Claims:1. A system for coating (110) a nanofiber material (114) over a sensing device (104), the system comprising:
a receptacle (116) having the nanofiber material solution (114);
a voltage source (120) electrically coupled with the receptacle (116);
a platform (108) configured to receive the sensing device (104), and the platform (108) is aligned and placed at a predefined distance from the receptacle (116), and the platform is electrically coupled with the voltage source (120), wherein the nanofiber material solution (114) is configured to be coated over the sensing device (104) by spraying the nanofiber material solution (114) from the receptacle (116), under high voltage provided by the voltage source, over the sensing device (104) for a predefined time period.
2. The system as claimed in claim 1, wherein the nanofiber material solution (114) comprises any or combination of polyvinyl alcohol (PVA) and reduced graphene oxide (rGO).
3. The system as claimed in claim 1, wherein the receptacle (116) comprises any or combination of a syringe, a pneumatic pump.
4. The system as claimed in claim 3, wherein a needle of the syringe (116) is electrically coupled with a positive supply of the voltage source (120).
5. The system as claimed in claim 1, wherein the platform (108) is electrically coupled with a ground of the voltage source (120).
6. The system as claimed in claim 1, wherein the sensing device (104) comprises an etched fiber Bragg grating (eFBG) sensor.
7. The system as claimed in claim 1, wherein the platform (108) is made of customized aluminium.
8. The system as claimed in claim 1, wherein the coating of the nanofiber solution (114) is performed at a predefined flow rate, and at a predefined voltage.
9. The system as claimed in claim 1, wherein nanofiber coated sensing device is exposed to glutaraldehyde vapours to ensure proper cross linking of nanofibers and chemical binding of target molecules.
, Description:TECHNICAL FIELD
[0001] The present disclosure relates to the field of optical fiber sensors. More particularly the present disclosure relates to a system for coating nanofiber on the optical fiber sensor.

BACKGROUND
[0002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
[0003] Fiber Bragg Grating (FBG) sensors have been used for applications such as aeronautics, health monitoring of bridge structures, seismology, biomedical applications, gas sensing. Sensors are available commercially for sensing crack and vibrations, seismology, gas sensing, temperature and pressure sensing. These sensors work on the basic principle of the dependence of reflected Bragg wavelength on pitch (period) variations of gratings with applied stress and temperature. FBG sensors have various advantages such as: reliability, minimally invasive, electromagnetic immunity, small size, lightweight, good multiplexing capability, real time measurement capability, stability and safety in the probing environment.
[0004] Etched fiber Bragg grating (eFBG) sensors have their clad partially etched to increase their sensitivity to the surrounding media, and making them capable of detecting analytes attached to their surface. Various functionalization strategies have been reported, for facilitating the attachment of biomolecules on the eFBG sensor surface. Carbon nanotubes, gold nanoparticles and nanofilms, polymers, etc. have been used for detection of biomolecules in the pM (picomolar) range. eFBG sensors are capable of real time, multiplexed detection of a wide variety of analytes and can be used at point-of-care under normal temperature and pressure (NTP) conditions with minimal infrastructure and cost. Though there have been promising investigations in this area, the availability of the same in the market is almost nil. The contributing factors for this are: reproducibility of sensor response, sophistication of infrastructure to develop the sensor, difficulty in scaling to mass production.
[0005] Uniform coating on eFBG sensors play a crucial role for precise sensing. Mass production of uniformly coated eFBG sensors with the available technologies such as chemical vapour deposition (CVD), physical vapour deposition (PVD) and sputtering requires high vacuum chamber, high temperature, inflammable gases and substrate preprocessing. This leads to an increase in the cost of their production. Dip-coating, drop coating and spin-coating techniques are inexpensive and do not involve any complex procedures. However uniform dispersion and precise control over coating thickness of certain samples is difficult to achieve. Other techniques like CVD, PVD and sputtering can be utilized to achieve ultra-fine thickness of samples ranging from few angstroms to nanometers. However, these instruments are highly expensive, and require operation under high temperature and high vacuum conditions and require the use of inflammable gases, high power and a skilled operator.
[0006] There is, therefore, a need for a method of coating the eFBG sensors at a reduced cost and improved uniformity.

OBJECTS OF THE PRESENT DISCLOSURE
[0007] Some of the objects of the present disclosure, which at least one embodiment herein satisfies are as listed herein below.
[0008] It is an object of the present disclosure to provide a system for coating nanofiber on the optical fiber sensor with increased uniformity.
[0009] It is an object of the present disclosure to provide a system for coating nanofiber on the optical fiber sensor with reduced cost.
[0010] It is an object of the present disclosure to provide a system for coating nanofiber on the optical fiber sensor with reduced maintenance.
[0011] It is an object of the present disclosure to provide a system for coating nanofiber on the optical fiber sensor which requires NTP conditions with low power and low sample volume at minimum coating time and low operational cost.
[0012] It is an object of the present disclosure to provide a system for coating nanofiber on the optical fiber sensor that helps in development of portable, point-of-care, real time measuring eFBG sensors for mass production at low cost.
[0013] It is an object of the present disclosure to provide a system for coating nanofiber on the optical fiber sensor which increases dynamic range of the sensor.
[0014] It is an object of the present disclosure to provide a system for coating nanofiber on the optical fiber sensor which increases sensitivity of the sensor.
[0015] It is an object of the present disclosure to provide a system for coating nanofiber on the optical fiber sensor which increases reproducibility of the sensor.

