FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
BIOLOGICAL MATERIAL MEASUREMENT DEVICE
MITSUBISHI ELECTRIC CORPORATION, A CORPORATION ORGANISED AND
EXISTING UNDER THE LAWS OF JAPAN, WHOSE ADDRESS IS 7-3,
MARUNOUCHI 2-CHOME, CHIYODA-KU, TOKYO 100-8310, JAPAN
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE
INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.
2
DESCRIPTION
TECHNICAL FIELD
[0001]
The present invention relates to a biological 5 material
measurement device and, more particularly, to a biological
material measurement device measuring a biological material
such as sugar existing in a living body by using an infrared
light.
10 BACKGROUND ART
[0002]
Biological material measurement devices measuring
components of material in a living body such as blood sugar
include invasive devices using puncture or blood collection and
15 non-invasive devices not using puncture or blood collection.
A blood sugar level measurement device (blood sugar level sensor)
used on a daily basis is desirably a non-invasive measurement
device because of alleviation of patient discomfort. A
non-invasive blood sugar level measurement device is possibly
20 a sensor using an infrared light enabling detection of a
fingerprint spectrum of sugar. For example, Patent Document 1
discloses a blood sugar level sensor reflecting an infrared light
multiple times in a prism to improve an attenuation rate of
infrared light due to surface plasmon resonance and thereby
25 improving the sensitivity of the sensor (see, e.g., [0057]).
PRIOR ART DOCUMENT
PATENT DOCUMENT
3
[0003]
Patent Document 1: Japanese Laid-Open Patent Publication
No. 2012-070907
SUMMARY OF THE INVENTION
PROBLEM TO BE SOLVED 5 BY THE INVENTION
[0004]
However, infrared light is absorbed in a large amount by
water in the skin and therefore can only reach a skin surface.
Therefore, in the conventional technique, the effect of infrared
10 light absorption by sugar such as glucose inside the skin cannot
significantly be distinguished from the effect of infrared light
absorption by water, and a good signal-to-noise ratio (SN ratio)
cannot be obtained. Therefore, the blood sugar level cannot
stably and accurately be measured.
15 [0005]
Therefore, an object of the present invention is to provide
a non-invasive biological material measurement device capable
of stably and accurately measuring an amount of a biological
material.
20 MEANS FOR SOLVING PROBLEM
[0006]
An aspect of the present invention provides a biological
material measurement device comprising: a first light source
emitting a first light; an ATR prism including a front surface
25 and a back surface and allowing the first light made incident
from one end to be transmitted therethrough and emitted from
the other end; a hyperbolic metamaterial layer including a front
4
surface and a back surface and arranged on the front surface
of the ATR prism such that the back surface of the hyperbolic
metamaterial layer is in contact therewith; and a first light
detector detecting the first light emitted from the ATR prism,
wherein an amount of a biological material in 5 a living body is
measured from the detected first light.
EFFECT OF THE INVENTION
[0007]
The present invention can provide the non-invasive
10 biological material measurement device capable of stably and
accurately measuring an amount of a biological material.
BRIEF DESCRIPTION OF DRAWINGS
[0008]
Fig. 1 is a schematic diagram showing an example of use
15 of a non-invasive blood sugar level measurement device according
to a first embodiment of the present invention.
Fig. 2 is a schematic diagram showing a configuration of
the non-invasive blood sugar level measurement device according
to the first embodiment of the present invention.
20 Fig. 3 is a schematic cross-sectional view of an example
of a hyperbolic metamaterial of the non-invasive blood sugar
level measurement device according to the first embodiment of
the present invention.
Fig. 4 is a schematic cross-sectional view of another
25 example of the hyperbolic metamaterial of the non-invasive blood
sugar level measurement device according to the first embodiment
of the present invention.
5
Fig. 5a is a schematic top view of yet another example of
the hyperbolic metamaterial of the non-invasive blood sugar
level measurement device according to the first embodiment of
the present invention.
Fig. 5b is a perspective view showing 5 the hyperbolic
metamaterial of Fig. 5a.
Fig. 5c is a partial cross-sectional perspective view of
the hyperbolic metamaterial of Fig. 5b.
Fig. 6 is a schematic top view of still another example
10 of the hyperbolic metamaterial of the non-invasive blood sugar
level measurement device according to the first embodiment of
the present invention.
Fig. 7 is a diagram showing a dispersion relationship of
an ordinary material when a vertical axis is kz and a horizontal
15 axis is kx.
Fig. 8 is a diagram showing a dispersion relationship of
the hyperbolic metamaterial when the vertical axis is kz and the
horizontal axis is kx.
Fig. 9 is a schematic diagram showing optical paths of an
20 infrared light and an evanescent wave traveling through an ATR
prism, the hyperbolic metamaterial, and the skin.
Fig. 10 is a diagram showing an infrared light absorption
spectrum of sugar.
Fig. 11 is a perspective view showing a configuration
25 example of an infrared light detector of the non-invasive blood
sugar level measurement device according to the first embodiment
of the present invention.
6
Fig. 12 is a top view of an optical element of the infrared
light detector of the non-invasive blood sugar level measurement
device according to the first embodiment of the present
invention.
Fig. 13 is a cross-sectional view of the 5 optical element
of Fig. 12 as viewed in a direction X-X.
Fig. 14 is a perspective view showing an absorber of the
optical element of the infrared light detector of the
non-invasive blood sugar level measurement device according to
10 the first embodiment of the present invention.
Fig. 15 is a schematic diagram showing a configuration of
a non-invasive blood sugar level measurement device according
to a second embodiment of the present invention.
Fig. 16 is a schematic diagram showing a configuration of
15 a non-invasive blood sugar level measurement device according
to a first modification of the second embodiment of the present
invention.
Fig. 17 is a schematic diagram showing a configuration of
a non-invasive blood sugar level measurement device according
20 to a second modification of the second embodiment of the present
invention.
MODES FOR CARRYING OUT THE INVENTION
[0009]
A biological material measurement device according to an
25 embodiment of the present invention will now be described with
reference to the drawings. In each embodiment, the same
constituent elements are denoted by the same reference numerals
7
and will not be described.
[0010]
First Embodiment
Fig. 1 is a schematic diagram showing an example of use
of a non-invasive blood sugar level measurement 5 device generally
denoted by 80 according to a first embodiment of the present
invention. A head (distal end) 80a of the non-invasive blood
sugar level measurement device 80 is brought into contact with
a skin of a subject to measure a blood sugar level of the subject.
