Detection device and apparatus for optoacoustic analysis of objects, in particular biological tissue

Abstract

The disclosure relates to a detection device (7) for detecting ultrasound waves, in particular optoacoustic waves, emanating from an object (1), in particular biological tissue, in response to mid-infrared (mid-IR) radiation (3) impinging on the object (1), the detection device (7) comprising an ultrasound-sensitive medium (4) which is configured to convert at least a part of the ultrasound waves emanating from the object (1) into at least one electrical signal (S), and at least one electrically conductive layer (5, 6) which is coupled to the ultrasound-sensitive medium (4) to enable the electrical signal (S) to be tapped, wherein the ultrasound-sensitive medium (4) and the at least one electrically conductive layer (5, 6) are at least partially transparent in the mid-infrared spectral range so that at least a part of the mid-infrared (mid-IR) radiation (3) can pass the detection device (7) prior to impinging on the object (1). The disclosure further relates to an according apparatus for optoacoustic analysis of an object (1), in particular biological tissue.

Description

[0001] 120350P785PC

[0002] Detection device and apparatus for optoacoustic analysis of objects, in particular biological tissue

[0003] Description

[0004] Present disclosure relates to a detection device for detecting ultrasound waves, in particular optoacoustic waves, and an apparatus for optoacoustic analysis of objects, in particular of biological tissue.

[0005] Non-invasive glucose monitoring using mid-infrared (mid-IR) optoacoustics is usually performed in a so-called reflection mode, wherein a tissue of interest is exposed to pulsed mid-IR radiation from one side and ultrasound waves emitted by the tissue in response to the radiation exposure are detected by an ultrasound detector located at the same side of the tissue. In many cases, acoustic resonators (using gas as a couplant) are used to detect the ultrasound waves by which, however, depth information gets lost. As a result, a much higher signal is obtained from surface components (e.g. sweat and fatty acids on the skin) than from glucose in blood (vessels) beneath the skin surface. Thus, without the depth information it is impossible to discern the respective contributions to the overall signal. Alternatively, in a so-called transmission mode at skin folds the ultrasound waves travel from one side of a skin fold (where they are generated) to the other side (where they are detected). In between, however, considerable attenuation and loss of the higher frequency components may occur which reduces or even eliminates information about smaller features (like blood capillaries).

[0006] It is an object of the present disclosure to provide an improved detection device for detecting ultrasound waves, in particular optoacoustic waves, and an apparatus for optoacoustic analysis of objects, in particular biological tissue.

[0007] The object is achieved by a detection device and an apparatus according to the independent claims. Preferred embodiments are subject of the dependent claims. A first aspect of present disclosure relates to a detection device for detecting ultrasound waves, in particular optoacoustic waves, emanating from an object, in particular a biological tissue, in response to mid-infrared (mid-1 R) radiation impinging on the object and entering into the object, the detection device comprising: an ultrasound-sensitive medium which is configured to convert at least a part of the ultrasound waves emanating from the object into at least one electrical signal, and at least one electrically conductive layer which is coupled to the ultrasound-sensitive medium to enable the electrical signal to be tapped, wherein the ultrasound-sensitive medium and the at least one electrically conductive layer are at least partially transparent in the mid-infrared (mid-1 R) spectral range so that at least a part of the mid-infrared (mid-1 R) radiation can pass the detection device prior to impinging on the object.

[0008] A second aspect of present disclosure relates to an apparatus for optoacoustic analysis of objects, in particular biological tissue, the apparatus comprising at least one detection device according to the first aspect of present disclosure and at least one irradiation device configured to generate mid-infrared (mid-1 R) radiation.

