Description

GUIDED MODE RESONANCE FILTER INCLUDING HIGH REFRACTIVE INDEX ORGANIC MATERIAL AND OPTICAL BIOSENSOR INCLUDING THE GUIDED MODE RESONANCE

FILTER

Technical Field

[1] The present invention relates to a guided mode resonance filter and an optical biosensor including the same, and more particularly, to a guided mode resonance filter used to measure a change in the wavelength of light according to the interactions or deformation of biological materials, and an optical biosensor including the guided mode resonance filter. This work was supported by the IT R&D program of MIC/IITA. [2006-S-007-01, Ubiquitous Health Monitoring Module and System Development] Background Art

[2] Optical biosensors have been widely used to detect biological materials such as proteins, DNAs, hormones, and enzymes. Optical biosensors including a guided mode resonance filter use peaks of a reflection spectrum of a diffraction grating that can act as a high refractive index waveguide. The reflection spectrum, which is produced when there is coupling between light diffracted by the diffraction grating and a mode guided by the high refractive index waveguide, has a narrow linewidth, thereby enabling the optical biosensors to have high sensitivity.

[3] Conventional guided mode resonance filters include a nanometer- sized diffraction grating formed by E-beam lithography or imprinting that transfers a nano pattern using a stamp. The conventional guided mode resonance filters are manufactured by forming, on a transparent substrate, an inorganic layer having a refractive index which is higher than that of the transparent substrate, to form a diffraction grating and then by dry or wet-patterning the high refractive index inorganic layer, or by dry or wet- etching the substrate, forming a nano pattern on the substrate, and forming on the substrate an inorganic layer having a refractive index higher than that of the substrate. Alternatively, the conventional guided mode resonance filters are manufactured by forming an organic nano pattern on a substrate using a stamp formed of silicon or quartz to form a diffraction grating using imprinting. However, an organic material used to form the diffraction grating by the imprinting in the conventional guided mode resonance filters has a low refractive index, thereby failing to satisfy the resonance conditions for high sensitivity biosensors. Accordingly, a separate deposition process of forming an inorganic thin film having a high refractive index on the diffraction grating formed by the imprinting is required.

Disclosure of Invention Technical Problem

[4] As described above, the conventional guided mode resonance filters must be subjected to the separate process of forming the inorganic thin film to provide a refractive index high enough to satisfy the resonance conditions. The inorganic thin film exposed on a surface of the diffraction grating has a poor affinity for biological materials. Accordingly, in order to bind biological materials to the inorganic thin film, a separate modification process of introducing specific reactive groups on a surface of the inorganic thin film is also required. Hence, the conventional guided mode resonance filters are complex, expensive, and time consuming to manufacture, and there are limits to realizing stable biosensors. Technical Solution

[5] The present invention provides a guided mode resonance filter having a high affinity for biological materials, which can specifically bind to a target material, and providing a refractive index high enough to satisfy desired diffraction conditions such that, when being applied in an optical biosensor, the guided mode resonance filter can accurately measure a change in the wavelength of resonant light according to the interactions or deformation of the biological materials.

[6] The present invention also provides an optical biosensor including a guided mode resonance filter, which has a high affinity for biological materials and provides a refractive index high enough to satisfy desired resonance conditions such that the optical biosensor can detect a target material with high sensitivity and can be simply manufactured at low cost.

[7] According to an aspect of the present invention, there is provided a guided mode resonance filter comprising: a substrate; a diffraction grating formed on the substrate; and an organic layer exposed at a top surface of the diffraction grating which is opposite to a surface of the diffraction grating that faces the substrate.

[8] The organic layer may constitute at least a part of the diffraction grating and may be formed of an organic material having a refractive index of 1.4 to 2.5. The substrate may be formed of one selected from the group consisting of a semiconductor, glass, quartz, and polymer film.

[9] The organic layer may be a separate high refractive index organic thin film covering the top surface of the diffraction grating. The diffraction grating may be formed of an organic material or an inorganic material. The high refractive index organic thin film may be formed of an organic material having a refractive index of 1.4 to 2.5. The high refractive index organic thin film may include an organic thin film formed of an organic material, and a plurality of inorganic nanodots dispersed in the organic thin

film. Each of the plurality of inorganic nanodots may be formed of one selected from the group consisting of an oxide, a nitride, and a combination thereof.

