Patent Publication Number: US-2020284773-A1

Title: Fluid sensing device for a portable electronic device

Description:
The invention relates to a fluid sensing device for a portable electronic device equipped with a fluid sensor. 
     Small size fluid sensors, such as small size metal oxide (MOX) sensors or carbon nanotube (CNT) sensors are known and may be used, for example, to monitor indoor air quality, to estimate the blood alcohol content from a user&#39;s exhalation or for military purposes with wearable toxic-gas detectors. 
     Such fluid sensors may be directly integrated into a portable electronic device. In this case, the fluid sensor is accessible though openings in the housing, like the openings for a microphone as described in the prior art document EP3187865 A1; or via other openings, e.g. a speaker of the portable electronic device. As an alternative to built-in fluid sensors, plug-in fluid sensor modules may be connected to portable electronic devices. 
     However, depending on the sensing device&#39;s location, adding fluid analysis capability to smartphones and wearables may require to actively feed the fluid towards, through and/or out of the sensing device. Fluid moving means are known in the art and comprise mechanical moving parts, such as mechanical pumps or fans, that are not suitable for mobile devices like cell phones, smartphones, smartwatches, portable computers or tablet computers because of their high energy consumption, their bulkiness and the emitted noise level. 
     It is therefore an object of the present invention to provide a fluid sensing device for a portable electronic device that overcomes the problems mentioned above. In particular, it is the object of the present invention to provide a fluid sensing device that consumes less energy and/or less volume demanding than a mechanical gas moving device and/or operates more silently. It is also an object to provide a portable electronic device comprising such a fluid sensing device as well as a method for moving a fluid also overcoming the above mentioned problems. 
     The object of the invention is achieved with a fluid sensing device for portable electronic device according to claim  1 . The fluid sensing device comprises a fluid sensing means configured to analyze a sampling volume; and a fluid moving means comprising a motionless fluid pumping means using thermal transpiration for moving the sampling volume. The object of the invention is thus achieved with a motionless gas pump operating by thermal transpiration, also called a Knudsen pump. A Knudsen pump comprises narrow channels and/or a porous media under temperature gradient. By allowing the fluid to flow from the cold end to the hot end, i.e. by thermal transpiration, the Knudsen pump generates a flow of a fluid with no moving parts. Since Knudsen pumps do not comprise any moving parts, the inventive device operates more silently. Furthermore, the size of the fluid moving means is reduced, as Knudsen pumps can be more compact than mechanical pumps, and thus are suitable for portable electronic device. In addition, unlike mechanical gas pumps, Knudsen pumps only require heat, as an energy source. As a result, the inventive fluid sensing device comprising a motionless gas pump operating by thermal transpiration consumes less energy, takes less place and operates more silently compared to prior art fluid moving means. The Knudsen pump can be used to move the fluid towards the sensing means and/or to move it away from the sensing means after analysis. 
     The present fluid sensing device for a portable electronic device can be further improved according to various advantageous embodiments. 
     According to one embodiment of the invention, the fluid sensing device can operate with a gas as fluid. Hence, the fluid sensing device could be used, for example, to probe a user&#39;s breath for the purpose of monitoring blood alcohol content or some health indicators. In another example, the fluid sensing device could also be used to monitor the environment, i.e. ambient air, or to detect toxic gas. 
     According to one embodiment of the invention, the motionless gas pumping means can be powered by a heat source. Furthermore, according to another embodiment of the invention, the heat source of the motionless fluid pumping means can be based on Joule effect and/or solar energy. As a result, unlike mechanical gas pumps that rely on AC driving voltages; providing a heat source by means of DC voltages may be sufficient to power motionless fluid pumping means using thermal transpiration, which consequently, operate with simple electronic control circuitry and low energy consumption. 
