Patent Description:
This disclosure relates to a fluid monitoring apparatus and a method for analyzing blood sample properties.

Quantitative measurement of the complex dielectric permittivity of a material versus frequency (e.g., dielectric spectroscopy, also known as DS) can be a powerful monitoring technique with a broad range of applications. For example, DS can be utilized for chemical analysis of oil in the petroleum industry, analysis of substances for security or defense purposes, soil moisture monitoring in agriculture, fermentation monitoring during the production of alcoholic beverages, food quality/safety monitoring and drug development in the pharmaceutical industry. DS can also be used as an analytical tool in the biomedical field as a label-free, nondestructive and real-time method to study the interaction of RF/microwave fields with biological/biochemical samples with minimal sample preparation. Key molecular characteristics of biomaterials such as human blood, spinal fluid, breast tissue and skin have been studied using DS for applications in disease detection and clinical diagnosis. Typical DS systems tend to be large and expensive, making them cost-prohibitive in certain circumstances.

In the article, <NPL>", a convention sensor is provided for dielectric spectroscopy of human whole blood during coagulation. In the measurement results, the CaCl<NUM>-treated blood sample showed a peak in the normalized real permittivity at about <NUM> minutes which was consistent with the time of clot formation observed visually.

<CIT> provides a blood coagulation system analyzing method to acquire information relating to the blood coagulability based on a complex permittivity spectrum. In the analysis procedure, the platelet function of patients is evaluated based on the delay/shortening width (Δt) of the blood coagulation time until the spectrum peak after the addition of a platelet activating/inactivating agent.

In one aspect, claim <NUM> provides a fluid monitoring apparatus for analyzing blood sample properties.

In another aspect, claim <NUM> provides a method for analyzing blood sample properties.

This disclosure relates to dielectric sensing to determine properties of a sample. For example, a dielectric microsensor, associated interface electronics and computing device can be integrated in a portable apparatus (e.g., a handheld or desktop unit). The microsensor can be placed within a microfluidic channel to measure impedance characteristics of a sample under test (SUT) (e.g., a liquid (e.g., solution) or a gas) in the channel. The measured impedance can be used to compute corresponding dielectric permittivity values for the SUT over time during a measurement interval. The time-based dielectric permittivity values are analyzed to determine permittivity parameters that correlate to one or more properties of the SUT. Examples of permittivity parameters for a given SUT include a time to peak dielectric permittivity, a difference between peak and plateau permittivity values, rate of change (e.g., slope) in permittivity values associated with a portion of a time interval, as well as other functional characterizations of the dielectric permittivity values. In some examples, a disposable dielectric microsensor can be removably connected, such that the same monitoring apparatus can be reused for taking measurements for numerous different SUTs.

As an example where blood is used as the SUT, the dielectric permittivity values can be analyzed to provide an indication of an anticoagulation property of the blood SUT. According to the present invention, a difference between peak and plateau permittivity value is analyzed to provide an indication of platelet function for the blood SUT. These and other properties thus can be evaluated to determine an efficacy of a therapeutic agent, such as one or more pharmaceutical agents. As one example, where the therapeutic agent is an anticoagulant (e.g., a target-specific oral anticoagulant, such as a factor Xa inhibitor or direct thrombin inhibitor), the sensors, monitoring apparatuses, systems and methods disclosed herein can be employed to determine the efficacy of a current dosage and facilitate titration to achieve desired therapeutic results. As a result, the approach disclosed herein enables rapid, high-throughput, low-cost DS measurements that enables rapid and comprehensive diagnosis of platelet and coagulation defects, which can be utilized at the point of care.

<FIG> depicts an example of a system <NUM> to determine properties of a sample under test (SUT) based on dielectric permittivity measurements of the sample. The system <NUM> includes a sensing apparatus <NUM> and a sensor interface system <NUM>. The sensor interface system <NUM> can drive a dielectric sensor <NUM> with an RF input signal (RFIN). For example, the dielectric sensor <NUM> is a dielectric spectroscopy (DS) microsensor that includes circuitry (e.g., an arrangement of electrodes) residing in a fluid channel <NUM> to measure impedance of the microsensor. The dielectric sensor <NUM> is configured to have a dielectric permittivity that corresponds to its measured impedance and which depends on the SUT that is placed in the fluid channel <NUM>. For example, a fluid SUT can be provided (e.g., from a source of fluid, such as a micropipette) into the fluid channel <NUM> via one or more fluid ports <NUM>. In some examples, the fluid SUT can be substantially still within the channel <NUM> or, in other examples it can be flowing through the channel during measurements. The fluid channel <NUM> can be a microfluidic channel having a volume that is less than about <NUM>µL, for example.

As an example, the dielectric sensor <NUM> can include electrodes distributed in the channel <NUM> in an opposing and spaced apart relationship as to provide a capacitive sensing area between opposing surfaces of the spaced apart electrodes. For instance, a floating electrode can be fixed with respect to a given surface of the fluid channel in a spaced apart opposing relationship from a pair of sensing electrodes fixed with respect to another surface of the channel. The pair of sensing electrodes thus can be substantially coplanar along a given surface of the fluid channel <NUM> that opposes and is parallel to the surface of the floating electrode. One of the sensing electrodes can be configured to receive the RF input signal (RFIN) as an excitation signal from the sensor interface system <NUM> and the other sensing electrodes can provide a corresponding RF output signal (RFOUT) to the sensor interface system.

The sensor interface system <NUM> includes a transmitter <NUM> and a receiver <NUM> (e.g., may be integrated into a transceiver). The transmitter <NUM> is configured to provide the RF input signal at a desired excitation frequency. The excitation frequency, for example, can be in the microwave range. For instance, the transmitter <NUM> can provide the RF input signal that sweeps through a range of frequencies, such as from about <NUM> to about <NUM> (e.g., from about <NUM> to about <NUM>). The frequency range may be a continuous range through which the excitation is swept. In other examples, the transmitter <NUM> can provide RFIN at a plurality of different discrete excitation frequencies, which can be set according to the SUT and application requirements. As one example, for monitoring blood SUT's, the transmitter <NUM> can provide RFIN to include at least frequencies at about <NUM> and also at about <NUM>. The excitation frequency(ies) can be set in response to a program input signal (e.g., via user interface <NUM> of the apparatus or sent from a remote system <NUM>), such as to adjust the frequency according to application requirements to maximize sensitivity of the sensor. The frequency range for the excitation signal can be continuous across the range or be provided in two or more discrete frequency bands, which can be user programmable (e.g., in response to a user input).

