SAW SENSOR MODULE

Description

[0001] The present invention relates to a SAW sensor module comprising a cartridge with a sensor chip made of piezoelectric material and at least one SAW sensor formed thereon, and at least one control and readout device for the at least one SAW sensor.

[0002] A Surface Acoustic Wave (SAW) is an acoustic surface wave, i.e., a structure-borne sound wave that propagates planarly on a surface, meaning in only two dimensions. SAW waves penetrate the material on which they propagate only minimally; the penetration depth is limited to one wavelength.

[0003] In a SAW sensor, an acoustic surface wave is transmitted from a transmitter electrode located on a sensor surface to a receiver electrode. The respective selective receptor layer on a piezoelectric substrate is situated between the transmitter and receiver electrodes.

[0004] Preferably, interlocking metallic comb structures (so-called interdigital transducers - IDTs) are used as transmitters and receivers. An alternating voltage is applied to one comb structure, while the other is grounded. This creates a periodically changing electric field between the differently charged fingers. Since an externally applied electric field causes mechanical deformation of the piezoelectric substrate, the substrate is alternately stretched and contracted.

[0005] In the SAW sensor, two of these IDTs are applied side by side to the sensor substrate. One IDT serves as the transmitter and the other as the receiver. At the transmitter, the alternating voltage signal is converted into a surface acoustic wave and emitted into the substrate. The surface acoustic wave causes charge displacements in the piezoelectric substrate, which in turn generate an alternating voltage signal in the finger-like structures of the receiver.

[0006] SAW sensors can be operated as delay lines or as resonators. In the latter case, reflector structures are located on the outer surfaces of the IDTs.

[0007] The reflected radio signal is reflected as an echo by the respective reflector. The time interval between the original signal and the echo, as well as the changes in the magnitude and phase of the respective signal, depend, among other things, on the speed of sound of the sensor substrate material, the temperature, and mechanical stresses in the substrate. It has also been shown that the time interval, magnitude, and phase of a SAW sensor based on such reflection change depending on a receptor layer applied to the sensor substrate and bonding to the substrate surface. The resulting mass deposition on the sensor surface causes a change in the surface wave velocity. This effect is used, for example, in biological or chemical sample analysis to determine specific components of fluids. US2005 / 022581 A1 shows a known SAW sensor module.

[0008] The object of the present invention is to provide a practical device for the simple analysis of chemical and / or biological fluids based on SAW sensors. This object is achieved according to the invention by an SAW sensor module comprising a cartridge with a sensor chip made of piezoelectric material and at least one SAW sensor formed thereon, and at least one control and readout device for the at least one SAW sensor. The control and readout device has a circuit board on the front of which coupling electrodes are formed, which are connected to a device terminal formed on the circuit board by means of electrical conductors passing through the circuit board. The cartridge has coupling electrodes that are capacitively coupled on the one hand to the coupling electrodes and on the other hand to sensor electrodes of the at least one SAW sensor.wherein at least one magnetic element is formed on the device circuit board and the cartridge has at least one metallic and / or magnetic alignment element that aligns itself with the at least one magnetic element.

[0009] The SAW sensor module according to the invention comprises a variably and permanently usable control and readout device that can be used for a multitude of measurements. Furthermore, the SAW sensor module according to the invention includes a cartridge that is essentially a single-use, i.e., disposable, component. The SAW sensor component within the cartridge performs the sample-dependent measurement of the change in the generated surface acoustic waves. The control and readout of the SAW sensors used in this process is carried out by the control and readout device.

[0010] In the present invention, signal transmission from the control and readout device to the cartridge and back to the control and readout device is achieved simply and with low loss via capacitive coupling between the control and readout device and the cartridge. Two capacitive couplings are employed: Firstly, the device coupling electrodes are arranged opposite each other at a very small distance and can therefore be easily capacitively coupled; secondly, the cartridge coupling electrodes are capacitively coupled to the sensor electrodes via the piezoelectric substrate.

[0011] The respective electrodes are arranged directly one above the other. In the present invention, the alignment of the device coupling electrodes to the cartridge coupling electrodes is achieved simply by the magnetic attraction between the at least one alignment element and the at least one magnetic element, which automatically aligns the cartridge on the control and readout device. Therefore, no complex adjustment or wiring is necessary with the present invention. On the contrary, the cartridge simply needs to be placed on the control and readout device, rotates itself into the correct position, and the evaluation can begin. This alignment works in both rotation and translation. After successful alignment, the cartridge rests stably on the control and readout device in all axes.