     According to one embodiment of the invention, the fluid sensing device for a portable electronic device can further comprise a battery and/or electronic components used as the heat source of the motionless fluid pumping means. In particular, it is the battery and/or electronic components that can be used for other functionalities of the portable electronic device that can be used as the heat source for the Knudsen pump. This kind of heat source is already available in portable electronic devices so that no extra energy source needs to be added. The Knudsen pump takes thus advantage of unused wasted energy. Therefore, the number of components can be kept low, and consequently the weight of the fluid sensing device remains low. 
     According to one embodiment of the invention, the fluid moving means can be capable of adjusting the flow rate and/or the temperature of the sampling volume. Indeed, the fluid of the sampling volume can be processed and preheated by the fluid moving means, to prepare the sampling volume such that it can be analyzed by the fluid sensing means. Adjusting the flow rate and/or the temperature of the gas sampling volume can also exercised a catalytic effect on the fluid sensing means, in particular on metal oxide based fluid sensing means. 
     According to one embodiment of the invention, the fluid sensing means can be sensitive to at least one type of molecule. For example, the fluid sensing means can be sensitive to carbon dioxide (CO 2 ) in ambient air or in the exhaled air of a user. 
     According to one embodiment of the invention, the fluid sensing means comprises a metal oxide (MOX) sensor and/or a carbon nanotube (CNT) sensor. MOX sensors and CNT sensors can provide reliable fluid analysis. Moreover, the CNT sensor has, in particular, low energy consumption. 
     According to one embodiment of the invention, the fluid sensing device can further comprise a reverse thermal transpiration-based fluid pumping means configured for ejecting the sampling volume. Therefore, the fluid sensing device can expel the gas out of the fluid sensing device, once the gas has been analyzed by the fluid sensing means. 
     According to one embodiment of the invention, the motionless fluid pumping means can further comprise a reversible motionless fluid pumping means using thermal transpiration for moving the sampling volume with a bidirectional flow. Hence, the number of components can be reduced, as the same fluid pumping means is used to move the fluid towards the device as well as to eject it. 
     The object of the invention is also achieved with a portable electronic device, in particular a portable telecommunication device or a wearable device, comprising at least a fluid sensing device according one of the claims  1  to  9 , like described in the above embodiments. 
     According to an embodiment, the fluid sensing means can be positioned within the same opening of the portable device&#39;s housing than at least one other functional unit. Thus, fluid analyzing capability can be provided without having to provide one additional hole in the device&#39;s housing. 
     According to an embodiment, the fluid sensing means can be positioned further inside the housing than the at least one other functional unit. By using the motionless fluid moving means the design liberty for placing the fluid sensing device is improved. 
     The object of the invention is further achieved with a method for moving a fluid in a portable electronic device, according to claim  14 . The portable electronic device can be the one as described above. The inventive method for moving a fluid in a portable electronic device comprises the steps of feeding a sampling volume towards a fluid sensing means, analyzing the sampling volume by the fluid sensing means and ejecting the sampling volume from the fluid sensing means; wherein the first and/or the second steps comprise(s) a motionless fluid pumping means using thermal transpiration. The object of the invention is achieved with a method comprising a motionless gas pump operating by thermal transpiration, also called a Knudsen pump. Hence, by using a Knudsen pump, the size of the fluid moving means is reduced, as Knudsen pumps can be more compact than mechanical pumps, and thus is suitable for portable electronic device. Since Knudsen pumps do not comprise any moving parts, the inventive device operates more silently. In addition, unlike mechanical gas pumps, Knudsen pumps only require heat, like Joule heating, as an energy source. Consequently, the method for moving a fluid in a portable electronic device comprising a motionless gas pump operating by thermal transpiration provides a method that consumes less energy, takes less place and operates more silently than mechanical moving means. 
     According to one embodiment of the invention, the method for moving a fluid in a portable device comprises a motionless fluid pumping means using thermal transpiration that can adjust the flow rate and/or the temperature of the sampling volume. As a consequence, the gas of the sampling volume can be processed and preheated by the motionless fluid pumping means, which thus, at the same time prepares the sampling volume so that it can be analyzed in the fluid sensing means. Adjusting the flow rate and/or the temperature of the gas sampling volume can also exercise a catalytic effect on the fluid sensing means. 