The receiver <NUM> is configured to provide an output signal (OUT) representing measured sensor transmission characteristics based on the RF output signal from the dielectric sensor <NUM> implemented in the sensing apparatus <NUM>. The output signal can be an analog signal or be converted to a digital signal (e.g., via an analog-to-digital converter). The receiver <NUM> can include circuitry configured to process the RF output signal, such as by amplifying (e.g., variable gain) and filtering the RF output signal to ascertain complex signal components of RFOUT, which filtering can be configured according to the frequency or frequency range of the excitation signal RFIN. The RF output signal can be a complex signal corresponding to voltage transmission measurements through the dielectric sensor <NUM>, which varies as a function of the complex impedance or admittance as seen at an output node thereof (e.g., demonstrated at RFOUT in various figures herein). That is, RFOUT can have a predetermined relationship with respect to a change in dielectric permittivity caused by the SUT within the channel <NUM>.

The transmitter <NUM> and receiver <NUM> can be implemented in an integrated circuit chip (e.g., system on chip) or they could be implemented as separate components configured to perform the functions disclosed herein. While the transmitter <NUM> and receiver <NUM> are demonstrated in <FIG> as co-residing in the interface system <NUM> (e.g., in a single IC chip), in other examples, the transmitter and receiver could be implemented as independent separate circuits.

In the example of <FIG>, the sensor system <NUM> also includes a computing device <NUM>. The computing device <NUM> can include a processor (e.g., having one or more processor cores) <NUM> and memory <NUM>. The memory <NUM> can store instructions and data, and the processor <NUM> can access the memory to execute the instructions based on the stored data to perform functions and methods disclosed herein.

For example, the memory <NUM> stores control functions <NUM>, which when executed by the processor <NUM> control operation of the sensor interface system <NUM>. For example, the DS control <NUM> can selectively control the range of frequencies (e.g., frequency bands) of an RF output signal applied by the transmitter <NUM> to each respective DS sensor <NUM>. The control <NUM> also includes instructions executable by processor <NUM> to perform measurement functions <NUM> based on the output from the receiver.

As an example, the measurement function <NUM> is configured to measure complex impedance based upon amplitude and phase provided in the output signal RFOUT. For instance, the measurement function <NUM> cooperates with the sensor interface system <NUM> to operate as an impedance analyzer. In this way, the measurement function <NUM> measures the complex impedance, corresponding to the capacitance of the dielectric sensor <NUM> based on the SUT disposed within the fluid channel <NUM> in response to the input excitation signal RFIN. As mentioned, the transmitter <NUM> can provide RFIN as an excitation signal at one or more discrete frequencies or sweep across one or more predefined frequency bands. The measurement function <NUM> thus stores impedance (e.g., capacitance) measurement values and associated timestamps (e.g., a time index) as time-based impedance data in the memory <NUM> based on the RF output signal from the sensor <NUM>. Additional information (e.g., metadata) may also be stored in the impedance data, such as to specify the input signal frequency, temperature and/or other parameters associated with the SUT.

By way of further example, during the first portion of a test phase, control <NUM> can control the transmitter <NUM> to provide the RF output signal within a first range of frequencies (e.g., a low frequency range). During one or more subsequent or other different phases of the sensing process, control <NUM> can control the transmitter <NUM> to provide the RF input signal for one or more different range of frequencies for exciting the sensor and the associated SUT disposed in the fluid channel <NUM>. For example, different frequencies may be used extract different properties of the SUT. The receiver <NUM> thus can receive and provide corresponding output signals associated with each phase of the sensing process. The control <NUM> can also control the receiver <NUM> to provide the RF output data as a DC output voltage in the I-mode and another DC output voltage in the Q-mode. While the control and measurement functions <NUM> and <NUM> have been described as being part of the computing device <NUM>, in other examples, the measurement and control functions could be distributed between the sensor interface system <NUM> and the computing device or be implemented separately from the computing device (e.g., as part of the sensor interface or as a separate control system.

The computing device <NUM> further includes data processing methods and/or functions <NUM>, <NUM> and <NUM> for computing permittivity based on the output data provided by the measurement function <NUM> for a given measurement interval. Thus, the computing device <NUM> further can process the received input signals from a given sensor (or from multiple sensors) and provide output data that includes the impedance measurements as well as permittivity data and other information derived from the measurements to representing complex permittivity, raw data corresponding to the measurements RF output signal as well as other information derived therefrom.

As a further example, the computing device <NUM> includes a calibration function <NUM> programmed to determine a calibration permittivity for a given sensor <NUM>. For example, the control function <NUM> can control transmitter to provide RFIN that is at or includes a predetermined excitation frequency (or frequency band) in which two or more substantially different SUTs are known to have little or no difference in permittivity. Thus, different types of samples may utilize different excitation frequencies for calibration as well as for testing depending on the samples. For the example of a blood SUT, the calibration input frequency can be about <NUM>. In this way, the measured impedance (e.g., capacitance) corresponds to the capacitance of water, and the resulting permittivity derived (e.g., by permittivity calculator <NUM>) from RFOUT in response to RFIN at the calibration frequency provides a measure of water permittivity for the sensor <NUM>. That is, the calibration capacitance and permittivity represent the capacitance and permittivity of the sensor <NUM> with an SUT in the channel <NUM> with a known permittivity value (e.g. water has a known permittivity of approximately <NUM> at <NUM>). This calibration measurement of impedance (e.g., by measurement function <NUM>) and determination of the calibration permittivity (e.g., by permittivity calculator <NUM>) may be implemented as part of the normal sensing process while an SUT is within the fluid channel <NUM>, such as described above, so long as the excitation is provided at an appropriate calibration frequency.