10 The skin brought into contact with the head 80a of the
non-invasive blood sugar level measurement device 80 is
desirably a lip with thin keratin; however, the present invention
is not limited thereto, and the skin may be that of a cheek,
an earlobe, or a back of a hand, for example.
15 [0011]
Fig. 2 is a schematic diagram showing a configuration of
the non-invasive blood sugar level measurement device 80
according to the first embodiment of the present invention. The
non-invasive blood sugar level measurement device 80 includes
20 an infrared light source 32 emitting an infrared light having
a whole or a part of an absorption wavelength region of a
biological material (8.5 μm to 10 μm), an ATR prism 20 through
which the infrared light emitted from the infrared light source
32 is transmitted, and an infrared light detector 30 detecting
25 the intensity of the infrared light emitted from the ATR prism
20. The non-invasive blood sugar level measurement device 80
further includes a hyperbolic metamaterial 90 formed on the head
8
80a of the non-invasive blood sugar level measurement device
80. In other words, the hyperbolic metamaterial 90 is formed
on the ATR prism 20.
[0012]
The infrared light source 32 is a quantum 5 cascade laser
module, for example. The quantum cascade laser is a single light
source and has a large output and a high SN ratio, therefore
enabling highly accurate measurement. The quantum cascade
laser module is equipped with a lens for collimating a beam.
10 [0013]
The infrared light emitted from the infrared light source
32 is incident on the ATR prism 20. The incident infrared light
is transmitted through the ATR prism 20 while being repeatedly
totally reflected and is subsequently emitted from the ATR prism
15 20. Therefore, schematically, the infrared light emitted from
the infrared light source 32 is reflected by an end surface 20c
of the ATR prism 20. The reflected infrared light is transmitted
inside the ATR prism 20 and reflected by an end surface 20b,
is then transmitted inside the ATR prism 20 to reach an end
20 surface 20a, is transmitted through the hyperbolic metamaterial
90 and reflected by a surface (distal end surface) of the
hyperbolic metamaterial 90 in contact with a skin 49 of the
subject, and is then transmitted inside the hyperbolic
metamaterial 90 and inside the ATR prism 20 and reflected by
25 the end surface 20b of the ATR prism 20 again. The infrared light
is repeatedly reflected by the surface of the hyperbolic
metamaterial 90 and reflected by the end surface 20b of the ATR
9
prism 20 to reach the end surface 20d of the ATR prism 20 and
is reflected there and emitted from the ATR prism 20.
[0014]
An anti-reflection coating may be applied to a portion of
the ATR prism 20 where the infrared 5 light is emitted.
Alternatively, the infrared light emitted from the infrared
light source 32 may be p-polarized light, and the ATR prism 20
may be processed such that the incident angle and the emission
angle of the infrared light achieve Brewster's angle.
10 [0015]
For example, the material of the ATR prism 20 is a single
crystal of zinc sulfide (ZnS) transparent to light having a
wavelength in a mid-infrared region and having a relatively small
refractive index. The material of the ATR prism 20 may be a known
15 material such as zinc selenide (ZnSe). However, the material
of the ATR prism 20 is not limited thereto.
[0016]
A portion of the ATR prism 20 or the hyperbolic
metamaterial 90 coming into contact with the skin 49 may be coated
20 with a thin film containing SiO2 or SiN so as not to cause harm
to the human body.
[0017]
The infrared light emitted from the ATR prism 20 enters
the infrared light detector 30. The infrared light detector 30
25 is a module equipped with a MEMS (Micro Electro Mechanical
Systems) measurement device or an uncooled measurement device
such as a thermopile, for example. The infrared light detector
10
30 includes an electric circuit such as a preamplifier and a
lens for collecting the infrared light incident on the infrared
light detector 30 to an element of the measurement device.
Further details of the infrared light detector 30 will be
5 described later.
[0018]
The non-invasive blood sugar level measurement device 80
further includes a controller 52 electrically connected to the
infrared light source 32 and the infrared light detector 30.
10 The controller 52 can control the oscillation of the infrared
light source 32, the wavelength and the intensity of the infrared
light emitted from the infrared light source 32, etc. The
controller 52 receives intensity data of the detected infrared
light from the infrared light detector 30 and calculates a blood
15 sugar concentration in a living body based thereon.
[0019]
The non-invasive blood sugar level measurement device 80
further includes a user interface 54 electrically connected to
the controller. For example, the user interface 54 includes a
20 display 501 displaying measurement start means, measurement
condition setting means, etc. to a user, a vibrator 502 and a
speaker 503 notifying the user of a measurement status (e.g.,
measurement start and completion) with vibration and voice,
respectively, and a keyboard 504 for the user performing a
25 measurement start operation, a measurement condition setting
operation, etc.
[0020]
11
Fig. 3 shows a schematic cross-sectional view of an example
of the hyperbolic metamaterial 90. The hyperbolic metamaterial
90 has a multilayer structure in which metal layers 91 and
dielectric layers 92 are alternately laminated. The metal
layers 91 and the dielectric layers 92 desirably 5 have a thickness
less than 1/4 of a wavelength used. For example, when an infrared
light is used for detecting sugar, the thickness of each of the
metal layers 91 and the dielectric layers 92 is about 10 nm.
In Fig. 3, the hyperbolic metamaterial 90 has an eight-layer
10 structure; however, the number of layers is not limited thereto.
[0021]
The metal layers 91 of the hyperbolic metamaterial 90 are
made of a material generating surface plasmon in the wavelength
region of the light used. In the non-invasive blood sugar level
15 measurement device 80 using the wavelength of infrared light
for detecting a biological material such as sugar, the metal
layers 91 of the hyperbolic metamaterial 90 are made of gold
or silver, for example. The metal layers 91 of the hyperbolic
metamaterial 90 may be layers made of a compound such as titanium
20 nitride or graphene. Particularly, when infrared light is used,
graphene is a material with a low optical loss and is therefore
advantageous. Alternatively, the metal layers 91 of the
hyperbolic metamaterial 90 may be layers made of a semiconductor
material. The semiconductor material is advantageous since
25 desired physical properties can be obtained by adjusting a doping
concentration.
[0022]
12
The dielectric layers 92 of the hyperbolic metamaterial
90 are preferably made of silicon oxide (SiO2), silicon nitride
(SiN), aluminum oxide (Al2O3), or magnesium fluoride (MgF2);
however, the present invention is not limited thereto.
