Patent Publication Number: US-2021161433-A1

Title: Sensor Device and Method of Manufacturing a Sensor Device

Description:
This patent application is a national phase filing under section 371 of PCT/EP2019/069808, filed Jul. 23, 2019, which claims the priority of German patent application 10 2018 118 110.8, filed Jul. 26, 2018, each of which is incorporated herein by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a sensor device and a method of manufacturing a sensor device. 
     BACKGROUND 
     Smartwatches that monitor various body functions, such as heart rate or blood oxygen saturation, in addition to activity tracking, are becoming increasingly popular. 
     In addition to monitoring heart rate, which is done either via a pulse belt or, in the case of modern watches, via optical heart rate measurement, it is desirable to analyze body fluids, especially sweat. By analyzing the sweat contents, statements can be made, for example, regarding the athlete&#39;s fitness level, e.g. by means of a lactate analysis, the need for mineral intake, e.g. by means of an electrolyte analysis, or even possible diseases. 
     SUMMARY 
     Embodiments provide a sensor device that is suitable for use in the analysis of body fluids and, in particular, can be integrated into a smartwatch. Further embodiments provide a method for manufacturing a sensor device. 
     A sensor device comprises at least one light emitter configured to emit light and at least one light detector configured to detect light. The at least one light emitter and the at least one light detector are arranged in a housing. At least one channel extends through the housing. The at least one channel may be configured to receive body fluids. The at least one channel may have a diameter such that a fluid, in particular a body fluid such as sweat, may be drawn into the at least one channel by means of a capillary effect. For example, the at least one channel may have a diameter of at most 1 mm. However, the diameter may also be larger or smaller. 
     The at least one channel forms a through hole or passageway through the housing, i.e., the at least one channel extends from a first outer surface of the housing to a second outer surface of the housing, which may be opposite the first outer surface, for example. Accordingly, a liquid or gas entering the at least one channel at the first outer surface of the housing may exit the at least one channel at the second outer surface of the housing. Consequently, the sensor device is configured such that body fluid can be received into the at least one channel when the sensor device is suitably placed on the skin of a person, without the need for further devices, in particular pumps or the like. 
     In the sensor device, the at least one light emitter and the at least one light detector are arranged in such a way that the light emitted by the at least one light emitter at least partially first passes through the at least one channel and is then detected by the at least one light detector. 
     The light emitted by the at least one light emitter may pass through the at least one channel in any chosen direction, for example in a direction perpendicular or approximately perpendicular to the direction of propagation of the at least one channel, i.e., perpendicular to the direction of flow of the liquid or gas in the at least one channel. Furthermore, the light emitted by the at least one light emitter may also pass through the at least one channel, at least partially, multiple times, for example by means of one or more light reflecting surface(s), before the light impinges on the at least one light detector. 
     The light detected by the at least one light detector can be analysed using any analysis method known to the skilled person. For example, spectroscopic analysis methods are familiar to the skilled person. When light shines through or passes through the at least one channel, the light can be at least partially absorbed by the liquid or gas contained in the at least one channel. It is also possible that only light of certain wavelengths is absorbed. Based on the spectrum of the light emitted by the at least one light emitter and the spectrum of the light detected by the at least one light detector, conclusions can be drawn about the substances present in the at least one channel at that time. In particular, the concentration of certain substances can be determined. For example, the sensor device can be used to obtain data on mineral(s), lactate molecules and/or blood sugar (glucose) contained in the fluid. 
     The light emitted by the at least one light emitter or the light detected by the at least one light detector may be, for example, light in the visible range, ultraviolet (UV) light, and/or infrared (IR) light. 
     The at least one light emitter and/or the at least one light detector can be optoelectronic semiconductor components, in particular semiconductor chips. For example, a light emitter can be designed as a light-emitting diode (LED), as an organic light-emitting diode (OLED), as a light-emitting transistor or as an organic light-emitting transistor. Furthermore, an LED, an OLED or a correspondingly designed, in particular organic transistor, can also be designed as a light detector. The at least one light emitter and/or the at least one light detector can furthermore be part of an integrated circuit. 
     In addition to the at least one light emitter and/or the at least one light detector, other semiconductor devices and/or other components may be integrated into the sensor device. 
     The sensor device can be manufactured relatively inexpensively and also very compactly. This allows the sensor device to be used in consumer products, also called consumer goods or consumer products, and in particular in wearable electronic devices, such as a smartwatch. 
