Sweat analysis device and method

Abstract

This perspiration analysis device comprises: a wearable sensor for outputting an electrical signal derived from the electrolyte concentration and the perspiration amount of sweat secreted from the skin of a wearer; a perspiration amount calculation unit (50) for calculating a perspiration amount measurement value for the perspiration amount of the wearer on the basis of the electrical signal obtained by the wearable sensor; an electrolyte concentration calculation unit (51) for calculating an electrolyte concentration measurement value for the electrolyte concentration of the sweat of the wearer on the basis of the electrical signal obtained by the wearable sensor; and a correction unit (52) for calculating the true value of the electrolyte concentration and the true value of the perspiration amount corrected for the effect of sweat loss due to evaporation, the calculation being carried out on the basis of the perspiration amount measurement value, the electrolyte concentration measurement value, and a known physical quantity relating to evaporation of sweat.

Description

[Technical Field]

[0001] The present invention relates to a sweat analysis device and method that is worn on the human body to measure the amount of sweat of the wearer and the electrolyte concentration in the sweat. [Background technology]

[0002] Due to global warming, the number of heat waves occurring is increasing in most regions of the world. In Japan in recent years, the incidence of heatstroke has increased due to the increased frequency of extreme heat. The number of patients receiving medical transport due to heatstroke has remained at a high level since peaking in 2018, becoming a social problem (see Non-Patent Document 1).

[0003] Heatstroke refers to a state of multiple organ failure caused by high temperatures or strenuous exercise. Generally, human body temperature is maintained at approximately 37°C through the thermoregulatory process of the anterior hypothalamus. Physical phenomena related to sweating, such as evaporation, heat radiation, convection, and heat conduction, function to cool the body surface.

[0004] When body temperature rises, cutaneous vasodilation increases skin blood flow, initiating thermal sweating. Skin vasodilation causes a relative decrease in intravascular volume, resulting in heat syncope. Salt and water loss through sweating leads to dehydration and salt depletion, accompanied by heat exhaustion and convulsions. Further loss of salt and water reduces thermoregulatory function, and subsequently, shunting from the central circulation to the skin and muscles reduces blood flow to the internal organs, leading to organ failure and a condition known as heatstroke (see Non-Patent Document 2).

[0005] As mentioned above, water and salt in the human body play an important role in regulating body temperature. To prevent dehydration, which can lead to heat exhaustion, it is important to replenish adequate amounts of water and salt. Numerous studies have reported that the salt concentration in sweat increases linearly with increasing sweat rate. However, the rate of increase in salt concentration varies from person to person, depending on a person's sweating ability and the ability of sweat glands to reabsorb salt. It is also known that an individual's sweating ability and salt reabsorption ability change depending on their heat acclimation. Therefore, continuous monitoring of both a person's sweat rate and the salt concentration in sweat is considered effective for monitoring water and salt loss. As a prior art technique for realizing this monitoring, a wearable sensor that simultaneously measures the amount of sweat and electrolyte concentration has been proposed (see Patent Documents 1 and 2).

[0006] Fig. 13 is a cross-sectional view of the wearable sensor disclosed in Patent Document 1, and Fig. 14 is an enlarged view of Fig. 13. The wearable sensor 1 includes a substrate 10 having a through-hole 11 serving as a liquid flow path and a recess 12 communicating with the outlet end of the through-hole 11, an electrode 14 arranged on the surface of the substrate 10 where the inlet end of the through-hole 11 opens, a water-absorbent structure 15 arranged on the outlet-side surface (upper surface) of the substrate 10 so as to come into contact with the liquid that flows out from the outlet opening of the through-hole 11 into the recess 12, and a water-absorbent electrode 16 arranged on the surface of the water-absorbent structure 15 facing the substrate 10 so as to face the outlet opening of the through-hole 11. In Fig. 13, 13 denotes the recess formed on the lower surface of the substrate 10, 100 denotes the skin of a wearer of the wearable sensor 1, and 101 denotes the sweat glands of the wearer.

[0007] By using the wearable sensor 1, the amount of sweat produced by the wearer of the wearable sensor 1 and the electrolyte concentration in the sweat can be calculated based on the electrical conductivity between the electrodes 14 and 16 due to the sweat 102 that flows out from the through hole 11 into the recess 12.

[0008] Fig. 15 is a cross-sectional view of the wearable sensor disclosed in Patent Document 2, and Fig. 16 is an enlarged view of Fig. 15. Wearable sensor 1a includes substrate 10 having through-hole 11 and recess 12, water-absorbing structure 15, laser diode (LD) 18 disposed in recess 12 and emitting light along a path within recess 12 that passes over a position above the outlet opening of through-hole 11 along the outlet surface of substrate 10, and photodiode (PD) 19 disposed in recess 12 opposite LD 18 across the position above the outlet opening of through-hole 11 and receiving light from LD 18. Reference numeral 103 in Fig. 15 denotes light emitted from LD 18.

[0009] By using wearable sensor 1a, it is possible to calculate the amount of sweat produced by the wearer of wearable sensor 1a and the electrolyte concentration in the sweat based on the light receiving characteristics of PD 19 that receives light from LD 18.

[0010] As described above, the wearable sensors 1 and 1a disclosed in Patent Documents 1 and 2 can calculate the amount of sweat produced by the wearer and the electrolyte concentration in the sweat. However, when the amount of sweat produced is small, the effect of evaporation of the sweat that flows out from the through-hole 11 into the recess 12 becomes large, which may result in the amount of sweat being underestimated or the electrolyte concentration being overestimated. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] International Publication WO2021 / 038742 [Patent Document 2] International Publication WO2021 / 038758 [Non-patent literature]

[0012] [Non-Patent Document 1] A. Hirata, T. Miyazawa, R. Uematsu, S. Kodera, Y. Hashimoto, K. Takagahara, Y. Higuchi, H. Togo, T. Kawahara, H. Tanaka, “Body Core Temperature Estimation Using New Compartment Model With Vital Data From Wearable Devices”, IEEE Access 2021,9,124452-124462.(DOI:10.1109 / ACCESS.2021.3110252) [Non-patent document 2] T. Hifumi, Y. Kondo, K. Shimizu, Y. Miyake, “Heat stroke”, Journal of Intensive Care, 2018, 6, 1-8,<https: / / doi.org / 10.1186 / s40560-018-0298-4> Summary of the Invention [Problem to be solved by the invention]

[0013] The present invention has been made to solve the above-mentioned problems, and aims to provide a sweat analysis device and method that can reduce measurement errors in sweat volume and electrolyte concentration by taking into account the effects of sweat evaporation and performing corrections. [Means for solving the problem]

[0014] The sweat analysis device of the present invention is characterized by comprising: a wearable sensor configured to output electrical signals derived from the sweat rate and electrolyte concentration of sweat secreted from the wearer's skin; a sweat rate calculation unit configured to calculate a measured value of the wearer's sweat rate based on the electrical signal obtained by the wearable sensor; an electrolyte concentration calculation unit configured to calculate a measured value of the electrolyte concentration in the wearer's sweat based on the electrical signal obtained by the wearable sensor; and a correction unit configured to calculate a true value of the sweat rate and a true value of the electrolyte concentration, corrected for the effect of sweat loss due to evaporation, based on the measured sweat rate, the measured electrolyte concentration, and known physical quantities related to sweat evaporation.

[0015] In addition, in one configuration example of the perspiration analysis device of the present invention, the correction unit calculates the amount of sweat loss due to evaporation based on known physical quantities related to the evaporation of sweat, calculates the true value of the perspiration rate by adding the amount of sweat loss to the measured perspiration rate, and calculates the true value of the electrolyte concentration based on the true value of the perspiration rate, the measured perspiration rate, and the measured electrolyte concentration.

