The invention concerns a chalcogenide fiber sensor using evanescent infrared waves.
Chalcogenide glass is glass with a low melt temperature and low glass transition temperature and such glasses are highly original materials, difficult to synthesize and control. Their performance greatly extends the sensitivity of Fiber Evanescent Wave Spectroscopy sensors (FEWS). More particularly, these glasses containing sulfur, selenium and/or tellurium allow light to pass over a broad wavelength range in the infrared, which is not the case for conventional oxide glasses. In addition, the glassy nature of the material allows the forming thereof to fabricate optical fibers. Finally, they are glasses which entail chemical elements that are close to one another in the periodic table which therefore maintain highly covalent bonds between each other. This nature of the chemical bonds makes the material hydrophobic which is most positive when they are used as sensor in media with high water content such as biological samples.
One of the fields of application of this sensor is effectively the biomedical field.
The document “IR optical fiber sensor for biomedical applications” by J. Keirsse, C. Boussard-Plédel, O. Loréal, 0. Sire, B. Bureau, P. Leroyer, B. Turlin, J. Lucas, Vibrational Spectroscopy 32 (2003), pages 23 to 32, describes the principle of said sensor in the mid-infrared range. In this device, a single Te2As3Se5 fiber is used as waveguide and as detection element. This fiber has a spectral window ranging from 800 to 4,000 cm−1. To improve the sensitivity of this sensor, its diameter is locally reduced to create a tapered U-shaped detection zone which is brought into contact with a sample to be analyzed. The diameter of this fiber of 400 micrometers is reduced to 100 micrometers in this detection zone. The fiber is coupled to a FTIR spectrometer. The principle of measurement is to send an infrared wave into the fiber which propagates along the fiber via successive reflections on its outer surface. In the detection zone in contact with the sample, the evanescent wave propagating along the outer wall of the fiber is partly absorbed by the target substance. The spectrometer analyzes the wave received at the other end of the fiber to deduce information on the sample therefrom.
The document “Advances in chalcogenide, fiber evanescent wave biochemical sensing” by Pierre Lucas, Mark R. Riley, Catherine Boussard-Plédel, Bruno Bureau, Analytical Biochemistry (2006), pages 1 to 10, describes a chalcogenide fiber sensor specifying that the radius of curvature of the fiber depends on its diameter and may reach 2 centimeters for a 100 micrometer fiber.
The problems raised by the sensor are its lack of compactness, fragility, low sensitivity in the detection zone.
The invention sets out to obtain a sensor using at least one fiber in chalcogenide glass operating on the principle of absorption via evanescent waves that is compact, robust and sensitive to signatures in the mid-infrared of the target molecules.
The first subject of the invention is a sensor meeting these criteria, comprising at least one fiber allowing the propagation of infrared light at least at one infrared wavelength of between 0.8 and 25 micrometers, and outwardly generating evanescent waves to detect infrared signatures of an outside medium, said at least one fiber being of composition of XY type where X is chosen from among Ge, As or Sb or a mixture of two or more than two of these components, and where Y is chosen from among S, Se, Te or a mixture of two or more than two of these components,
the fiber successively comprising over its length a first fiber section for guiding the infrared wave, at least one second fiber section having a detection function and intended to come in contact with the outside medium to detect infrared signatures perturbing the propagation of evanescent waves propagating along the fiber, and a third fiber section for guiding the infrared wave,
characterized in that
in the second fiber section having the detection function, the fiber is formed of at least one bent part whose radius of curvature is locally smaller than 2.3 millimeters.
Surprisingly, the sensitivity of the sensor is increased at the contact zone by means of this small radius of curvature.
According to one embodiment of the invention the mechanical compressive strength of the bent part of the second fiber section (25), in the direction in which it is sought to draw together two separate points belonging to the bent part, that is equal to or higher than 1 N.
According to one embodiment of the invention, said at least one bent part has a fiber radius of curvature equal to or less than 1 millimeter.