5 [0023]
Fig. 4 is a schematic cross-sectional view showing another
example of the hyperbolic metamaterial denoted by reference
numeral 95. The hyperbolic metamaterial 95 includes at least
one defect layer 93 in a laminated structure of the metal layers
10 91 and the dielectric layers 92. As used herein, "defect" means
being different from surrounding regularity. The thickness of
the defect layer 93 is different from the thicknesses of the
metal layers 91 and the dielectric layers 92. The defect layer
93 is a metal layer or a dielectric layer.
15 [0024]
In the periodic laminated structure of the hyperbolic
metamaterial, a functional wavelength region can be designed
by adjusting the number of layers, the layer thickness, the
materials, etc. By introducing the defect layer 93 disturbing
20 the periodicity into the periodic laminated structure, a light
having a certain wavelength can be confined in the defect layer
93, or transmittance of a light having a certain wavelength can
be improved. For example, while the infrared light having a
wavelength absorbed by a biological material such as glucose
25 is directly transmitted, a dispersion relationship of the
laminated structure can be used as a dispersion relationship
of the hyperbolic metamaterial for visible light.
13
[0025]
As described above, by introducing the defect layer 93,
the dispersion relationship of the stacked structure can be
controlled in accordance with a wavelength. Additionally, a
degree of freedom of measurement can be improved. 5 Therefore,
the accuracy of measurement can be improved. In a second
embodiment described below, the defect layer 93 may also be
introduced and has the same effect as described above.
[0026]
10 Figs. 5a to 5c are diagrams showing another example of a
hyperbolic metamaterial denoted by reference numeral 96. Fig.
5a is a top view of the hyperbolic metamaterial 96. Fig. 5b is
a perspective view of the hyperbolic metamaterial 96. Fig. 5C
is a partial cross-sectional perspective view showing a partial
15 cross-section of the hyperbolic metamaterial 96 taken along a
line 5c-5c of Fig. 5a.
[0027]
The hyperbolic metamaterial 96 is made up of multiple metal
rods 91a and a dielectric 92a filling a space around the metal
20 rods 91a. In the example of Figs. 5a to 5c, the metal rods 91a
have a circular cylindrical shape with a bottom surface shape
formed into a circle having a diameter D. Alternatively, the
shape of the metal rods 91a is not limited to a circular
cylindrical shape with a circular bottom surface shape and may
25 be an elliptical cylindrical shape with an elliptical bottom
surface shape or a quadrangular prism shape with a square or
rectangular bottom surface shape as long as the characteristics
14
of the hyperbolic metamaterial are satisfied. As shown in the
top view of Fig. 5a, the metal rods 91a are two-dimensionally
arranged in a radial direction in a period P in planar view.
As with the metal layers 91 described above (see Figs. 3 and
4), the metal rods 91a are made of a material 5 generating surface
plasmon in the wavelength region of the light used.
[0028]
The thickness D and the period P of the metal rod 91a are
desirably less than 1/4 of the wavelength used. For example,
10 when an infrared light is used for detecting sugar, the thickness
and the period P of the metal rods 91a are each about 10 nm.
Figs. 5A to 5C merely show an example of arrangement of the metal
rods 91a, and the arrangement of the metal rods 91a is not limited
thereto.
15 [0029]
Fig. 6 is a top view showing another example of a hyperbolic
metamaterial denoted by reference numeral 97. In the periodic
structure of the hyperbolic metamaterial, a functional
wavelength region can be designed by adjusting the number,
20 thickness, period, material, etc. of the metal rods 91a. The
hyperbolic metamaterial 97 shown in Fig. 6 includes a defect
rod 91b disturbing the regularity of size, period, etc. of the
metal rods 91a. For example, the defect rod 91b is made of the
same material as the metal rods 91a and has a thickness E
25 different from the metal rods 91a. By introducing the defect
rod 91b disturbing the regularity into the structure having the
regularity as described above, a light having a specific
15
wavelength can be confined around the defect rod 91b, or
transmittance of a light having a certain wavelength can be
improved.
[0030]
In Fig. 6, a specific metal rod is selected 5 from the metal
rods 91a, and the thickness of the selected metal rod is increased
to form the defect rod 91b as a defect region. The method of
forming the defect region is not limited thereto, and the defect
region may be formed by a method such as changing the shape of
10 the metal rod 91a from a circular cylinder to a quadrangular
prism, arranging a metal rod at a position disturbing the
periodicity of arrangement of the metal rods 91a, or changing
the material of the metal rod 91a, for example.
[0031]
15 By introducing the defect rod 91b as described above, for
example, while the infrared light having a wavelength absorbed
by a biological material such as glucose is directly transmitted,
a dispersion relationship of the laminated structure can be used
as a dispersion relationship of the hyperbolic metamaterial for
20 visible light.
[0032]
The principle of blood sugar measurement by the
non-invasive blood sugar level measurement device 80 will be
described. When an infrared light is totally reflected at an
25 interface between the ATR prism 20 and the hyperbolic
metamaterial 90 and/or at an interface between the hyperbolic
metamaterial 90 and the skin 49, an evanescent wave is generated.
16
This evanescent wave penetrates into the skin 49 and is absorbed
by a biological material such as sugar in the living body of
the subject. Since the evanescent wave is absorbed in this
manner, the intensity of the infrared light is attenuated. If
an amount of the biological material is large, 5 the evanescent
wave is more absorbed, so that the intensity of infrared light
is further attenuated.
[0033]
The skin 49 is made up of the epidermis near the surface
10 and the dermis under the epidermis. The epidermis includes the
stratum corneum, the stratum granulosum, the stratum spinosum,
and the stratum basale in order from near the surface. The
respective thicknesses are about 10 μm, several μm, 100 μm, and
several μm. Cells are generated in the stratum basale, and the
15 cells are stacked up into the stratum spinosum. Since water
(tissue interstitial fluid) does not reach the stratum
granulosum above the stratum spinosum, cells die out. In the
stratum corneum above the stratum granulosum, dead cells are
in a hardened state. Sugar and other biological materials are
20 present in the tissue interstitial fluid in the epidermis. The
tissue interstitial fluid increases from the stratum corneum
to the stratum spinosum. Therefore, the degree of attenuation
of the totally reflected infrared light also changes depending
on a length of penetration of the evanescent wave into the skin.
25 [0034]
The intensity of the evanescent wave exponentially
attenuates from a reflecting surface toward the skin, and the
17
length of penetration into the skin is about the wavelength of
infrared light. Therefore, when the non-invasive blood sugar
level measurement device 80 uses an infrared light having a
wavelength of 8.5 μm to 10 μm absorbed by sugar, the sugar present
from the skin surface to a position at a depth 5 of 8.5 μm to 10
μm can be detected.