[0016] In one configuration example of the perspiration analysis device of the present invention, the electrical signal is a current that changes due to droplets that are intermittently generated in the wearable sensor due to sweating by the wearer, and the sweat rate calculation unit calculates a measured value of the sweat rate of the wearer based on the period of the peaks of the current, and the correction unit calculates a true value of the sweat rate by solving an equation for the time derivative of the dynamic contact angle of the droplet and an equation for the integral of the amount of sweat loss due to evaporation during the period between the peaks of the current based on a known physical quantity related to sweat evaporation, the measured sweat rate, and the period of the peaks of the current, and calculates a true value of the electrolyte concentration based on the true value of the sweat rate, the measured sweat rate, and the measured electrolyte concentration.

[0017] In one configuration example of the perspiration analysis device of the present invention, the electrical signal is a current that changes due to droplets that are intermittently generated in the wearable sensor due to sweating by the wearer, the sweat rate calculation unit calculates the measured value of the sweat rate of the wearer based on the period of the peaks of the current, the correction unit sets multiple estimates of the true value of the sweat rate within a predetermined range, and calculates, for each estimate, a dynamic contact angle of the droplets during the period between the peaks of the current based on a known physical quantity related to sweat evaporation and the estimated value, calculates an evaluation function for each estimate based on the known physical quantity related to sweat evaporation, the measured sweat rate, the estimated value, the period of the peaks of the current, and the calculation result of the dynamic contact angle, and determines the estimated value that yields the best evaluation function as the true value of the sweat rate, and calculates the true value of the electrolyte concentration based on the true value of the sweat rate, the measured sweat rate, and the measured electrolyte concentration.

[0018] In one configuration example of the perspiration analyzer of the present invention, the electrical signal is a current that changes due to droplets that intermittently form in the wearable sensor due to sweating by the wearer, the perspiration rate calculation unit calculates the measured perspiration rate of the wearer based on the period of the peaks of the current, the correction unit calculates the amount of sweat loss due to evaporation based on a known physical quantity related to the evaporation of sweat, and calculates a true value of the perspiration rate by adding the measured perspiration rate to the amount of sweat loss, sets a plurality of estimates of the true value of the electrolyte concentration within a predetermined range, and calculates a theoretical value equivalent to the measured electrolyte concentration for each estimate based on the known physical quantity related to the evaporation of sweat, the true value of the perspiration rate, the estimate, and the period of the peaks of the current, calculates an evaluation function for each estimate to evaluate the accuracy of the estimate based on the measured electrolyte concentration and the theoretical value, and determines the estimate that yields the best evaluation function as the true value of the electrolyte concentration.

[0019] In one configuration example of the perspiration analyzer of the present invention, the electrical signal is a current that changes due to droplets that are intermittently generated in the wearable sensor due to sweating by the wearer, the perspiration amount calculation unit calculates the measured perspiration amount of the wearer based on the period of peaks of the current, and the correction unit sets a plurality of pairs of estimated values ​​of the true values ​​of the electrolyte concentration and the true values ​​of the perspiration amount within a predetermined range, and calculates a first theoretical value and a previous theoretical value corresponding to the measured electrolyte concentration based on a known physical quantity related to evaporation of sweat, the estimated value of the true value of the electrolyte concentration, the estimated value of the true value of the perspiration amount, and the period of peaks of the current. a second theoretical value corresponding to the static contact angle of the droplet is calculated for each set of estimated values; a third theoretical value corresponding to the measured value of the sweat rate is calculated for each set of estimated values ​​based on a known physical quantity related to sweat evaporation, the estimated value of the true value of the sweat rate, and the first and second theoretical values; an evaluation function for evaluating the correctness of the set of estimated values ​​is calculated for each set of estimated values ​​based on the measured value of the electrolyte concentration, the first theoretical value, the measured value of the sweat rate, and the third theoretical value; and the set of estimated values ​​for which the best evaluation function is obtained is determined to be the true value of the electrolyte concentration and the true value of the sweat rate.

[0020] In addition, in one configuration example of the sweat analysis device of the present invention, the electrical signal is a current that changes due to droplets that are intermittently generated in the wearable sensor due to sweating by the wearer, the sweat amount calculation unit calculates a measured value of the sweat amount of the wearer based on the period of the peaks of the current, and the electrolyte concentration calculation unit calculates a measured value of the electrolyte concentration in the sweat of the wearer based on the peak value of the current.

[0021] The sweat analysis method of the present invention is characterized by including a first step of detecting electrical signals derived from the sweat rate and electrolyte concentration of sweat secreted from the wearer's skin using a wearable sensor; a second step of calculating a measured value of the wearer's sweat rate based on the electrical signal obtained by the wearable sensor; a third step of calculating a measured value of the electrolyte concentration in the wearer's sweat based on the electrical signal obtained by the wearable sensor; and a fourth step of calculating a true value of the sweat rate and a true value of the electrolyte concentration, corrected for the effect of sweat loss due to evaporation, based on the measured value of the sweat rate, the measured electrolyte concentration, and known physical quantities related to sweat evaporation. [Effects of the Invention]

[0022] According to the present invention, a wearable sensor, a sweat rate calculation unit, an electrolyte concentration calculation unit, and a correction unit are provided, and the true values ​​of the sweat rate and electrolyte concentration, which are corrected for the effect of sweat loss due to evaporation, are calculated by the correction unit, thereby reducing the possibility of underestimating the sweat rate or overestimating the electrolyte concentration. As a result, the present invention can achieve highly accurate measurement of the sweat rate and electrolyte concentration. [Brief explanation of the drawings]

[0023] [Figure 1] FIG. 1 is a diagram showing an example of changes in the value of a current flowing between electrodes, as measured by a wearable sensor. [Figure 2] FIG. 2 is a block diagram showing the configuration of a perspiration analyzer according to a first embodiment of the present invention. [Figure 3] FIG. 3 is a functional block diagram of the MCU unit of the perspiration analyzer according to the first embodiment of the present invention. [Figure 4] FIG. 4 is a flowchart illustrating the operation of the perspiration analyzer according to the first embodiment of the present invention. [Figure 5] FIG. 5 is a flowchart illustrating the operation of the correction unit of the perspiration analyzer according to the first embodiment of the present invention. [Figure 6]FIG. 6 is a flowchart illustrating the operation of the correction unit of the perspiration analyzer according to the second embodiment of the present invention. [Figure 7] FIG. 7 is a flowchart illustrating the operation of the correction unit of the perspiration analyzer according to the third embodiment of the present invention. [Figure 8] FIG. 8 is a flowchart illustrating the operation of the correction unit of the perspiration analyzer according to the fourth embodiment of the present invention. [Figure 9] FIG. 9 is a flowchart illustrating the operation of the correction unit of the perspiration analyzer according to the fifth embodiment of the present invention. [Figure 10] FIG. 10 is a block diagram showing the configuration of a perspiration analyzer according to a sixth embodiment of the present invention. [Figure 11] FIG. 11 is a functional block diagram of the MCU unit of a perspiration analyzer according to a sixth embodiment of the present invention. [Figure 12] FIG. 12 is a block diagram showing an example of the configuration of a computer that realizes the perspiration analyzers according to the first to sixth embodiments of the present invention. [Figure 13] FIG. 13 is a cross-sectional view of a conventional wearable sensor. [Figure 14] FIG. 14 is an enlarged cross-sectional view of a conventional wearable sensor. [Figure 15] FIG. 15 is a cross-sectional view of another conventional wearable sensor. [Figure 16] FIG. 16 is an enlarged cross-sectional view of another conventional wearable sensor. DETAILED DESCRIPTION OF THE INVENTION

[0024] [First correction method] In the present invention, the sweat rate and electrolyte concentration in sweat of a wearable sensor wearer are measured using the sweat analyzer disclosed in Patent Documents 1 and 2. The measured sweat rate of the wearer is Q [L / s], the true value of the sweat rate is Q' [L / s], the measured electrolyte concentration in the wearer's sweat is C [mol / L], and the true value of the electrolyte concentration is C' [mol / L]. In the first correction method of the present invention, the true value of the sweat rate Q' and the true value of the electrolyte concentration C' can be calculated using equations (1) and (2).

[0025]

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[0026]

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[0027] The second term on the right side of equation (1) represents the amount of sweat lost due to evaporation. In other words, equation (1) means that the true value of sweat rate Q' is the sum of the measured sweat rate Q and the amount of sweat lost due to evaporation.

