Sweat detection device

Abstract

A sweat sensing device 100 is provided. The device includes a body 102 for placement against skin 104. The body defines a recess 108 for receiving sweat from an area of ​​skin. The device further includes an optical detection assembly 114 configured to detect discrete sweat droplets 106 protruding into the recess from sweat pores 110 on the area of ​​skin, and a fluid system 116 configured to remove and transport the sweat droplets 106 from the recess 108 after the sweat droplets are detected by the optical detection assembly 114.

Description

Technical Field

[0001] The present invention relates to a sweat detection device.

Background Art

[0002] WO2019 / 210240A1 discloses a flexible and body-conforming sweat detection device configured to measure the sweating rate or the concentration of one or more analytes in sweat related to the physiological state of the device wearer.

[0003] "Ratiometric sweat secretion optical test in cystic fibrosis, carriers and healthy subjects" by Bergamini G. et al., JOURNAL OF CYSTIC FIBROSIS, ELSEVIER, Netherlands, vol. 17, no. 2, December 29, 2017 (2017-12-29), pages 186-189, ISSN: 1569-1993, DOI: 10.1016 / J.JCF.2017.12.003 discloses a simplified procedure for measuring the sweating rate in individual human sweat glands.

[0004] "In Vivo Readout of CFTR Function: Ratiometric Measurement of CFTR-Dependent Secretion by Individual, Identifiable Human Sweat Glands" by Wine J.J. et al., PLOS ONE, vol. 8, no. 10, October 24, 2013 (2013-10-24), pages 1-16 discloses a bioassay for concurrently monitoring and comparing CFTR-dependent and CFTR-independent sweat secretion for a plurality of (~50) individual identified sweat glands of each subject to evaluate the function of CFTR in vivo.

[0005] Non-invasive, semi-continuous, and long-term monitoring of biomarkers indicating disease / health status and wellness is needed, for example, in the monitoring of dehydration, stress, sleep, children's health, and perioperative monitoring.

[0006] Sweat, tear fluid, and saliva can all be collected non-invasively. Sweat is a particularly accessible biological fluid and a rich source of information regarding the physiological functions and metabolism of the subject.

[0007] Some examples of clinically relevant sweat components include Na + , Cl - , and / or K + , lactate as an early warning of inflammation (associated with sepsis), glucose for diabetics and neonates, and cortisol related to the monitoring of sleep apnea and stress.

[0008] Continuous monitoring using a device that monitors sweat biomarkers in high-risk patients such as those with severe chronic diseases, pre- or post-operative patients, and the elderly can provide higher-quality diagnostic information than the regular biomarker extraction tests that are usually performed by repeatedly collecting multiple blood samples. Such continuous monitoring is carried out in a hospital facility or other locations. Human sweat is an easily accessible source for biomarker measurement in skin-mounted devices, either alone or as a mixture with the lipids of sebum. For example, cholesterol is an important biomarker associated with an increased risk of the onset of cardiovascular disease. Cytokines such as inflammatory markers or interleukins (e.g., TNF-a, IL-6) play important roles in immune responses and detection or disease monitoring in joint disorders in rheumatoid and psoriatic arthritis and in bowel diseases.

[0009] Examples of biomarkers that can be detected in eccrine / apocrine sweat using appropriate capture species (such as antibodies, aptamers, molecularly imprinted polymers, etc.) include low molecular weight compounds such as urea, creatinine, cholesterol, triglyceride, steroid hormones (cortisol), glucose, melatonin, etc.; cytokines such as IL-1α, IL-1β, IL-6, TNFα, IL-8, and TGF-βIL-6, cysteine protease, DNAseI, lysozyme, Zn-α2-glycoprotein, cysteine-rich secretory protein-3, peptides and proteins including dermcidin; and large biomarkers such as hepatitis C virus.