SUMMARY
[0016] The present disclosure relates to the field of optical fiber sensors. More particularly the present disclosure relates to a system for coating nanofiber on the optical fiber sensor.
[0017] An aspect of the present disclosure pertains to a system for coating a nanofiber material over a sensing device. The system includes a receptacle having the nanofiber material solution. A voltage source electrically coupled with the receptacle. A platform configured to receive the sensing device and placed at a predefined distance from the receptacle. The platform is electrically coupled with the voltage source. The nanofiber material solution is configured to be coated over the sensing device by spraying the nana-fiber material solution from the receptacle, under high voltage provided by the voltage source, over the sensing device for a pre-defined time period.
[0018] In an aspect, the nanofiber material solution may include any or combination of poly vinyl alcohol (PVA), and reduced graphene oxide (rGO). The receptacle may include any or combination of a syringe and pneumatic pump. The platform may be electrically coupled with a ground of the voltage source. The receptacle may be electrically coupled with a positive supply of the voltage source. The sensing device may include an eFBG sensor. The platform may be made of aluminium customized as a bridge, and the coating of the nanofiber solution may be performed at a predefined flow rate, and at a predefined voltage. Nanofiber coated sensing devices may be exposed to glutaraldehyde vapours to ensure proper cross linking of nanofibers and chemical binding of target molecules.
[0019] Various objects, features, aspects and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.