[0012] In a particularly mechanically stable embodiment of the present invention, the cartridge has a carrier board located between the sensor chip and the device circuit board, on which the cartridge coupling electrodes are formed. The carrier board provides a stable base on which the cartridge coupling electrodes can advantageously be formed and on which, furthermore, the sensor chip and other components of the cartridge, such as its housing, can advantageously be mounted. However, the sensor electrodes of the sensor chip can also be capacitively coupled directly to the device coupling electrodes of the device circuit board.

[0013] Fluid analysis is particularly easy and reliable using the SAW sensor module according to the invention when a fluid frame is mounted on the SAW sensor component, enclosing a fluid reservoir, and a cap is formed around the fluid frame on the sensor chip, wherein the cap and the fluid frame cover the sensor electrodes and reflectors of the at least one SAW sensor. The fluid reservoir ensures that, when the SAW sensor module has several SAW sensors, the travel distances or tracks of all these SAW sensors can be of the same length, which facilitates the calculation of the differences between the signals of these SAW sensors.

[0014] The fluid frame forms a mechanically particularly stable and tight frame around the fluid basin if the fluid frame is a lever structure that is suspended on one side in a groove formed on the cap and on the other side presses against a sensor chip front of the sensor chip and is sealed there.

[0015] The fluid basin can be filled with fluid particularly easily if the fluid frame forms a funnel with sloping walls on which at least one SAW sensor is mounted, or if such a funnel is placed on the fluid frame.

[0016] The cap is preferably an injection-molded plastic part through which at least one alignment element passes. This allows the cartridge to be manufactured with high reproducibility in large quantities and therefore cost-effectively.

[0017] As long as the SAW sensor module according to the invention is not yet in use, the at least one SAW sensor can be protected particularly effectively from external influences if a cover film is laminated over the fluid frame.

[0018] If the cartridge has several strip-shaped SAW sensors arranged parallel to each other, at least one of these SAW sensors can be used as a reference sensor. For example, this reference sensor can be designed without a selective receptor layer. Furthermore, one of these SAW sensors can be used to compensate for environmental or temperature effects.

[0019] It is advantageous if the parts of the measuring and reference SAW sensor paths that are in contact with the fluid being analyzed are of the same length.

[0020] The SAW sensors are preferably separated from each other by means of partition walls.

[0021] If at least two of the SAW sensors have different travel distances, they can be connected electrically in parallel or in series and read out together via a coupling link. Signals from these sensors can then be separated by evaluation electronics based on their travel time.

[0022] In a further advantageous embodiment of the present invention, each of the SAW sensors is assigned a separate capacitive connection. This allows the SAW sensors to measure and evaluate simultaneously, thereby reducing measurement errors.

[0023] It is particularly advantageous if at least one RFID chip is integrated on the sensor chip and / or the carrier board, which is connected to the device interface via at least one capacitive coupling. The RFID chip allows the cartridge and the fluid sample analysis performed within it to be uniquely identified and thus assigned to the recorded measured values, with data transmission occurring simply via the at least one capacitive coupling.

[0024] Advantageous protection of the control and readout device, for example from dirt or moisture, is achieved when a dielectric protective membrane is placed between the cartridge and the control and readout device. Such a protective membrane serves as a dielectric for the capacitive coupling between the control and readout device and the cartridge and does not impair it.

[0025] Preferred embodiments of the present invention, their structure, function and advantages are explained in more detail below with reference to figures, wherein Figure 1 schematically shows an embodiment of a SAW sensor module according to the invention in a top view; Figure 2 schematically shows a device board of the SAW sensor module made of Figure 1 Figure 3 shows a top view; Figure 3 shows a schematic representation of an embodiment of a SAW sensor module according to the invention in a cutaway side view; Figure 4 shows a schematic representation of part of a sensor chip, a cap and a fluid reservoir of an embodiment of the SAW sensor module according to the invention in a cutaway side view; and Figure 5 shows a schematic top view of SAW sensors of an embodiment of the SAW sensor module according to the invention.