[0009] Preferred aspects of present disclosure are based on the approach of designing the detection device at least partially transparent in the mid-infrared (mid-1 R) spectral range so that at least a part of the mid-infrared (mid-1 R) radiation can pass the detection device prior to impinging on the object. Specifically, both the ultrasound-sensitive medium, by which ultrasound waves emanating from the object are converted into an electrical signal, and the at least one electrically conductive layer, which is coupled to the ultrasoundsensitive medium for tapping the electrical signal generated by the ultrasound-sensitive medium, are at least partially transparent in the mid-infrared (mid-1 R) spectral range. In this way, the mid-1 R radiation can pass, in particular perpendicularly, through the ultrasound detection device so that the optical focus (of the impinging mid-1 R radiation) and acoustic focus (of the detection device) can be aligned. Since there is no need for a central bore in the ultrasound detection device to let the mid-1 R radiation through, the central region (in the symmetry axis) of the ultrasound detection device can be used for detecting ultrasound waves. It is very beneficial to be able to use the region at or close to the symmetry axis of the detection device for detecting the ultrasonic waves since the path length differences of two ultrasound waves being separated by a finite angle element are minimal for angle at or close to 0°, i.e. when the ultrasound waves travel perpendicularly to the object and the detection device. Thus, the area of the detection device closest to the centerline is optimal for sensitive reception, as it yields the lowest phase shift. In summary, the detection device and apparatus enable an improved detection of ultrasound waves, in particular optoacoustic waves, and optoacoustic analysis of objects, in particular biological tissue, respectively.

[0010] Within the context of present disclosure, the term “mid-infrared radiation” or “mid-1 R radiation” preferably relates to electromagnetic radiation in a spectral range from approx. 2.5 pm to approx. 1 mm, preferably from 3 pm to 16 pm, in particular from 8 pm to 12 pm.

[0011] Further, within the context of present disclosure, the expression “at least partially transparent in the mid-infrared (mid-IR) spectral range” and its variants is preferably to be understood that electromagnetic radiation having one or more wavelengths or wavelength ranges in the mid-I spectral range can pass the detection device, in particular the ultra- sound-sensitive medium and the at least one electrically conductive layer, without being blocked and / or attenuated considerably so that, after having passed the detection device, the mid-IR radiation impinging on the object is (still) strong enough to excite optoacoustic waves in the object. Preferably, the detection device, in particular the ultrasoundsensitive medium and / or the at least one electrically conductive layer, has a transmittance which is higher than 30%, preferably higher than 50%, more preferably higher than 70%, most preferably higher than 90%, in the mid-IR spectral range, in particular at one or more wavelengths or wavelength ranges in the mid-IR spectral range.

[0012] Preferably, the at least one electrically conductive layer comprises and / or is formed by at least one octahedrally-coordinated heavy-metal chalcogenide. Heavy-metal chalcogenides are chemical compounds of one or more chalcogen elements, preferably selenium (Se) and / or tellurium (Te), as anions with heavy-metal elements as cations, preferably lead (Pb) and / or bismuth (Bi). Preferably, each heavy-metal element, e.g. Bi, and six chalcogen elements, e.g. Se, form six bonds, in which the bond length of four long bonds and the bond length of two short bonds form an octahedron.

[0013] Preferably, the at least one electrically conductive layer comprises and / or is formed by at least one solid solution of at least one octahedrally-coordinated heavy-metal chalcogenide. Preferably, the term “solid solution” refers to a homogeneous mixture of the two different kinds of atoms (i.e. the heavy-metal and chalcogen elements) in solid state and having a single crystal structure (i.e. octahedral). Preferably, the at least one electrically conductive layer comprises and / or is formed by at least one solid solution of at least one octahedrally-coordinated heavy-metal chalcogenide with shallow-level defects. Preferably, shallow-level defects (shallow energy level defects) such as anion vacancies are introduced in the crystals (i.e. the octahedrally-co- ordinated heavy-metal chalcogenides) to obtain particularly good electrical conductivity under the premise of mid-1 R transparency. Preferably, the electrons in the conductive layer mainly come from anion, in particular Se and / or T e, vacancies. Se and / or T e vacancies, as a kind of shallow energy level defect, can generate free electrons through thermal excitation at room temperature. For example, Se vacancies in bismuth selenide (BixSey) layers can be mainly derived from an evaporation of Se atoms during film sputtering, in particular because among all types of point defects (vacancies, interstitial atoms, and anti-site atoms) Se vacancies have the lowest formation energy and are most easily formed in selenium-deficient bismuth selenide.

[0014] Preferably, the at least one electrically conductive layer comprises and / or is formed by at least one of the following, preferably sputtered, compounds: Bi2Te2 4, Bi2Sei.8Te0.7, Bi2Se2 4and / or PbSei.6.

