for at least the width of the assembly of the two guiding layers 21 spaced apart.
  • the curves shown in Figures 9a and 9b refer to an optical sensor 10 respectively like the one shown in Figure la and Figure 2a having a guiding layer 21 with thickness equal to 250 gm, a first metallic gold layer with thickness equal to 60 nm in direct contact with the second face 25 of the guiding layer 21.
  • Numerical simulations show a sensitivity DA/Dn(where A is the wavelength and n is the refractive index) sufficient to monitor the change in refractive index of the polymeric material layer 32 due to the bond with the analyte.
  • a plurality of optical sensors 10 can be made in such a way that the optical sensors 10 are integral with each other, realising a sensor system 100.
  • the optical sensors 10 are made in such a way to have at least one layer in common.
  • the sensor system 100 comprises a plurality of optical sensors 10 arranged on a same plane according to any reticular scheme.
  • the sensor system 100 comprises a plurality of optical sensors 10 that have a same substrate 80 and a same base layer 20 in common.
  • the optical sensors 10 are arranged in a matrix pattern but may be arranged in any reticular scheme.
  • the sensor system 100 comprises at least two optical sensors 10 that are made on opposite sides with respect to the same lying plane XY.
  • the sensor system 100 may comprise at least two optical sensors 10 that have a same substrate 80 in common and are made on opposite sides of said substrate 80, like for example in the embodiment illustrated in Figures 6a, 6b, 6c and 6d.
  • the sensor system 100 may comprise at least two optical sensors 10 that have a same base layer 20 in common and are made on opposite sides of said base layer 20, like for example in the embodiment illustrated in Figures 6e and 6f.
  • the sensor system 100 comprises a plurality of pairs of opposite optical sensors arranged in any pattern such that there are two grids of optical sensor 10 facing opposite sides with respect to the layer in common.
  • optical sensors 10 may be coupled together according to any combination of the embodiments described so far.
  • the detection system 50 to detect the presence and/or concentration of an analyte in a solution comprises at least one optical sensor 10 and at least one first optoelectronic card 40 lying on a plane parallel to the lying plane XY and opposed to the at least one optical sensor 10.
  • the at least one first optoelectronic card 40 comprises at least one light source 41 positioned facing a first one 34 of the reflective portions 34, 35 and at least one first optical detection device 42 positioned facing a second one 35 of the reflective portions 34, 35 aligned along the longitudinal direction X to the sensitive portion 30.
  • the light source can be a LED.
  • the first optical detection device 42 can be a photo-detector or more particularly a photo-diode which measures the intensity of the optical signal, or a detection optical fibre connected to a spectrophotometer for measuring the spectrum of light exiting from the optical sensor 10.
  • the at least a first optoelectronic card 40 comprises a second optical detection device (not illustrated) facing a second one 35 of the reflective portions aligned along the longitudinal direction X to the sensitive portion 30 of the second guiding layer 21.
  • the at least a first optoelectronic card 40 comprises a second optical sensing device 45 facing the second reflective portion 35 aligned along the longitudinal direction X with the guiding layer portion 21 without the sensitive portion 30.
  • the detection system 50 comprises a sensor system 100 and the at least one first optoelectronic card 40 comprises a plurality of respective light sources 41 and respective first 42 and possibly second 45 optical detection devices.
  • the detection system 50 comprises a second optoelectronic card (not illustrated) with respective light sources and optical detection devices positioned similarly to those of the first optoelectronic card 40.
  • the first optoelectronic card 40 may further comprise one or more inlet lenses 43, for example cylindrical lenses, positioned between the light source 41 and the respective first reflective portion 34 in order to direct the light emitted by the light source 41 onto the respective reflective face 36, and one or more outlet lenses and/or filters (not illustrated) positioned between the second reflective portion 35 and the respective optical detection device 42, 44, 45 in order to direct the light reflected by the second reflective portion 35 onto the respective optical detection device 42, 45.
  • inlet lenses 43 for example cylindrical lenses
  • outlet lenses and/or filters not illustrated
  • the inlet lenses 43 and the outlet lenses and/or filters are mounted on the first optoelectronic card 40.
  • the inlet lenses 43 serve to adapt the beam of the LED to the shape of the mirror illuminating the at least one guiding layer 21, i.e., they serve to adapt the divergence of the beam emitted by the LED to that of the excitable beam in the at least one guiding layer 21.
  • Each light source 41 is associated with a control unit (not illustrated). If the at least one first optoelectronic card 40 comprises a plurality of light sources, the detection system 50 can comprise a central control unit configured to selectively drive the light sources 41.
  • the detection system 50 allows implementing the detection method which will be described below with an exemplary and non-limiting reference to the case in which the detection system 50 comprises a single optical sensor 10 and a relative first optoelectronic card 40.
  • This method is based on the observation of the variation of the plasmon resonant excitation in the case in which the sensitive portion 30 is contacted with the solution containing the analyte to be detected with respect to a reference case.
  • the reference case may vary as the embodiment of the optical sensor 10 varies as will be clear below.