By way further example, if the sensor apparatus <NUM> is being used to measure the permittivity of blood, at <NUM>, the permittivity of blood is close to that of water, (e.g., εr,blood(@<NUM>MHz) ≅ εr,water(@<NUM>MHz) ≅ <NUM>). This relationship and calibration frequency thus may be used for water-based substances other than blood. In particular, this relationship can be used to implement a simplified calibration procedure for blood that can be implemented while the blood SUT remains in the sensing apparatus. Other relationships and different calibration frequencies may be determined and used for other types of SUTs in a like procedure.

In the example to determine the permittivity of blood at <NUM>, the following procedure may be used. After the sensing apparatus is attached to the system <NUM>, blood may be inserted into the sensor (e.g., using a micropipette). The admittance for blood (i.e., Ys,blood) is measured over multiple frequencies (e.g., sweep <NUM> to <NUM>, or at <NUM> and <NUM>), as disclosed herein.

The nominal capacitance for the sensor in the absence of an SUT (i.e., air-gap capacitance or C<NUM>) is calculated, such as follows: <MAT> where εr,blood(@<NUM>MHz) is taken as εr,blood(@<NUM>MHz) ≅ εr,water(@<NUM>MHz) ≅ <NUM>.

The permittivity calculator <NUM> then computes the permittivity of blood at the frequency of interest (i.e. εr,blood(@<NUM>MHz)) such as follows: <MAT> where C<NUM> was calculated above based on the measured admittance of blood at the calibration frequency (e.g., <NUM>).

Alternatively, the calibration measurement can be performed as a separate process for each SUT, such as before any SUT is placed in the fluid channel <NUM>. The calibration function <NUM> stores the calibration permittivity value (e.g., corresponding to the air gap permittivity or capacitance) in the memory <NUM>. In some types of sensing, such as for TPEAK, calibration function <NUM> may be omitted since the time to peak for a given type of material is not affected by calibrating or not calibrating permittivity of the sensor.

The permittivity calculator <NUM> is also executed by the processor <NUM> to determine dielectric permittivity of the SUT. This may include for determining the calibration permittivity as mentioned above, as well as more generally during sensing. The permittivity calculator <NUM> thus determines the dielectric permittivity for the dielectric sensor <NUM> and the SUT over a corresponding measurement time interval. This interval can range from the time in which the control <NUM> activates the sensor interface <NUM> to provide the RF input signal until a subsequent time in which the control <NUM> deactivates the sensor interface <NUM> when sensing is complete. The measurement interval may be a fixed time or it can be controlled and terminated based on monitoring the measured capacitance or determined permittivity.

As an example, the permittivity calculator <NUM> can determine a relative permittivity of the SUT based on a measured impedance at one or more measurement frequencies (e.g., one or more frequency bands) and based on the calibration permittivity (e.g., determined by calibration function <NUM>). For example, the permittivity calculator <NUM> can compute the permittivity at a given time index and input frequency by dividing the measured impedance value (e.g., capacitance) by the calibration capacitance value (e.g., air gap capacitance) to provide a relative permittivity value for the SUT at the given time index. Additionally, in some examples, the permittivity values over the measurement interval may be normalized with respect to the permittivity at the first measurement point, peak permittivity or another value. The normalized, relative permittivity value can be computed for each of the plurality of measurement data points over a range of time indices that define the measurement time interval. Each permittivity value can be stored as permittivity data in the memory <NUM> for further processing and analysis. As mentioned, in some measurements (e.g., time-to-peak), calibration may be omitted and the permittivity calculator <NUM> can determine a permittivity of the SUT in the absence of the calibration permittivity and, in some cases without normalization.

The processor <NUM> can also execute a permittivity analyzer <NUM> that is programmed to determine one or more permittivity parameters based upon the dielectric permittivity values computed by the permittivity calculator <NUM>. The permittivity analyzer <NUM> can determine parameters for one or more different portions of the measurement time interval, including up to the entire interval. As one example, the permittivity analyzer <NUM> analyzes the stored dielectric permittivity values over a portion of the measurement time interval to determine a time that it takes to reach a peak dielectric permittivity value (TPEAK). For instance, the permittivity analyzer <NUM> employs a peak detector function to ascertain the peak permittivity value, and the time interval (e.g., an elapsed time) to reach the peak dielectric permittivity thus can be stored in memory as TPEAK for the SUT. This time value TPEAK may be the time index associated with when the associated impedance measurement was made or it may be determined as the difference between the start time and the time when the measurement occurred to provide TPEAK. For the example where the SUT is a blood SUT, the TPEAK value thus can provide an indication of an anticoagulation property of the blood sample. The TPEAK value can be stored in the memory <NUM>.

In the present invention, the permittivity analyzer <NUM> is programmed to analyze the stored dielectric permittivity values to determine a difference between the peak dielectric permittivity value (TPEAK) and a plateau permittivity value. The plateau permittivity value represents a permittivity value that remains substantially constant over time, such as at a tail end portion of the measurement time interval. As used herein, the term substantially constant is intended to refer to a sufficiently small rate of change from a given value over time (e.g., about + <NUM>% or less). The permittivity analyzer <NUM> can determine the plateau permittivity value, for example, by determining that the time derivative of the permittivity values remains less than a predetermined value or is zero over a period of time. The difference between peak permittivity and plateau permittivity values is used to provide an indication of additional properties associated with the SUT. According to the present invention, the difference between peak permittivity and plateau permittivity values provides an indication of platelet function for the analysed blood SUT.

In yet another example, the permittivity analyzer <NUM> can evaluate the dielectric permittivity values for the SUT over a portion of a time interval to determine the rate of change in permittivity values, such as corresponding to a slope of a portion of a curved representing the dielectric permittivity values. For instance, the permittivity analyzer <NUM> can determine a rising edge slope between the beginning of the measurement interval and the peak dielectric value. The permittivity analyzer <NUM> also may compute a falling edge slope such as between the TPEAK value and the plateau dielectric permittivity value. Further analysis can be made with respect to the tail portion between the peak and the plateau dielectric values to provide an indication of other properties associated with the SUT.