According to one embodiment of the invention, the first fiber section (23) and the third fiber section are distant from one another by a width of less than 2.8 mm transverse to the length of the fiber and occupy a space of width less than 2.8 mm transverse to the length of the fiber.
According to one embodiment of the invention, the bent part (28) comprises a winding.
According to one embodiment of the invention, the bent part (28) comprises a winding comprising at least one turn,
the bent part of the second fiber section (25) having a mechanical compressive strength, in the direction in which it is sought to draw together two separate points belonging to the bent part, equal to or higher than 1 N per turn.
According to one embodiment of the invention, at least one transverse dimension (D1) of the fiber in the winding is smaller than at least one transverse dimension (D2) of the fiber in the first and third sections.
According to one embodiment of the invention, the second fiber section has a fiber diameter (or thickness D2) of between 50 and 450 micrometers.
According to one embodiment of the invention, on the first, second and third sections (23, 25, 27), the fiber has a thickness of between 50 and 450 micrometers that is constant over these first, second and third sections (23, 25, 27).
According to one embodiment of the invention, the first and third fiber sections are inserted in a protective sheath, the second section projecting at least partly from one end of the sheath and being intended to come into contact with the medium being examined, whether this is solid and/or liquid and/or gaseous.
According to one embodiment of the invention, the first and third fiber sections are inserted in an operative channel of a medical diagnostic device, the second section projecting at least partly from one end of the channel and being intended to come into contact with a tissue or a biological fluid in vivo and/or ex vivo.
According to one embodiment of the invention, the proportion of X by weight is equal to or higher than 10% and equal to or lower than 70%, whilst the proportion of Y by weight is equal to or higher 30% and equal to or lower than 90%.
A second subject of the invention is a method for fabricating a said sensor such as described above, characterized in that
the chalcogenide fiber has a composition of type XY where X is chosen from among Ge, As or Sb or a mixture of two or more than two of these components, and where Y is chosen from among S, Se, Te or a mixture of two or more than two of these components, the chalcogenide fiber having a glass transition temperature Tg, the fiber successively comprising over its length—between two first and second ends of the fiber—the first fiber section, an intermediate part which is to form the second fiber section and the third fiber section,
a core is heated having a contact zone of transverse dimensions smaller than 4.6 millimeters, to a certain temperature, and the intermediate part of the fiber is applied against said contact zone of the core so that the intermediate part in contact with the core zone has a temperature T2 with:
1.05·Tg≦T2≦1.5·Tg,
the intermediate part of the fiber is wound around the contact zone of the core at a winding angle of at least 180° so as to form said bent part in said intermediate part of the fiber thereby forming said second fiber section with a radius of curvature locally smaller than 2.3 millimeters.
According to one embodiment of the invention, the core comprises first and second portions between which said contact zone is located, the core being heated by at least one of the first and second portions.
According to one embodiment of the invention, the core is cylindrical having any cross-section.
According to one embodiment of the invention, the temperature T2 exceeds the glass transition temperature Tg by 10% to 20%.
According to one embodiment of the invention, the intermediate part has a fiber diameter (D2) of between 50 and 450 micrometers.
The invention will be better understood on reading the following description given solely as a non-limiting example with reference to the appended drawings in which:
In the Figures, the sensor 1 comprises a fiber 2 in chalcogenide glass. The fiber has a composition of XY type where X is Ge, As or Sb or a mixture of two or more than two of these components, and where Y is S, Se, Te or a mixture of two or more than two of these components. For example, the proportion of X by weight is equal to or higher than 10% and equal to or lower than 70%, whilst the proportion of Y by weight is equal to or higher than 30% and equal to or lower than 90%. The fiber is used for guiding infrared waves.
In one example of embodiment, the fiber is in As2Se3.
In another example of embodiment, the fiber is in Te2As3Se5.