[0028] D[m 2 / s] is the known diffusion coefficient of water vapor in sweat at a measured electrolyte concentration of C, C v,0 [kg / m 3 ] is the known density of water vapor near the gas-liquid interface of the sweat droplet 102a generated at the opening of the through-hole 11 in FIGS. 13 to 16, C v,∞ [kg / m 3 ] is the known density of water vapor at a sufficient distance from the gas-liquid interface of the sweat droplet 102a, ρ [kg / m 3 ] is the known density of water.

[0029] r [m] is 1 / 2 of the dimension of the opening of the through-hole 11 (the diameter if the cross section of the opening is circular), θ c [rad] is the angle (static contact angle) between the surface of the electrode 16 or the surface of the water-absorbing structure 15 and the surface of the sweat droplet 102a. v,0 ,C v,∞the density of water ρ, the value r of half the size of the opening of the through-hole 11, and the static contact angle θ c is a known physical quantity related to the evaporation of sweat.

[0030] [Second correction method] In the second correction method of the present invention, equations (3) and (4) are solved for the true value Q' of the sweat rate, and the true value C' of the electrolyte concentration is calculated using equation (2).

[0031]

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[0032]

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[0033] Equation (3) is the time derivative of the dynamic contact angle θ [rad] as it continuously changes after the sweat droplet 102a lands on the electrode 16 or the water-absorbing structure 15. T [s] is the measured value of the period of the upward peaks of the current flowing between the electrodes 14 and 16 in FIG. 13, or the measured value of the period of the downward peaks of the photocurrent flowing through the PD 19 in FIG. 15. Equation (4) is the integral of the amount of sweat loss due to evaporation during the period T.

[0034] An example of the change in the value of the current flowing between the electrodes measured by the wearable sensor disclosed in Patent Document 1 is shown in Figure 1. As explained above, in the structure shown in Figures 13 and 14, current continues to flow while sweat droplets 102a are present between electrodes 14 and 16, and the cycle of current flow changes depending on the flow rate of sweat into the wearable sensor, i.e., the amount of sweat produced, and the peak current during current flow changes depending on the electrolyte concentration.

[0035] On the other hand, in the wearable sensor disclosed in Patent Document 2, when droplets 102a of sweat 102 are formed, the photocurrent of PD 19 decreases, and when the droplets 102a disappear, the photocurrent of PD 19 increases. In other words, the period of the downward peaks of the photocurrent of PD 19 changes depending on the amount of sweat, and the peak current changes depending on the concentration of electrolytes.

[0036] [Third correction method] Next, a third correction method of the present invention will be described. The dynamic contact angle θ of the sweat droplet 102a at time t is defined as θ(t). A small non-zero value (e.g., 0.1 deg or 1 deg) is set as the initial value θ(0) of the dynamic contact angle at time t=0. Furthermore, a value within the range of the measured sweat rate Q and a predetermined sweat rate value is set as the estimated value of the true sweat rate Q', and the following equations (5) and (6) are calculated.

[0037] The above-mentioned predetermined value of the amount of sweating is the amount of sweating where the influence of evaporation is negligible, or the upper limit of the amount of sweating Q max There is an upper limit Q max For this purpose, it is sufficient to set a value that corresponds to the actual situation based on the results of past measurements.

[0038]

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[0039]

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[0040] Here, Δt [s] is the calculation interval, and f(Q') is the evaluation function for evaluating the accuracy of the estimated value of the true value Q' of the sweat rate. Equation (6) means that the evaluation function f(Q') is the difference between the total amount of estimated values ​​of the true value Q' of the sweat rate during the current peak period T (= Q'T) and the total amount of measured sweat rate Q (= QT), minus the amount of sweat loss due to evaporation during period T.

[0041] While changing the estimated value of the true value Q' by a predetermined step width of the sweat rate (for example, 0.01 μL / min), the calculations of formulas (5) and (6) are performed for each estimated value of the true value Q'. Then, the square of the evaluation function f(Q') calculated for each estimated value of the true value Q', f(Q'), 2 The estimated value that minimizes this is taken as the true value Q' of the sweat rate. Furthermore, the true value C' of the electrolyte concentration is calculated using equation (2).

[0042] [Fourth correction method] In the fourth correction method of the present invention, the true value Q' of the amount of sweat is calculated by equation (1). The time before the formation of the sweat droplet 102a shown in Figures 14 and 16 is set to 0 [s]. The electrolyte concentration C in the forming droplet 102a when NΔt (N is an integer equal to or greater than 0) has elapsed since time 0 [s] is NΔt is calculated using equations (7) and (8) based on the true value Q' of the amount of sweating calculated using equation (1).

[0043]

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[0044]

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[0045] where θ NΔt [rad] is the dynamic contact angle of the sweat droplet 102a at time NΔt, and D[x][m 2 / s] is the known diffusion coefficient of water vapor in sweat when the electrolyte concentration in sweat is x (x is an arbitrary value), and Δt is the calculation interval.

[0046] A non-zero, minute value (for example, 0.1 deg or 1 deg) is set as the initial value θ0 of the dynamic contact angle at time 0 [s]. Furthermore, a value within the range of a predetermined concentration value or more and a measured electrolyte concentration value C or less is set as the estimated value C0 of the true electrolyte concentration, and equations (7) and (8) are calculated. The predetermined concentration value is the lower limit C of the electrolyte concentration in sweat. min There is a lower limit C minFor this purpose, it is sufficient to set a value that corresponds to the actual situation based on the results of past measurements.

[0047] The calculation of formula (7) and formula (8) is performed for each estimated value C0 while changing the estimated value C0 of the true value of the electrolyte concentration by a predetermined step width of the electrolyte concentration (for example, 1 mM). Note that formula (7) is the electrolyte concentration C in the droplet 102a when (N+1)Δt has elapsed since time 0 [s]. (N+1)Δt On the other hand, what is actually sought is the electrolyte concentration C when the current peak period corresponding to the measured sweat rate Q and the elapsed time NΔt match. NΔt Electrolyte concentration C NΔt is the theoretical value corresponding to the measured electrolyte concentration C.

[0048] The measured electrolyte concentration C and the theoretical value C NΔt Square of the difference (CC NΔt ) 2 The estimated value C0 at which is the smallest is taken as the true value C' of the electrolyte concentration.

[0049] [Fifth correction method] Next, the fifth correction method of the present invention will be described. A small non-zero value (for example, 0.1 deg or 1 deg) is set as the initial value θ0 of the dynamic contact angle at time 0 [s]. Furthermore, a value within the range of equal to or greater than the predetermined concentration value and equal to or less than the measured electrolyte concentration value C is set as the estimated value C0 of the true value of the electrolyte concentration. Furthermore, a value within the range of equal to or greater than the measured sweat rate Q and equal to or less than the predetermined sweat rate value is set as the estimated value Q0 of the true value of the sweat rate, and calculations are performed using equations (9) and (10).

[0050]

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[0051]

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[0052] The estimated value C0 of the true value of the electrolyte concentration is changed by a predetermined step width of the electrolyte concentration (e.g., 1 mM), and the estimated value Q0 of the true value of the sweat rate is changed by a predetermined step width of the sweat rate (e.g., 0.01 μL / min), and the calculations of equations (9) and (10) are performed for each pair of estimated values ​​Q0 and C0 until the current peak period corresponding to the measured value Q of the sweat rate matches the time NΔt. The time NΔt that matches the current peak period is defined as N max Let Δt.

[0053] By calculating equations (9) and (10), the time N max Electrolyte concentration C at 1 Δt before Δt (Nmax-1)Δt and time N max The dynamic contact angle θ of the droplet 102a at a time 1Δt before Δt (Nmax-1)Δt and are obtained for each pair of estimated values ​​Q0 and C0. (Nmax-1)Δt is the theoretical value corresponding to the measured electrolyte concentration C. The dynamic contact angle θ (Nmax-1)Δt is the static contact angle θ c This is the theoretical value equivalent to

[0054] Equation (11) allows us to calculate the theoretical value Q" corresponding to the measured value Q of the amount of sweating. Equation (11) means that the theoretical value Q" is calculated by subtracting the amount of sweat loss due to evaporation from the estimated true value Q of the amount of sweating.