[0015] The preferred embodiments of the compounds described above, alone or in combination, or the electrically conductive layer produced therefrom have a relatively high optical dielectric constant (Eopf) which is preferably larger than 10, more preferably larger than 15, whereas infrared transparent conductors according to the prior art have a relatively low Opt which is typically between 2 and 7. As a result, the plasma absorption edge (Ap) of these compounds increases to values larger than 5 pm, preferably larger than 15 pm, whereas infrared transparent conductors according to the prior art have a Apof typically less than 5 pm. Thus, these compounds are at least partially transparent in the mid-I spectral range, in particular in the range between 8 pm to 12 pm which is particularly suitable for glucose monitoring, and have a relatively high electrical conductivity (a) at the same time. For example, the electrical conductivity of an r-Bi2Se2 4film is

[0016] 1049.4 S / cm and the transmittances at 3 to 5 pm and 8 to 12 pm are as high as 85% and 98%, respectively.

[0017] Alternatively or additionally, the at least one electrically conductive layer comprises and / or is formed by a semiconductor-metal-semiconductor (SMS) sandwich structure comprising a metal layer between two semiconductor layers, wherein the semiconductor layers comprise and / or are formed by at least one heavy-metal chalcogenide. Preferably, the semiconductor layers comprise and / or are formed by bismuth selenide (Bi2Se3), and the metal layer comprises and / or is made by titanium (Ti). Using an SMS sandwich structure film is an effective way to combine transparency and conductivity. Further, rather than using metal oxides such as ITO (which can only achieve transparency and conductivity in the visible to near-infrared band) as the semiconductor material, bismuth selenide is used as semiconductor material and Ti as metal to construct an SMS sandwich and achieve excellent mid-1 R transparent conductive properties. Bi2Se3ensures the mid-1 R transparency and at the same time protects the metal to a certain extent. The metal layer acts as a conductive path, which greatly improves the conductivity.

[0018] Either of the electrically conductive and mid-1 R-transparent layers according to present disclosure can be combined with and / or provided on bulk piezoelectric material (also referred to as “ultrasound-sensitive medium”) to form an ultrasound transducer (also referred to as “detection device”). Preferably, two electrically conductive and mid-1 R transparent layers would “sandwich” the bulk piezoelectric material to achieve this.

[0019] Preferably, the ultrasound-sensitive medium comprises and / or is formed by a piezoelectric material, in particular ZnSe, ZnS and / or PVDF, which is at least partially transparent in the mid-1 R spectral range. Both ZnSe and ZnS show piezoelectric behavior and are mid-1 R transparent and therefore particularly preferred choices. Alternatively or additionally, the piezoelectric polymer PVDF is another suitable material: While not fully mid-1 R- transparent over the whole desired spectrum, it can preferably be used in thin layers due to its excellent piezoelectric properties and therefore still achieve a sufficient mid-1 R- transparency.

[0020] Preferably, the ultrasound-sensitive medium comprises at least one piezoelectric micromechanical ultrasound transducer (PMUT) and / or at least one capacitive micro-mechanical ultrasound transducer (CMUT). With PMUTs and / or CMUTs the acoustic detection does not rely on (thick) bulk material, but due to the micro-mechanic nature can be much thinner. This yields to reduced requirements for transparency in the relevant spectral region (i.e. mid-IR). Preferably, the at least one PMUT and / or CMUT comprises and / or is formed by a microstructure comprising a plurality of, in particular predominantly or substantially, ultra- sound-sensitive regions which are provided and / or arranged in lateral proximity, in particular close lateral proximity, to a plurality of, in particular predominantly or substantially, mid-1 R transparent regions, so that mid-1 R transparency and ultrasound sensitivity of the at least one PMUT and / or CMUT (considered as a whole or on a macroscopic scale) is achieved on a microscopic scale (i.e. considered in the scale of the microstructure) by the different ultrasound-sensitive and mid-1 R transparent regions which are laterally close to each other. In other words, due to the microstructuring in PMUTs and CMUTs, predominantly ultrasound-sensitive regions (which might have sub-optimal mid-1 R transparency) can be in close lateral proximity to predominantly mid-1 R transparent regions (which might have only a minor or no contribution to the ultrasound-sensitivity). The two properties “mid-1 R transparency” and “ultrasound sensitivity” may therefore be achieved microscopically in different localized regions that are laterally close to each other, similar to black and white fields making up a chess board. These two regions together then form a macroscopically homogeneous layer that is both mid-IR transparent and ultrasound sensitive, similar to a chess board appearing grey (instead of black and white) when viewed from afar.