[10] According to another aspect of the present invention, there is provided an optical biosensor comprising: a guided mode resonance filter comprising: a substrate; a diffraction grating formed on the substrate; and an organic layer exposed at a top surface of the diffraction grating which is opposite to a surface of the diffraction grating that faces the substrate; antibodies specifically bindable to antigens included in a target sample and directly adsorbed or bound to the organic layer of the guided mode resonance filter; a light source emitting light to the guided mode resonance filter; a reflected light detector detecting light reflected by the guided mode resonance filter; a transmitted light detector detecting light transmitted through the guided mode resonance filter of light emitted by the light source; and a micro lens directing light from the light source to the guided mode resonance filter and reflecting light reflected by the guided mode resonance filter to the reflected light detector.

[11] The optical biosensor may further comprise blocks formed on the organic layer of the guided mode resonance filter to prevent nonspecific interactions and binding between the antibodies or the antigens and the exposed organic layer. Advantageous Effects

[12] According to another aspect of the present invention, the organic layer formed of the organic material having a high refractive index, or the organic thin film formed of the organic material and having dispersed therein the plurality of inorganic nanodots each having a high refractive index is exposed at the top surface of the diffraction grating of the guided mode resonance filter. Accordingly, biological materials can be adsorbed or bound to the organic layer with a high affinity.

[13] The optical biosensor can be simply manufactured at low cost. Since the biological materials are bound to the guided mode resonance filter with a high affinity, the detection efficiency of the optical biosensor can be improved. Description of Drawings

[14] The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which:

[15] FIG. 1 is a cross-sectional view of a guided mode resonance filter according to an embodiment of the present invention;

[16] FIG. 2 is a cross-sectional view of a guided mode resonance filter according to another embodiment of the present invention;

[17] FIG. 3 is a cross-sectional view of a guided mode resonance filter according to another embodiment of the present invention;

[18] FIG. 4 is a cross-sectional view of a guided mode resonance filter according to another embodiment of the present invention; and

[19] FIG. 5 is a cross-sectional view of an optical biosensor according to an embodiment of the present invention. Best Mode

[20] The present invention will now be described more fully with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown.

[21] FIG. 1 is a cross-sectional view of a guided mode resonance filter 100 according to an embodiment of the present invention.

[22] Referring to FIG. 1, the guided mode resonance filter 100 includes a substrate 110, and a high refractive index organic diffraction grating 120 formed on the substrate 110.

[23] The high refractive index organic diffraction grating 120 may be formed of an organic material having a refractive index of approximately 1.4 to 2.5. In particular, the high refractive index organic diffraction grating 120 may be formed of a material having an average transmittance of 50 % or more at a wavelength of 400 to 900 nm. For example, the high refractive index organic diffraction grating 120 may be formed of a (meth)acrylate based polymer or an acetylene based polymer.

[24] The substrate 110 may be a semiconductor, glass, quartz, or a transparent substrate formed of polymer film.

[25] The high refractive index organic diffraction grating 120 may be formed on the substrate 110 by coating an organic material on a surface of the substrate 110 using a wet process, such as spin coating or dipping, to form an organic thin film having a predetermined thickness and etching the organic thin using photolithography or forming recesses using nanoimprinting.

[26] Light diffracted by the diffraction grating 120 of the guided mode resonance filter

100 is guided by a high refractive index waveguide to form a resonance spectrum. The grating period of the diffraction grating 120 may be less than the average wavelength of light emitted to the guided mode resonance filter 100.

[27] Since the high refractive index organic diffraction grating 120 formed of an organic material is exposed at a top surface of the guided mode resonance filter 100, biological materials can be adsorbed or bound to the high refractive index organic diffraction grating 120 with a high affinity without requiring a separate process such as complex surface treatment or vacuum deposition. If necessary, the exposed high refractive index organic diffraction grating 120 may be subjected to oxygen plasma treatment or surface treatment using an acid solution, such as a sulphuric acid, to make the biological materials more easily adsorbed or bound to the high refractive index organic diffraction grating 120.