     Finally, the object of the invention is also achieved by the use of a fluid sensing device, in a portable electronic device, with a motionless fluid pumping means operating by thermal transpiration for moving a fluid towards and/or from the fluid sensing means. 
    
    
     
       Additional features and advantages of the present invention will be described with reference to the drawings. In the description, reference is made to the accompanying figures that are meant to illustrate preferred embodiments of the invention. It is understood that such embodiments do not represent the full scope of the invention. 
         FIG. 1  illustrates a schematically, perspective view of a portable electronic device comprising a fluid sensing device according to a first embodiment of the invention; 
         FIG. 2  illustrates a block diagram with the components of the fluid sensing device according to the first embodiment; 
         FIG. 3  illustrates a block diagram with components of a fluid sensing device according to a second embodiment; 
         FIG. 4  illustrates a block diagram with components of a fluid sensing device according to a third embodiment; 
         FIG. 5  illustrates a flowchart with the steps of a method for moving a fluid in a portable electronic device according to a fourth embodiment of the invention; 
         FIG. 6  illustrates a chart with the steps of a method for moving a fluid within a portable electronic device according to a fifth embodiment of the invention; 
         FIG. 7  illustrates a block diagram with the components of the fluid sensing device according to the sixth embodiment of the invention. 
     
    
    
     The portable electronic device  1  illustrated in  FIG. 1  represents a portable telecommunication device such as a mobile phone. The portable electronic device  1  can also be a smartphone, a tablet, a laptop, a personal electronic assistant, a tracking device, an electronic wearable or the like. 
     The portable electronic device  1  comprises a housing  2  which in this embodiment has a rectangular shape. One of the two main sides of the portable electronic device  1 , i.e. the front side  3 , is provided with a display device  5 , such as a screen, and interfacing elements like a button  7 , allowing the user to interact with the portable electronic device  1 . 
     The portable electronic device may comprise one or more openings. The front side  3  is further provided with an opening  9  for a loudspeaker. The opening  9  is protected from dirt, like dust particles, by a grid  10 . The housing  2  may comprise further openings  13 ,  15 , e.g. on the lower side  11  of the display device  5 . Also, the side-wall  17  of the housing  2  may be provided with another opening  19 . A microphone, a loudspeaker, a headphone jack hole, a charger hole and/or the like can be provided in openings like the openings  13  and/or  15  and/or  19 . 
     The dotted lines on  FIG. 1  represent inner portions  21 ,  23 ,  25 ,  27  having various possible shapes inside the openings  9 ,  13 ,  15 ,  19  of the housing  2  of the portable electronic device  1 . In the tubular-shaped duct  29  of the opening  13 , a fluid sensing device  100  according to a first embodiment of the invention, is mounted. The fluid sensing device  100  comprises a fluid moving means  200  for moving a sampling volume towards a fluid sensing means  300  for analyzing the sampling volume. The fluid sensing device  100  will be described in more detail in  FIG. 2 . 
     The fluid sensing means can be a metal oxide (MOX) sensor and/or a carbon nanotube (CNT) sensor. The fluid sensing means  300  of the fluid sensing device  100  can also comprise gold nanoparticles, a silicon nanowire, a quartz crystal microbalance, a colorimetric sensor and/or a conductive polymer; which represent other low energy consumption sensing means. The fluid moving means  200  is in a fluid connection with the opening  13  of the tubular-shaped duct  29 . 
     In this embodiment, the opening  13  receiving the fluid sensing device  100  can be located near the fluid to analyze, e.g. located near the mouth of a user for the purpose of analyzing the user&#39;s exhaled air while the user talks on the portable electronic device  1 . In other variants the fluid sensing device  100  could be positioned elsewhere like in the inner portions  21 ,  23  or  27  of the other openings  9 ,  15  or  19 , depending on the available space inside the housing  2 . 