[0035]
The characteristics of the hyperbolic metamaterial 90 will
be described. First, properties of a flat thin film will
10 generally be described. It is assumed that an x axis and a y
axis are perpendicular to each other and a thin film extends
in the x-y plane. A direction perpendicular to the x axis and
the y axis is defined as a z direction. The wave numbers in the
x-, y-, and z-axis directions are kx, ky, and kz, respectively.
15 A dielectric constant ε and a magnetic permeability μ can be
written as follows.
[0036]
[Math. 1]
�� = ��
������ 0 0
0 ������ 0
0 0 ������
�� …(1)
20 [Math. 2]
�� = ��
������ 0 0
0 ������ 0
0 0 ������
�� …(2)
[0037]
If the material of the thin film is uniaxial crystal (i.e.,
in the case of εxx=εyy≡εzz), this can be written as εxx=εyy≡ε, εzz=ε//,
25 μxx=μyy≡μ, μzz=μ//, and therefore, the dielectric constant ε and
18
the magnetic permeability μ can be written as Eqs (3) and (4),
respectively.
[0038]
[Math. 3]
�� = ��
���� 0 0
0 ���� 0
0 0 ��∥
5 �� …(3)
[Math. 4]
�� = ��
���� 0 0
0 ���� 0
0 0 ��∥
�� …(4)
[0039]
Generally, the dispersion relationship of light is
10 represented by Eq. (5) below.
[0040]
[Math. 5]
����
��������
��
��∥
+
���� ��
����
= ��
��
��
��
��
…(5)
where, ω is the frequency of light, and c is the speed of
15 light.
[0041]
For an ordinary material (i.e., a material that is not a
hyperbolic metamaterial), the values of ε// and ε are equal and
are positive values. Therefore, Eq. (6) is satisfied.
20 [0042]
[Math. 6]
��∥ = ���� > 0 …(6)
[0043]
Fig. 7 shows a dispersion relationship of an ordinary
19
material (i.e., a material that is not a hyperbolic metamaterial)
when a vertical axis is kz and a horizontal axis is kx. S in
Fig. 7 represents a pointing vector. As shown, the dispersion
relationship represented in the wavenumber space is a sphere
5 and is closed.
[0044]
In contrast to the ordinary material described above, an
electrical hyperbolic metamaterial is a material satisfying Eqs.
(7) and (8) or Eqs. (7) and (9) below.
10 [0045]
[Math. 7]
���� = ��∥ > 0 …(7)
[Math. 8]
��∥ < 0 and ���� > 0 …(8)
15 [Math. 9]
��∥ > 0 and ���� < 0 …(9)
[0046]
Therefore, the dispersion relationship for the electrical
hyperbolic metamaterial has a hyperbolic shape as shown in Fig.
20 8. Therefore, the wave number can be present regardless of how
large it is. This means that the evanescent wave does not
attenuate in the hyperbolic metamaterial.
[0047]
Furthermore, in the non-invasive blood sugar level
25 measurement device 80 according to the first embodiment of the
present invention, a difference in refractive index can be
reduced (the refractive indexes can be matched) between the skin
20
49 and the hyperbolic metamaterial 90 by adjusting the material
and the thicknesses of the layers of the hyperbolic metamaterial
90 coming into contact with the skin 49. Therefore, when the
non-invasive blood sugar level measurement device 80 according
to the first embodiment of the present invention 5 including the
hyperbolic metamaterial 90 is used, the length of penetration
of the evanescent wave into the skin 49 becomes longer as compared
to a conventional blood sugar level sensor using surface plasmon.
Therefore, the non-invasive blood sugar level measurement
10 device 80 according to the first embodiment of the present
invention can highly sensitively detect glucose in the skin.
[0048]
The hyperbolas representative of the dispersion
relationship of the hyperbolic metamaterial may not be separated
15 as shown in Fig. 8 (see, e.g., "Poddubny, A.; Iorsh, I.; Belov,
P.; Kivshar, Y. Hyperbolic metamaterials. Nature Photonics 2013,
7, 948-957").
[0049]
Fig. 9 is a schematic diagram showing the optical paths
20 of the infrared light and the evanescent wave traveling through
the ATR prism 20, the hyperbolic metamaterial 90, and the skin
49. When the infrared light traveling through the ATR prism 20
reaches the interface between the ATR prism 20 and the hyperbolic
metamaterial 90, the evanescent wave generated by the infrared
25 light and/or the total reflection at the interface Propagates
inside the hyperbolic metamaterial 90.
[0050]
21
Whether only the infrared light, only the evanescent wave,
or both of them penetrate into the hyperbolic metamaterial 90
can be selected by adjusting the layer thicknesses, the number
of layers, the materials, etc. of the hyperbolic metamaterial
5 90.
[0051]
As described above, since the length of penetration of the
evanescent wave into the skin 49 becomes longer, a distance
required for phase matching between an incident wave and a
10 reflected wave increases (Goos-Hanchen shift, corresponding to
a of Fig. 9).
[0052]
Furthermore, in the hyperbolic metamaterial 90, the
wavelength dependence of the light reflection angle becomes
15 greater as compared to ordinary materials. Specifically, when
the light having the wavelength to be measured and the light
having the other wavelength are emitted from the hyperbolic
metamaterial 90, a difference between the emission angle of the
light having the wavelength to be measured and the light having
20 the other wavelength is large as compared to when the lights
are emitted from the ordinary materials. Therefore, if the
infrared light detector 30 is disposed at the position of
incidence of the light having the wavelength to be measured
enters, the light having the other wavelength does not enter
25 the infrared light detector 30, so that noises caused by the
light having the other wavelength are not detected. Therefore,
when the hyperbolic metamaterial 90 is used, the S/N ratio
22
becomes favorable, and highly accurate measurement can be
performed.
[0053]
The hyperbolic metamaterial 90 can easily be manufactured
by alternately laminating metal and insulating 5 layers by
sputtering. When graphene is adopted as the material of the
metal layers 91 of the hyperbolic metamaterial 90, graphene
formed by chemical vapor deposition on a copper foil is
transferred onto an insulating film. Alternatively, graphene
10 may be formed by screen printing, a solution coating method,
etc.
[0054]
In the above description, the object to be measured by the
non-invasive blood sugar level measurement device 80 according
15 to the first embodiment of the present invention is a blood sugar
level. Fig. 10 shows an infrared light absorption spectrum of
sugar. However, the object to be measured is not limited to the
blood sugar level and may be an amount of another biological
material.