In some examples, an output generator <NUM> can utilize the computed permittivity parameter TPEAK value to present associated information on a corresponding display <NUM> of the apparatus <NUM>. The output generator can provide the output as including a presentation on the display <NUM>, such as a graphical and/or textual representation of one or more permittivity parameters. An audio output may also be provided based on the one or more permittivity parameters. For example, the output generator <NUM> can display time to peak value, TPEAK, and/or a graphical output of a curve representing the permittivity values over the measurement interval or a portion thereof. As another example, the output generator <NUM> can provide an indication of the difference between peak and plateau permittivity values to the display <NUM>, such as may be calculate permittivity difference or a scaled version thereof. The output generator <NUM> further may be programmed to provide an indication of slope of the permittivity curve to the display <NUM> associated with other corresponding properties of the SUT determined by the permittivity analyzer <NUM>.

In some cases, the display <NUM> may also present comparative results, which determined by the permittivity analyzer <NUM> based on comparing the current results relative to a known standard or to one or more previous results for the same patient or a patient population. For use as a patient or point-of-care apparatus, for example, a set of instructions can also be generated and provided as an output to the display <NUM>. If the TPEAK value is outside of expected parameters, for example, the output generator <NUM> can also send an alert to the display <NUM> to inform the user to seek medical assistance and/or adjust a prescribed medication. Additionally or alternatively, if the difference between permittivity value at TPEAK and the plateau permittivity is outside of expected parameters, the output generator <NUM> can provide an alert to the display. Corresponding results, including raw data and/or other computed permittivity information and analysis results, further may be provided to the display <NUM>.

As mentioned, the apparatus includes a user interface <NUM> to interact with the system <NUM>. The user interface <NUM> may include a touch screen interface, a keypad, a keyboard, a mouse, voice interface and/or a combination thereof. As an example, a user can use the user interface <NUM> to acknowledge information that is presented on the display such as before, during and after a measurement interval for a given SUT. Additionally or alternatively, a user may employ the user interface <NUM> to input information about the user (e.g., health and/or demographic information) and/or environment conditions. The user interface <NUM> can be utilized to program/configure the apparatus <NUM> for one or more parts of a sensing process such as disclosed herein. For instance, the user interface <NUM> can be utilized to set a range of one or more frequencies, including one or more frequency bands, to utilize for the excitation signal during testing of the SUT. For example, in response to instructions entered via the user interface <NUM>, the computing device <NUM> can employ control <NUM> to instruct the transmitter <NUM> to operate accordingly. The instructions can be stored in memory <NUM> or other memory (e.g., a program register) of the transmitter <NUM> to control the frequency of the excitation signal and duration thereof that is applied during a test process. Additionally or alternatively, the user interface <NUM> can also be utilized to control the information that is presented in the display <NUM> as well as to perform other post processing functions (e.g., reporting functions, recording user responses to questions, etc.) and data analysis.

In some examples, the computing device <NUM> employs the communications interface <NUM> to communicate with the remote system <NUM> via a communications link <NUM>. The communication link <NUM> can be implemented to include one or more physical connections (e.g., an electrically conductive connection or optical fiber), one or more wireless links (e.g., implemented according an <NUM>. 11x standard or other short range wireless communication) or a network infrastructure that includes one or more physical and/or wireless communications links.

The remote system <NUM> can include a server, a general purpose computing device (e.g., notebook computer, laptop, desktop computer, workstation, smartphone or the like) and/or it can be a special purpose system configured to interact with one or more of the apparatuses <NUM> via the link <NUM>. For instance the computing device <NUM> employs the communications interface <NUM> to send the remote system <NUM> permittivity-related information based on measurement results for a given SUT. As another example, the remote system <NUM> may send program instructions to the apparatus to configure and/or update its operating program instructions. In an example where the remotes system comprises a back office system of a healthcare provider, the computing device <NUM> may send a copy of the raw measurement data and/or the results determined the permittivity analyzer <NUM> using a secure communications over the link <NUM> (e.g., HIPPA compliant communications). In such an example, the remote system <NUM> may communicate with a plurality of apparatuses.

As mentioned, such communications can include an alert issued in response to the analyzer <NUM> determining that one or more SUT properties is outside of expected parameters. In other examples, the remote system can perform such analysis and return an alert to the apparatus via the link. In response, the alert can be presented on the display to the user (e.g., a patient or care provider). Regardless of where the alert originates (e.g., generated by the apparatus or remote system <NUM>) such alert can trigger a corresponding notification to be sent to alert to one or more individuals (e.g., health care professionals). The corresponding notification may be delivered to each such recipient via a communications protocol, such as email, SMS text message, pager, telephone call or the like.

<FIG> and <FIG> demonstrate an example of a three-dimensional dielectric microsensor <NUM> (e.g., corresponding to the sensing apparatus <NUM>). The microsensor <NUM> can be electrically coupled to a sensor interface system (e.g., interface <NUM>), such as via electrical contacts. Other types of connections (e.g., electrically conductive or wireless) could also be utilized to provide for bi-directional communication with respect to the DS sensing apparatus <NUM>.

In the example of <FIG> and <FIG>, the interface system (e.g., transmitter <NUM>) provides an RF input signal to an input <NUM> of the microsensor <NUM>. The microsensor <NUM> includes circuitry having a complex admittance (e.g., capacitance) that varies as a function of dielectric permittivity of an SUT within a fluid channel <NUM>, such as disclosed herein. The microsensor <NUM> includes an output <NUM> that provides an RF output signal to the interface system (e.g., interface <NUM>) via an output connection (e.g., a pin or other type of electrical connection), which RF output signal varies as a function of time based on the input frequency and the dielectric permittivity of the SUT.