     According to further variants the fluid sensing device  100  could be placed inside one of the openings  9 ,  13 ,  15  or  19  together with one or more other functional features, like the microphone, the speaker or alike. In particular, due to the use of the fluid moving means  200 , the fluid sensing device  100  could be positioned further inside the housing  2  than the other functional feature. 
       FIG. 2  illustrates a block diagram of the fluid sensing device  100  according to the first embodiment of the present invention, as illustrated in  FIG. 1 . Elements with the same reference numeral already used in  FIG. 1  will not be described in detail again but reference is made to their description above. 
       FIG. 2  illustrates the motionless fluid pumping means  200  powered by a heat source  400  and the fluid sensing means  300 . 
     The motionless fluid pumping means  200  generates a gas flow based on thermal transpiration using, e.g. narrow channels and/or a porous media which allowing thermal transpiration to occur to generate a flow of a fluid entering the motionless fluid pumping means  200 . With a temperature gradient applied along the narrow channel, which is not represented in  FIG. 2 , the fluid flows from the cold end to the hot end. As the Knudsen pump  200  does not comprise moving parts, it operates more silently than mechanical gas pumps, and thus is well-adapted for use in portable electronic device. 
     To create the temperature gradient, the motionless fluid pumping means  200  uses a heat source  400  of the portable electronic device  1 . The motionless fluid pumping means  200  operates with simple electronic control circuitry and low energy consumption. 
     The heat source  400 , represented in  FIG. 2 , can be a battery  400  enclosed in the housing  2  of the portable electronic device  1 . The battery  400  can, for example, be a rechargeable battery used to run the various functionalities of the portable electronic device  1 . By placing the heat source  400  in the vicinity of the motionless fluid pumping means  200  one can take advantage of the heat  43  created by the battery  400 . Thus, the usually wasted thermal energy can be used according to the invention to run the motionless fluid pumping means  200 . 
     The heat source  400  can also comprise any of the other components of the portable electronic device  1  that heat up during use or the heat a solar energy conversion means. 
     The fluid sensing device  100  according to the first embodiment functions as follows: a sampling volume  41  of a fluid to be analyzed, e.g. the breath of a user or the ambient air, is drawn into the opening  13  in the housing  2  by the motionless fluid pumping means  200  of the fluid sensing device  100 . Due to the temperature gradient provided by the heat source  400 , the sampling volume is then moved towards the fluid sensing means  300 , as illustrated by reference numeral  45 . 
     The parameters of the sampling volume  41 , like temperature, pressure and/or flow rate, can be controlled when passing through the motionless fluid pumping means  200 . 
     It becomes thus possible to prepare the sampling volume  41  such that its temperature and/or flow rate is adjusted in accordance with the operating parameters imposed by the fluid sensing means  300 . Hence, additional preheating operations required inside the fluid sensing means  300  can be reduced or even eliminated. By adjusting the flow rate and/or the temperature of the gas sampling volume  41 , it becomes, for example, possible to enable a catalytic effect needed for sensing the sampling volume  45  in the fluid sensing means  300 . 
     As illustrated in  FIG. 2 , the sampling volume  45  is analyzed by the fluid sensing means  300  which is sensitive to at least one type of molecule. The fluid sensing means  300  can be configured to analyze ambient air, e.g. for checking air quality, and/or to analyze a user&#39;s exhalation, e.g. for measuring blood alcohol content. 
     The sampling volume then leaves the fluid sensing means  300  via opening  13  as illustrated by reference numeral  47 . 
     Instead of taking different paths as illustrated in  FIG. 2  but leaving via the same opening  13 , the input sampling volume  41  and the output sampling volume  47  can move through different openings and paths of the housing  2  (not shown). 
     The  FIG. 3  illustrates a block diagram of a fluid sensing device  103  according to a second embodiment of the present invention. Elements with the same reference numeral already used in  FIGS. 1 and 2  will not be described in detail again but reference is made to their description above. 