[0021] It is preferred that the ultrasound-sensitive medium comprises and / or is formed by a gas. Preferably, the gas is sandwiched between two self-supporting layers of mid-IR transparent conductive material. For example, the self-supporting layers of transparent conductive material can be achieved by sputtering or other suitable methods.

[0022] Preferably, the at least one electrically conductive layer is provided on a support layer, which is at least partially transparent in the mid-infrared spectral range. Preferably, the support layer comprises and / or is formed by polyethylene. Although polyethylene is not fully transparent in the mid-IR spectrum, the absorption is sufficiently weak to make thin enough layers quasi-transparent (i.e. with high transmittance values) to mid-IR. Therefore, polyethylene can serve as a substrate to support the transparent conductive layer that acts as electrode.

[0023] Preferably, the at least one detection device, which is at least partially transparent to mid-IR radiation, is arranged between the at least one irradiation device and the object. In this preferred setup, at least a part of the pulsed mid-IR radiation emitted by the at least one irradiation device passes the at least one detection device and subsequently impinges on the object to cause it to emit ultrasound waves. This so-called reflection mode, wherein both the exposure of the object to pulsed mid-IR radiation and the detection of ultrasound waves emitted by the object in response to the radiation exposure occur at the same side of the object or half-space above the object, is particularly suitable for non-invasive glucose monitoring in biological tissue.

[0024] Preferably, a processor is provided which is configured to determine, based on the at least one electrical signal generated by the ultrasound-sensitive medium and tapped via the at least one electrically conductive layer, at least one parameter characterizing at least one property of the object, in particular regarding a presence and / or concentration of a biomolecule of interest, in particular glucose, in biological tissue.

[0025] Further advantages, features and examples of the present disclosure will be apparent from the following description of following figures, wherein:

[0026] Fig. 1 shows a schematic cross-sectional view of an exemplary apparatus for optoacoustic analysis of a tissue;

[0027] Fig. 2 shows a schematic cross-sectional view of an exemplary detection device;

[0028] Fig. 3 shows a schematic cross-sectional view of an exemplary alternative embodiment of a mid-IR transparent electrically conductive layer; and

[0029] Fig. 4 shows a schematic cross-sectional view of another exemplary embodiment of mid-IR transparent electrically conductive layers.

[0030] Figure 1 shows a schematic cross-sectional view of an exemplary apparatus for optoacoustic analysis of a tissue 1. The apparatus comprises at least one irradiation device 2 configured and / or arranged to irradiate the tissue 1 with pulsed mid-IR radiation 3, preferably in a wavelength range between 8 and 12 pm, and at least one detection device 7 configured to detect ultrasound waves but also referred to as “optoacoustic waves”, generated in and emitted by the tissue 1 in response to irradiation with the pulsed mid-IR radiation 3. The detection device 7 comprises an ultrasound-sensitive medium 4 which is configured to convert at least a part of the ultrasound waves emanating from the tissue 1 into at least one electrical signal S, and two electrically conductive layers 5, 6 which are provided at each side of the ultrasound-sensitive medium 4 and electrically coupled thereto to enable the electrical signal S to be tapped and forwarded to a processor 8.

[0031] The processor 8, which is preferably provided in a mobile computer device (e.g. a smart phone or smartwatch), is configured to determine at least one parameter characterizing at least one property of the tissue 1 based on the electrical signal S. Preferably, the at least one parameter characterizes the presence and / or concentration of a biomolecule of interest, in particular glucose, in the tissue 1.

[0032] The ultrasound-sensitive medium 4 and the electrically conductive layers 5, 6 are at least partially transparent in the mid-IR spectral range so that at least a part of the mid-IR radiation emitted by the irradiation device 2 can pass the detection device 7 prior to impinging on the tissue 1 . In other words, the detection device 7 is a mid-IR transparent ultrasound detector.