20 [0055]
Although the non-invasive blood sugar level measurement
device 80 uses infrared light has been described, the light used
is not limited to infrared light. For example, the non-invasive
blood sugar level measurement device 80 may use visible light
25 or light having a wavelength in the THz region instead of infrared
light.
[0056]
23
As described above, by using the non-invasive blood sugar
level measurement device 80 according to the first embodiment
of the present invention, the length of penetration of the
evanescent wave into the skin becomes longer as compared to
conventional blood sugar level sensors, and 5 the absorption of
infrared light by biological materials in the skin increases.
Additionally, the distance required for phase matching between
the incident wave and the reflected wave (Goos-Hanchen shift)
increases. Furthermore, the difference between the emission
10 angle of the light having the wavelength to be measured and the
emission angle of the light of the other wavelength is large,
so that the light having the wavelength to be measured can be
detected without detecting the light having the other wavelength,
and high-precision measurement can be performed.
15 [0057]
A configuration of the infrared light detector 30 included
in the non-invasive blood sugar level measurement device 80 will
be described in detail.
[0058]
20 Fig. 11 is a perspective view showing a configuration
example of the infrared light detector 30. For convenience of
description, Fig. 11 shows an X axis, a Y axis perpendicular
to the X axis, and a Z axis perpendicular to the X axis and the
Y axis. The infrared light detector 30 includes a substrate 1
25 parallel to the X-Y plane, a sensor array 1000 arranged on the
substrate, and a detection circuit 1010 arranged around the
sensor array 1000. The sensor array 1000 includes multiple
24
pixels (semiconductor optical elements) 100 arranged in a matrix
shape (an array shape) in two directions (X and Y directions)
orthogonal to each other. Fig. 11 shows the 54 (9×6) optical
elements 100. The detection circuit 1010 processes signals
detected by the optical elements 100. The 5 detection circuit
1010 may detect an image by processing the signals detected by
the optical elements 100. In the non-invasive blood sugar level
measurement device 80, the infrared light detector 30 is arranged
such that the infrared light enters the optical elements 100
10 of the sensor array 1000 vertically (in a direction parallel
to the Z axis).
[0059]
The optical elements 100 are thermal infrared sensors, for
example.
15 [0060]
Fig. 12 is a top view of the optical element 100. In Fig.
12, a protective film on a wiring, a reflective film, and an
absorber described later are omitted so as to clearly show the
structure of the optical element 100. Fig. 13 is a
20 cross-sectional view of the optical element 100 of Fig. 12 as
viewed in a direction X-X. Fig. 13 shows an absorber 10 without
omission.
[0061]
As shown in Fig. 13, a hollow part 2 is disposed on the
25 substrate 1. A temperature detection part 4 detecting a
temperature is arranged above the hollow part 2. The
temperature detection part 4 is supported by two support legs
25
3. As shown in Fig. 2, the support legs 3 have a bridge shape
bent into an L-shape when viewed from above. The support legs
3 include a thin-film metal wiring 6 and a dielectric film 16
supporting the thin-film metal wiring 6.
5 [0062]
The temperature detection part 4 includes a detection film
5 and the thin-film metal wiring 6. The detection film 5 is made
of a diode using crystalline silicon, for example, and has a
value of electric resistance changing depending on a temperature.
10 The thin-film metal wiring 6 electrically connects an aluminum
wiring 7 covered with an insulating film 12 to the detection
film 5. The thin-film metal wiring 6 is made of a titanium alloy
having a thickness of about 100 nm, for example. An electric
signal output by the detection film 5 is transmitted to the
15 aluminum wiring 7 via the thin-film metal wiring 6 formed on
the support leg 3 and is taken out by the detection circuit 1010
(Fig. 11). The electric connections between the thin-film metal
wiring 6 and the detection film 5 and between the thin-film metal
wiring 6 and the aluminum wiring 7 are achieved via conductors
20 (not shown) extending in a vertical direction as needed.
[0063]
A reflection film 8 reflecting infrared rays is arranged
to cover the hollow part 2. However, the reflection film 8 and
the temperature detection part 4 are not thermally connected.
25 The reflection film 8 is arranged to cover above at least a
portion of the support legs 3.
[0064]
26
A support column 9 is disposed above the temperature
detection part 4 and supports the absorber 10 thereon.
Therefore, the absorber 10 is thermally connected to the
temperature detection part 4 by the support column 9. Thus, a
temperature change generated in the absorber 5 10 is transmitted
to the temperature detection part 4. On a back surface, i.e.,
on the support column 9 side, of the absorber 10, an absorption
prevention film 13 preventing light absorption from the back
surface is disposed. A metal film described later (a metal film
10 42 of Fig. 14) is disposed on a surface of the absorber 10 and
is not shown in Fig. 13.
[0065]
On the other hand, the absorber 10 is disposed above the
reflective film 8 and is not thermally connected to the
15 reflective film 8. The absorber 10 extends in a plate shape
laterally (in a direction X-Y) so as to cover at least a portion
of the reflection film 8. Therefore, as shown in Fig. 14
described later, when the optical element 100 is viewed from
above, only the absorber 10 is visible. In another form, the
20 absorber 10 may be formed directly on the temperature detection
part 4.
[0066]
Fig. 14 is a perspective view showing the absorber 10 of
the optical element 100. The absorber 10 includes on a surface
25 thereof a wavelength selection structural part 11 selectively
absorbing a light having a specific wavelength. Since the
wavelength selection structural part 11 may also absorb light,
27
the wavelength selection structural part 11 is included in the
absorber 10.
[0067]
The optical element 100 utilizes surface plasmon in the
wavelength selection structural part 11. 5 When a periodic
structure made of metal is disposed on an incidence plane of
light, and a light having a wavelength corresponding to the
surface periodic structure is made incident, surface plasmon
occurs, and the light is absorbed. This can be utilized so that
10 the wavelength of the light absorbed by the absorber 10 can be
selected by making the surface of the absorber 10 from metal
and adjusting the wavelength of the incident light, the incident
angle, and a pitch p of the periodic structure of the metal
surface.
15 [0068]
In this description, when light is made incident, the
generation of a surface mode to which free electrons inside a
metal film contribute and the generation of a surface mode
attributable to a periodic structure are considered to have the
20 same meaning from the viewpoint of light absorption, and both
are referred to as surface plasmon, surface plasmon resonance,
or simply resonance without distinction. Additionally, the
phenomena described above are sometimes referred to as pseudo
surface plasmons or metamaterials; however, the phenomena are
25 essentially the same in terms of absorption and are therefore
not distinguished.