[0055]

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[0056] The measured electrolyte concentration C and the theoretical value C NmaxΔt The square of the difference between the measured value and the measured value C {(CC NmaxΔt ) / C} 2 and the square of the difference between the measured sweat rate Q and the theoretical value Q” divided by the measured value Q {(QQ”) / Q} 2 The sum of NmaxΔt ) / C} 2 +{(QQ”) / Q} 2The pair of estimated values ​​Q0 and C0 that minimizes this is found, and the estimated value Q0 at this time is taken as the true value Q' of the sweat rate, and the estimated value C0 is taken as the true value C' of the electrolyte concentration.

[0057] [First Example] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Fig. 2 is a block diagram showing the configuration of a perspiration analyzer according to a first embodiment of the present invention. The perspiration analyzer includes a wearable sensor 1, an AFE (Analog Front End) unit 2, a data recording unit 3, a memory unit 4, an MCU (Micro Control Unit) unit 5, a communication unit 6, and a power supply unit 7.

[0058] Wearable sensor 1 outputs an electrical signal (for example, a current with the waveform shown in FIG. 1) derived from the amount of sweat secreted from the skin of the wearer and the electrolyte concentration. The AFE unit 2 includes an analog front end and amplifies the weak electrical signal output from the wearable sensor 1.

[0059] The data recording unit 3 includes an ADC (Analog Digital Converter), and converts the analog signal amplified by the AFE unit 2 into digital data at a predetermined sampling frequency and stores the digital data in the storage unit 4.

[0060] The storage unit 4 stores the digital data output from the data recording unit 3. The storage unit 4 is realized by a non-volatile memory such as a flash memory, or a volatile memory such as a DRAM (Dynamic Random Access Memory).

[0061] The MCU unit 5 is a circuit that performs signal processing to calculate the amount of sweat and the electrolyte concentration from the digital data stored in the storage unit 4.

[0062] The communication unit 6 includes a circuit for wirelessly or wiredly transmitting the measurement results and analysis results obtained by the MCU unit 5 to an external device (not shown) such as a smartphone. Examples of wireless communication standards include Bluetooth (registered trademark) Low Energy (BLE). Examples of wired communication standards include Ethernet (registered trademark). The power supply unit 7 is a circuit that serves to supply power to the perspiration analyzer.

[0063] The wearable sensor 1 in this embodiment is the same as that disclosed in Patent Document 1, so the structure of the wearable sensor 1 will be described with reference to FIGS. The wearable sensor 1 comprises a substrate 10 having a through hole 11 and a recess 12 communicating with the outlet end of the through hole 11, an electrode 14 arranged on the surface of the substrate 10 where the inlet end of the through hole 11 opens, a water-absorbing structure 15 arranged on the outlet surface (upper surface) of the substrate 10 so as to come into contact with the liquid that flows out from the outlet opening of the through hole 11 into the recess 12, and a water-absorbing electrode 16 arranged on the surface of the water-absorbing structure 15 facing the substrate 10 so as to face the outlet opening of the through hole 11.

[0064] The substrate 10 may be made of, for example, a hydrophilic glass material or a resin material. Alternatively, the substrate 10 may be made of a water-repellent material, the surface of which and the inner surfaces of the through-holes 11 have been subjected to a surface treatment to impart hydrophilic properties. The upper surface of the substrate 10 is formed with recesses 12 that are recessed into the upper surface so as to communicate with the through-holes 11. Conversely, the lower surface of the substrate 10 is formed with recesses 13 that are recessed into the lower surface so as to communicate with the through-holes 11.

[0065] The electrode 14 is made of, for example, a thin metal film formed on the surface (lower surface) of the substrate 10 where the entrance ends of the through-holes 11 are open. Examples of the water-absorbing structure 15 include fibers such as cotton and silk, and porous ceramic substrates. Examples of the electrode 16 include a porous thin metal film formed on the surface of the water-absorbing structure 15 by plating, for example, a water-absorbing structure 15 in which the fibers are impregnated with a conductive polymer, or a structure in which conductive fibers are woven.

[0066] Wearable sensor 1 is attached to the body of a wearer so that the lower surface of substrate 10 faces skin 100 of the wearer, as shown in Fig. 13. Reference numeral 101 in Fig. 13 denotes sweat glands of the wearer. When the wearer sweats, the sweat 102 is introduced into the through-holes 11 from the recesses 13 of the base material 10 by capillary action. Furthermore, as the amount of sweat increases, the sweat 102 rises inside the through-holes 11 and reaches the recesses 12.

[0067] As shown in the enlarged view of Fig. 14, a water-repellent portion 17 is provided on the inner surface of the recess 12. When a hydrophilic material is used for the substrate 10, the water-repellent portion 17 can be formed by performing a water-repellent surface treatment on the inner surface of the recess 12. When a water-repellent material is used for the substrate 10, the water-repellent portion 17 can be provided by leaving only the inner surface of the recess 12 made of a water-repellent material.

[0068] When the sweat 102 reaches the recess 12, it turns into a spherical droplet 102a as shown in FIG. 14. As the amount of sweat increases, the diameter of the droplet 102a increases and finally reaches the electrode 16 and the water-absorbent structure 15. The droplet 102a that has reached the electrode 16 and the water-absorbent structure 15 passes through the numerous pores in the electrode 16 and the numerous pores in the water-absorbent structure 15 by capillary action, and evaporates while moving within the water-absorbent structure 15. As a result, the droplet 102a disappears. In this way, the formation and disappearance of the droplet 102a repeatedly generates electricity between the electrodes 14 and 16 of the wearable sensor 1.

[0069] 13 and 14 are used as examples of the structure of wearable sensor 1, but the structure is not limited to these. Wearable sensors with other structures may be used as long as they allow current to flow intermittently between the electrodes due to droplets that are intermittently formed inside the wearable sensor as the wearer sweats.

[0070] 3 is a functional block diagram of the MCU unit 5 of this embodiment. The MCU unit 5 functions as a sweat rate calculation unit 50, an electrolyte concentration calculation unit 51, and a correction unit 52.

[0071] The sweat rate calculation unit 50 calculates a measured value Q of the amount of sweat of the wearer based on the current flow characteristics between the electrodes of the wearable sensor 1. The electrolyte concentration calculation unit 51 calculates a measured value C of the electrolyte concentration in the sweat of the wearer based on the current flow characteristics between the electrodes of the wearable sensor 1.

[0072] The correction unit 52 calculates the true value Q' of the sweat rate and the true value C' of the electrolyte concentration, corrected for the effect of sweat loss due to evaporation, based on the measured value Q of the sweat rate, the measured value C of the electrolyte concentration, and known physical quantities related to sweat evaporation.

[0073] 4 is a flowchart illustrating the operation of the perspiration analyzer of this embodiment. The AFE unit 2 detects the current flowing between the electrodes 14 and 16 of the wearable sensor 1 (step S1 in FIG. 4).

[0074] The data recording unit 3 converts the signal detected and amplified by the AFE unit 2 into digital data at a predetermined sampling rate (step S2 in FIG. 4) and stores it in the memory unit 4 (step S3 in FIG. 4). At this time, the data recording unit 3 adds information about the sampling time to the digital data and stores it in the memory unit 4. In this way, the memory unit 4 stores time-series data of the current.

[0075] The perspiration rate calculation unit 50 calculates the measured perspiration rate Q [L / s] of the wearer of the wearable sensor 1 based on the digital data stored in the memory unit 4 (step S4 in FIG. 4). Specifically, the perspiration rate calculation unit 50 can calculate the measured perspiration rate Q [L / s] by dividing the volume V [L] of the perspiration droplet 102a by the period T [s] from the immediately preceding current peak to the latest current peak.

[0076] As described in Patent Document 1, the volume V of sweat droplet 102a generated between electrodes 14 and 16 of wearable sensor 1 can be calculated in advance as an actual value.