[0033] In the given example, the mid-IR transparent ultrasound detector 7 is placed on the surface 10 of the tissue 1 and comprises three layers: A first electrically conductive layer 6, also referred to as the “lower electrode”, is provided close to and touching the surface 10. A second electrically conductive layer 5, also referred to as the “upper electrode”, is located furthest away from the surface 10. Both the bottom electrode 6 and top electrode 5 are electrically conductive mid-IR transparent coatings. Sandwiched between top electrode 5 and bottom electrode 6 is a mid-IR transparent piezoelectric bulk material as the ultrasound-sensitive medium 4. As the three constituting layers 5, 4 and 6 of the detection device 7 are each mid-IR transparent, respectively, the mid-IR radiation 3 emanating from the irradiation device 2 can pass all three layers 5, 4 and 6 and subsequently impinge on the surface 10 of the tissue 1 and enter it.

[0034] The pulsed mid-IR radiation 3 is then absorbed in the tissue 1 , creates a sudden increase in temperature and therefore a thermal expansion. This shock wave (i.e. ultrasound waves, also referred to as “optoacoustic waves”) travels then to the tissue sur- face 10 and towards the mid-IR transparent ultrasound detector 7, where an optoacoustic signal can be tapped and / or measured as a voltage and / or charge between top electrode 5 and bottom electrode 6.

[0035] For example, the electrodes 5, 6 may comprise and / or be formed by bismuth selenide (BixSey) that is sputtered onto the mid-IR transparent piezoelectric bulk material 4 which may comprise and / or be formed by zinc selenide (ZnSe).

[0036] However, other combinations of compounds for the electrodes 5, 6 and / or the ultra- sound-sensitive medium 4 are possible. For example, the electrodes 5, 6 may comprise and / or be formed by a solid solution of an octahedrally-coordinated heavy-metal chalcogenide with shallow-level defects. Preferably, the electrodes 5, 6 may comprise and / or be formed by at least one of the following, preferably sputtered, compounds: Bi2Te2 4, Bi2Sei.8Te0.7, Bi2Se24and / or PbSei.6. For further details it is referred to the above description.

[0037] Alternatively to ZnSe, the ultrasound-sensitive medium 4 may comprise and / or be formed by ZnS and / or preferably thin layers of PVDF (polyvinylidene fluoride).

[0038] Further alternatively, the ultrasound-sensitive medium 4 may comprise at least one piezoelectric micro-mechanical ultrasound transducer (PMUT) and / or at least one capacitive micro-mechanical ultrasound transducer (CMUT). PMUTs use the piezoelectric effect, where mechanical stress applied to piezoelectric materials (like lead zirconate titanate) generates an electric charge. A thin piezoelectric membrane is suspended over a cavity. When an alternating voltage is applied, the membrane vibrates, producing ultrasound waves. Conversely, incoming ultrasound waves induce membrane vibrations that generate a detectable electrical signal. PMUTs are highly sensitive, have a broad bandwidth, and are effective for low-frequency applications, such as medical imaging and underwater communication. CMUTs, on the other hand, rely on electrostatic forces. They consist of a flexible membrane suspended over a fixed conductive substrate, forming a capacitor. Applying a DC bias voltage pulls the membrane towards the substrate, and an AC signal superimposed on the bias voltage causes the membrane to vibrate, generating ultrasound waves. Incoming ultrasound waves cause the membrane to move, changing the capacitance, which is then converted into an electrical signal. CMUTs are known for their wide bandwidth, tunability, and integration potential with CMOS technology, making them particularly suitable for high-frequency applications like optoacoustic sensing and / or imaging.

[0039] Figure 2 shows a schematic cross-sectional view of an exemplary detection device 7 to illustrate the advantages of using a mid-1 R transparent ultrasound transducer. The above explanations on the detection device 7 shown in Fig. 1 , in particular on the ultrasoundsensitive medium 4 and the electrically conductive layers 5, 6, including preferred embodiments and alternatives, apply accordingly.