[0026] Figure 1Figure 1 schematically shows an embodiment of a SAW sensor module 1 according to the invention in a top view. Hidden structures of the SAW sensor module 1 are shown in gray. Figure 3 Figure 1 is a schematic representation of an embodiment of the SAW sensor module 1 according to the invention, shown in a cutaway side view.

[0027] The SAW sensor module 1 has a Figure 3 schematically represented control and readout device 4 with a device board 40, which is in Figure 2 The device board 40 is shown individually in a top view. It is an electrically non-conductive circuit board on which electrically conductive structures are formed. The device board 40 has on its Figure 2 The front of the device circuit board 41 shown has two device coupling electrodes 43, 44, which in the embodiment shown are annular in shape, but which can also have other shapes.

[0028] The device coupling electrodes 43, 44 are connected to an electrical device connection 47 on the back of the device board 42 via electrical conductors 45, 46 passing through the device board 40.

[0029] Furthermore, the device board 40 has two magnetic elements 51, 52 which are accessible via the front surface 41 of the device board. In other embodiments of the invention, only one magnetic element or more than two magnetic elements 51, 52 may be formed on the front surface 41 of the device board.

[0030] A cartridge 2, which can also be referred to as a cartridge, is placed on the control and readout device 4. The control and readout device 4 is intended for continuous use, while the cartridge 2 is designed for single use, i.e., as a disposable element. A dielectric protective membrane 8, such as Kapton tape, is arranged between the control and readout device 4 and the cartridge 2.

[0031] The cartridge 2 comprises a SAW sensor component 3. In the illustrated embodiment, the SAW sensor component 3 comprises a carrier board 20 and a sensor chip 30 with at least one SAW sensor 33, preferably several SAW sensors 33, 34, 35, located thereon. In other embodiments of the invention not shown, the SAW sensor component 3 may also comprise only a single substrate, which combines the elements of the carrier board 20 and the sensor chip 30 described below on this substrate.

[0032] The carrier board 20 has rear cartridge coupling electrodes 23, 24 on its rear side 27, which are opposite the device coupling electrodes 43, 44. In the illustrated embodiment, the device coupling electrodes 43, 44 have a larger diameter than the rear cartridge coupling electrodes 23, 24. The device coupling electrodes 43, 44 and the rear cartridge coupling electrodes 23, 24 formed on a cartridge rear side of the cartridge 2 can be concentric with each other, but need not be.

[0033] The only barrier between the rear cartridge coupling electrodes 23, 24 and the device coupling electrodes 43, 44 is the dielectric protective membrane 8. Since the control and readout device 4 must be disinfected regularly, the dielectric protective membrane 8 provides advantageous protection against disinfectants, as well as against dirt and moisture in general. The rear cartridge coupling electrodes 23, 24 and the device coupling electrodes 43, 44 are not coupled via electrical conductors, but capacitively.

[0034] On a carrier board front side 28 of the carrier board 20 are front cartridge coupling electrodes 25, 26, which are electrically connected to the rear cartridge coupling electrodes 23, 24 via electrical conductors 48, 49 passing through the carrier board 20.

[0035] In the illustrated embodiment, the carrier board 20 is a printed circuit board made of electrically non-conductive material on which electrically conductive structures are formed. The carrier board 20 serves to establish a capacitive coupling between the sensor chip 30 of the cartridge 2 and the control and readout device 4. Furthermore, the carrier board 20 has a support function by carrying the sensor chip 30. Additionally, matching components, such as coils and / or capacitors, can be provided on the carrier board 20 for power matching.

[0036] The carrier board 20 may also have markings that can be used to place the sensor chip 30 on the carrier board 20.

[0037] The electrical connections between the electrical contacts or electrodes on the front 28 and rear 27 of the carrier board 20 can be designed as desired. This allows for mechanical and electrical flexibility.

[0038] The sensor chip 30 consists of piezoelectric material. The sensor chip 30 has at least one SAW sensor 33 on its front surface 37. The at least one SAW sensor 33 is operated by means of sensor electrodes 31, 32 also located on the front surface 37 of the sensor chip.

[0039] The sensor electrodes 31, 32 are capacitively coupled to the front-side cartridge coupling electrodes 25, 26. The piezoelectric material of the sensor chip 30 forms a dielectric for this capacitive coupling arrangement.