[0077] The electrolyte concentration calculation unit 51 calculates the electrical resistivity Rρ of sweat, which varies depending on the electrolyte concentration C [mol / L] in the sweat of the wearer, and calculates the measured value C [mol / L] of the electrolyte concentration in the sweat from this electrical resistivity Rρ (Step S5 in Figure 4).

[0078] Specifically, electrolyte concentration calculation unit 51 calculates the resistance by dividing the value of the known voltage applied between electrodes 14 and 16 by AFE unit 2 by the current peak value at the most recent time of current application, which is indicated by the digital data stored in memory unit 4. Then, electrolyte concentration calculation unit 51 calculates the electrical resistivity Rρ based on the resistance, the known distance between electrodes 14 and 16, and the cross-sectional area of ​​the sweat between electrodes 14 and 16. For the cross-sectional area of ​​the sweat, a specified value that is used when the cross-sectional area of ​​the sweat between electrodes 14 and 16 is considered to be constant may be used.

[0079] It is known that there is a linear relationship between the electrical resistivity Rρ of sweat and the electrolyte concentration C (mainly the concentration of NaCl) in sweat. Electrolyte concentration calculation unit 51 calculates the measured value C [mol / L] of the electrolyte concentration from the electrical resistivity Rρ based on the known relationship between the electrical resistivity Rρ and the electrolyte concentration C.

[0080] Next, the correction unit 52 corrects the measured value Q of the amount of sweat calculated by the amount of sweat calculation unit 50 and the measured value C of the electrolyte concentration calculated by the electrolyte concentration calculation unit 51 (step S6 in FIG. 4). FIG. 5 is a flowchart illustrating the operation of the correction unit 52.

[0081] The correction unit 52 calculates the diffusion coefficient D of water vapor in sweat when the electrolyte concentration calculated by the electrolyte concentration calculation unit 51 is C, and the density C of water vapor near the gas-liquid interface of the sweat droplet 102a generated at the opening of the through-hole 11 of the wearable sensor 1. v,0 and the known density C of water vapor sufficiently far from the gas-liquid interface of the droplet 102a. v,∞ the density ρ of water, a value r that is half the size of the opening of the through-hole 11 (the diameter if the cross section of the opening is circular), and a known static contact angle θ of the droplet 102a. cBased on the above, the true value Q' of the amount of sweating corrected for the effect of sweat loss due to evaporation is calculated using equation (1) (step S100 in FIG. 5). c For example, a value determined by a prior experiment may be set as the density of water vapor. Although the density of water vapor strictly varies depending on the temperature, the density may be set to a value that is closest to the actually measured value in the assumed environment of high temperature and humidity.

[0082] Furthermore, the correction unit 52 calculates the true value C' of the electrolyte concentration corrected for the effect of sweat loss due to evaporation, using equation (2) based on the true value Q' of the sweat rate, the measured value Q of the sweat rate, and the measured value C of the electrolyte concentration (step S101 in FIG. 5).

[0083] The communication unit 6 transmits the calculation result of the sweat rate calculation unit 50, the calculation result of the electrolyte concentration calculation unit 51, and the correction result of the correction unit 52 to an external device (not shown) such as a smartphone (step S7 in FIG. 4).

[0084] The perspiration analyzer repeatedly executes the processes of steps S1 to S7 until, for example, an instruction to end the measurement is received from the wearer (YES in step S8 in FIG. 4).

[0085] As described above, according to this embodiment, by providing the correction unit 52, the true value of the sweat rate and the true value of the electrolyte concentration can be calculated, thereby reducing the possibility of underestimating the sweat rate or overestimating the electrolyte concentration.

[0086] [Second Example] In the first embodiment, the sweat rate and electrolyte concentration are corrected based on a first correction method. In the second embodiment of the present invention, the sweat rate and electrolyte concentration are corrected based on a second correction method. The difference between this embodiment and the first embodiment is the operation of the correction unit 52. The operation of the correction unit 52 in this embodiment will be described with reference to FIG. 6.

[0087] The correction unit 52 calculates the measured sweat rate Q, the diffusion coefficient D of water vapor in sweat when the electrolyte concentration is C, and the density C of water vapor near the gas-liquid interface of the sweat droplet 102a generated at the opening of the through-hole 11 of the wearable sensor 1. v,0 and the density C of water vapor at a location sufficiently far from the gas-liquid interface of the droplet 102a. v,∞ Based on the water density ρ, half the size r of the opening of the through-hole 11, and the current peak period T used by the sweat rate calculation unit 50 to calculate the measured sweat rate Q, the true value Q' of the sweat rate is calculated by solving equation (3) for the time derivative of the dynamic contact angle θ of the sweat droplet 102a and equation (4) for the integral of the amount of sweat lost due to evaporation during the period T (step S200 in Figure 6).

[0088] Furthermore, the correction unit 52 calculates the true value C' of the electrolyte concentration using equation (2) based on the true value Q' of the sweat rate, the measured value Q of the sweat rate, and the measured value C of the electrolyte concentration (step S201 in FIG. 6). Other configurations of the perspiration analyzer are the same as those in the first embodiment.

[0089] [Third Example] In a third embodiment of the present invention, the sweat rate and electrolyte concentration are corrected based on a third correction method. The difference between this embodiment and the first embodiment is the operation of the correction unit 52. The operation of the correction unit 52 in this embodiment will be described with reference to FIG. 7.

[0090] The correction unit 52 sets a small non-zero value as the initial value θ(0) of the dynamic contact angle of the sweat droplet 102a at time t = 0 (step S300 in FIG. 7). The correction unit 52 also sets a value within a range equal to or greater than the measured value Q of the sweat rate and equal to or less than a predetermined value Q of the sweat rate as an estimate of the true value Q' of the sweat rate (step S301 in FIG. 7).

[0091] The correction unit 52 calculates the initial value θ(0) of the dynamic contact angle, the estimated true value Q′ of the amount of sweat, the diffusion coefficient D of water vapor in sweat when the electrolyte concentration is C, and the density C of water vapor near the gas-liquid interface of the sweat droplet 102a. v,0 and the density C of water vapor at a location sufficiently far from the gas-liquid interface of the droplet 102a. v,∞Based on the density ρ of water and the value r of half the dimension of the opening of the through-hole 11, the sweat rate calculation unit 50 calculates the dynamic contact angle θ of the droplet 102a during the current peak period T used to calculate the sweat rate measurement value Q at every calculation interval Δt using equation (5) (step S302 in Figure 7).

[0092] Next, based on the measured sweat rate Q, the estimated value of the true sweat rate Q', the current peak period T used by the sweat rate calculation unit 50 to calculate the measured sweat rate Q, and the calculation result of step S302, the correction unit 52 calculates an evaluation function f(Q') for evaluating the accuracy of the estimated value of the true sweat rate Q' by subtracting the amount of sweat loss due to evaporation during period T from the difference between the total amount of estimated values ​​of the true sweat rate Q' during the current peak period T (=Q'T) and the total amount of measured sweat rate Q (=QT), as shown in equation (6) (step S303 in Figure 7).

[0093] If the calculation process of steps S302 and S303 has not been completed for all estimated values ​​of the true value Q' of the sweat rate (NO in step S304 in FIG. 7), the correction unit 52 returns to step S301 and changes the estimated value of the true value Q' of the sweat rate. As described above, the correction unit 52 changes the estimated value by a predetermined step width of the sweat rate. In this way, the correction unit 52 calculates the evaluation function f(Q') for each of the multiple estimated values ​​of the true value Q' of the sweat rate.

[0094] The correction unit 52 is configured to correct the estimated value of the predetermined number of estimated values ​​when the calculation process of steps S302 and S303 is completed, or when the estimated value starting from the measured sweat rate Q reaches a predetermined sweat rate value (for example, an upper limit value Q max ), it is determined that the calculation process of steps S302 and S303 has ended.

[0095] The correction unit 52 determines the best evaluation function f(Q') among the evaluation functions f(Q') calculated for each estimate of the true value Q' of the sweat rate as the true value Q' of the sweat rate (step S305 in FIG. 7). Specifically, the correction unit 52 determines the square of the evaluation function f(Q') 2 The estimated value that minimizes this is taken as the true value Q' of the sweat rate.