[0040] As illustrated in Fig. 2, two soundwaves w1 , w2 originating from an origin 11 at a depth D in the tissue 1 and being separated by a finite angle element da have a finite a path length difference when impinging on interface 10 (surface of the tissue 1) when they hit the interface 10 at a finite angle a. In contrast, path length differences are minimal for an angle a of 0° or close to 0°, i.e. when the soundwaves travel essentially perpendicularly to the tissue 1 and the ultrasound transducer, i.e. the detection device 7, and their interface 10.

[0041] Thus, the transducer area closest to the centerline 12 is optimal for a particularly sensitive ultrasound waves reception, as it yields the lowest phase shift. Furthermore, the transducer area closest to the centerline 12 has also the shortest distance to the origin 11 of the acoustic waves and the sound waves therefore experience the lowest possible amount of attenuation.

[0042] Additionally, as in optoacoustics small features yield to higher ultrasound frequency components and, at the same time, higher frequencies are attenuated more strongly, longer distances between the origin 11 and the transducer area on which the soundwaves impinge would yield to an increased loss of information about small tissue features. Therefore, also in this regard the best position of the transducer area is the one closest to the centerline.

[0043] To particularly benefit from these advantageous effects, it is preferred to coalign the origin 11 of the acoustic waves with an optical focal point of the mid-I irradiation. For example, the mid-IR radiation passing the detection device 7 has at least one focal point, focal line or focal region which is located beneath the detection device 7 at or within the tissue 1. Further, the detection device 7 has a reception field, within which it is sensitive to ultrasonic waves and which is usually described by a cone or a lobe-shaped area and depends on i.a. the size and shape of the ultrasound transducer and / or possible ultrasound focusing measures. Preferably, the irradiation device 2 (see Fig. 1) and / or the detection device 7 is or are designed and / or controlled such that the at least one focal point, focal line or focal region of the mid-IR radiation passing the detection device 7 coincides and / or overlaps with the reception field of the detection device 7.

[0044] Although the examples given in figures 1 and 2 show a tissue 1 , in particular a biological tissue, the device and apparatus according to present disclosure can also be used for detecting ultrasound waves emanating from and / or optoacoustic analysis of any biological and / or non-biological objects, samples, materials, substances, etc.

[0045] Figure 3 shows a schematic cross-sectional view (not true to scale) of an exemplary alternative embodiment of a mid-IR transparent electrically conductive layer or electrode 5, 6 comprising and / or being formed by a semiconductor-metal-semiconduc- tor (SMS) sandwich structure comprising a metal layer 14 between two semiconductor layers 15, 16, wherein the semiconductor layers 15, 16 comprise and / or are formed by at least one heavy-metal chalcogenide. Preferably, the semiconductor layers 15, 16 comprise and / or are formed by bismuth selenide (Bi2Se3), and the metal layer 14 comprises and / or is made by titanium (Ti).

[0046] For example, the SMS sandwich structure comprises a multilayer 15, 14, 16 of Bi2Se3(20 nm) / Ti (5 nm) / Bi2Se3(20 nm), which is preferably prepared using a magnetron sputtering system. Preferably, Bi2Se3is deposited at a power of 60 W, Ti is deposited at a power of 40 W, Argon gas flow is 80 seem and sputtering pressure is 1 Pa. In this way, the conductivity of the SMS sandwich structure is preferably increased by 3.8 times compared with the bismuth selenide, with preferably only 3% decrease in the transmittance in 8-12 pm.

[0047] Figure 4 shows a schematic cross-sectional view (not true to scale) of another exemplary embodiment of mid-IR transparent electrically conductive layers 5, 6, wherein each of the layers 5, 6 is provided on a support layer 17, which is at least partially transparent in the mid-infrared spectral range. Preferably, the support layer 17 comprises and / or is formed by polyethylene. The support layer 17 ensures a high mechanical stability even if the thickness and / or mechanical stability of the respective layer 5, 6 itself is low. In other words, the electrically conductive layer 5, 6 can be made just thin enough to achieve the desired and / or required electrical conductivity without compromising mechanical stability.