     The sensor device, in particular the housing of the sensor device, may have a size, i.e. extension, of at most 10 mm in a first dimension. Also in a second dimension, the sensor device may have a size of at most 10 mm. In a third dimension, the sensor device may have a size of at most 3 mm. The three dimensions may each be orthogonal to each other and be described, for example, by the x, y and z axes of a Cartesian coordinate system. 
     In one embodiment, the sensor device comprises a substrate having at least one opening, which is in particular a through hole. The at least one light emitter and the at least one light detector are mounted on the substrate, and the at least one channel extends through the at least one opening. In particular, the at least one channel is arranged between the at least one light emitter and the at least one light detector. 
     The substrate can, for example, be a lead frame that is overloaded with a mold compound, in particular a plastic. Furthermore, the substrate can be a so-called QFN (quad flat no leads package) flat old. A QFN flat old consists of a lead frame, in particular a coated copper lead frame, which is overloaded by a mold compound, wherein the mold compound has the same height as the lead frame, i.e., no cavities are created. The at least one opening may extend through the lead frame and/or the mold compound. The substrate may further be a printed circuit board (PCB), a ceramic substrate, or any other suitable substrate. 
     A transparent body may be mounted on the at least one opening of the substrate. The transparent body includes at least one passageway, i.e., a channel. The at least one passageway forms a portion of the at least one channel. For example, the transparent body may be mounted on the substrate above the at least one opening and may not extend into the at least one opening. In this case, the at least one opening in the substrate may form the at least one channel together with the at least one passageway in the transparent body. In particular, a liquid may be drawn into the at least one channel by a capillary effect. For example, the transparent body may be a glass capillary. 
     Transparent in this context means that the body is at least transparent to at least part of the light emitted by the at least one light emitter or at least to light in a certain wavelength range, such that the light of this wavelength range is absorbed as little as possible by the body itself. 
     As an alternative to a body placed on the substrate, a transparent body may be inserted into the at least one opening in the substrate. The body has a plurality of microchannels forming at least a portion of the at least one channel or forming the entire at least one channel. The microchannels provide an enhanced capillary effect to draw fluid into the microchannels. The microchannels may each comprise a diameter in the range of 1 μm to 1,000 μm, and in particular in the range of 200 m to 300 μm. 
     The at least one light emitter and the at least one light detector may be encapsulated with a transparent material. Again, transparent means that the material is at least transparent to at least a portion of the light emitted by the at least one light emitter or at least to light in a particular wavelength range. For example, the transparent material may be a transparent silicone. 
     A light-reflecting or reflective material can be applied to the transparent material. Reflective here means that the material is at least reflective to at least a portion of the light emitted by the at least one light emitter, or at least to light in a particular wavelength range. The light reflective material may have the function of guiding the light generated by the at least one light emitter to the at least one channel with as little loss as possible to pass through the liquid or gas in the at least one channel, and then guiding the light to the at least one light detector with as little loss as possible. For example, the reflective material may be a silicone with TiO 2 . 
     The interface between the transparent material in which the light is guided and the reflective material adjacent to the transparent material may have a particular shape that allows light emitted from the at least one light emitter to be guided to the at least one light detector. For example, the shape of at least a portion of the interface may be like a parable or parabolic. 
     The transparent material and the light reflective material may encapsulate the at least one light emitter and the at least one light detector, and may form at least a portion of a housing. 
     Instead of passing the liquid or gas to be analysed through a body having at least one passageway or a plurality of microchannels, such a body can be dispensed with and the channel can be formed by the opening in the substrate, the transparent material, and the light reflective material. In this case, the sidewalls of the at least one channel are formed at least partly by the transparent material and the light reflective material. 
     According to a further embodiment, the sensor device comprises a substrate on which the at least one light emitter and the at least one light detector are mounted. The substrate may be configured as the substrate described above, but doesn&#39;t need to comprise an opening. The at least one channel extends above the at least one light emitter as well as the at least one light detector. In other words, the at least one light emitter as well as the at least one light detector are arranged between the substrate and the at least one channel. The at least one channel may extend in a direction substantially parallel to a major surface of the substrate. Further, the channel may include a plurality of microchannels, particularly having the embodiments described above. Further, a body having a plurality of microchannels may be arranged on the at least one light emitter as well as the at least one light detector. 