BRIEF DESCRIPTION OF DRAWINGS
[0020] The accompanying drawings are included to provide a further understanding of the present disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure. The diagrams are for illustration only, which thus is not a limitation of the present disclosure.
[0021] In the figures, similar components and/or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label with a second label that distinguishes among the similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label.
[0022] An embodiment of the present disclosure pertains to a system for coating a nanofiber material over a sensing device. The system includes a receptacle having the nanofiber material solution. A voltage source electrically coupled with the receptacle. A platform configured to receive the sensing device and place at a predefined distance from the receptacle. The platform is electrically coupled with the voltage source. The nanofiber material solution is configured to be coated over the sensing device. This includes initial nanofiber material coating from the receptacle, under high voltage provided by the voltage source, across the bridge for a predefined time period. This is followed by nanofiber material coating from the receptacle, under high voltage provided by the voltage source over the sensing device placed across the coated layer for a pre-defined time period.
[0023] In an embodiment, the nanofiber material solution can include any or combination of PVA, and rGO.
[0024] In an embodiment, the receptacle can include any or combination of a syringe, a pneumatic pump. The platform can be electrically coupled with a ground of the voltage source. The receptacle can be electrically coupled with a positive supply of the voltage source.
[0025] In an embodiment, the sensing device can include an eFBG sensor. The platform can be made of customized aluminium, and the coating of the nanofiber solution can be performed at a predefined flow rate, and at a predefined voltage.
[0026] In an embodiment, nanofiber coated sensing devices can be exposed to glutaraldehyde vapours to ensure proper cross linking of nanofibers and chemical binding of target molecules.
[0027] FIG. 1 illustrates a system for coating nanofiber material over an eFBG sensor, in accordance with an embodiment of the present disclosure.
[0028] FIG. 2A illustrates a SEM image of PVA rGO coating, in accordance with an embodiment of the present disclosure.
[0029] FIG. 2B illustrates density of the nanofiber post processing, in accordance with an embodiment of the present disclosure.
[0030] FIG. 3 shows the response curves of the PVA rGO nanofiber coated eFBG sensor and dip coated eFBG sensor, in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION
[0031] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
[0032] In the following description, numerous specific details are set forth in order to provide a thorough understanding of embodiments of the present invention. It will be apparent to one skilled in the art that embodiments of the present invention may be practiced without some of these specific details.
[0033] The present disclosure relates to the field of optical fiber sensors. More particularly the present disclosure relates to a system for coating nanofiber on the optical fiber sensor.
[0034] FIG. 1 illustrates a system for coating nanofiber material over eFBG sensors, in accordance with an embodiment of the present disclosure.
[0035] As illustrated, a system for coating 110 nanofiber material over a sensing device can include a receptacle 116 having the nanofiber material solution 114. The sensing device 104 can include but not limited to an eFBG sensor with core (106) and clad (102). Reflected Bragg wavelength (?B) is proportional to the period of the gratings (?) and the effective refractive index (neff) of the LP01 mode within the core of the fiber. The equation for the reflected Bragg wavelength is:
?B=2?neff
The change in ?B is monitored using a commercially available interrogator 112, which has an inbuilt broadband laser source from 1510 nm to 1590 nm along with a spectrum analyzer and has a resolution of 1pm. The interrogator comes along with software that displays the ?B on the readout device 118.
[0036] In an embodiment, a platform 108 (also referred as substrate, herein) can be configured to receive the sensing device 104 and can be placed at a predefined distance from the receptacle 116. The receptacle 116 can include but not limited to a syringe. The platform 108 can be made of aluminium and can be electrically coupled with the voltage source. The aluminium foil of approximate thickness of 11µm to 18 µm can be used as a cathode for electrospinning. The substrate 108 can be covered by a customized aluminium foil to collect aligned nanofibers on eFBG sensors. The substrate can be designed to optimize electrospinning coating time along with nanofiber deposition on eFBG sensors. The coating thickness can be optimized as per the requirement by fine tuning the electrospinning parameters. The electrospinning parameters can include but without limiting to viscosity of polymer, polymer-additives ratio, applied voltage, flow rate of sample, distance between the needle tip (of the syringe) and collector.
[0037] In an embodiment, for performing the electrospinning, a needle of the receptacle 116 can be electrically coupled to a positive supply of the voltage source 120 and the platform 108 can be electrically coupled with a ground of negative supply of the voltage source 120. The coating of the nanofiber solution 114 can be performed at a predefined flow rate, and at a predefined voltage. Value of electrospinning parameters used in the experiment was 13 kV voltage (predefined voltage), 0.2 mL/h flow rate (pre-defined flow rate) and 8-12 cm distance from a needle tip of the receptacle 116 to the platform 108. The receptacle 116 can include but without limiting to a syringe, a pneumatic pump. The electrospinning can performed for 3 to 6 mins (also referred as pre-defined time period)
[0038] In an embodiment, the nanofiber material solution 114 can be configured to be coated over the sensing device by spraying the nanofiber material solution from the receptacle, under high voltage provided by the voltage source, over the sensing device 104 for a pre-defined time period. This process can be referred to as electrospinning. Electrospinning is a technique that uses electric force to draw charged threads of polymer solution up to fiber diameter of some hundred nanometers. The nanofiber material solution 114 can include but without limiting to PVA and rGO. A voltage source can be electrically coupled with the receptacle.
[0039] In an embodiment, the voltage source 120 can be a high voltage source that can be used to produce an effect of electrospinning. rGO (0.005% to 0.05 %) can be dispersed in the PVA solution for preparing the nanofiber material solution. The nanofiber coated sensing device can be exposed to glutaraldehyde vapours (also referred as post processing, herein) to ensure proper cross linking of nanofibers and chemical binding of target molecules. The sensing device can be spliced to a patch cord to connect to an interrogator, and the sensor can be dip coated in tris buffer for providing optimum pH for DNA attachment (122).
[0040] FIG. 2A illustrates a SEM image of PVA rGO coating, in accordance with an embodiment of the present disclosure.
[0041] FIG. 2B illustrates density of the nanofiber post processing, in accordance with an embodiment of the present disclosure.
[0042] FIG. 3 shows a response curve of the PVA rGO nanofiber coated eFBG sensor and a response curve of dip coated eFBG sensor, in accordance with an embodiment of the present disclosure.
[0043] In an embodiment, the proposed system provides an efficiently PVA rGO coated eFBG sensor with increased sensitivity and increased dynamic range. Table 1 shows a comparison between conventional dip coated and proposed PVA rGO nanofiber coated eFBG sensors for analyte detection:
S.no Method LoD Dynamic Range Sensitivity
1. rGO dip coated sensor 1 fg/ml 1 fg/ml - 100 pg/ml -11.63 pm g-1 ml
2. PVA-rGO electrospun sensor 100 ag/ml 100 ag/ml - 10 ug/ml -242.2 pm g-1 ml
Table 1
It can be observed that the sensor sensitivity of the proposed PVA rGO nanofiber coated eFBG sensor is increases by 1982 % and the dynamic range is increased to (100 ag/mL - 10 µg/mL) from (1 fg/ml -100 pg/ml).
[0044] Moreover, in interpreting the specification, all terms should be interpreted in the broadest possible manner consistent with the context. In particular, the terms “comprises” and “comprising” should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced. Where the specification claims refer to at least one of something selected from the group consisting of A, B, C ….and N, the text should be interpreted as requiring only one element from the group, not A plus N, or B plus N, etc.
[0045] While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.

ADVANTAGES OF THE INVENTION
[0046] The proposed invention provides a system for coating nanofiber on the optical fiber sensor with increased uniformity.
[0047] The proposed invention provides a system for coating nanofiber on the optical fiber sensor with reduced cost.
[0048] The proposed invention provides a system for coating nanofiber on the optical fiber sensor with reduced maintenance.
[0049] The proposed invention provides a system for coating nanofiber on the optical fiber sensor which requires NTP conditions with low power and low sample volume at minimum coating time and low operational cost.
[0050] The proposed invention provides a system for coating nanofiber on the optical fiber sensor that helps in development of portable, point-of-care, real time measuring eFBG sensors for mass production at low cost.
[0051] The proposed invention provides a system for coating nanofiber on the optical fiber sensor which increases dynamic range of the sensor.
[0052] The proposed invention provides a system for coating nanofiber on the optical fiber sensor which increases sensitivity of the sensor.
[0053] The proposed invention provides a system for coating nanofiber on the optical fiber sensor which increases reproducibility of the sensor.