Claims

Patent Claims1. A detection device (7) for detecting ultrasound waves, in particular optoacoustic waves, emanating from an object (1), in particular a biological tissue, in response to mid-infrared (mid-IR) radiation (3) impinging on the object (1), the detection device (7) comprising:- an ultrasound-sensitive medium (4) which is configured to convert at least a part of the ultrasound waves emanating from the object (1) into at least one electrical signal (S), and- at least one electrically conductive layer (5, 6) which is coupled to the ultra- sound-sensitive medium (4) to enable the electrical signal (S) to be tapped, wherein the ultrasound-sensitive medium (4) and the at least one electrically conductive layer (5, 6) are at least partially transparent in the mid-infrared spectral range so that at least a part of the mid-infrared (mid-IR) radiation (3) can pass the detection device (7) prior to impinging on the object (1).

2. The detection device (7) according to claim 1 , wherein the at least one electrically conductive layer (5, 6) comprises and / or is formed by at least one octahedrally- coordinated heavy-metal chalcogenide.

3. The detection device (7) according to claim 1 or 2, wherein the at least one electrically conductive layer (5, 6) comprises and / or is formed by at least one solid solution of at least one octahedrally-coordinated heavy-metal chalcogenide.

4. The detection device (7) according to any one of the preceding claims, wherein the at least one electrically conductive layer (5, 6) comprises and / or is formed by at least one solid solution of at least one octahedrally-coordinated heavy-metal chalcogenide with shallow-level defects.

5. The detection device (7) according to any one of the preceding claims, wherein the at least one electrically conductive layer (5, 6) comprises and / or is formed by at least one of the following, preferably sputtered, compounds: Bi2Te2 4, Bi2Sei.8Te0.7, Bi2Se24and / or PbSei.6.

6. The detection device (7) according to any one of the preceding claims, wherein the at least one electrically conductive layer (5, 6) comprises and / or is formed by a semiconductor-metal-semiconductor sandwich structure comprising a metal layer (14) between two semiconductor layers (15, 16), wherein the semiconductor layers (15, 16) comprise and / or are formed by at least one heavy-metal chalcogenide.

7. The detection device (7) according to claim 6, wherein the semiconductor layers (15, 16) comprise and / or are formed by Bi2Se3, and the metal layer (14) comprises and / or is made by Ti.

8. The detection device (7) according to any one of the preceding claims, wherein the at least one electrically conductive layer (5, 6) is provided on a support layer (17), which is at least partially transparent in the mid-infrared spectral range.

9. The detection device (7) according to claim 8, wherein the support layer (17) comprises and / or is formed by polyethylene.

10. The detection device (7) according to any one of the preceding claims, wherein the ultrasound-sensitive medium (4) comprises and / or is formed by a piezoelectric material, in particular ZnSe, ZnS and / or PVDF, and / or by a gas.11 . The detection device (7) according to any one of the preceding claims, wherein the ultrasound-sensitive medium (4) comprises at least one piezoelectric micromechanical ultrasound transducer (PMUT) and / or at least one capacitive micromechanical ultrasound transducer (CMUT).

12. The detection device (7) according to claim 11 , wherein the at least one PMUT and / or CMUT comprises and / or is formed by a microstructure comprising a plurality of, in particular predominantly or substantially, ultrasound-sensitive regions which are provided and / or arranged in lateral proximity, in particular close lateral proximity, to a plurality of, in particular predominantly or substantially, mid-IR transparent regions, so that mid-IR transparency and ultrasound sensitivity of theat least one PMUT and / or CMUT is achieved on a microscopic scale by the different ultrasound-sensitive and mid-1 R transparent regions which are laterally close to one another.

13. An apparatus for optoacoustic analysis of an object (1), in particular a biological tissue, the apparatus comprising at least one detection device (7) according to any one of the preceding claims and at least one irradiation device (2) configured to generate mid-infrared (mid-I ) radiation.

14. The apparatus according to claim 13, wherein the at least one detection device (7) is arranged between the at least one irradiation device (2) and the ob- ject (1).

15. The apparatus according to claim 13 or 14, further comprising a processor (8) configured to determine, based on the at least one electrical signal (S), at least one parameter characterizing at least one property of the object (1), in particular regarding a presence and / or concentration of a biomolecule of interest, in particu- lar glucose, in the object.

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