[0069]
28
The wavelength selection structural part 11 includes a
main body 43, a metal film 42 formed on the main body 43, and
multiple concave parts 45 periodically disposed on the main body
43. The material of the metal film 42 is selected from metals
such as Au, Ag, Cu, Al, Ni, or Mo causing the 5 surface plasmon
resonance. The material of the metal film 42 may be a metal
nitride such as TiN, a metal boride, a metal carbide, etc. causing
the surface plasmon resonance.
[0070]
10 The thickness of the metal film 42 may be a thickness not
allowing transmission of the incident light. This is because,
when the thickness of the metal film 42 is such a thickness,
only the surface plasmon resonance on the surface of the absorber
10 affects absorption and emission of electromagnetic waves,
15 and the material under the metal film 42 does not have an optical
influence on the absorption and emission. The thickness not
allowing transmission of the incident light is related to a
thickness of skin effect (skin depth) δ1 represented by Eq. (10)
below. Specifically, if the thickness of the metal film 42 is
20 equal to or greater than twice of δ1 (e.g., 10 nm to several
hundred nm), almost no incident light passes through the metal
film 42. Therefore, leakage of the incident light below the
absorber 10 can sufficiently be reduced.
[0071]
25 [Math. 10]
�� = ��2
����������
��⁄��
…(10)
where μ represents the magnetic permeability of the metal
29
film 42, σ represents the electric conductivity of the metal
film 42, and ω represents the angular frequency of the incident
light.
[0072]
The main body 43 of the wavelength selection 5 structural
part 11 is made of a dielectric or a semiconductor. For example,
the main body 43 of the wavelength selection structural part
11 is made of silicon oxide (SiO2). The metal film 42 is made
of gold, for example. Since the heat capacity of silicon oxide
10 is smaller than the heat capacity of gold, the absorber 10 having
the main body 43 made of silicon oxide and the metal film 42
made of gold has a smaller heat capacity as compared to an
absorber made of only gold. As a result, the response of the
optical element 100 can be made faster. Additionally, costs can
15 be reduced as compared to an absorber made of only metal such
as gold.
[0073]
The concave parts 45 of the wavelength selection
structural part 11 have a circular cylindrical shape with a
20 diameter of 4 μm and a depth of 1.5 μm, for example. The
wavelength selection structural part 11 has the circular
cylindrical concave parts 45 arranged in a square lattice shape
with a period (pitch) of 8 μm. In this case, the wavelength of
the light absorbed by the absorber 10 is about 8 μm. The circular
25 cylindrical concave parts 45 may be arranged in a square lattice
shape at a period of 8.5 μm. In this case, the wavelength of
the light absorbed by the absorber 10 is about 8.5 μm.
30
[0074]
It was found that the relationships of the wavelength of
the light absorbed by the absorber 10 (hereinafter, referred
to as "absorption wavelength") and the wavelength of the light
emitted from the absorber 10 (hereinafter 5 referred to as
"emission wavelength") with the period p of the concave parts
45 are substantially the same between when the concave parts
45 are arranged in a square lattice shape and when the concave
parts 45 have a two-dimensional periodic structure other than
10 the square lattice shape. In other words, in either case, the
absorption wavelength and the emission wavelength are
determined by the period p of the concave parts 45.
[0075]
In this regard, theoretically, considering a reciprocal
15 lattice vector of the periodic structure, it may be considered
that, while the absorption wavelength and the emission
wavelength are substantially equal to the period p in square
lattice arrangement, the absorption wavelength and the emission
wavelength are a period p×√3/2 in triangular lattice arrangement.
20 However, actually, since the absorption wavelength and the
emission wavelength slightly change depending on a diameter d
of the concave part 45, a light having a wavelength substantially
equal to the period p is considered to be absorbed or emitted
in any two-dimensional periodic structure.
25 [0076]
Therefore, the arrangement of the concave parts 45 is not
limited to the square lattice and may be a two-dimensional
31
periodic structure other than the square lattice such as a
triangular lattice.
[0077]
As described above, the wavelength of the light absorbed
by the absorber 10 can be controlled by adjusting 5 the period
p of the concave parts 45. Generally, the diameter d of the
concave part 45 is desirably equal to or greater than 1/2 of
the period p. When the diameter d of the concave part 45 is
smaller than 1/2 of the period p, the resonance effect is reduced,
10 and the absorptance of the incident light tends to decrease.
However, since the resonance is three-dimensional resonance in
the concave parts 45, sufficient absorption may be achieved in
some cases even if the diameter d is smaller than 1/2 of the
period p. Therefore, the value of the diameter d relative to
15 the period p may individually be designed as appropriate. What
is important is that the absorption wavelength is determined
mainly based on the period p and can therefore be controlled
by adjusting the period p. If the diameter d is equal to or
greater than a certain value relative to the period p, the
20 absorber 10 has sufficient absorption characteristics.
Therefore, the design conditions of the absorber can flexibly
be determined.
[0078]
On the other hand, it is known from the dispersion
25 relationship of the surface plasmon that the light absorbed by
the absorber 10 is independent of the depth of the concave parts
45 and depends only on the period p.
32
[0079]
The absorber 10 including the periodically arranged
concave parts 45 has been described. However, the wavelength
selection structural part 11 of the absorber 10 may include
periodically arranged convex parts protruding 5 from the surface.
Such a configuration has the same effects as described above.
[0080]
In the above description, the concave parts 45 have a
circular cylindrical shape; however, for example, the shape of
10 the concave part 45 as viewed from above may be rectangular or
elliptical. The arrangement of the concave parts 45 is not
limited to the two-dimensional periodic arrangement and may be
one-dimensional periodic arrangement, for example. In these
cases, the absorption of the incident light depends on
15 polarization of the incident light. For example, when the light
emitted from the light source has a polarized light, the absorber
10 capable of absorbing only the polarized light can be designed.
As a result, the SN ratio can be improved.
[0081]
20 The absorption of the incident light by the absorber 10
is maximized when the incident light is perpendicularly incident
on the absorber. If the angle of incidence on the absorber 10
deviates from being perpendicular, the absorption wavelength
changes, and the absorptance of the incident light decreases.
25 [0082]
A method of manufacturing the absorber 10 will be described.