[0096] Furthermore, the correction unit 52 calculates the true value C' of the electrolyte concentration using equation (2) based on the true value Q' of the sweat rate, the measured value Q of the sweat rate, and the measured value C of the electrolyte concentration (step S306 in FIG. 7). Other configurations of the perspiration analyzer are the same as those in the first embodiment.

[0097] [Fourth Example] In a fourth embodiment of the present invention, the sweat rate and electrolyte concentration are corrected based on a fourth correction method. The difference between this embodiment and the first embodiment is the operation of the correction unit 52. The operation of the correction unit 52 in this embodiment will be described with reference to FIG. 8.

[0098] The correction unit 52 calculates the diffusion coefficient D of water vapor in sweat when the electrolyte concentration calculated by the electrolyte concentration calculation unit 51 is C, and the density C of water vapor near the gas-liquid interface of the sweat droplet 102a. v,0 and the density C of water vapor at a location sufficiently far from the gas-liquid interface of the droplet 102a. v,∞ the density of water ρ, the value r of half the size of the opening of the through-hole 11, and the static contact angle θ of the droplet 102a. c Based on this, the true value Q' of the amount of sweating corrected for the effect of sweat loss due to evaporation is calculated using equation (1) (step S400 in FIG. 8).

[0099] The correction unit 52 sets a small non-zero value as the initial value θ0 of the dynamic contact angle at time 0 [s] (Step S401 in FIG. 8). The correction unit 52 also sets a value within a range equal to or greater than a predetermined concentration value and equal to or less than the measured value C of the electrolyte concentration as the estimated value C0 of the true value of the electrolyte concentration (Step S402 in FIG. 8).

[0100] The correction unit 52 calculates the true value Q' of the sweat rate, the initial value θ0 of the dynamic contact angle, the estimated true value C0 of the electrolyte concentration, and the density C of the water vapor. v,0 ,C v,∞ The density of water ρ, the value r of half the size of the opening of the through-hole 11, and the electrolyte concentration in sweat x (x is C0, C Δt ,C NΔtBased on the known diffusion coefficient D[x] of water vapor in sweat at the time of NΔt and equation (8) for calculating the dynamic contact angle θ of the droplet 102a, the electrolyte concentration C when the current peak period T=NΔt has elapsed from time 0 [s] before the droplet 102a was formed can be calculated. NΔt (Step S403 in FIG. 8). NΔt is the theoretical value corresponding to the measured electrolyte concentration C.

[0101] If the calculation process of step S403 has not been completed for all of the estimated values ​​C0 of the true value of the electrolyte concentration (NO in step S404 in FIG. 8), the correction unit 52 returns to step S402 and changes the estimated value C0. As described above, the correction unit 52 changes the estimated value C0 by a predetermined step width of the electrolyte concentration. In this way, the correction unit 52 calculates the theoretical value C0 for each of the multiple estimated values ​​C0. NΔt Calculate.

[0102] The correction unit 52 performs the calculation of the estimated values ​​C0 in step S403 or when the calculation of the estimated values ​​C0 reaches a predetermined concentration value (for example, a lower limit C min ) reaches the measured value C of the electrolyte concentration, the calculation process of step S403 is determined to be completed.

[0103] Then, the correction unit 52 calculates the measured value C of the electrolyte concentration and the theoretical value C NΔt Based on the above, an evaluation function for evaluating the accuracy of the estimated value C0 of the true value of the electrolyte concentration is calculated for each estimated value C0, and the estimated value C0 for which the best evaluation function is obtained is determined as the true value C' of the electrolyte concentration (step S405 in FIG. 8). NΔt Square of the difference (CC NΔt ) 2 The estimated value C0 at which is the smallest is taken as the true value C' of the electrolyte concentration. Other configurations of the perspiration analyzer are the same as those in the first embodiment.

[0104] [Fifth Example] In a fifth embodiment of the present invention, the sweat rate and electrolyte concentration are corrected based on a fifth correction method. The difference between this embodiment and the first embodiment is the operation of correction unit 52, and the operation of correction unit 52 in this embodiment will be described with reference to FIG.

[0105] The correction unit 52 sets a non-zero, minute value as the initial value θ0 of the dynamic contact angle at time 0 [s] (step S500 in FIG. 9). The correction unit 52 also sets a value within a range of equal to or greater than a predetermined concentration value and equal to or less than a measured value C of the electrolyte concentration as the estimated value C0 of the true value of the electrolyte concentration (step S501 in FIG. 9). The correction unit 52 also sets a value within a range of equal to or greater than the measured value Q of the sweat rate and equal to or less than a predetermined sweat rate value (step S502 in FIG. 9).

[0106] The correction unit 52 calculates the initial value θ0 of the dynamic contact angle, the estimated value C0 of the true value of the electrolyte concentration, the estimated value Q0 of the true value of the sweat rate, and the density C of the water vapor. v,0 ,C v,∞ The density of water ρ, the value r of half the size of the opening of the through-hole 11, and the electrolyte concentration in sweat x (x is C0, C Δt ,C NΔt Based on the known diffusion coefficient D[x] of water vapor in sweat at the time of NΔt and equation (10) for calculating the dynamic contact angle θ of the droplet 102a, the electrolyte concentration C just before the elapsed time from time 0 [s] reaches the current peak period T = NΔt is calculated. (Nmax-1)Δt and dynamic contact angle θ (Nmax-1)Δt (Step S503 in FIG. 9). (Nmax-1)Δt is the theoretical value corresponding to the measured electrolyte concentration C. The dynamic contact angle θ (Nmax-1)Δt is the static contact angle θ c This is the theoretical value equivalent to

[0107] The correction unit 52 calculates the estimated true value of the sweat rate Q0 and the water vapor density C v,0 ,C v,∞ The density of water ρ, the value r of half the size of the opening of the through-hole 11, and the electrolyte concentration in sweat C (Nmax-1)ΔtThe known diffusion coefficient of water vapor in sweat at (Nmax-1)Δt ] and the dynamic contact angle θ of the droplet 102a (Nmax-1)Δt Based on this, a theoretical value Q″ corresponding to the measured value Q of the amount of sweating is calculated using equation (11) (step S504 in FIG. 9).

[0108] If the calculation process of steps S503 and S504 has not been completed for all combinations of the estimated value C0 of the true value of the electrolyte concentration and the estimated value Q0 of the true value of the sweat rate (NO in step S505 of Figure 9), the correction unit 52 returns to step S501 and changes at least one of the estimated value C0 of the true value of the electrolyte concentration and the estimated value Q0 of the true value of the sweat rate.

[0109] As described above, the correction unit 52 changes the estimated value C0 by a predetermined step size of the electrolyte concentration, and changes the estimated value Q0 by a predetermined step size of the sweat rate. In this way, the correction unit 52 calculates the theoretical value C0 for each of a plurality of pairs of the estimated values ​​Q0 and C0. NmaxΔt ,θ (Nmax-1)Δt , Q" are calculated. The correction unit 52 determines that the calculation process is complete when the processes of steps S503 and S504 have been completed for all possible combinations of the estimated values ​​C0 and Q0.

[0110] Then, the correction unit 52 calculates the measured value C of the electrolyte concentration and the theoretical value C NmaxΔt Based on the measured value Q and theoretical value Q″ of the amount of sweating, an evaluation function for evaluating the accuracy of the estimated value C0 of the true value of the electrolyte concentration and the estimated value Q0 of the true value of the amount of sweating is calculated for each pair of estimated values ​​Q0, C0. The estimated value Q0 of the combination that yields the best evaluation function is determined to be the true value Q′ of the amount of sweating, and the estimated value C0 of the combination that yields the best evaluation function is determined to be the true value C′ of the electrolyte concentration (step S506 in FIG. 9).