In the example of <FIG> and <FIG>, the microsensor <NUM> includes a fluid channel <NUM> into which a volume of an SUT (e.g., liquid or gas) can be introduced via ports <NUM> (e.g., inlet and outlet holes). For purposes of clarity, the following discussion presumes that the SUT is a fluid, such as blood. Of course, other types of SUTs could be used in other examples.

The microsensor <NUM> includes a capacitive sensor <NUM> is disposed within the fluid channel <NUM>. For example, the capacitive sensor <NUM> includes a floating electrode <NUM> spaced apart from and opposing sensor electrodes <NUM> and <NUM> within the fluid channel <NUM> to provide a volumetric sensing area (e.g., corresponding to the area of overlap between the floating electrode and associated sensor electrodes). The capacitance of the sensor <NUM> is based on permittivity of material (or the absence) between electrodes <NUM>, <NUM> and <NUM>. The sensor electrodes <NUM> and <NUM> in the capacitive sensor <NUM> can be electrically isolated from each other. The RF input signal is coupled to the input sensor electrode <NUM> for excitation of the capacitive sensor <NUM> and the other sensor electrode <NUM> is coupled to provide RFOUT.

As demonstrated in the cross-sectional view of <FIG>, the sensor <NUM> includes planar sensor electrodes are separated from a floating electrode through a microfluidic channel <NUM> to form a capacitive sensing area with nominal air-gap capacitance, C<NUM>, which is defined by the overlapping electrode area and microfluidic channel height. For example, at the excitation frequency, ω, the capacitive sensing area admittance is <MAT>, when the channel is loaded with an SUT having a complex dielectric permittivity of <MAT>. In the example of <FIG>, the sensing structure is electrically connected to the output node, to provide an output signal RFOUT such as <MAT> when the sensor is driven by the input signal RF/microwave signal (VRF) and the fluid channel <NUM> is loaded with an SUT having Δεr.

As also demonstrated in the cross sectional view of <FIG> (and the assembly view of <FIG>), the microsensor <NUM> can be fabricated in multiple parts that are attached together to provide a resultant sensor structure. As shown in <FIG>, for example, the microsensor <NUM> includes a top part <NUM> and a bottom part <NUM> that is spaced apart from the top part by an intermediate channel layer <NUM>. The bottom part <NUM> includes a floating electrode <NUM> fabricated on a surface of the substrate layer. Electrodes <NUM> and <NUM> are disposed on a corresponding surface of its substrate layer. In this example, the sensing electrodes <NUM> and <NUM> each extend from opposite side edges of the substrate beyond a central longitudinal axis of the microsensor <NUM> to terminate in respective ends near a central portion of the substrate. The middle part <NUM> has a thickness that determines a volume of the channel <NUM> formed therein. The top part <NUM> can include the inlet/outlet ports <NUM> to provide fluid communication for accessing the volume defined by the channel <NUM>. For example, the channel <NUM> in part <NUM> and associated ports <NUM> can be fabricated by micromachining (e.g., laser micromachining) or by other types of machining or etching techniques. In some examples, the surface of channel <NUM> further can be coated with a polymer or other material (e.g., electrically insulating film, such as poly(ethylene glycol)) to help protect against protein adsorption onto the surfaces that contact the protein solutions. The polymer can be applied via physisorption or chemisorptions, for example.

As a further example, <FIG> illustrates an example of the sensor fabrication and assembly that can be employed to produce the sensing apparatus <NUM> of <FIG> and the sensor <NUM> of <FIG>. For purposes of clarity, the discussion of <FIG> uses the same reference numbers as in <FIG>.

As an example, the substrate layers for the top and bottom parts <NUM> and <NUM> can be fabricated using poly(methyl methacrylate) (PMMA). The intermediate channel substrate layer <NUM> can be formed of a thin film layer of double-sided-adhesive (DSA) material having a thickness that is much less than the electrode-containing substrate layers <NUM> and <NUM>. As one example, each of the layers <NUM> and <NUM> may be about <NUM> thick, whereas the layer <NUM> is about <NUM> thick. Other relative thicknesses can be utilized according to application requirements.

Each of the floating electrode <NUM> and sensor electrodes <NUM> and <NUM> can be formed by deposition of electrically conductive material deposited at a desired location (e.g., aligned with the sensing electrodes and within the channel <NUM>) on the respective opposing surfaces of substrate layers <NUM> and <NUM>. For instance, the floating electrode <NUM> can be an electrically conductive material (e.g., gold, copper or aluminum) deposited on the inner top surface of the cap by sputter deposition using a shadow mask and lift-off process. As an example, <NUM>-Å/<NUM>,<NUM>-Å Cr/Au layer is evaporated on the channel surface of the substrate to form respective sensor electrodes <NUM> and <NUM>. Similarly, the floating electrode <NUM> can be deposited on the surface of the layer <NUM> by evaporating a <NUM>,<NUM>-Å Au layer and patterning with lift-off.

As shown in <FIG>, to facilitate construction of the sensing apparatus <NUM>, each of the layers <NUM>, <NUM> and <NUM> can include a plurality of alignment holes <NUM>. Each of the layers can be connected together and held in place by inserting corresponding alignment pins <NUM> can be inserted into the holes <NUM>. In some examples, a thin film coating of a barrier material can be deposited on the surfaces of the layers <NUM>, <NUM> and <NUM> to protect the metal and plastic surfaces from direct contact with the SUT. In other examples, such as for blood SUT, no coating may be used to help increase sensitivity.

In some examples, microfluidic inlet/outlet holes <NUM> in the layer <NUM> can be configured with a diameter to fit a standard micropipette tip. As one example, the microfluidic channel <NUM> has a total sample volume of less than about <NUM>µL (e.g., about <NUM>-9µL) and a volume of less than about <NUM>µL (e.g., about <NUM>. 8µL or less) in the sensing area over the floating electrode <NUM>. Other volumes for the channel and sensing area can be implemented according to application requirements. The microsensor <NUM> can be assembled by attaching the substrate layers <NUM> and <NUM> together using the DSA film layer <NUM> interposed therebetween. As mentioned, the alignment holes <NUM> and pins <NUM> can be used to align the floating electrode over the sensing electrodes within the microfluidic channel.