  • the optical properties thereof that is the refractive index
  • the detection method is based on the fact that the variation of the optical properties of the layer of molecularly imprinted polymeric material 32 due to the bond with the analyte involves the shift of the resonance wavelength of the surface plasmons.
  • This spectral shift is linked to the concentration value of the analyte in the solution.
  • the light source 41 emits an optical signal in a predetermined wavelength interval, for example in the wavelength range of red, and the concentration of the analyte is then determined on the basis of the variation in intensity of the optical signal detected in case of presence of the analyte with respect to an optical reference signal detected in case of absence of the analyte.
  • the variation between the intensities of the two signals is linked to the frequency shift of the surface plasmon resonance and, therefore, to the concentration of the analyte to be detected.
  • the optical signal generated by the light source 41 is white light, for example in an interval between 350nm and 750nm, and the concentration of the analyte is then determined on the basis of the spectral shift of the surface plasmon resonance detected by means of a spectrophotometer with respect to the optical reference signal detected in case of absence of the analyte.
  • the reference optical signal is the optical signal detected when the guiding layer 21 is not in contact with the solution in which the analyte to be detected is present.
  • a structure identical to that of the optical sensor 10 may be made by replacing the layer of molecularly imprinted polymeric material 32 with a layer of the same not imprinted polymeric material (NIP).
  • the reference optical signal is the optical signal detected at the outlet of the structure with the NIP layer. If the optical sensor 10 comprises only a guiding layer 21 like for example shown in Figure 2a, the reference optical signal is the one detected by the second optical detection device 45.
  • the reference optical signal is the one detected by the respective second optical detection device not wetted by the solution under test or with NIP layer.
  • optical sensor 10 The procedure for making the optical sensor 10 according to the present invention will be described below. In particular, the realization of a single optical sensor 10 will be described first, since this description can be extended to the realization of the sensor system 100.
  • a substrate 80 is prepared, for example of Silicon or other suitable material, having a thickness ranging between 500 and 1000 microns.
  • Said base layer 20 is deposited on the substrate 80 until reaching a thickness ranging between 5 pm and 50 pm, for example by means of the "spinning" technique.
  • Said base layer 20 can be an adhesive material, for example of the silicone or epoxy type, having a refractive index for example around 1.4 at the wavelengths of visible light.
  • a plate 60 of the material of the guiding layer 21 is glued onto the base layer 20.
  • said plate 60 may have a thickness ranging between 100 pm and 1000 pm.
  • the plate 60 is made up of a material having a refractive index higher than the base layer 20, for example of PMMA.
  • the reflective portions 34, 35 are made up of the same material as the guiding layer 21
  • a first photolithography template is deposited on the plate 60 and at least a first chemical etching is performed obtaining both the guiding layer 21 and the reflective portions 34, 35, as illustrated in Figure 8b.
  • the reflective portions 34, 35 are made up of the same material as the base layer 20
  • a first photolithography template is deposited on the plate 60 and a first chemical etching is performed obtaining the guiding layer 21.
  • the space left free by the removed material of the plate 60 is filled with the material of the base layer 20.
  • a lapping of the second face 25 of the guiding layer 21 is carried out so as to remove any excess material of the base layer.
  • a continuous free surface is obtained at the same level as the second face 25 of the guiding layer 21.
  • At least a second photolithography template is deposited on the continuous free surface and at least a second chemical etching is performed, obtaining both the guiding layer 21 with any first 28 and second 29 confinement layer, and the reflective portions 34, 35.
  • the aforesaid chemical etchings can be done through the Deep Reactive Ion Etching process in Oxygen, 02/Ar or in 02/CHF3 at powers between 10 and 60W.
  • the procedure comprises the step of depositing, for example by means of the sputtering technique, the first metallic layer 31 in direct contact or indirect contact with the second face 25 of the guiding layer 21.
  • the first metallic layer 31 is a gold film having a thickness ranging between 40 nm and 70 nm.
  • the step of depositing the first metallic layer 31 is preceded by a step in which a photoresist layer 33 is deposited on the second face 25 of the guiding layer 21, for example by means of the spinning technique.
  • the photoresist layer 33 has a refractive index around 1.5 at the wavelengths of visible light and a thickness of less than 1 pm.
  • the layer of molecular imprinted polymeric material 32 is deposited, for example by means of the spinning technique.
  • the portions of the first metallic layer 31, the photoresist layer 33, if any, and the layer of molecularly imprinted polymeric material 32 in excess with respect to the sensitive portion 30 are removed.
  • the substrate 80 is made up of PMMA, it may be considered as a substrate for an optical sensor 10 and as a guiding layer for another optical sensor 10 like in the embodiments illustrated in Figures 6e and 6f.
  • the procedure for making the optical sensor 10 includes preparing a substrate 80, for example of Silicon or other suitable material (glass, plastic, resin, etc), having a thickness ranging between 500 and 1000 microns. Then a recessed seat is made in said substrate 80.
  • This step of making the recessed seat can be performed for example by photolithography.
  • at least a third photolithography template is deposited on the continuous free surface and at least a third chemical etching is carried out obtaining a recessed portion.