[0111] Specifically, the correction unit 52 calculates the measured value C of the electrolyte concentration and the theoretical value C NmaxΔt The square of the difference between the measured value and the measured value C {(CC NmaxΔt ) / C} 2 and the square of the difference between the measured sweat rate Q and the theoretical value Q” divided by the measured value Q {(QQ”) / Q} 2 The sum ofNmaxΔt ) / C} 2 +{(QQ”) / Q} 2 The pair of estimated values ​​Q0 and C0 that minimizes this is found, and the estimated value Q0 at this time is taken as the true value Q' of the sweat rate, and the estimated value C0 is taken as the true value C' of the electrolyte concentration. Other configurations of the perspiration analyzer are the same as those in the first embodiment.

[0112] [Sixth Example] 10 is a block diagram showing the configuration of a perspiration analyzer according to a sixth embodiment of the present invention. The perspiration analyzer includes a wearable sensor 1a, an AFE unit 2, a data recording unit 3, a memory unit 4, an MCU unit 5a, a communication unit 6, and a power supply unit 7.

[0113] The wearable sensor 1a in this embodiment is the same as that disclosed in Patent Document 2, so the structure of the wearable sensor 1a will be described with reference to FIGS. The wearable sensor 1a comprises a substrate 10 having a through hole 11 and a recess 12, a water-absorbing structure 15, an LD 18 arranged within the recess 12 and emitting light along a path within the recess 12 that passes along the outlet side surface of the substrate 10 and above the opening of the outlet side of the through hole 11, and a PD 19 arranged within the recess 12 facing the LD 18 across the opening of the outlet side of the through hole 11 and receiving light from the LD 18.

[0114] Examples of the water-absorbing structure 15 include fibers such as cotton and silk, and porous ceramic substrates. Note that the water-absorbing structure 15 does not need to cover the entire surface of the outlet opening of the through-hole 11 and the recess 12, as long as it is positioned so as to be able to come into contact with droplets that flow out from the outlet opening of the through-hole 11 into the recess 12.

[0115] Wearable sensor 1a is attached to the body of a wearer so that the lower surface of base material 10 faces skin 100 of the wearer, as shown in FIG. When the wearer sweats, the sweat 102 is introduced by capillary action from the recesses 13 of the base material 10 into the through-holes 11. Furthermore, as the amount of sweat increases, the sweat 102 rises inside the through-holes 11 and reaches the recesses 12 provided on the top surface of the base material 10 so as to communicate with the through-holes 11.

[0116] As shown in the enlarged view of Figure 16, a water-repellent portion 17 is provided on the inner surface of the recess 12. When sweat 102 reaches the recess 12, it turns into spherical droplets 102a as shown in Figure 16. As the amount of sweat increases, the diameter of the droplets 102a increases and finally reaches the absorbent structure 15. The droplets 102a that have reached the absorbent structure 15 pass through the many pores of the absorbent structure 15 due to capillary action and evaporate while moving within the absorbent structure 15. As a result, the droplets 102a disappear.

[0117] When measuring the amount of sweat, the light-emitting element LD18 emits light along a path within the recess 12 that passes through a position above the outlet opening of the through-hole 11 along the outlet surface (top surface) of the substrate 10, as shown in Figures 15 and 16. The PD 19, which is a light receiving element, receives the light from the LD 18.

[0118] When a droplet 102a of sweat 102 is formed, light 103 emitted from LD 18 propagates through the air in recess 12, droplet 102a, and air in recess 12 in this order, and then enters PD 19. When droplet 102a disappears, light 103 propagates through the air in recess 12 and then enters PD 19. When droplet 102a is formed again, light 103 propagates through the air in recess 12, droplet 102a, and air in recess 12 in this order, and then enters PD 19. In this way, the difference in the medium through which light 103 propagates is reflected in the amount of light received by PD 19. In other words, the formation and disappearance of droplet 102a changes the photocurrent flowing through PD 19.

[0119] The configurations of the AFE unit 2, data recording unit 3, memory unit 4, communication unit 6, and power supply unit 7 of the perspiration analyzer are the same as those in the first embodiment. The AFE unit 2 only needs to amplify the output signal (photocurrent) of the PD 20.

[0120] 11 is a functional block diagram of the MCU unit 5a of this embodiment. The MCU unit 5a functions as a sweat rate calculation unit 50a, an electrolyte concentration calculation unit 51a, and a correction unit 52a.

[0121] The perspiration rate calculation unit 50a calculates a measured value Q of the amount of perspiration of the wearer based on the light receiving characteristics of the PD 19. The electrolyte concentration calculation unit 51a calculates a measured value C of the electrolyte concentration in the sweat of the wearer based on the light receiving characteristics of the PD 19.

[0122] The correction unit 52a calculates the true value Q' of the sweat rate and the true value C' of the electrolyte concentration, corrected for the effect of sweat loss due to evaporation, based on the measured value Q of the sweat rate, the measured value C of the electrolyte concentration, and known physical quantities related to sweat evaporation.

[0123] The processing flow of the perspiration analyzer of this embodiment is the same as that of the first embodiment, so the operation of the perspiration analyzer will be explained using FIG. The AFE unit 2 detects the photocurrent of the PD 19 of the wearable sensor 1a (step S1 in FIG. 4).

[0124] The data recording unit 3 converts the signal detected and amplified by the AFE unit 2 into digital data at a predetermined sampling rate (step S2 in FIG. 4), and stores the digital data in the storage unit 4 (step S3 in FIG. 4).

[0125] The perspiration rate calculation unit 50a calculates the measured perspiration rate Q of the wearer of the wearable sensor 1a based on the digital data stored in the storage unit 4 (Step S4 in FIG. 4). Specifically, the perspiration rate calculation unit 50a calculates the measured perspiration rate Q by dividing the volume V of the sweat droplet 102a by the period T from the immediately preceding current peak to the latest current peak.

[0126] In this embodiment, when a sweat droplet 102a is formed in the recess 12, the photocurrent of the PD 19 decreases, and when the droplet 102a disappears, the photocurrent of the PD 19 increases. Therefore, the sweat rate calculation unit 50a calculates the measured sweat rate Q using the period T of the downward peaks of the photocurrent of the PD 19.

[0127] The electrolyte concentration calculation unit 51a calculates a measured value C of the electrolyte concentration in the sweat of the wearer based on the amount of light received by the PD 19 (step S5 in FIG. 4). In this embodiment, the laser wavelength of the LD 18 is set to the absorption wavelength of a specific component in the sweat. This allows the electrolyte concentration calculation unit 51a to calculate the measured value C of the electrolyte concentration based on the amount of light received by the PD 19 when the amount of light reaches a minimum value.

[0128] The correction unit 52a corrects the measured value Q of the amount of sweat calculated by the sweat rate calculation unit 50a and the measured value C of the electrolyte concentration calculated by the electrolyte concentration calculation unit 51a (step S6 in FIG. 4). In this embodiment, the correction is performed using the first correction method. The operation of the correction unit 52a is the same as that of the correction unit 52 in the first embodiment.

[0129] The communication unit 6 transmits the calculation results of the sweat rate calculation unit 50a, the calculation results of the electrolyte concentration calculation unit 51a, and the correction results of the correction unit 52a to an external device such as a smartphone (Step S7 in FIG. 4).

[0130] The perspiration analyzer repeatedly executes the processes of steps S1 to S7 until, for example, an instruction to end the measurement is received from the wearer (YES in step S8 in FIG. 4). Thus, in this embodiment, as in the first embodiment, it is possible to reduce the possibility of underestimating the amount of sweat or overestimating the electrolyte concentration.

[0131] In this embodiment, the sweat rate and electrolyte concentration are corrected based on the first correction method, but correction may also be performed based on the second correction method. In this case, the operation of the correction unit 52a is the same as that of the correction unit 52 of the second embodiment. The difference from the correction unit 52 is that the correction unit 52a calculates the true value Q' of the sweat rate using the period T of the downward peaks of the photocurrent of the PD 19 instead of the period of the peaks of the current flowing between the electrodes 14 and 16.

[0132] The sweat rate and electrolyte concentration may also be corrected based on a third correction method. In this case, the operation of the correction unit 52a is the same as that of the correction unit 52 of the third embodiment. The difference from the correction unit 52 is that the correction unit 52a calculates the evaluation function f(Q') using the period T of the downward peaks of the photocurrent of the PD 19 instead of the period of the peaks of the current flowing between the electrodes 14 and 16.

