LU Fortmann Tegethoff
STRATEC SE oa a 30001.20381LU ET LU103097
OPTICAL FLUID VERIFICATION FOR AIR BUBBLE DETECTION IN FLUID
FILLED HOSES
DESCRIPTIONField of the Invention[0001] The invention relates to a device and a method for an optical fluid verification for air bubble detection in fluid filled hoses.
Brief description of the related art[0002] Devices for use in clinical diagnostics and life sciences are produced by a number of companies. For example. STRATEC* SE, Germany. manufactures numerous devices for diagnostic specimen handling and detection for use in automated analyser systems and other laboratory instrumentation.
[0003] In compiex medical devices. liquids are transported during various processing steps of samples. To ensure à correct analysis process, monitoring of the liquid flow without influencing it during the measurement 1s essential.
[0004] The prior art relates to optical sensors which are attached to or clipped onto a hose. Such sensors measure absorption for identifying air-bubbles in the hose. The reaction time is between ps and | ms. The use of said sensors is related to the use of hoses which are made of an appropriate material with respect to the thickness of the hose material and its absorption properties.
[0005] Published Japanese patent application JPS 57163849 A relates to optically detect a bubble mixed into a fluid flowing in piping by detecting the reduction of transmitted light due to reflection. refraction, ete.. by the mixed bubble by using light transmitted through the fluid 1
STRATEC SE Fortmann Tegethoff 30001.20381LU PET LU103097 in the piping. The document teaches a device which uses a light emitting diode for emitting light which is transmitted through water to illuminate a flowing bubble at a critical angle or above, total reflection is caused. and the light never reaches a phototransistor. so that a flowing current has a minimum value. Even if the projected light is made incident to the bubble at the critical angle and below, reflection and refraction are caused. and the light never reaches the phototransistor. When the emitted light is projected upon the center part of the bubble. it is transmitted through the bubble to reach the phototransistor. If a bubble resides in the flowing water, an output voltage drops trom a first voltage to a second voltage and after it rises up to the first voltage. it drops down to the second voltage again and then rises up to the first voltage.
[0006] Published Japanese patent application JPH 11241995 A provides a bubble detector/direction sensor for detecting the presence of liquid or gas in the flow of a liquid segment or gas scgment passing through a slender transparent pipe and sensing the flowing direction of the flow. The device comprises a direction sensor which has first and second light sources. first and second input optical fiber bundles. and first and second collection optical fiber bundles. The first and second input optical fiber bundles are connected to a pipe so that a light passes through the pipe. When the pipe is filled with a liquid, the light transmitted by the pipe from cach light source passes first and second prescribed areas, When the pipe is filled with gas, the light passing through the pipe advanced to the outer part of the prescribed areas.
Further. this device has circuits for generating each signal instructing the presence of the liquid in the pipe or the presence of the gas in the pipe. and the direction of the liquid or gas passing through the pipe on the basis of the light received by cach collection optical fiber bundles.
[0007] Published U.S. patent application US 2018/289882 A1 discloses a system and method for the detection of a transient air bubble in an arterial blood flow path during dialysis (e.g. hemodialysis). The system uses measurements from an optical sensor to remove one or more effects of common factors affecting the absorbance of the light incident on the arterial tubing.
These factors include color of medium within the arterial tubing. tubing color. angle of illumination. and temperature of the optical detector. A variance of the measurements from the optical sensor are used to determine whether an air bubble is present.
[0008] Published Japanese patent application JP 2013113652 A provides an air bubble detector capable of certainly detecting air bubbles even when liquid stored in a tube body is the one 2
STRATEC SE Fortmann Jegethofi 30001.20381LU WE LU103097 containing a scatterer. An air bubble detector which detects air bubbles in liquid stored in a nozzle chip consisting of a translucent material includes: a light emission part which irradiates light with the same wavclength as that of absorption peak wavelength of water toward the nozzle chip: a light receiving part which is installed on the opposite side of the light emission part on both sides of the nozzle chip. and detects light volume of the light passed through the nozzle chip: a Z driving part which relatively moves the nozzle chip in the axis direction: and a control part which controls drive of the Z driving part, and determines presence/absence of the air bubbles on the basis of variation of transmitted light volume in accordance with relative movement of the nozzle chip in the axis direction.