     A light reflective layer can be arranged above the at least one channel. The light reflective layer can in particular be a mirror. Consequently, the light emitted by the at least one light emitter first passes through the at least one channel, is then reflected by the reflective layer, and passes through the at least one channel in the reverse direction to reach the at least one light detector. An advantage of this embodiment is that the light passes through the at least one channel twice and consequently the absorption by the liquid in the at least one channel is increased accordingly. 
     To prevent light from traveling directly from the at least one light emitter to the at least one light detector and thus falsifying the measurement results, a light reflective material or a light absorbing material may be applied to the substrate between the at least one light emitter and the at least one light detector. 
     The sensor device may include an analysis unit that performs the above-described analysis of a liquid and/or gas located in the at least one channel based on light emitted from the at least one light emitter and light detected by the at least one light detector. 
     The analysis unit may be arranged on the substrate together with the at least one light emitter and the at least one light detector, but may also be arranged on a separate substrate or circuit board. In particular, the analysis unit may be an integrated circuit (IC) and may comprise a data memory. 
     It can be provided that the sensor device comprises exactly one light emitter and/or exactly one light detector. However, the sensor device may also include multiple light emitters and/or multiple light detectors. In the latter case, at least two of the light emitters may emit light of different wavelengths and/or at least two of the light detectors may detect light of different wavelengths. 
     The sensor device may be integrated into a wearable electronic device. The wearable electronic device may be a so-called “wearable”, i.e., an electronic device that is attached to the user&#39;s body or integrated into the user&#39;s clothing, such as an activity or fitness tracker or a smartwatch. A smartwatch (English for “smart watch”) is an electronic wristwatch that has additional sensors, actuators, and/or computer functionality or connectivity. Further, the sensor device may be integrated into a piece of jewellery, such as a finger ring, earring, or necklace. Wearing the device directly on the user&#39;s body provides a simple means of collecting body fluids, particularly sweat, into the at least one channel for subsequent analysis. Further, the wearable electronic device may be a handheld device or portable device, such as a smartphone, tablet, or handheld medical device. 
     The wearable electronic device may include an attachment device connected to the sensor device for attaching the sensor device to a body part of a person. For example, the attachment device may be a wristband or a heart rate belt or chest strap. 
     The sensor device described in the present application can be used to analyse body fluids, in particular sweat. The analysis of sweat represents a very simple alternative compared to blood glucose testing, via which many similar conclusions, e.g., lactate and blood glucose concentration, are possible. 
     A method of manufacturing a sensor device comprises providing at least one light emitter and at least one light detector, as well as encapsulating the at least one light emitter and the at least one light detector in a housing. At least one channel forms a passageway through the housing. Further, the at least one light emitter and the at least one light detector are arranged such that light emitted from the at least one light emitter at least partially passes through the at least one channel and is thereafter detected by the at least one light detector. 
     The method of manufacturing a sensor device may include the sensor device embodiments described above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the following, embodiments of the invention are explained in more detail with reference to the accompanying drawings. 
         FIGS. 1A to 1B  show illustrations of an embodiment of a sensor device with a channel for receiving body fluids; 
         FIG. 2  shows an illustration of an embodiment of a method of manufacturing a sensor device; 
         FIG. 3  shows an illustration of an embodiment of a wearable electronic device with a sensor device; 
         FIGS. 4A to 4B  show illustrations of an embodiment of a sensor device with a plurality of microchannels; 
         FIG. 5  shows an illustration of an embodiment of a sensor device having a channel in a layer of transparent and reflective material; and 
         FIG. 6  shows an illustration of an embodiment of a sensor device with a plurality of horizontally running microchannels. 
     
    
    
     In the following detailed description, reference is made to the accompanying drawings, which form a part of this description and in which specific embodiments in which the invention may be practiced are shown for illustrative purposes. Since components of embodiments may be positioned in a number of different orientations, the directional terminology is for illustrative purposes and is not limiting in any way. It is understood that other embodiments may be used and structural or logical changes may be made without departing from the scope of protection. It is understood that the features of the various embodiments described herein may be combined with each other, unless specifically indicated otherwise. Therefore, the following detailed description is not to be construed in a limiting sense. In the figures, identical or similar elements are provided with identical reference signs where appropriate. 
     DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
       FIG. 1A  schematically shows a sensor device  10  in a sectional view.  FIG. 1B  shows the sensor device  10  in a top view from above. 
     The sensor device  10  includes a substrate  11  on which a light emitter  12  in the form of an LED semiconductor chip and a light detector  13  also in the form of an LED semiconductor chip are mounted. 