[0133] The sweat rate and electrolyte concentration may also be corrected based on a fourth correction method. In this case, the operation of the correction unit 52a is the same as that of the correction unit 52 of the fourth embodiment. The difference from the correction unit 52 is that the correction unit 52a calculates the electrolyte concentration C using the period T of the downward peaks of the photocurrent of the PD 19 instead of the period of the peaks of the current flowing between the electrodes 14 and 16. NΔt The purpose is to calculate

[0134] The sweat rate and electrolyte concentration may also be corrected based on a fifth correction method. In this case, the operation of the correction unit 52a is the same as that of the correction unit 52 of the fifth embodiment. The difference from the correction unit 52 is that the correction unit 52a calculates the electrolyte concentration C using the period T of the downward peaks of the photocurrent of the PD 19 instead of the period of the peaks of the current flowing between the electrodes 14 and 16. (Nmax-1)Δt and dynamic contact angle θ (Nmax-1)Δt The purpose is to calculate the following.

[0135] The data recording unit 3, storage unit 4, MCU units 5, 5a, and communication unit 6 described in the first to sixth embodiments can be realized by a computer equipped with a CPU (Central Processing Unit), a storage unit, and an interface, and a program that controls these hardware resources. An example of the configuration of this computer is shown in Figure 12.

[0136] The computer includes a CPU 200, a storage device 201, and an interface device (I / F) 202. The I / F 202 is connected to hardware such as an ADC of the data recording unit 3 and hardware such as the communication unit 6. In such a computer, a program for implementing the perspiration analysis method of the present invention is stored in the storage device 201. The CPU 200 executes the processes described in the first to sixth embodiments in accordance with the program stored in the storage device 201. [Industrial Applicability]

[0137] The present invention can be applied to a technique for analyzing the amount of sweat and the electrolyte concentration in sweat of a person. [Explanation of symbols]

[0138] 1,1a...wearable sensor, 2...AFE unit, 3...data recording unit, 4...memory unit, 5,5a...MCU unit, 6...communication unit, 7...power supply unit, 10...substrate, 11...through hole, 12,13...recess, 14,16...electrode, 15...water-absorbing structure, 17...water-repellent unit, 18...laser diode, 19...photodiode, 50,50a...sweating rate calculation unit, 51,51a...electrolyte concentration calculation unit, 52,52a...correction unit.

Claims

1. a wearable sensor configured to output an electrical signal derived from the amount of sweat secreted from the skin of a wearer and the electrolyte concentration; a sweat rate calculation unit configured to calculate a sweat rate measurement value of the wearer based on the electrical signal obtained by the wearable sensor; an electrolyte concentration calculation unit configured to calculate a measured electrolyte concentration in the sweat of the wearer based on the electrical signal obtained by the wearable sensor; a correction unit configured to calculate true values ​​of the sweat rate and the electrolyte concentration, corrected for the effect of sweat loss due to evaporation, based on the measured sweat rate, the measured electrolyte concentration, and known physical quantities related to sweat evaporation.

2. The sweat analyzer according to claim 1, The correction unit calculates the amount of sweat loss due to evaporation based on a known physical quantity related to the evaporation of sweat, calculates the true value of the sweat rate by adding the amount of sweat loss to the measured sweat rate, and calculates the true value of the electrolyte concentration based on the true value of the sweat rate, the measured sweat rate, and the measured electrolyte concentration.

3. The sweat analyzer according to claim 1, the electrical signal is a current that changes due to droplets that are intermittently generated in the wearable sensor due to sweating by the wearer; the sweat rate calculation unit calculates a sweat rate measurement value of the wearer based on the period of the peaks of the current; The correction unit calculates the true value of the sweat rate by solving an equation for the time derivative of the dynamic contact angle of the droplet and an equation for the integral of the amount of sweat loss due to evaporation during the period between the current peaks, based on a known physical quantity related to sweat evaporation, the sweat rate measurement value, and the period of the current peaks, and calculates the true value of the electrolyte concentration based on the true value of the sweat rate, the sweat rate measurement value, and the electrolyte concentration measurement value.

4. The sweat analyzer according to claim 1, the electrical signal is a current that changes due to droplets that are intermittently generated in the wearable sensor due to sweating by the wearer; the sweat rate calculation unit calculates a sweat rate measurement value of the wearer based on the period of the peaks of the current; the correction unit sets a plurality of estimates of the true value of the sweat rate within a predetermined range, calculates the dynamic contact angle of the droplet during the period between the peaks of the current for each estimate based on a known physical quantity related to sweat evaporation and the estimated value, calculates an evaluation function for each estimate based on the known physical quantity related to sweat evaporation, the measured sweat rate, the estimated value, the period of the current peaks, and the calculation result of the dynamic contact angle, determines the estimated value for which the best evaluation function is obtained as the true value of the sweat rate, and calculates the true value of the electrolyte concentration based on the true value of the sweat rate, the measured sweat rate, and the measured electrolyte concentration.

5. The sweat analyzer according to claim 1, the electrical signal is a current that changes due to droplets that are intermittently generated in the wearable sensor due to sweating by the wearer; the sweat rate calculation unit calculates a sweat rate measurement value of the wearer based on the period of the peaks of the current; the correction unit calculates the amount of sweat loss due to evaporation based on a known physical quantity related to the evaporation of sweat, calculates the true value of the sweat rate by adding the measured amount of sweat loss to the measured amount of sweat, sets a plurality of estimates of the true value of the electrolyte concentration within a predetermined range, calculates a theoretical value equivalent to the measured electrolyte concentration for each of the estimates based on the known physical quantity related to the evaporation of sweat, the true value of the sweat rate, the estimate, and the period of the current peak, calculates an evaluation function for each of the estimates based on the measured electrolyte concentration and the theoretical value to evaluate the accuracy of the estimate, and determines the estimate that yields the best evaluation function as the true value of the electrolyte concentration.

6. The sweat analyzer according to claim 1, the electrical signal is a current that changes due to droplets that are intermittently generated in the wearable sensor due to sweating by the wearer; the sweat rate calculation unit calculates a sweat rate measurement value of the wearer based on the period of the peaks of the current; the correction unit sets a plurality of pairs of estimated values ​​of the true electrolyte concentration and estimated values ​​of the true sweat rate within a predetermined range, calculates a first theoretical value corresponding to the measured electrolyte concentration and a second theoretical value corresponding to the static contact angle of the droplet for each pair of estimated values ​​based on a known physical quantity related to sweat evaporation, the estimated value of the true electrolyte concentration, the estimated value of the true sweat rate, and a period of the current peaks, calculates a third theoretical value corresponding to the measured sweat rate for each pair of estimated values ​​based on the known physical quantity related to sweat evaporation, the estimated value of the true sweat rate, and the first and second theoretical values, calculates an evaluation function for each pair of estimated values ​​based on the measured electrolyte concentration, the first theoretical value, the measured sweat rate, and the third theoretical value, and determines the pair of estimated values ​​that yields the best evaluation function as the true electrolyte concentration and the true sweat rate.

7. The sweat analyzer according to claim 1, the electrical signal is a current that changes due to droplets that are intermittently generated in the wearable sensor due to sweating by the wearer; the sweat rate calculation unit calculates a sweat rate measurement value of the wearer based on the period of the peaks of the current; The sweat analysis device is characterized in that the electrolyte concentration calculation unit calculates a measured value of the electrolyte concentration in the sweat of the wearer based on the peak value of the current.

8. A first step of detecting an electrical signal derived from the amount of sweat secreted from the skin of a wearer and the electrolyte concentration using a wearable sensor; a second step of calculating a sweat rate measurement of the wearer based on the electrical signal obtained by the wearable sensor; a third step of calculating a measured electrolyte concentration in the sweat of the wearer based on the electrical signal obtained by the wearable sensor; and a fourth step of calculating true values ​​of the sweat rate and the electrolyte concentration, corrected for the effect of sweat loss due to evaporation, based on the measured sweat rate, the measured electrolyte concentration, and known physical quantities related to sweat evaporation.

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