[0009] Some of the available technologies are related to the disadvantage that they are very sensitive to changes in material, size and the position of the tubing attached to the sensor. Other already available sensors are only suitable for a particular size of tubing and cannot be easily adapted to other tubing sizes by means of a link/adapter. The systems use the optical principle of absorption and are thus sensitive to the color of the liquid as well as to particles that may be present in liquids, e.g. red blood cells.
[0010] Thus, there is a need for a method and device avoiding the disadvantages from solutions known from the prior art.
Summary of the [Invention[0011] The present invention provides an optical sensor system for analysing fluids. comprising a housing with a first optical element for guiding a light beam to a measuring channel and a second optical element for guiding reflected light from the measuring channel. and wherein the measuring channel has a volume for receiving a fluid which is to be analysed. wherein the material of the optical sensor system has a refractive index which corresponds to the refractive index of the fluid which is to be analysed in the measuring channel. and wherein the first and second optical element are arranged offset with respect to the direction of the light beam.
[0012] A further aspect relates to the offset arrangement of first and second optical element which relates to the critical angle œ from the refractive index of the two phases forming the interface, which can be calculated according to: 3
LU
STRATEC SE Fortmann Tegethoff in C2) ac = arcsin (— c n,
[0013] Another embodiment of an optical sensor system provides first and second element as optical fibres, channels or wherein the first optical element comprises a light source and/or the second optical element comprises a detector.
[0014] It is envisaged that the channel wall surrounding the volume of the measuring channel has at least a partially flat, round or elliptical shape. 10015] The optical sensor system may comprise further optical elements arranged in the light beam comprising lenses and apertures.
[0016] It is intended that the light source can be a single LED or a LED assembly.
[0017] Another object of the present disclosure is a method for analysing properties of a fluid, comprising the steps of: - Providing a fluid to an optical sensor system comprising a housing with a first optical element for guiding a light beam to a measuring channel and a second optical element for guiding reflected light from the measuring channel, whèrein the measuring channel has a volume for receiving the fluid: - Emitting a light beam through the first optical element in the direction of the measuring channel; - Detecting the amount of reflected light from the measuring channel through the second optical clement; - Analysing presence and properties of the fluid through the amount of detected reflected light.
[0018] The properties which are to be analysed comprise the detection of gas, air, gascous or air-bubbles, solids or colour changes in the fluid,
[0019] The method may comprise a step for determining the refractive index of the fluid prior to providing it to the optical sensor system. 4
LU Fortmann Tegethoff
STRATEC SE Les te Tenue US 30001.20381LU a N LU103097
[0020] The material of the measuring channel which is used in the method. may have a refractive index which corresponds to the refractive index of the fluid to be analysed. so that the material of the measuring chamber has a refractive index allowing a light beam to pass through the material of the measuring chamber and a fluid filled volume of the measuring chamber without reflection and to reflect the light beam at the boundary between the material of the measuring chamber and an air-filled volume of the measuring chamber.
[0021] The may comprise a step of calculating a critical angle for the material of the measuring channel and the fluid prior to providing the fluid in the measuring channel.
[0022] The method may further comprise the step of using a single wavelength for the emitted light or using a combination of multiple wavelengths,
[0023] Still other aspects, features, and advantages of the present invention are readily apparent from the following detailed description, simply by illustrating preferable embodiments and implementations. The present invention is also capable of other and different embodiments and its several details can be modified in various obvious respects. all without departing from the spirit and scope of the present invention. Accordingly. the drawings and descriptions are to be regarded as illustrative in nature. and not as restrictive. Additional objects and advantages of the invention will be set forth in part in the description which follows and in part will be obvious from the description. or may be learned by practice of the invention.