Mode for Invention

[28] FIG. 2 is a cross-sectional view of a guided mode resonance filter 200 according to another embodiment of the present invention. [29] Referring to FIG. 2, the guided mode resonance filter 200 includes a substrate 210, and an organic diffraction grating 220 formed on the substrate 210. [30] The organic diffraction grating 120 includes an organic diffractive thin film 222, and a plurality of inorganic nanodots 224 dispersed in the organic diffractive thin film 222. [31] The organic diffractive thin film 222 may be formed of a (meth)acrylate based polymer substituted or not substituted with a fluorine atom, or an acetylene based polymer substituted or not substituted with a fluorine atom. [32] Each of the plurality of inorganic nanodots 224 may have a particle size of 1 to 200 nm. The plurality of inorganic nanodots 224 may be formed of an oxide, a nitride, or a combination thereof. For example, each of the plurality of inorganic nanodots 224 may be formed of one selected from the group consisting of SiO , TiO , InSnO, ZnO, SnO , NiO, Cu SrO , Si N , GaN, and In N or a combination thereof.

2 2 2 3 4 3 2

[33] The organic diffraction grating 220 may be formed on the substrate 210 by coating an organic solution in which the inorganic nanodots 224 are dispersed on a surface of the substrate 210 using a wet process, such as spin coating or dipping, to form an organic thin film having a predetermined thickness in which the inorganic nanodots 224 are dispersed and etching the organic thin film using photolithography or forming recesses using nanoimprinting.

[34] Each of the plurality of inorganic nanodots 224 may consist of inorganic atoms included in an organic compound constituting the organic diffractive thin film 222. In this case, the organic diffraction grating 220 may be formed by coating the organic compound including the inorganic atoms on the substrate 210 to form an organic thin film in which the inorganic atoms are dispersed and etching the organic thin film using photolithography or forming recesses using nanoimprinting.

[35] Since the guided mode resonance filter 200 includes the organic diffraction grating

220 including the organic diffractive thin film 222 and the plurality of inorganic nanodots 224 dispersed in the organic diffractive thin film 222, the organic diffractive thin film 222 formed of the organic material is exposed at a top surface of the guided mode resonance filter 200. Accordingly, biological materials can be adsorbed or bound to the organic diffractive thin film 222 with a high affinity. If necessary, the exposed organic diffraction grating 220 may be subjected to oxygen plasma treatment or surface treatment using an acid solution, such as, sulfuric acid to make the biological materials more easily adsorbed or bound to the organic diffractive thin film 222.

[36] The substrate 210 is the same as the substrate 110 described with reference to FIG. 1.

[37] FIG. 3 is a cross-sectional view of a guided mode resonance filter 300 according to

another embodiment of the present invention.

[38] Referring to FIG. 3, the guided mode resonance filter 300 includes a substrate 310, a diffraction grating 320 formed on the substrate 310, and a high refractive index organic thin film 330 formed on the diffraction grating 320.

[39] The diffraction grating 320 may be formed of an organic material or an inorganic material. For example, the diffraction grating 320 may be formed of a (meth)acrylate based polymer substituted or not substituted with a fluorine atom or an acetylene based polymer substituted or not substituted with a fluorine atom . Alternatively, the diffraction grating 320 may be formed of an inorganic material such as SiO , Si N , or TiO 2 .

[40] The diffraction grating 320 may be formed in a similar manner to the high refractive index organic diffraction grating 120 described with reference to FIG. 1.

[41] The high refractive index organic thin film 330 may be formed of an organic material having a refractive index of approximately 1.4 to 2.5. In particular, the high refractive index organic thin film 330 may be formed of a material having an average transmittance of 50 % or more at a wavelength of 400 to 900 nm. For example, the high refractive index organic thin film 330 may be formed of an organic material including a (meth)acrylate based polymer or an acetylene based polymer.

[42] The high refractive index organic thin film 330 may be formed on the diffraction grating 320 by a wet process such as spin coating or dipping.

[43] Since the high refractive index organic thin film 330 is formed on the diffraction grating 320 of the guided mode resonance filter 300, the high refractive index organic thin film 330 formed of the organic material is exposed at a top surface of the guided mode resonance filter 300. Accordingly, biological materials can be adsorbed or bound to the high refractive index organic thin film 330 with a high affinity. If necessary, the exposed high refractive index organic thin film 330 may be subjected to oxygen plasma treatment, or surface treatment using an acid solution, such as sulfuric acid, to make the biological materials more easily adsorbed or bound to the high refractive index organic thin film 330.

[44] The substrate 310 is the same as the substrate 110 described with reference to FIG. 1.