The periodic concave parts 45 are formed on the surface of the
33
main body 43 made of a dielectric or a semiconductor by
photolithography and dry etching. Subsequently, the metal film
42 is formed on the entire surface of the main body 43 including
the concave part 45 by sputtering etc. Similarly, the metal film
42 is formed on the back surface. Since the 5 diameter d of the
concave parts 45 illustrated in the figure is as small as about
several μm, the process of forming the metal film 42 after forming
the concave parts 45 by etching the main body 43 is easier to
perform than the process of forming the concave parts by directly
10 etching the metal film 42.
[0083]
Second Embodiment
Fig. 15 is a schematic diagram showing a configuration of
a non-invasive blood sugar level measurement device denoted by
15 81 according to the second embodiment of the present invention.
The non-invasive blood sugar level measurement device 81
includes the infrared light source 32 emitting an infrared light
having a whole or a part of an absorption wavelength region of
a biological material (8.5 μm to 10 μm), the ATR prism 20 through
20 which the infrared light emitted from the infrared light source
32 is transmitted, and the hyperbolic metamaterial 90 formed
on the ATR prism 20, a controller not shown, and a user interface
not shown. Fig. 15 is a diagram during use, and the hyperbolic
metamaterial 90 on a head of the non-invasive blood sugar level
25 measurement device 81 is in contact with the skin 49 of the
subject.
[0084]
34
The non-invasive blood sugar level measurement device 81
according to the second embodiment of the present invention
includes a visible light source 71 emitting a visible light
toward the ATR prism 20, and a visible light detector 72 detecting
the intensity and position of the visible light 5 transmitted and
emitted through the ATR prism 20.
[0085]
The visible light emitted from the visible light source
71 is incident on the ATR prism 20. The incident visible light
10 is transmitted through the ATR prism 20 while being repeatedly
totally reflected, is subsequently emitted from the ATR prism
20, and enters the visible light detector 72.
[0086]
The infrared light emitted from the infrared light source
15 32 reaches the skin 49 of the subject via the ATR prism 20 and
the hyperbolic metamaterial 90. The infrared light is absorbed
by a biological material (e.g., glucose) in the skin 49, thereby
generating heat. The temperature of the ATR prism 20 increases
due to the generated heat. As the temperature increases, an
20 optical constant such as a refractive index of the ATR prism
20 changes, and the emission angle of the visible light emitted
from the ATR prism 20 changes. The change in the emission angle
changes a position where the visible light reaches. Therefore,
the change in the optical constant of the ATR prism 20, and thus,
25 the generated heat, can be determined by the visible light
detector 72 detecting the position where the visible light
reaches. Specifically, when the amount of the biological
35
material is larger, the absorbed amount of the visible light
becomes larger, and when the absorbed amount is larger, the
generated heat more increases. Therefore, when the amount of
the biological material is larger, the change in the emission
angle of the visible light emitted from the ATR 5 prism 20 becomes
larger. In this way, the amount of the biological material in
the skin 49 can be determined.
[0087]
When the optical element of the visible light detector 72
10 has a single pixel, the reaching position of the emitted light
can be specified by mechanical scanning, and the change in the
emission angle of the visible light from the ATR prism 20 can
be calculated.
[0088]
15 As described above, the amount of the biological material
can be determined by using the heat generated by absorbing the
infrared light. This method is referred to as a light/heat
method.
[0089]
20 In such a measurement device, by forming the hyperbolic
metamaterial 90 on the ATR prism 20, the change in the emission
angle of the visible light from the ATR prism 20 can further
be increased. When the hyperbolic metamaterial 90 is disposed
on the ATR prism 20, the visible light incident on the ATR prism
25 20 and/or the evanescent wave generated by total reflection of
the visible light at the interface between the ATR prism 20 and
the hyperbolic metamaterial 90 passes through the hyperbolic
36
metamaterial 90. An optical constant such as a refractive index
of the hyperbolic metamaterial 90 changes due to temperature.
Particularly, when the hyperbolic metamaterial 90 is used, the
change in the emission angle of the visible light has greater
temperature dependence as compared to when 5 a material having
an ordinary dispersion relationship is used. Therefore, by
using the hyperbolic metamaterial 90, the emission angle of the
visible light can further significantly be changed. Therefore,
even if an amount of the visible light absorbed by the biological
10 material is slight, the change in the emission angle can be made
larger, so that the measurement accuracy is improved.
[0090]

Fig. 16 is a schematic diagram showing a configuration of
15 a non-invasive blood sugar level measurement device generally
denoted by 82 according to a first modification of the second
embodiment of the present invention. In the first modification
of the second embodiment of the present invention, the visible
light detector 72 includes multiple pixels (semiconductor
20 optical elements) 73 arranged in a matrix shape (an array shape)
in two directions orthogonal to each other.
[0091]
By forming the visible light detector 72 as an array, an
intensity of visible light can be detected for each of the pixels
25 73. Therefore, a position with the largest amount of visible
light can finely be specified. As a result, the emission angle
of the visible light from the ATR prism 20 can accurately be
37
detected. Therefore, an amount of generated heat, i.e., an
amount of the biological material, can accurately be measured
from an amount of change in the emission angle.
[0092]
Although Fig. 16 shows the twelve pixels 5 73, the number
of the pixels 73 is not limited thereto. The visible light
detector 72 may be an image sensor.
[0093]

10 Fig. 17 is a schematic diagram showing a configuration of
a non-invasive blood sugar level measurement device generally
denoted by 83 according to a second modification of the second
embodiment of the present invention. In the second modification
of the second embodiment of the present invention, the visible
15 light source 71 includes multiple light source elements 74
arranged in a matrix shape (an array shape) in two directions
orthogonal to each other.
[0094]
The multiple light source elements 74 may emit visible
20 lights having the same wavelength. Since the multiple light
source elements 74 are arranged at different positions, the
visible lights emitted from the light source elements 74 are
incident on the ATR prism 20 at different positions or incident
angles. Therefore, the visible lights emitted from the light
25 source elements 74 are respectively incident at different
positions on the skin 49. If the incident position on the skin
49 is different, the influence of the temperature is different,
38
so that the changes in emission angle of the visible lights from
the ATR prism 20 due to the temperature become different from
each other. By calculating a change in the emission angle due
to a difference in the incident position of the visible light,
the measurement accuracy 5 can be improved.
[0095]
Unlike the above description, at least one of the multiple
light source elements 74 may emit a visible light having a
wavelength different from the other light source elements 74.
10 By calculating a change in the emission angle due to a difference
in the wavelength of the visible light, the measurement accuracy
can be improved.