[0040] Typically, the sensor chip 30 is glued to the carrier board 20. The adhesive used then forms part of the aforementioned dielectric.

[0041] Thus, the sensor electrodes 31, 32 are connected to the device connection 47 of the control and readout device 4 via the front cartridge coupling electrodes 25, 26, the rear cartridge coupling electrodes 23, 24 and the device coupling electrodes 43, 44, so that at least one SAW sensor 33 can be electrically contacted and its signals can be read out.

[0042] Above the at least one SAW sensor 33, a fluid basin 70 is formed in the cartridge 2. The fluid basin 70 is laterally bounded by a fluid frame 7.

[0043] The fluid frame 7 can, for example, be used as shown in Figure 4The schematic representation shows that the structure is formed by inclined walls which form a funnel on the sensor chip 30, above the at least one SAW sensor 33. The inclined walls can be arranged as shown in Figure 4 The levers can be seen as being designed in the form of levers that are, on one hand, hooked into a groove 72 of a cap 71 surrounding the fluid reservoir 70 and, on the other hand, rest on the sensor chip 30, against which they are sealed by means of a seal 75. The seal 75 can, for example, be an adhesive bead.

[0044] In the embodiment shown, the cap 71 is designed as a plastic injection-molded part.

[0045] The cap 71, together with the fluid frame 7, covers the sensor electrodes 31, 32 and reflectors of the at least one SAW sensor 33.

[0046] A fluid to be detected can be introduced into the fluid basin 70. The size of the fluid basin 70 defines the volume of fluid that can be analyzed. Molecules of such a fluid can bind to the surface of the at least one SAW sensor 33, thereby changing its surface waveguide properties and enabling the detection of the corresponding fluid.

[0047] The fluid basin 70 is covered by a cover film 9 as long as the cartridge 2 is not in use. The cover film 9 is removable.

[0048] In the illustrated embodiment, at least one RFID chip 10 is arranged on the sensor chip 30. The RFID chip 10 is also capacitively coupled via the sensor chip 30 to cartridge coupling electrodes of the carrier board 2 and, in turn, capacitively coupled via these to device coupling electrodes of the device board 40. The RFID chip 10 allows the cartridge 2 and the fluid sample analysis performed therein to be uniquely identified and thus assigned to the recorded measured values. In other embodiments of the invention, the RFID chip 10 can also be arranged on the carrier board 20.

[0049] Preferably, the RFID chip 10 is not based on SAW technology but on semiconductor technology. The RFID chip 10 can, for example, record what type of test is currently being performed by the SAW sensor module 1. It can also be read from the RFID chip 10 whether the SAW sensor module 1 has already been used. Furthermore, batch numbers, expiration dates, etc., can be stored in the RFID chip 10.

[0050] In the illustrated embodiment, three SAW sensors 33, 34, 35 are formed on the sensor chip 30. The SAW sensors 33, 34, 35 have, as shown in Figure 5 The schematic shows different running paths L1, L2, L3. This allows the signals from the SAW sensors 33, 34, 35 to be easily distinguished from one another.

[0051] In the illustrated embodiment, the SAW sensors 33, 34, 35 are 300 MHz SAW sensors, but can also be SAW sensors based on a different frequency. The SAW sensors 33, 34, 35 are strip-shaped and parallel to each other. The fluid basin 70 is located above a central area of ​​the SAW sensors 33, 34, 35.

[0052] Between the SAW sensors 33, 34, 35 are photolithographically produced partitions 38. The partitions 38 protect the individual areas of the SAW sensors 33, 34, 35, but also their IDTs from each other.

[0053] Furthermore, a cover is formed over areas of the sensor chip 30 that are not in contact with the fluid to be analyzed. The cover is formed by photolithographic layer structuring.

[0054] In the illustrated embodiment, the SAW sensors 33, 34, 35 are connected in series and use only one common pair of capacitive coupling electrodes for contact. However, this is not mandatory; for example, the SAW sensors 33, 34, 35 could be addressed and read sequentially via a multiplexer. A parallel connection of the individual SAW sensors 33, 34, 35 is also possible.

[0055] In the Figure 5 In the illustrated embodiment, the SAW sensor 33 forms a sample channel, i.e. the actual measuring channel, the SAW sensor 34 a compensation channel for compensating for temperature effects, and the SAW sensor 35 a reference channel, i.e., it does not have a selective receptor layer.