     As already described with respect to the first embodiment and illustrated  FIG. 2 , an input sampling volume  41  is moved towards the fluid sensing means using the motionless fluid pumping means  200 . In this embodiment, however, an additional reverse thermal transpiration-based fluid pumping means  205  is used to move the output sampling volume  47  out of the fluid sensing means  300  towards the opening  13  or any other opening in the portable electronic device  1  (as indicated by the reference numeral  49 ). 
     The reverse thermal transpiration-based fluid pumping means  205  operates in the opposite flow direction compared to the motionless fluid pumping means  200 . The motionless fluid pumping means  200  and the reverse motionless fluid pumping means  205  can have a common heat source  400 , like illustrated in  FIG. 3  to provide the necessary heating  43  to each one of the motionless fluid pumping means  200 ,  205 . 
     In a variant, not illustrated in  FIG. 3 , each one of the motionless fluid pumping means  200 ,  205  has its own heat source. 
     Depending on the process parameters, the ejected sampling volume  47  is cooled down in the motionless fluid pumping means  205  before leaving the portable electronic device  1 . 
       FIG. 4  illustrates a block diagram of a fluid sensing device  105  according to a third embodiment of the present invention. Elements with the same reference numeral already used in  FIGS. 1, 2 and 3  will not be described in detail again but reference is made to their description above. 
     The fluid sensing means  105  represented in  FIG. 4  comprises a reversible motionless fluid pumping means  207  configured to operate in two opposite directions. 
     In configuration A, the reversible motionless fluid pumping means  207  forces the fluid from the opening  13  towards the fluid sensing means  300 . In this configuration, the cold side of the motionless fluid pumping means  207  is located in the area  209 , facing the opening  13  in the housing  2 , whereas the hot side of the pumping means  207  is located in the area  211 , facing the fluid sensing means  300 . 
     In configuration B, the reversible motionless fluid pumping means  207 , forces the fluid from the fluid sensing means  300  towards the opening  13  of the housing  2 . The cold side of the pumping means  207  is then located in the area  211  facing the fluid sensing means  300 , whereas the hot side of the pumping means  207  is located in the area  209 , facing the opening  13 . The reversible motionless fluid pumping means  207  comprises a thermoelectric material to be able to change the direction of the pumping by reversing the electrical current passing through the thermoelectric material, and thus the hot side and the cold side of the reversible motionless fluid pumping means  207  can be exchanged. 
     In use, the fluid sampling volume  51  is dragged into the housing  2  via the opening  13  by the reversible motionless fluid pumping means  207  in configuration A and pushed (indicated by reference numeral  53 ) towards the fluid sensing means  300 , where it is analyzed. 
     Once the sampling volume  53  has been analyzed, a controlling means  405  changes the operational state of the reversible motionless fluid pumping means  207  to operate in configuration B. Hence, the sampling volume  53  is moved away from the fluid sensing means  300  towards the opening  13  of the fluid sensing means  105 . The sampling volume  51  is then expelled from the housing  2  of the portable electronic device  1 . 
       FIG. 5  illustrates a flowchart  150  illustrating the steps in a method for moving a fluid in a portable electronic device according to the fourth embodiment of the invention. Elements with the same reference numeral already used in the embodiments 1 to 3 illustrated in  FIGS. 1 to 4  will not be described in detail again but reference is made to their description above. 
     In the first step  501  of the method for moving a fluid in a portable device  1  a sampling volume is fed towards the fluid sensing means  300  using a motionless fluid pumping means  200 ,  207  using thermal transpiration like described above with respect to one of embodiments 1 to 3. While moving the sampling volume towards the fluid sensing means  300 , the fluid parameters, such as fluid temperature, flow rate and/or pressure can be adjusted. 
     In the next step  503  the sampling volume is analyzed by the fluid sensing means  300  as described above. 
     In step  505  the sampling volume is ejected from the fluid sensing means  300  using the motionless fluid pumping means  200 ,  205 ,  207 . 