Summary of the Figures[0024] The invention will be described based on figures. It will be understood that the embodiments and aspects of the invention described in the figures are only examples and do not limit the protective scope of the claims in any way. The invention is defined by the claims and their equivalents. It will be understood that features of one aspect or embodiment of the invention can be combined with a feature of a different aspect or aspects of other embodiments of the invention, in which:
LU Fortmann Tegethoff
STRATEC SE [ore aa 30001.20381LU PT ET LU103097
[0025] FIG. 1a-f show different embodiments of an optical sensor system according to the present disclosure.
[0026] FIG. 2 shows the difference between a fluid-filled measuring channel and an air-filled measuring channel.
[0027] FIG. 3 shows schematically a situation with a fluid film in the measuring channel.
[0028] FIG. 4 shows an exemplary arrangement of the invention with fluid (left part) and air (right part) in the measuring channel.
[0029] FIG. 5 shows an optic assembly with apertures.
[0030] FIG. 6 shows an optic assembly with lenses.
[0031] FIG. 7 shows an optical assembly with tube connections on two sides of the optical assembly. (0032] FIG. 8 shows a supply and discharge of the liquid to the optics assembly via collecting channels.
Detailed Description of the Invention and the Figures
[0033] The technical problem is solved by the independent claims. The dependent claims cover further specific embodiments of the invention.
[0034] The present invention comprises an optical sensor system for simple optical fluid testing in medical applications for instance. Fluid testing according to the present disclosure is based on the principle of total internal reflection. This monitors the fluid flow and assists in the detection of air during pipetting operations as well as the analysis of the pipetted fluid volume.
In the invention, the fluid flow is not affected during measurement. Method and device according to the present disclosure are based on an optical sensor technology which enables non-invasive volume monitoring. 6
LU
STRATEC SE rorim ann Jegethoii 30001.20381LU PORTE ns A LU103097
[0035] A fluid within the meaning of the present disclosure relates to a liquid, a gas or a mixture thereof that is capable of flowing, wherein the fluid may comprise solids like particles.
[0036] An offset arrangement of light source and detector means that the detector is not arranged in the direction of the light beam emitted from the light source.
[0037] Total internal reflection is a physical principle of light impingement on an interface between a medium with a high refractive index (n_1} and a medium with a low refractive index (n_2). For example, when light passes through the medium of water to an interface with the medium of air, all the incident light that hits the surface of air at a certain critical angle (or at a higher angle) is reflected at that surface. This means that no light passes this surface. The required minimum angle (critical angle wo.) results from the refractive index of the two phases forming the interface: m5 æ, = arcsin (— € nr
This principle of total internal reflection is used in the invention to detect air in the measurement channel.
[0038] FIG. 1a-f show different embodiments of an optical sensor system | according to the present disclosure. FIG. la shows an embodiment of an optical sensor system | which is arranged in a housing 7 and comprises a first optical element 10 which is configured for transferring a light beam to a measuring chamber 25 with volume 30 for receiving a fluid. The first optical element 10 can be a channel or an optical fibre and can comprise or can be connect a light source 11 (comp. FIG. 1b) like a LED or the like, wherein the light source 11 can also be an external light source.
[0039] Returning to FIG. la, the optical sensor system | which is arranged in housing 7 comprises further a second optical clement 20. The second optical element 20 guides a light beam away from measuring channel 25. The second optical element 20 can also be a channel or an optical fibre and it can comprise or can be connected to a detector 29 (comp. FIG. Ic). 7
STRATEC SE Fortmann Tegethoff 30001.20381LU PTE LU103097
The detector 29 can be arranged externally and can be an optical sensor, comprising photodiodes. phototransistors, cameras. and the like.