[0096]
In the second modification of the second embodiment of the
15 present invention, the emission angle of the visible light can
further significantly be changed by using the hyperbolic
metamaterial 90. Therefore, even if an amount of the visible
light absorbed by the biological material is slight, the change
in the emission angle can be made larger, so that the measurement
20 accuracy is improved.
EXPLANATIONS OF LETTERS OR NUMERALS
[0097]
10 absorber, 11 wavelength selection structural part, 20 ATR
prism, 30 infrared light detector, 32 infrared light source,
25 52 controller, 54 user interface, 71 visible light source,
72 visible light detector, 74 light source element, 80
non-invasive blood sugar level measurement device, 90
39
hyperbolic metamaterial, 91 metal layer, 92 dielectric layer,
93 defect layer, 100 optical element, 1000 sensor array, 1010
detection circuit.
40
We Claim :
1. A biological material measurement device
comprising:
a first light source emitting a first light;
an ATR prism including a front surface 5 and a back surface
and allowing the first light made incident from one end to be
transmitted therethrough and emitted from the other end;
a hyperbolic metamaterial layer including a front surface
and a back surface and arranged on the front surface of the ATR
10 prism such that the back surface of the hyperbolic metamaterial
layer is in contact therewith; and
a first light detector detecting the first light emitted
from the ATR prism, wherein
an amount of a biological material in a living body is
15 measured from the detected first light.
2. The biological material measurement device
according to claim 1, wherein
the first light made incident on the ATR prism is reflected
by the back surface of the ATR prism as well as the front surface
20 of the ATR prism and/or the front surface of the hyperbolic
metamaterial layer and is transmitted through the ATR prism,
and wherein
the hyperbolic metamaterial layer is brought into contact
with a living body to measure the amount of the biological
25 material in the living body from the amount of the first light
absorbed by the living body.
3. The biological material measurement device
41
according to claim 1 or 2, wherein
the first light detector includes a plurality of concave
parts or convex parts arranged on a surface thereof separately
from each other in a constant period in one direction or in two
directions intersecting each other and having 5 at least surfaces
made of metal, and wherein
the constant period is a period of surface plasmon
generated in the concave parts or the convex parts due to the
incidence of the first light.
10 4. The biological material measurement device
according to any one of claims 1 to 3, wherein
the first light source, the ATR prism, the first light
detector, and the hyperbolic metamaterial layer are arranged
such that the first light emitted from the ATR prism is
15 perpendicularly incident on the surface of the first light
detector.
5. The biological material measurement device
according to any one of claims 1 to 4, wherein the first light
is an infrared light.
20 6. The biological material measurement device
according to claim 1 or 2, further comprising
a second light source emitting a second light, wherein
the first light made incident on the ATR prism is reflected
by the back surface of the ATR prism as well as the front surface
25 of the ATR prism and/or the front surface of the hyperbolic
metamaterial layer and is transmitted through the ATR prism,
and wherein
42
while the hyperbolic metamaterial layer is in contact with
a living body, the second light is applied to the living body
to measure the amount of the biological material from a change
in the first light due to a heat generated by the biological
material in the living body absorbing 5 the second light.
7. The biological material measurement device
according to claim 6, wherein the change in the first light is
a change in an emission angle of the first light attributable
to a change in a refractive index of the ATR prism and/or the
10 hyperbolic metamaterial layer due to the heat.
8. The biological material measurement device
according to claim 6 or 7, wherein
the first light detector includes a plurality of light
detectors arranged at different positions, and wherein
15 the amount of the biological material is calculated by
using an intensity of the first light at each of the different
positions and position data.
9. The biological material measurement device
according to any one of claims 6 to 8, wherein
20 the first light is a visible light, and wherein the second
light is an infrared light.
10. The biological material measurement device
according to any one of claims 6 to 9, wherein the first
light source includes a plurality of light sources emitting first
25 lights having wavelengths different from each other.
11. The biological material measurement device
according to any one of claims 1 to 10, wherein the hyperbolic
43
metamaterial layer has a structure in which metal layers
containing metal and dielectric layers are alternately
laminated.
12. The biological material measurement device
according to claim 11, wherein the number of 5 layers, thickness,
and materials of the hyperbolic metamaterial layer are
determined such that surface plasmon resonance occurs when the
first light is made incident on the hyperbolic metamaterial
layer.
10 13. The biological material measurement device
according to claim 11 or 12, wherein the number of layers,
thickness, and materials of the hyperbolic metamaterial layer
are determined such that an optical constant of the hyperbolic
metamaterial layer changes due to a temperature change.
15 14. The biological material measurement device
according to any one of claims 11 to 13, wherein a thickness
of each of the metal layers and/or a thickness of each of the
dielectric layers of the hyperbolic metamaterial layer is
smaller than 1/4 of the wavelength of the first light.
20 15. The biological material measurement device
according to any one of claims 11 to 14, wherein at least one
layer of the metal layers and the dielectric layers of the
hyperbolic metamaterial layer has a thickness different from
thicknesses of the other layers, and wherein the thicknesses
25 of the other layers are equal.
16. The biological material measurement device
according to any one of claims 1 to 10, wherein the hyperbolic
44
metamaterial layer includes metal rods containing a metal and
having a columnar shape with a central axis defined in a thickness
direction of the hyperbolic metamaterial layer, and a dielectric
filling a space spreading in a radial direction perpendicular
to the central axis around 5 the metal rods.
17. The biological material measurement device
according to claim 16, wherein the metal rods of the hyperbolic
metamaterial layer are one-dimensionally or two-dimensionally
periodically arranged in the radial direction, and wherein a
10 thickness, an arrangement period, and a material of the metal
rods are determined such that surface plasmon resonance occurs
when the first light is made incident on the hyperbolic
metamaterial layer.
18. The biological material measurement device
15 according to claim 16 or 17, wherein the metal rods of the
hyperbolic metamaterial layer are one-dimensionally or
two-dimensionally periodically arranged in the radial direction,
and wherein a thickness, an arrangement period, and a material
of the metal rods are determined such that an optical constant
20 of the hyperbolic metamaterial layer changes due to a temperature
change.
19. The biological material measurement device
according to any one of claims 16 to 18, wherein the thickness
and/or the arrangement period of the metal rods of the hyperbolic
25 metamaterial layer is smaller than 1/4 of the wavelength of the
first light.
20. The biological material measurement device
according to any one of claims 16 to 19, wherein
of the metal rods has a thickness different from thickness
of the other metal rod
21. The biological material 5 measurement device
according to any o
includes graphene.
Dated this 08th day of
10
15
45
he rods.
one of claims 11 to 20, wherein