[45] FIG. 4 is a cross-sectional view of a guided mode resonance filter 400 according to another embodiment of the present invention.

[46] Referring to FIG. 4, the guided mode resonance filter 400 includes a substrate 410, a diffraction grating 420 formed on the substrate 410, and a high refractive index thin film 430 formed on the diffraction grating 420.

[47] The diffraction grating 420 may be formed of an organic material or an inorganic material. For example, the diffraction grating 420 may be formed of an organic material including a (meth)acrylate based polymer substituted or not substituted with a

fluorine atom or an acetylene based polymer substituted or not substituted with a fluorine atom. Alternatively, the diffraction grating 420 may be formed of an inorganic material such as SiO , Si N , or TiO .

2 3 4 2

[48] The diffraction grating 420 may be formed on the substrate 410 in a similar manner to the high refractive index organic diffraction grating 120 described with reference to FIG. 1.

[49] The high refractive index thin film 430 includes an organic thin film 432 and a plurality of inorganic nanodots 434 dispersed in the organic thin film 432.

[50] The organic thin film 432 may be formed of an organic material including a

(meth)acrylate based polymer substituted or not substituted with a fluorine atom or an acetylene based polymer substituted or not substituted with a fluorine atom.

[51] Each of the plurality of inorganic nanodots 434 may have a particle size of approximately 1 to 200 nm. Each of the plurality of inorganic nanodots 434 may be formed of an oxide, a nitride, or a combination thereof. For example, each of the plurality of inorganic nanodots 434 may be formed of one selected from the group consisting of SiO 2 , TiO2 , InSnO, ZnO, SnO 2 , NiO, Cu 2 SrO2 , Si3 N4 , GaN, and In

N , or a combination thereof.

[52] The high refractive index thin film 430 may be formed on the diffraction grating 420 by coating an organic solution in which the inorganic nanodots 434 are dispersed on a surface of the diffraction grating 420 using a wet process such as spin coating or dipping.

[53] Alternatively, the plurality of inorganic nanodots 434 may consist of inorganic atoms included in an organic compound constituting the organic thin film 432. In this case, the high refractive index thin film 430 may be formed by coating the organic compound including the inorganic atoms on the diffraction grating 420.

[54] Alternatively, the high refractive index thin film 430 may be formed by making the organic compound including the inorganic atoms self-assembled on a surface of the diffraction grating 420.

[55] Since the guided mode resonance filter 400 includes the high refractive index thin film 430 including the organic thin film 432 and the plurality of inorganic nanodots 434 dispersed in the organic thin film 432, the organic thin film 432 formed of the organic material is exposed at a top surface of the guided mode resonance filter 400. Accordingly, biological materials can be adsorbed or bound to the organic thin film 432 with a high affinity. If necessary, the exposed high refractive index thin film 430 may be subjected to oxygen plasma treatment, or surface treatment using an acid solution, such as sulfuric acid, to make the biological materials more easily adsorbed or bound to the organic thin film 432.

[56] The substrate 410 is the same as the substrate 110 described with reference to FIG. 1.

[57] In the guided mode resonance filters 100, 200, 300, and 400, the diffraction gratings

120, 220, 320, and 420 or the high refractive index thin films 330 and 430 formed on the diffraction gratings 320 and 420 are formed of organic materials or organic materials including inorganic nanodots. Accordingly, when the guided mode resonance filters 100, 200, 300, and 400 are applied to optical biosensors, an affinity for biological materials which can specifically bind to a target material can be enhanced and detection efficiency can be improved.

[58] FIG. 5 is a cross-sectional view of an optical biosensor 500 according to an embodiment of the present invention.

[59] Referring to FIG. 5, the optical biosensor 500 includes a guided mode resonance filter 510.

[60] The guided mode resonance filter 510 may be any one of the guided mode resonance filters 100, 200, 300, and 400 described with references to FIGS. 1 through 4. In FIG. 5, the guided mode resonance filter 510 has the same construction as that of the guided mode resonance filter 400 of FIG. 4. However, the present embodiment is not limited thereto, and the guided mode resonance filter 510 may have various other constructions within the scope of the present invention. A detailed explanation of the guided mode resonance filter 510 will not be given and for details of the guided mode resonance filter 510, refer to the guided mode resonance filters 100, 200, 300, and 400 of FIGS. 1 through 4.