The fiber 2 of the sensor 1 extends in a general longitudinal direction L between a first end 21 and a second end 22. The fiber 2, from the first end 21 to the second end 22, comprises a first fiber section 23 for guiding infrared waves, this first section 23 being connected on its side distant from the first end 21 to a first point 24 of a second detection section 25, said second section 25 is connected via a second point 26 distant from the first point 24 to a third fiber section 27 for guiding infrared waves.
In one embodiment, the second detection section 25 of the fiber 2 has a transverse width D1 in at least one dimension, a diameter D1 or cross-section D1 which are smaller than the transverse width D2 or diameter D2 or cross-section D2 of the first section 23, and which are smaller than the transverse width D2, the diameter D2 or cross-section D2 of the third section 27. The second detection section 25 of the fiber 2 extends over a nonzero length L1 of the fiber between the first and second connecting points 24, 26 and between the first section 23 and the third section 27.
For example, the fiber 2 has a mean diameter D2 of about 400 micrometers in the first section 23 and in the third section 27, whilst the fiber 2 in the second detection section 25 has a mean diameter D1 of about 100 micrometers for a length L1 of the second detection section of about 10 centimeters. The length of the first section 23 is longer than the length of the second detection section 25. The length of the third section 27 is longer than the length L1 of the second detection section 25.
The first connecting point 24 is formed for example by a zone with cross-section tapering from the first section 23 to the second detection section 25, being of truncated cone shape for example as illustrated in
In another embodiment, the second detection section 25 of the fiber 2 has a transverse width (or thickness) in at least one dimension, a diameter or a cross-section which are equal to the transverse width or the diameter or the cross-section of the first section and/or which are equal to the transverse width (or thickness), the diameter or the cross-section of the third section 27. For example, the fiber 2 has a cross-section and/or diameter that are constant in the first, second and third sections 23, 25 and 27.
In one embodiment the fiber—on the first, second and third sections 23, 25 and 27—has a fiber diameter (or thickness) for example of between 50 and 450 micrometers.
For example in one embodiment—on the first, second and third sections 23, 25 and 27—the fiber has a diameter (or thickness) of between 50 and 450 micrometers that is constant on these first, second and third sections 23, 25 and 27.
The second detection section 25 is intended to come into contact with an outside medium to detect the perturbations caused by this outside medium to the propagation of infrared waves in the fiber 2, and forms a detection head of the sensor. The first and second sections 23, 27 are sections conveying infrared waves.
When an outside medium is contacted with the second detection section 25, the propagation of the wave O in this second section 25 is perturbed since part of the wave O passes from the second section 25 towards the outside medium.
As a result, the contacting of the second detection section 25 with an outside medium will have an influence on the wave O which is transmitted from the first section 23 to the third section 27.
According to the invention, the second detection section 25 comprises at least one bent fiber part 28 having a fiber radius of curvature smaller than 2.3 millimeters.
The bent part 28 is in the form of a winding for example having one or more turns, or may be of solenoid shape for example. In another example the bent part 28 may be U-shaped. The second section is in the form of an open loop for example. Evidently it is possible to have any number of bent parts 28 e.g. n open loops of any geometry, n≧1.
In
For example, after bending, the sections 23 and 27 face one another. For example, the sections 23 and 27 are parallel to each other.
For example, the radius of curvature of the bent part 28 of the second section 25 is equal to or smaller than 1.4 mm, and in particular equal to or smaller than 1 mm.
For example, in the embodiments shown in the Figures, the first fiber section 23 and the third fiber section 25 are spaced apart by a width of less than 2.8 mm transverse to the length of the fiber and occupy a space of width smaller than 2.8 mm transverse to the length of the fiber.
Some embodiments of the second section 25 are illustrated in
In the embodiments shown
In the embodiment shown
In the embodiment illustrated
Provision could also be made for single helical turn, or one and a half helical turns 29.