[0056] In other embodiments of the present invention, the SAW sensors 33, 34, 35 can also be used to measure different analytes.

[0057] A metallic or magnetic alignment element 6 is guided through the cartridge 2. In the illustrated embodiment, this element is formed from a metallic wire, such as a steel wire. The at least one alignment element 6 is advantageously guided through pre-drilled holes in the cartridge 2, for example, in the corners of the cartridge 2. A magnetic yoke can also be used as the alignment element 6 instead of the steel wire.

[0058] The ends of the alignment element 6 terminate on the back of the carrier board 27, opposite the magnetic elements 51, 52. Through the interaction between the ends of the alignment element 6 and the magnetic elements 51, 52, the cartridge 2 automatically aligns itself on the device board 40 when it is placed on the device board 40. This automatic alignment ensures that the cartridge coupling electrodes 23, 24 automatically align with the device coupling electrodes 43, 44.

Claims

1. SAW sensor module (1) comprising a cartridge (2) with a sensor chip (30) of piezoelectric material and at least one SAW sensor (33, 34, 35) formed thereon and at least one control and reading device (4) for the at least one SAW sensor (33, 34, 35), characterized in that the control and reading device (4) comprises a device board (40), on whose device board front side (41) device coupling electrodes (43, 44) are formed, which are connected to a device connection (47) formed on the device board (40) by means of electrical conductors (45, 46) passing through the device board (40), and the cartridge (2) comprises cartridge coupling electrodes (23, 24; 25, 26), which are each capacitively coupled to the device coupling electrodes (43, 44) on the one hand and on the other hand to sensor electrodes (31, 32) of the at least one SAW sensor (33, 34, 35), wherein at least one magnetic element (51, 52) is formed on the device board (40), and the cartridge (2) comprises at least one metallic and / or magnetic alignment element (6) aligning with the at least one magnetic element (51, 52).

2. SAW sensor module according to claim 1, characterized in that the cartridge (2) comprises a carrier board (20) located between the sensor chip (30) and the device board (40), on which carrier board (20) the cartridge coupling electrodes (23, 24; 25, 26) are formed.

3. SAW sensor module according to one of the preceding claims, characterized in that a fluid frame (7) enclosing a fluid basin (70) is constructed on a SAW sensor component (3), and a cap (71) is formed on the sensor chip (30) around the fluid frame (7), wherein the cap (71) and the fluid frame (7) cover the sensor electrodes (31, 32) and reflectors of the at least one SAW sensor (33, 34, 35).

4. SAW sensor module according to claim 3, characterized in that the fluid frame (7) is a lever structure which is suspended in a groove (72) formed on the cap (71) on the one hand and on the other hand presses on a sensor chip front side (37) of the sensor chip (30) and is sealed there.

5. SAW sensor module according to claim 3 or 4, characterized in that the fluid frame (7) forms a funnel comprising oblique walls on the at least one SAW sensor (33, 34, 35) or such a funnel is placed on the fluid frame (7).

6. SAW sensor module according to one of claims 3 to 5, characterized in that the cap (71) is a plastic injection-molded part through which the at least one alignment element (6) runs.

7. SAW sensor module according to one of claims 3 to 6, characterized in that a cover film (9) is laminated over the fluid frame (7).

8. SAW sensor module according to one of the preceding claims, characterized in that the cartridge (2) comprises a plurality of strip-shaped SAW sensors (33, 34, 35) arranged parallel to one another.

9. SAW sensor module according to claim 8, characterized in that between the SAW sensors (33, 34, 35), partition walls (38) are formed.

10. SAW sensor module according to claim 8 or 9, characterized in that at least two of the SAW sensors (33, 34, 35) have different propagation paths (L1, L2, L3).

11. SAW sensor module according to one of claims 8 to 10, characterized in that a separate capacitive connection is associated to each of the SAW sensors (33, 34, 35).

12. SAW sensor module according to one of the preceding claims, characterized in that at least one RFID chip (10) is formed on the sensor chip (30) and / or on the carrier board (20), said RFID chip being connected to the device connection (47) via at least one capacitive coupling.

13. SAW sensor module according to one of the preceding claims, characterized in that a dielectric protective membrane (8) is arranged between the cartridge (2) and the control and reading device (4).