[0040] It is also within the scope of the present invention that the first optical element 10 comprises or is connected to a light source 11 and the second optical element 20 comprises or is connected to a detector 29 (comp. FIG. 1d). The optical sensor element | may comprise a light source 11 instead of the first optical element 10 and/or a detector 29 instead of a second optical element 20 (comp. FIG. le and FIG. 1f).Thus, the optical sensor system can be adapted to light sources and/or detector which are already present so that they do not have to be part of the optical sensor system. {004 1] FIG. 2 shows schematically the working principle of the optical sensor system |. A light source (not shown or part of first optical clement 10) emits light which is transferred through the first optical clement 10 to the measuring channel 25 which comprises a volume 30 for recciving a fluid. The detector is arranged behind — with respeet to the direction of the light bcam - the second optical element 20 or is part of the second optical element 20 or can be the second optical element 20. 10042] According to the above discussed principle of total reflection and taking into account that the refractive index of the material of the measuring chamber 25 and the fluid in volume 30 are in the same range, a light beam 21 (solid line) will be reflected at the channel wall 26. when the volume 30 of the measuring chamber is filled with air. Due to the angled arrangement of the first and second optical element 10, 20. the reflected light will enter the second optical element 20 and be guided to a detector. If the volume 30 of the measuring channel 25 is filled with the fluid, light beam 22 (dashed line} will pass channel wall 26 and volume 30 without being reflected so that no light is guided through the second optical element 20 to the detector.
Air bubbles in the fluid will thus be detected because of the light beam or parts of the light beam which are reflected into the second optical clement guiding it to detector.
[0043] It is thus intended that the refractive index of the material of the measuring chamber 25 is adapted to the refractive index of the fluid filling the volume 30 of the measuring chamber so that a light beam pass through the material of the measuring chamber and a fluid filling the volume of the measuring chamber without reflection and the light beam will be reflect at 8
Lu Fortmann Tegethoff 20001 2038140 EER LU108097 the boundary between the material of the measuring chamber and an air-filled volume of the measuring chamber.
[0044] FIG. 3 shows schematically a situation of an optical sensor system | according to the present disclosure, with a fluid film 5 covering channel wall 26 of the measuring channel 25. A light beam 21 which is guided through the first optical element 10 to the volume 30 of the measuring channel 25 will be reflected at boundary 6 between the fluid film 5 and the air in volume 30 of the measuring channel 25. The light beam 21 (solid line) will be reflected into the second optical clement 20 to a detector. When the volume 30 of measuring channel 25 is filled with a fluid. a light bcam 22 (dashed line) will pass channel wall 26 and the fluid so that nearly no light will be guided by the second optical element 20 towards a detector.
[0045] FIG. 4 shows in both parts an exemplary arrangement of an optical sensor system according to the present disclosure. A light beam. indicated by the solid arrows, is guided through the first optical element 10 towards volume 30 of measuring channel 25. The measuring channel 25 has a flat surface 24 towards the first and second optical element 20. Depending on whether the volume is filled with fluid (left part of FIG. 4), the light will pass the volume without a reflection of light into the second element 20. If the volume is filled with air or an air bubble. the light 21 will be reflected at the flat surface 24 into the second optical element 20 (right part of FIG, 4).
[0046] By adapting the light color or using several wavelengths, the wavelength can be flexibly adapted to the fluid used. so that. for example. the concentration of red blood ceils in the liquid can be detected/measured without significantly affecting the basic principle of total reflection.
[0047] Furthermore. the design of the optical sensor system | can be adapted depending on the application and the available installation space. The used radiation angles with respect to the orientation of the first and second optical element 10. 20 to another may be adapted to such requirements and further to used wavelengths as well as the shape of the housing 7 of the optical sensor system |.
[0048] As already mentioned. first and second optical elements 10, 20 can be optical fibres for guiding a light beam so that they must match the properties of the fluid which is to be analysed 9
LU Fortmann Tegethoff
STRATEC SE Pr 30001.2038114) IE LU103097 and the available installation space. Depending on the geometry of the first and second optical element 10, 20. additional optical components such as apertures 12 (FIG. 5) or lenses 14 (FIG. 6) can also be arranged in the light pass to limit or shape the light beam angle from the light source and/or towards the detector (indicated by arrows). In addition, the channel wall 26 surrounding volume 30 of measuring channel 25 can have a flat shape (comp. FIG. 1), round shape (FIG. 2) or elliptical shape (not shown).