In the embodiment illustrated
In the embodiment illustrated
A method for obtaining the bent part 28 in the second detection section 25 shown
The tapering 24, 26 is optional when forming the head 28. To fabricate the sensor 1 of the invention, a chalcogenide glass fiber is drawn to a determined mean diameter e.g. 400 micrometers to form the first and third sections 23, 27. The second section 25 having a smaller transverse width than the sections 23, 27 in at least one dimension is formed for example by accelerating the rate of drawing, by chemical attack with a sulfuric acid solution and hydrogen peroxide or by hot crushing at a temperature of Tg+15%, Tg being the glass transition temperature of the material of the fiber 2. For example a section 25 is obtained able to be reduced to less than 100 micrometers in at least one transverse dimension.
The glass transition temperature Tg is measured by differential calorimetric analysis with a temperature rise of 10° C. per minute.
The fiber 2 then extends in the longitudinal direction L as shown
The section 25 is then bent by hot forming. To do so, the section 25 of fiber 2 is applied against a heated core 50 so that the intermediate part 25 which is placed in contact with the core 50 is at a temperature T2 such that:
1.05·Tg≦T2≦1.5·Tg,
and in particular
1.1·Tg≦T2≦1.219 Tg.
In one example of embodiment, the glass transition temperature Tg is exceeded by 10% to 15% to heat the section 25 which is to be bent.
The contact zone 53 of the core 50 against which the section 25 is applied has transverse dimensions (e.g. diameter) of less than 4.6 mm for the winding of the section 25 in accordance with the radius of curvature imposed by this contact zone 53. For example, the contact zone 53 of the core 50 has transverse dimensions (e.g. diameter) equal to or less than 2.4 mm, and for example equal to or less than 2 mm. The transverse dimensions or diameter of the zone 53 around which the section 25 of the fiber 2 is wound are between 1.5 and 4 mm for example.
In general for the chalcogenide glass used, the glass transition temperature Tg is equal to or higher than 90° C., and equal to or lower than 400° C.
The heating of the core 50 takes place for example in two first and second portions 51, 52 thereof, between which there is a third contact zone 53 against which the intermediate section 25 of the fiber 2 is applied. The heating of this third zone 53 takes place by thermal conduction for example from the portions 51, 52, the core being metallic for example, means for heating the core 50 being provided. The core 50 is of oblong shape for example between the portions 51, 52. At least in its contact zone 53, or entirely, the core 50 is of cylindrical shape for example, in particular circular cylindrical. Evidently, the core 50 could solely be heated from only one of the two portions 51, 52.
To achieve bending, the intermediate section 25 is applied against the core 50 thus heated and having the desired radius of curvature. This core is in stainless steel for example and is of circular cross-section for example to form a circular winding in the section 25. In this manner, the section 25 is wound in controlled manner around the heated core 50 to form the bent part, for example by one or more turns of the winding 28 i.e. turning by at least 360° around the core 50, the bent part 28 therefore being bent with the radius of curvature of the core 50.
The section 25 is then cooled in controlled manner, for example at 2° C. per minute and the core 50 is then removed.
In this manner, several bent parts 28 were fabricated formed of a winding having between one and five turns plus one half turn according to
Therefore it is the core 50—around which the fiber is wound—that is heated to transmit its heat to the fiber. This provides a chalcogenide fiber sensor having better mechanical strength in the bent part 28 since the inner surface 283 of the bent part 28 which has been heated undergoes annealing via this localized heating.
The hot forming obtained by this localized heating via the core 50 reinforces the mechanical strength of the chalcogenide fiber sensor significantly by removing the residual stresses generated during the bending of the fiber. For example, the inventors have determined a strength value of 4 Newtons for a bent part 28 with three turns having a fiber diameter of 200 μm and a radius of curvature of 1 mm as in
In one embodiment, the heated core 50 around which the fiber is wound comprises a core in copper or stainless steel coated with a layer of Teflon to prevent the fiber from adhering to the core 50. In general, the core 50 in a first metal material is coated with an outer layer in a different second material which is anti-adhesive for the fiber e.g. Teflon.