     In the present embodiment, the substrate  11  is a QFN flatmold comprising a coated copper lead frame  14  that has been overmolded by a mold compound  15 . The mold compound  15  has the same height as the lead frame  14 , i.e., the top and bottom surfaces of the lead frame  14  are not covered by the mold compound  15 . The LED semiconductor chips of the light emitter  12  and the light detector  13  each have an electrode on their bottom side and their top side. The light emitter  12  and the light detector  13  are soldered with their electrode on the bottom side to a respective contact element of the lead frame  14 . A bonding wire  19  leads from the electrodes on the upper sides of each of the light emitter  12  and the light detector  13  to a further contact element of the lead frame  14 . 
     The substrate  11  further includes an opening  16  in the form of a recess extending completely through the substrate  11 . A body  17  is applied over the opening  16  in the substrate  11 , which comprises transparent side walls and through which a passageway  18  extends in the vertical direction. The body  17  may be, for example, a thin glass capillary. The opening  16  in the substrate  11  and the passageway  18  through the body  17  form a channel  20 . The channel  20  is arranged between the light emitter  12  and the light detector  13 . 
     The light emitter  12  and the light detector  13  are encapsulated with a transparent material  21 , which may be a transparent silicone. A highly reflective material  22  is applied to the transparent material  21 , which may be, for example, a silicone mixed with TiO 2  particles. The transparent material  21  and the highly reflective material  22 , together with the substrate  11 , form a housing  25  in which the light emitter  12  and the light detector  13  are arranged. 
     The channel  20  forms a passageway through the housing  25 , i.e., it extends from a bottom surface  26 , i.e., a first outer surface, to a top surface  27 , i.e., a second outer surface, of the housing  25 . 
     An interface  28  between the transparent material  21  and the highly reflective material  22  has a predetermined shape. In the sectional view of  FIG. 1A , the interface  28  is parabolic. 
     In addition to the light emitter  12  and the light detector  13 , further light emitters and/or light detectors can be mounted on the substrate  11 . In particular, the further light emitters or detectors can be designed to generate or detect light of different wavelengths. 
     The sensor device  10  resp. the housing  25  may have a size in the x-direction shown in  FIGS. 1A and 1B  of at most 10 mm. In the y-direction, the sensor device  10  resp. the housing  25  may also have a size of at most 10 mm. In the z-direction, the sensor device  10  resp. the housing  25  may have a size of at most 3 mm. 
     During operation of the sensor device  10 , a portion of the light emitted from the light emitter  12  travels directly to the light detector  13 . The light thereby passes through the transparent material  21  and the channel  20  located between the light emitter  12  and the light detector  13 . Light that is not emitted from the light emitter  12  in a direct direction to the light detector  13  is reflected at the interface  28  by the highly reflective material  22  and is reflected toward the channel  20  due to the shape of the interface  28 . It passes through the channel  20  and can be detected by the light detector  13  after any possible further reflection at the interface  28 . Consequently, the design of the interface  28  causes a large portion of the light emitted by the light emitter  12  to pass through the channel  20  and subsequently be detected by the light detector  13 . In  FIG. 1A , the beam path of the light emitted by the light detector  13  is symbolically represented by an arrow  29 . 
       FIG. 2  schematically illustrates a method of manufacturing the sensor device  10  shown in  FIGS. 1A and 1B . 
     In a step  31 , the substrate  11  with the opening  16  is provided. The substrate  11  can be pre-produced. 
     In a step  32 , the transparent body  17  is applied to the substrate  11  such that the opening  16  in the substrate  11  and the passageway  18  through the body  17  form the channel  20 . The body  17  may, for example, be glued to the substrate  11  or otherwise attached to the substrate  11 . 
     In a step  33 , the light emitter  12  and the light detector  13  are soldered to the substrate  11  and the bonding wires  16  are generated. 
     In a step  34 , the light emitter  12  and the light detector  13  are encapsulated with the transparent material  21 . 
     In a step  35 , the highly reflective material  22  is applied to the transparent material  21 . 
       FIG. 3  schematically shows a wearable electronic device  40 , for example an activity or fitness tracker or a smartwatch, with the sensor device  10  described above in a sectional view. 
     The sensor device  10  may be integrated into the device  40  such that the bottom surface  26  and/or the top surface  27  of the housing  25  are exposed. However, it is also conceivable that the bottom surface  26  and/or the top surface  27  are not exposed. In many applications, however, it should be ensured that during operation of the device  40  a surface of the device  40 , for example the bottom surface  26  or the top surface  27  of the housing  25 , rests on the skin of the user, so that body fluid  41 , in particular sweat, enters the channel  20 , in particular by a capillary effect, and can be analysed by means of the light emitted by the light emitter  12  and detected by the light detector  13 . 