As show in the example of <FIG>, electrical connections to the sensing electrodes <NUM> and <NUM> may be made through contact openings <NUM> in opposed side edges of the substrate layer <NUM>, which can be electrically connected to the sensor interface system (e.g., to transmitter <NUM> and receiver <NUM> of interface <NUM>). Thus connectors (e.g., pins) from associated circuitry of a connector interface (e.g., of sensing apparatus <NUM>) can extend into the openings <NUM> to contact the respective electrodes <NUM> and <NUM> when the microsensor <NUM> is connected to the monitoring apparatus, for example.

In the example of <FIG>, the sensor <NUM> is demonstrated along with its terminals that can be electrically connected to interface electronics on a printed-circuit board (PCB). In some examples, the connection between the microsensor <NUM> and interface system <NUM> can be configured as a plug-and-play-type modular connection between the sensor contact pads and PCB input/output pads (e.g., using spring-loaded contact pins to provide an electrical connection). The connection method facilitates DS measurements with potentially hazardous or contaminating solutions, since the low-cost sensor can be replaced after a measurement has been made for a given SUT without contaminating the entire instrument. That is, in some examples, the microsensor <NUM> is intended for single use, which can be discarded and replaced after each use, while the interface system <NUM> and associated electronics can be re-used over and over again. In other examples, a given sensor can be repeatedly reused for a plurality of measurements with the same or different SUTs.

<FIG> demonstrates another example of a dielectric microsensor <NUM> (e.g., corresponding to apparatus <NUM>) that can be utilized in the system <NUM>. The apparatus <NUM> includes a three-dimensional, parallel-plate, capacitive sensing structure <NUM>. The capacitive sensing structure <NUM> includes two planar sensing electrodes <NUM> and <NUM> that are spaced apart and are separated from a floating electrode <NUM> according to a height of a microfluidic channel <NUM> to form a 3D capacitive sensing area disposed within the microfluidic channel. The capacitive sensing structure <NUM> is disposed within a substrate material <NUM>. The sensing apparatus <NUM> includes ports <NUM> (e.g., inlet and outlet holes) through which a volume of fluid (e.g., liquid or gas) can be introduced.

A cross sectional view of the sensing apparatus <NUM> would be the same as shown in the example of <FIG>, and reference may be made back to <FIG> and its discussion for an understanding of how different portions are constructed and attached together resulting sensing apparatus. In the example <FIG>, the sensing electrodes are formed of parallel electrodes that extend from a common side edge of a corresponding substrate layer (instead of from opposed side edges as in the example <FIG>). Other configurations may be used for the sensing apparatus <NUM>, such as example embodiments disclosed in<CIT>.

Applying the sensing apparatus <NUM> in the context of the system <NUM>, an input RF signal (e.g., sweeping over one or more frequency bands) can be applied (e.g., by transmitter <NUM>) to an input electrode <NUM> for exciting the sensing circuit. A resulting RF output signal can be measured at the other sensing electrode <NUM> (e.g., by receiver <NUM>). The measured signal can be filtered and amplified (e.g., by analog and/or digital circuitry of receiver <NUM>) and processed (e.g., by methods/functions executed by computing device <NUM>) to calculate permittivity for the SUT that resides within the channel <NUM>. As disclosed herein, the data processing can be implemented to accurately measure real and/or imaginary parts of the complex relative permittivity over one or more predetermined frequencies or frequency bands.

<FIG> depicts an example graph <NUM> of normalized permittivity as a function of time demonstrating examples of permittivity parameters that can be determined (e.g., by permittivity analyzer <NUM>) for a given SUT based on permittivity values over a measurement time interval. In the illustrated example, the measurement data and permittivity values are normalized to the peak permittivity value <NUM> that occurs at time TPEAK, demonstrated at <NUM>. In the example graph <NUM>, the following permittivity parameters are shown: the time of peak permittivity (TPEAK), at <NUM>, the initial slope (S1), at <NUM>, the slope of permittivity decline after TPEAK (S2), at <NUM>, and the magnitude of the permittivity change after TPEAK (Δεr,max), at <NUM>. In other examples, other permittivity parameters could be determined from analysis of the permittivity values (e.g., performed by permittivity analyzer <NUM>), such as associated with the tail portion of the permittivity values at the end portion of the measurement interval. Each of the permittivity parameters determined from the permittivity values <NUM> thus may provide an indication to quantify properties of a given SUT based on the DS measurements. For the example of blood SUT, some properties may include cellular properties (e.g., platelet function based on Δεr,max <NUM>) and/or molecular properties (e.g., coagulation factor based on TPEAK) of the blood SUT.

<FIG> depicts a plot <NUM> of dielectric permittivity as a function of time for plurality of different blood SUTs, demonstrated at <NUM>. In the example of <FIG>, the plotted permittivity values of respective measurements intervals demonstrates that the approach disclosed herein yields reproducible results in relation to a time-to-peak (TPEAK) parameter, demonstrated at <NUM>. In this example, the plot is normalized to a first measurement point as the permittivity is taken at <NUM>.

<FIG> depicts an example plot <NUM> of dielectric permittivity for a plurality of different blood SUTs exhibiting different coagulation properties. In the example plot <NUM>, the permittivity values represent blood SUTs from patients with coagulopathy, with different samples exhibiting different times to reach a peak (TPEAK). In this example plot <NUM>, permittivity is normalized to a first measurement point as the permittivity is taken at <NUM>.

<FIG> show that the sensor apparatus and its use according to systems and methods disclosed herein are capable of capturing various properties associated with the hemostatic process, including platelet activation and adhesion, coagulation factor assembly and thrombin generation, and fibrin formation. By way of comparison, the time to reach a peak (TPEAK) in the plots of <FIG> showed a statistically significant difference between the normal blood SUTs of <FIG> relative to the coagulopathy SUTs of <FIG>. The approach disclosed herein further is believed to exhibit improved sensitivity as compared to conventional screening coagulation assays, such as including activated partial thromboplastin time (aPTT) and prothrombin time (PT).