The manner used to measure the mechanical strength of the bent part 28 of the chalogenide fiber according to the invention is the same as illustrated in
In
For example in
In the comparative example in
A mechanical compressive strength was measured of F=0.03 N as shown in
The sensor of the invention therefore intrinsically has a greater mechanical strength than the bent fibers of the prior art in chalcogenide.
Chalcogenide fibers of the prior art are effectively known to break easily on account of their composition.
The detection head formed by the bent part 28 of the invention is more resistant and more rigid, which allows better contact with the substrate being examined. For example, the good mechanical strength of the bent part 28 allows easy handling of the sensor, in particular for its insertion into any suitable sheath or tube or more generally in any suitable box or casing for use thereof, and also allows the bent part 28 forming the detection head to be applied and abutted with some force against a substrate of solid consistency that is to be examined to ensure that the detection part 25 is in contact with this substrate, such as a body organ or part of a living human or living animal body.
In general, the bent part 28 may have any number of n+½ turns 29 where n is a natural integer equal to or more than zero, to cause the first and third sections 23 and 27 to face one another being substantially parallel for example.
In
With this detection method it is possible for example on a sample 30 to evidence metabolic anomalies which reflect a pathological condition in a serum or in hepatic biopsies, or a bacterial contamination of an organic medium.
The spectrometer 101 emits in the mid-infrared. The spectrometer comprises a spectra analysis algorithm of the sent signal and of the received signal. The sent signal may also be in the far infrared. The outside medium with which the intermediate detection section 25 is placed in contact may be solid, liquid or gaseous.
For example, the first fiber section 23 and the third fiber section 27 are spaced apart by a width of less than twice the maximum radius of curvature of the winding 28 transverse to the length of the fiber and occupy a space having a width of less than twice the maximum radius of curvature of the winding 28 transverse to the length of the fiber.
In the embodiments shown
The sections 23 and 27 are parallel for example. The sensor 1 extends globally between a first side 10 where the first and second ends 21, 22 are positioned, and a second side 11 where the second detection section 25 is positioned, the fiber following an outward pathway from the first side 10 to the second side 11 via the first section 23, then a return pathway from the second side 11 to the first side 10 via the third section 27. Evidently, the first or second end 21, 22 may project beyond the first side 10.
In the embodiment illustrated
The body 41 and the conduit 42 extend as far as a detection end 43. The second detection section 25 projects at least partly, for example fully as shown in
The sensor 1 described above can be inserted in the operating channel of a medical device so that the detection head 28 is in contact with a medium or biological tissue which may be solid or liquid for example, in vivo or in vitro. For example it may be inserted in a catheter, in a medical diagnosis device, inside a living being or against a living being (e.g. the skin), in a medical analysis device (e.g. in vitro blood analysis).
The sensor 1 may also be used to detect the presence in the outside medium of one or more chemical substances having an infrared signature in the spectrum of the fiber ranging from 0.8 to 25 micrometers, or to measure the quantity of such substances in the outside medium.
A test was performed on the sensor 1 in
It can be seen that the curve C3 has very high absorbency compared with the curves C1 and C2. The peak P at about 9.5 micrometers corresponds to a spectral ray of the ethanol which is therefore better detected by the sensor of the invention having the detection section 25.
By means of the high sensitivity of the detection head 28 of the invention, it is possible to detect molecular signatures in the infrared in the outside medium with which this head 28 is placed in contact, and in particular to detect the presence of molecules in smaller quantities for one same molecular formula but also a higher number of molecules having different molecular formulas.
Number | Date | Country | Kind |
---|---|---|---|
10 52457 | Apr 2010 | FR | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/EP2011/055038 | 3/31/2011 | WO | 00 | 12/12/2012 |