[61] Antibodies 502, which can specifically bind to antigens 600 included in a target sample (not shown), are directly adsorbed or bound to an organic layer of the guided mode resonance filter 510 of the optical biosensor 500. The optical biosensor 500 may further include blocks 610 formed on the organic layer of the guided mode resonance filter 510 to prevent the antibodies 502 or the antigens 600 from nonspecifically binding to an exposed surface of the organic layer.

[62] While the organic layer of the guided mode resonance filter 510 is the high refractive index thin film 430 formed on the diffraction grating 420 in FIG. 5, the present embodiment is not limited thereto, and various modifications can be made. For example, the organic layer of the guided mode resonance filter 510 may have the same construction as that of the high refractive index organic diffraction grating 120 of FIG. 1, the organic diffraction grating 220 of FIG. 2, or the high refractive index organic thin film 330 of FIG. 3.

[63] The optical biosensor 500 includes a light source 512 emitting light to the guided mode resonance filter 510, a reflected light detector 514 detecting light reflected by the guided mode resonance filter 510, and a transmitted light detector 516 detecting light emitted by the light source 512 and transmitted through the guided mode resonance filter 510. The light source 512 may be a white light source or a laser light source

having a specific wavelength. A micro lens 518 is disposed between the guided mode resonance filter 510 and the reflected light detector 514 to direct light from the light source 512 to the guided mode resonance filter 510 and reflect light reflected by the guided mode resonance filter 510 to the reflected light detector 514.

[64] The operation of the optical biosensor 500 of FIG. 5 will now be explained.

[65] When the blocks 610 are adsorbed or bound to the high refractive index thin film 430 formed on the diffraction grating 420 of the guided mode resonance filter 510 to prevent nonspecific interactions and binding between the antibodies 502 and particular biological materials, the test sample is applied to the guided mode resonance filter 510. When the antibodies 502, which can specifically bind to the antigens 600, exist in the test sample, the antibodies 502 specifically bind to the antigens 600, thereby changing the optical refractive index of the guided mode resonance filter 510. In order to detect a change in the resonance wavelength of the guided mode resonance filter 510 when the refractive index is changed, the transmitted light detector 516 detecting light transmitted through the guided mode resonance filter 510 or the reflected light detector 514 detecting light reflected by the guided mode resonance filter 510 is used. That is, light emitted by the light source 512 fixed to a fixing unit 700 is transmitted through or reflected by the guided mode resonance filter 510 via the micro lens 518. The transmitted or reflected light is detected by the transmitted light detector 516 or the reflected light detector 514. Each of the transmitted light detector 516 and the reflected light detector 514 may be a photodetector, or a spectrometer measuring a spectrum.

[66] The optical biosensor 500 constructed as described above can act as a biosensor when biological materials, such as proteins, DNAs, hormones, or enzymes, are adsorbed or bound to the high refractive index thin film 430 formed of the organic material on the diffraction grating 420 of the guided mode resonance filter 510.

[67] If necessary, the surface of the high refractive index thin film 430 formed of the organic material on the diffraction grating 420 may be subjected to oxygen plasma treatment to make the biological materials more easily adsorbed or bound to the high refractive index thin film 430 by applying a radio frequency (RF) power less than 100 W using O , Ar, and N . Alternatively, the surface of the high refractive index thin film 430 may be subjected to surface treatment using an acid or alkaline solution to form reactive groups, such as -OH groups, on the surface of the high refractive index thin film 430. A solution used to form the reactive groups on the surface of the organic layer may be an acid solution, such as H SO , HF, HNO , HCl, or H PO , or an alkaline solution, such as NaOH, KOH, Ca(OH) , NH OH.

[68] Although the optical biosensor 500 has been described above, the present embodiment is not limited thereto, and various modifications can be made within the scope of claims, the detailed description, and drawings. For example, while the

diffraction grating of the guided mode resonance filter or the high refractive index thin film formed on the diffraction grating are formed of the organic material, the present embodiment is not limited thereto. As long as an organic layer is exposed at a top surface opposite to the substrate, that is, as long as antibodies, which can specifically bind to antigens included in a target sample, can be adsorbed or bound to the organic layer, various modifications in construction can be made within the scope of the present invention. Industrial Applicability

[69] The optical biosensor can be simply manufactured at low cost. Since the biological materials are bound to the guided mode resonance filter with a high affinity, the detection efficiency of the optical biosensor can be improved.