<FIG> depicts a graph <NUM> showing another example of dielectric permittivity as a function of time showing a comparison between blood samples. In <FIG>, the plot is normalized to a first measurement point as the permittivity is taken at <NUM>. The example plot <NUM> of <FIG> demonstrates that the sensing apparatus and related systems and methods disclosed herein can provide a quantitative indication for the efficacy of target-specific oral anticoagulants (TSOACs). For example, the permittivity values for the plots in <FIG> show that patients on TSOACs exhibit a prolonged TPEAK for rivaroxaban SUT. Error bars shown in <FIG> indicate duplicate measurements and are presented as mean ± standard error of the mean (SEM).

<FIG> depicts another plot <NUM> showing an example of dielectric permittivity as a function of time demonstrating different platelet function properties for a plurality of samples. For example, SUTs treated with cytochalasin D (CyD) exhibited a decrease in the difference between the peak permittivity and plateau permittivity values (i.e. Δεr,max parameter), demonstrated at <NUM>, <NUM> and <NUM>, which indicate a sensitivity to platelet inhibition. Error bars in the graph <NUM> indicate duplicate measurements and are presented as mean ± SEM. In the example of <FIG>, the permittivity values shown for each CyD-treated SUT are normalized to the permittivity at TPEAK demonstrated at <NUM> for an excitation frequency at about <NUM>.

<FIG> demonstrate examples plots <NUM> and <NUM> showing permittivity parameters, which have been determined the sensing apparatus and related systems and methods disclosed herein, correlated with respect to rotational thromboelastometry (ROTEM) parameters. The correlation information shown in plot <NUM> of <FIG> was derived from whole blood samples from healthy donors were mixed at various concentrations of thrombin and anti-thrombin to modulate the ROTEM clotting time (CT) parameter of the prepared samples. Anti-thrombin has inhibitory effect and thrombin has accelerating effect on the final common pathway of coagulation (i.e., fibrin generation/crosslinking), prolonging and hastening, respectively, the clotting time in ROTEM measurements. In <FIG>, the TPEAK parameter determined according to the approach disclosed herein showed very strong correlation to ROTEM CT parameter.

For the example plot <NUM> in <FIG>, whole blood samples were mixed with various concentrations of CyD to modulate platelet activity, which in turn affects the maximum clot firmness, MCF, parameter in ROTEM measurements. In <FIG>, the Δεr,max parameter determined from DS measurements, according to the approach disclosed herein, demonstrates strong correlation to ROTEM MCF parameter. Error bars in <FIG> indicate duplicate measurements and are presented as mean ± SEM.

The sensing apparatus and monitoring system disclosed herein are sensitive to a wide range of hemostatic defects arising from cellular (i.e., platelet) as well as molecular (i.e., coagulation factor) components of clotting, and has promising correlative sensitivity when compared to clinically relevant diagnostic parameters of ROTEM.

As a further example, <FIG> depicts another example of a DS microsystem <NUM> that can be implemented as an integrated handheld system (e.g., the system <NUM>), which can utilize plug-and-play sensors (e.g., sensor <NUM>, <NUM> or <NUM>). The components of the sensor system <NUM> can be constructed of biocompatible materials, such as including gold, glass and PMMA, commonly used in biomicrofluidic devices.

In the following description of <FIG>, for sake of clarity, components of the system <NUM> are referred to using similar reference numbers refer to components previously introduced with respect to <FIG>. The system <NUM> can include a sensing apparatus <NUM> and associated interface electronics <NUM>. In the example of FIG. <NUM>, the sensing apparatus <NUM> includes a dielectric sensor <NUM> (e.g., corresponding to the example sensor <NUM> or <NUM>). Thus, the sensor <NUM> and interface electronics <NUM> can be configured to produce a complex output that depends on (e.g., varies as a mathematical function of) the complex permittivity of the SUT disposed in a microfluidic sensor channel of the sensor <NUM> in response to an excitation signal.

As an example, a micropipette (or other device) <NUM> can be employed to inject a SUT into the microfluidic channel of the sensor <NUM>. The sensor interface electronics <NUM> includes transmitter circuitry <NUM> to provide an excitation signal (e.g., at single frequency or frequency range of one or more bands) to an input of a given sensor containing a volume of the SUT. The output of sensor <NUM> is coupled to respective front-end RF modules <NUM> (demonstrated at FE) of a receiver (e.g., receiver <NUM>). Each front-end RF module <NUM> is configured to preprocess (e.g., perform down-conversion, filtering and amplification) each transmitted signal received in response to an excitation signal and provide corresponding IF signals. The IF signals from a given one of the front-end RF module <NUM> can be selectively provided to other receiver circuitry <NUM> for further processing, such as including conversion to a digital version of the signal and provided to computing module <NUM>. The computing module <NUM> can calculate permittivity for the SUT based on the system output signal to provide corresponding output permittivity values stored in memory <NUM> as permittivity data. The permittivity data can include complex permittivity values (e.g., real and imaginary permittivity) computed over the aggregate range of excitation frequencies, including different subranges provided to the sensor <NUM>. Permittivity data can also include raw signal measurements and the input excitation frequencies. The computing module <NUM> can also analyze the permittivity data to determine permittivity parameters of the SUT, such as disclosed herein, which can be used to provide an indication of properties of the SUT. One or more permittivity parameters and/or properties of the SUT may be rendered on a display <NUM>. The system <NUM> may include a user interface (UI) <NUM> that provide a human-machine interface to enable user interaction with the system <NUM>, such as to review results, reset the system or perform other human-machine interactions.

The computing module <NUM> can further provide the permittivity data and analysis thereof to a communication module <NUM>. The communication module <NUM> can send the output data and raw measurement data to a remote system. For example, the communication module <NUM> can transmit the output data to a back office system (e.g., a server) that can be programmed to analyze the data and store the results and raw data in a database. The remote system can also communicate command information to the system <NUM> to program one or more of the system parameters (e.g., signal gain and/or frequency range) to control its operation and/or provide instructions to the user, such as disclosed herein. The system <NUM> of <FIG> can include a housing that contains the sensor interface electronics <NUM>, computing module <NUM> and communication module <NUM> such that it can provide a portable, handheld device. The system <NUM> may also include a power supply <NUM>, such as an internal battery and or a power interface to connect to an external supply.