     For analysing the body fluid  41 , the device  40  has an analysis unit not shown in  FIG. 3 , which may in particular be designed as an integrated circuit. The analysis unit evaluates the light detected by the light detector using methods familiar to those skilled in the art, and can draw conclusions about the fluid  41  therefrom. The analysis unit may be integrated into the sensor device  10  or may be located outside the sensor device  10  in the device  40 . 
       FIG. 4A  schematically shows a sensor device  50  in a sectional view.  FIG. 4B  shows the sensor device  50  in a top view. 
     The sensor device  50  corresponds in large parts to the sensor device  10  described above. However, unlike the sensor device  10 , the sensor device  50  does not include the transparent body  10  with the passageway  18 , but a transparent body  51  with a plurality of microchannels forming a plurality of channels  20 . 
     Furthermore, the body  51  is not placed on the opening  16  in the substrate  11 , but is inserted into the opening  16 . Consequently, the microchannels of the body  51  extend from the bottom  26  to the top 27 of the housing  25 . 
     The microchannels can each have a diameter in the range from 1 μm to 1,000 μm and in particular in the range from 200 m to 300 μm. The advantage of the many thin microchannels is the enhanced capillary effect, through which the body fluid is transported into the microchannels more quickly or more easily. 
       FIG. 5  schematically shows a sensor device  60  in a sectional view similar to sensor devices  10  and  50 . However, the sensor device  60  does not include a transparent body with a passageway or a plurality of microchannels. 
     After the light emitter  12  and the light detector  13  have been applied to the substrate  11 , they are overmolded with a transparent material  21 , e.g. by transfer molding, also called injection molding. In this process, a recess is kept free in the transparent material  21  above the opening  16  in the substrate  11 . 
     A reflective mold compound is then applied as reflective material  22  in a further transfer molding step. A recess is also kept free in the reflective material  22  above the opening  16  in the substrate  11 . The mold compound may contain, for example, an epoxy resin or a silicone. 
     The recesses in the transparent and reflective materials  21 ,  22 , together with the opening  16  in the substrate  11 , form the channel  20  into which the body fluid can be introduced for analysis. Consequently, the side walls of the channel  20  are formed by the substrate  11 , the transparent material  21  and the reflective material  22 . Thus, the transparent body with a passageway or a plurality of microchannels can be saved. 
     During operation of the sensing device  60 , light emitted from the light emitter  12  reflects off the reflective material  22  and travels in a horizontal direction after passing through the channel  20  to the light detector  13 . 
       FIG. 6  schematically shows a sensor device  70  in a sectional view. 
     In the sensor device  70 , the light emitter  12  and the light detector  13  are mounted on a substrate  11 , which may be a QFN flatmold, a printed circuit board, a ceramic substrate, or any other suitable substrate. In the present embodiment, an optional filter  71  is also mounted on the light detector. 
     After the light emitter  12  and the light detector  13  are applied, both are embedded in a transparent material  21 , for example an epoxy resin or a silicone. The space or spaces between the light emitter  12  and the light detector  13  are then filled with a highly reflective material  22  such that there is no line of sight between the light emitter  12  and the light detector  13  and light emitted by the light emitter  12  can only reach the light detector  13  via the liquid to be analysed. 
     In a subsequent step, a transparent body  72  having a plurality of microchannels is applied to the transparent material  21  and the highly reflective material  22 . The microchannels in the body  72  form the plurality of channels  20 . The microchannels of the body  72  may be formed similarly to the microchannels of the body  51  described above, but the microchannels in the sensor device  70  extend horizontally, i.e., the microchannels extend parallel to a main surface of the substrate  11 . The microchannels may each have a diameter in the range of 1 μm to 1,000 μm, and in particular in the range of 200 μm to 300 μm. 
     A mirror  73  is then placed on the body  72 . 
     During operation of the sensor device  70 , light from the light emitter  12  passes through the fluid in the microchannels of the body  72  and is reflected back via the mirror  73 , causing the reflected light to pass to the light detector  13 . 
     Although the invention has been illustrated and described in detail by means of the preferred embodiment examples, the present invention is not restricted by the disclosed examples and other variations may be derived by the skilled person without exceeding the scope of protection of the invention.