     In a variant, fluid parameters, such as fluid temperature, flow rate and/or pressure can be adjusted by the motionless fluid pumping means  200 ,  205 ,  207  prior to leaving the opening  9 ,  13 ,  15  or  19  of the housing  2  of the portable electronic device  1 . As a consequence, the fluid parameters can be controlled before to be ejected and thus, before that the fluid may come into contact with user&#39;s skin, hair or any material near the openings  9 ,  13 ,  15 ,  19  of the housing  2 .  FIG. 6  illustrates a chart  160  with processing steps in accordance with the method for moving a fluid within a portable electronic device comprising a fluid sensing device according to a fifth embodiment of the invention. Elements with the same reference numeral already described in embodiments 1 to 4 and illustrated  FIGS. 1 to 5  will not be described in detail again but reference is made to their description above. 
     The sampling fluid to be analyzed, illustrated by reference numeral  41 , is moved towards the fluid sensing means  300  by the motionless fluid pumping means  200 . 
     Using the motionless fluid pumping means  200 , the fluid parameters, such as the fluid flow rate, the fluid temperature and/or the pressure can be adapted. Indeed, the parameters of the sampling volume  41  are adjusted in accordance with the operating parameters of the fluid sensing means  300  and/or in accordance with a desired catalytic effect. 
     At step  211 , it is therefore determined whether the fluid parameters of the sampling volume  41  have to be adjusted or are within the range needed by the fluid sensing means  300 . 
     If the parameters of the sampling volume  41  have to be adjusted, the sampling volume  42  is returned to the motionless fluid pumping means  200 . 
     If the parameters of the sampling volume  41  do not have to be further adjusted, the sampling volume  45  can thus be fed into the fluid sensing means  300 . 
     The sampling volume  45  is then analyzed by the fluid sensing means  300 . 
     Once the sampling volume  45  is analyzed by means of the fluid sensing means  300 , the sampled volume  47  is ejected from the portable electronic device  1 . In this embodiment, the sampling volume  45  is ejected by means of the reverse thermal transpiration-based fluid pumping means  205  of the second embodiment. The reverse motionless fluid pumping means  205  operates in the opposite flow direction of the motionless fluid pumping means  200 . As an alternative, the reversible motionless fluid pumping means  207  of the third embodiment may also be used. 
     At step  213 , the portable electronic device  1  determines whether the fluid parameters of the sampled volume  47  have to be adjusted before ejection. 
     If the parameters of the sampling volume  47  do not have to be adjusted, the sampling volume  49  is expelled out of the portable electronic device  1  via the reverse motionless fluid pumping means  205 . 
     If the parameters of the sampling volume  47  have to be adjusted, the sampling volume  48  is returned to the motionless fluid pumping means  205 , e.g. as they are too hot which might represent a risk of injury to the user of the portable electronic device  1 . 
       FIG. 7  illustrates a block diagram of a fluid sensing device  107  according to a sixth embodiment of the invention. Elements with the same reference numeral already described in embodiments 1 to 5 and illustrated in  FIGS. 1 to 6  will not be described in detail again but reference is made to their description above. 
       FIG. 7  illustrates the fluid sensing device  105  comprising the reversible motionless fluid pumping means  207  and the fluid sensing means  300  according to the third embodiment, as described in  FIG. 4 . 
     According to the sixth embodiment of the invention, the fluid sensing device  105  is placed inside the opening  13  together with another functional unit  107 , e.g. a microphone. In particular, due to the use of the reversible fluid moving means  207 , the fluid sensing device  105  is positioned further inside the housing  2  than the microphone  107 , in particular behind the functional feature  107  of the portable electronic device  1 . 
     As a consequence, no additional hole is necessary in the device&#39;s housing  2  and the fluid sensing device  105  can be positioned anywhere inside the housing where sufficient space is available. 
     The fluid sensing device  100 ,  103 ,  105  can, e.g., be positioned on an existing structure inside the portable electronic device  1 , like on the printed circuit board PCB. 
     The various individual features of the embodiments 1 to 6 can be independently combined to create further variants according to the invention.