[0049] As already mentioned. clectronic components like the light source or the detector can be part of the optical sensor system | or can be external parts which are connected to the optical assembly via optical fibers, so that it is possible to outsource these electronic components. For this purpose, optical fibers are used to guide the light beams from the light source to the sample plane and from the sample plane to the detector.
[0050] FIG. 7 shows an optical sensor system 1 with hose connections 40 on two sides of the optical sensor system 1 for providing a fluid flow through measuring channel 25 (not shown in
FIG. 7) so that the fluid can be monitored. First and second optical elements 10. 20 which are also depicted in FIG. 7, may comprise identical optical fibres so that both optical clements may serve as first optical element 10 or second optical clement 20, respectively, depending on available external light sources and detector. The same applies for the hose connections 40 which may both serve for providing or draining fluids.
[0051] Alternatively, the optical assembly | can also be connected to other components. e.g. a hose connection can be attached to one side of the measuring channel and a component. e.g. a pump or pipetting needle, can be located on the other side.
[0052] FIG. 8 shows a supply and discharge of the fluid to the optical sensor system | as described above via a first and a second collecting channel 27. 28. When monitoring multiple fluid streams. multiple optical sensor systems 1 can be arranged side by side. Each optical sensor system 1 has a light source (not shown in detail) and a detector (not shown in detail) as described above. For this reason. when several optical sensor systems | are arranged side by side, it is advantageous to optically isolate them from another to avoid mutual interference of the signals. The teed and/or discharge of the fluid into the optical sensor system | can be single- channel. multi-channel or via the collecting channels as shown in FIG. 8.
iu Fortmann Tegethoff
STRATEC SE Fore ne Te 30001.20381LU Km ene LU103097
[0053] From the analysis of the signals from the detector, information about the following points can be evaluated: - Differentiation of air and liquid: detection of an air bubble in the measuring channel. - Quantitative determination of the liquid volume. - Temporal relation to the pump start, lift position, etc. - Detection of leakage or clogging. - Predictive maintenance of external components (e.g. pump). - In case of several sensors in parallel, the individual channels can be compared against each other. - Detection and readjustment of sensor aging (contamination, turbidity, fiber breakage. etc.)
[0054] With a suitable choice of the light color. other parameters can be determined, such as - Color of the solution - Concentration measurement via color - Particle concentration (blood. magnetic particles, ...)
[0055] Either a fixed light color can be used. or the light color can be dynamically adjusted to the respective application. In addition. a broadband white light source could also be used or several colored light sources simultancously.
[0056] On the receiver side (detector). if only one light color is used. a broadband receiver can be used without additional filtering, If several light colors are used simultaneously. filtering of the information on the receiver side is necessary. This filtering can be done either by optical filters or electrically.
[0057] In the case of electrical filtering, for example, each light color is pulsed with a different pulse frequency and the desired pulse frequency can be isolated again on the receiver side via corresponding (electrical) bandpass filters.
[0058] The advantages of the invention relate to 11
Ww Fortmann Tegethoff
STRATEC SE TT en 30001.20381LU LE LU103097 - Providing a system for a more accurate determination of pipetted liquid volume in medical applications without direct access to the liquid. - Since the optical components are fully integrated into the optics assembly. no adjustment is required and tolerances are low by design. - The system is not dependent on the availability of special tubing or tubing materials for an optics assembly. Material properties (e.g. transparency) for total reflection need only be met for the optics assembly and not for the entire monitored hose. 10059] The foregoing description of the preferred embodiment of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention 10 the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The embodiment was chosen and described in order to explain the principles of the invention and its practical application to enable one skillcd in the art to utilize the invention in various embodiments as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto, and their equivalents. The entirety of each of the aforementioned documents is incorporated by reference herein. 12
STRATEC SE Fortmann Tegethoff 30001.20381LU Been LU103097
Reference Numerals l optical sensor system fluid film 6 boundary 7 housing first optical clement 11 light source 12 aperture 14 lens second optical clement 21 light beam air filled hose 22 light beam fluid filled hose 24 flat surface measuring channel 26 channel wall 27 first collecting channel 28 second collecting channel 29 detector volume of measuring channel hose connector 13