While the example system of <FIG> is in the context of a handheld device, in other examples, the system <NUM> may be implemented as a bench top system. In this example, the system <NUM> may be configured to measure dielectric permittivity of a plurality of dielectric sensors <NUM>, each having a respective SUT. Each sensor can include or share corresponding interface to provide respective measurement data to the computing module <NUM> for computing permittivity values for each of the respective SUTs. In this way a laboratory or other provider can monitor a plurality of samples concurrently.

<FIG> is a flow diagram depicting an example of a method <NUM> to measure dielectric permittivity and determine properties of an SUT. The method begins at <NUM> by attaching a dielectric microsensor (e.g., sensor <NUM>) to an interface system (e.g., interface <NUM>). For example, the dielectric microsensor includes a capacitive sensing structure integrated into a microfluidic channel (e.g., channel <NUM>) that includes a fluid input to receive a sample volume of the SUT. The attachment at <NUM> thus can connect a transmitter and a receiver of the interface system with respective inputs and outputs of the dielectric microsensor.

At <NUM>, the SUT is placed within the microfluidic channel of the dielectric microsensor. Once the SUT is within the dielectric microsensor, the method proceeds to <NUM> and an input radio frequency (RF) signal is provided to the dielectric microsensor. For example, a transmitter (e.g., transmitter <NUM>) of the interface system provides the RF input signal to an input of the microsensor. The RF input signal can include one or more frequencies, including a calibration frequency that is used (e.g., by permittivity calculator <NUM>) to determine a calibration permittivity for the dielectric microsensor such as corresponding to a dielectric permittivity of an air gap, as disclosed herein.

At <NUM>, an output RF signal is received from the dielectric microsensor in response to the input RF signal. The RF output signal represents a measure of impedance (e.g., capacitance) of the SUT disposed in the dielectric microsensor. The input and output signals can be communicated between the dielectric microsensor and the interface system over a measurement time interval, for example, a fixed time or a time that depends on the measurements.

At <NUM>, dielectric permittivity values of the SUT are calculated over a measurement time interval based on the output RF signal. As disclosed herein, the permittivity may be computed as a relative permittivity and be normalized to a selected permittivity value (e.g., peak permittivity). For example, the calibration permittivity may also be applied to the dielectric permittivity values (e.g., dividing measured permittivity values by the calibration permittivity value) to provide relative dielectric permittivity values for the SUT. The permittivity values may be stored in memory (e.g., memory <NUM>).

At <NUM>, the dielectric permittivity values of the SUT are analyzed over at least a portion of the measurement time interval to determine one or more permittivity parameters for the SUT. For example, the analysis at <NUM> includes determining a time to reach a peak dielectric permittivity value. For instance, where the SUT includes a blood sample, the analysis can include determining an indication of an anticoagulation property of the blood sample based on the time to reach the peak dielectric permittivity value. The indication of the anticoagulation property further may represent a therapeutic effect of an anticoagulation therapy, such as a target-specific oral anticoagulant.

In the present invention, the analysis at <NUM> includes determining a difference between the peak dielectric permittivity value and a plateau permittivity value, such as disclosed herein. The difference is utilized to determine an indication of platelet function for the blood sample. The dielectric permittivity values may be analyzed to determine other parameters that may be indicative of cellular and/or molecular properties of the SUT, such as disclosed herein. After the measurement time interval is complete, the method proceeds to <NUM> and the dielectric microsensor may be removed from an interface system. Another dielectric microsensor may be attached and the method <NUM> repeated for analyzing properties of another SUT. In some examples, the dielectric microsensors used in the method <NUM> are disposable, single use devices that can be attached for sensing properties of the SUT and, after completing the test, removed and disposed of according to appropriate disposal procedures.

In view of the foregoing, the DS microsystem disclosed herein thus can provide a low-power, low-cost and portable instrument for rapidly extracting key information that characterizes the molecular and/or cellular properties of biological or other sample solutions in a broad frequency range using µL-sample volumes. The proposed measurement technique at the sensor level can be utilized to achieve high resolution in permittivity measurements.

What have been described above are examples. It is, of course, not possible to describe every conceivable combination of structures, components, or methods, but one of ordinary skill in the art will recognize that many further combinations and permutations are possible. Accordingly, the invention is intended to embrace all such alterations, modifications, and variations that fall within the scope of the appended claims.

Claim 1:
A fluid monitoring apparatus for analyzing blood sample properties, comprising:
a dielectric microsensor (<NUM>, <NUM>, <NUM>) comprising a capacitive sensing structure (<NUM>) integrated into a microfluidic channel (<NUM>, <NUM>), the microfluidic channel (<NUM>, <NUM>) including a fluid input to receive a sample volume of a given blood sample under test, SUT;
a transmitter (<NUM>) for providing an input radio frequency, RF, signal to an RF input of the dielectric microsensor (<NUM>, <NUM>, <NUM>);
a receiver (<NUM>) for receiving an output RF signal from the dielectric microsensor (<NUM>, <NUM>, <NUM>); and
a computing device (<NUM>) adapted to compute dielectric permittivity values of the given blood SUT that vary over a time interval based on the output RF signal;
wherein the computing device (<NUM>) is adapted to determine at least one permittivity parameter for the given blood SUT based on the computed dielectric permittivity values over at least a portion of the time interval;
wherein the computing device (<NUM>) is adapted to determine a first permittivity parameter corresponding to a difference between a peak dielectric permittivity value and a plateau permittivity value,
wherein the plateau permittivity value represents a permittivity value that remains substantially constant over time, and
wherein the computing device (<NUM>) is adapted to analyze the difference to determine an indication of platelet function for the given blood SUT.