  • the at least one third chemical etching may be carried out in the same manner as the at least one first and at least one second chemical etchings described above.
  • the recessed seat can be made by mechanical removal of the material or by additive or subtractive techniques of 3D deposition of polymeric or similar materials.
  • the base layer 20 is deposited on the substrate 80 in such a way that the latter also covers the inner surfaces of the previously obtained recessed seat.
  • the base layer 20 may have a thickness ranging between 5 pm and 50 pm, for example by "spinning" technique.
  • said base layer 20 may be made up of a glassy material such as silicon dioxide (Si02) or boron phosphosilicate glass (BPSG), or a resin or polymer with refractive index lower than that of the guiding layer 21.
  • a glassy material such as silicon dioxide (Si02) or boron phosphosilicate glass (BPSG)
  • BPSG boron phosphosilicate glass
  • the recessed seat coated by the base layer 20 is then filled with the material of the guiding layer 21, for example made up of a material having a refractive index higher than that of the base layer 20, for example of PMMA.
  • the reflective portions 34, 35 are subjected to a vacuum etching with Plasma with Argon in a manner per se known to the state of the art.
  • the second metallic layers 36, 37 have been deposited, they assume the surface roughness of the layers lying beneath them.
  • the procedure described above can be carried out in such a way as to obtain a plurality of optical sensors arranged on the same plane, using a substrate 80, a base layer 20 and a plate 60 having adequate dimensions.
  • a sensor system is obtained which can be cut with known cutting techniques to obtain single optical sensors 10 or any sensor system.
  • the optical sensor is simple and easy to couple both in input with a light source and in output with an optical detection device thanks to the presence of the reflective portions integrated in the structure of the optical sensor itself that allow the use of sensor systems even differing from each other.
  • Such reflective portions may have high roughness and therefore do not require complex roughness reduction operations.
  • the high roughness of the reflective portions allows reflecting incident light at a variety of angles toward the input of the guiding layer. This leads to an increased possibility of coupling with the guiding layer and a consequent increased possibility of exciting the surface plasmon with an appropriate intensity.
  • optical sensors are very versatile and can be combined together according to any scheme so as to realise the sensor system described above.
  • the detection system according to the present invention is very simple as it does not require complex lens and mirror systems for coupling the light both in and out of the optical sensor.
  • the procedure for making the optical sensor, according to the present invention is suitable for being used for large-scale productions, as it does not require artesanal processing but can be automated. Furthermore, the use of adhesive material as base layer 20 makes the realization of the optical sensor very simple as there is no need for an additional deposition step for the guiding layer but a simple gluing of the above described plate.
  • optical sensor the sensor system, the detection system and the procedure for making the optical sensor thus conceived are susceptible of numerous modifications and variations, all of which are within the scope of the invention; furthermore, all the details can be replaced by technically equivalent elements.
  • materials used, as well as the dimensions thereof, can be of any type according to the technical requirements.

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  • Investigating Or Analysing Materials By Optical Means (AREA)

Abstract

L'invention concerne un capteur optique (10) pour détecter la présence et/ou la concentration d'un analyte dans une solution, le capteur optique (10) comprenant : une couche de base (20) se trouvant sur un plan de couchage XY et constituée d'un matériau ayant un premier indice de réfraction ; au moins une couche de guidage (21) se développant en longueur dans une direction longitudinale X entre deux extrémités longitudinales (22, 23) et est constituée d'un matériau ayant un second indice de réfraction, la ou les couches de guidage (21) présentant une première face (24) en contact direct avec la couche de base (20) et une deuxième face (25) qui sont opposées l'une à l'autre et parallèles au plan de couchage XY, une troisième face (26) et une quatrième face (27) opposées l'une à l'autre, la ou les couches de guidage (21) comprenant une partie (30) sensible à l'analyte à détecter s'étendant sur une étendue de longueur et comprenant au-dessus de ladite deuxième face (25) en succession l'une par rapport à l'autre le long d'une direction orthogonale au plan de couchage XY une première couche métallique (31) et une couche de matériau polymère à empreinte moléculaire (32) ; le capteur optique (10) étant caractérisé en ce qu'il comprend en correspondance de deux extrémités longitudinales de la couche de base (20), deux parties réfléchissantes (34, 35) opposées aux extrémités longitudinales (22, 23) de la ou des couches de guidage (21), les parties réfléchissantes (34, 35) ayant des faces réfléchissantes respectives définissant avec le plan de couchage XY un angle supérieur à 90 et étant au moins partiellement recouvertes par des secondes couches métalliques respectives (36, 37), une seconde couche métallique (36) d'une première partie réfléchissante (35) ayant une rugosité de surface comprise entre 100 nm et 1 000 nm, tandis qu'une seconde couche métallique (37) d'une seconde partie réfléchissante (35) a une rugosité comprise entre 2 et 50 nm.
PCT/IB2021/054001 2020-05-12 2021-05-11 Capteur spr avec guide d'ondes et miroirs pour coupler la lumière dans le guide d'ondes et hors du guide d'ondes WO2021229432A1 (fr)

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