[0010] As summarized by Mena-Bravo and de Castro in "Sweat: A sample with limited present applications and promising future in metabolomics", J. Pharm. Biomed. Anal. 90, 139 - 147 (2014), the results obtained from sweat detection can be highly variable, and there appears to be no correlation for various biomarkers between the values determined from blood and sweat samples. In this regard, previous studies in the field have included relatively crude sampling methods such as collecting large amounts of sweat in bags or cloths. The deficiencies of such methods may have contributed to the appearance of no correlation. The investigation by Mena-Bravo and de Castro emphasizes further major drawbacks of conventional sweat detection methods regarding the difficulty of sweating sufficient amounts for analysis, the problem of sample evaporation, the lack of appropriate sampling devices, the need for trained personnel, and the issue of normalization of sampling amounts.

[0011] Efforts have been made to address these issues by bringing wearable sensors into contact with sweat almost immediately after it emerges from the skin. As an example, there is the wearable patch presented by Gao et al. in "Fully integrated wearable sensor arrays for multiplexed in situ perspiration analysis", Nature 529, 509 - 514 (2016). The patch is equipped with a sensor array for measuring Na + , K + , glucose, lactate, and skin temperature. However, this research has focused on the development and integration of the sensors themselves, and while clearly important, does not address the issues related to sweat sample collection. Sweat sample collection is mainly done by placing an absorbent pad of several centimeters 2 in size between the skin and the sensor. When a sufficient amount of sweat is produced (and thus the tests are conducted on people who are exercising), it is assumed that the pad will absorb the sweat for analysis and that newly generated sweat will fill the pad and wash away the old sweat. However, the time-dependent response of the sensor may not directly reflect the actual biomarker levels over a period of time due to the accumulation effect. There may also be cases where the collection and presentation of samples for the disclosed sensors cannot be well controlled, making continuous and reliable detection over a long period difficult. Also, such patches are not designed to handle the trace amounts of sweat that occur under normal conditions, i.e., on the order of a few nanoliters per minute per sweat gland. SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0012] An object of the present invention is to provide an improved sweat detection device. The present invention is defined by the independent claims. The dependent claims define advantageous embodiments. MEANS FOR SOLVING THE PROBLEM

[0013] According to one aspect, there is provided a sweat detection device comprising a body for placement against the skin, the body defining a recess for receiving sweat from a skin area, and an optical detection assembly configured to detect discrete sweat droplets protruding from sweat pores in the skin area.

[0014] Since the optical detection assembly enables the detection of discrete sweat droplets protruding from individual sweat pores, the sweat detection device enables the monitoring of sweating from individual sweat glands, and sweat pores extend from the sweat glands.

[0015] Optically investigating the sweat excretion behavior of individual sweat glands in this way enables the determination of the sweating rate for each sweat gland, thereby having various related advantages such as, for example, being able to convert the analyte concentration in sweat to the calculated blood concentration. Alternatively or additionally, the optical investigation of the sweat excretion behavior of individual sweat glands is used in the process of identifying the type of sweat gland, that is, whether it is eccrine or apocrine.

[0016] The sweat detection device comprises a fluid system configured to remove and transport sweat droplets from the recess after the sweat droplets are detected by the optical detection assembly. This makes it easier to count the sweat droplets continuously generated in the skin area.

[0017] In a first set of embodiments, the optical detection assembly comprises an optical detector and a waveguide for carrying light to the optical detector, and the waveguide is arranged such that light is extracted from the waveguide when it comes into contact with a sweat droplet protruding into the recess.

[0018] Due to the extraction, the light intensity detected by the optical detector will decrease compared to a scenario where the sweat droplet does not contact the waveguide. This relatively simple detection principle has the advantage that it can be implemented using a relatively simple and low-cost optical detector such as a photodiode.

[0019] The optical detection assembly comprises, for example, an illumination unit for supplying light carried to the optical detector by the waveguide.

[0020] Alternatively or additionally, the sweat detection device comprises a window through which ambient light passes and is supplied to the waveguide. In this case, the ambient light is carried by the waveguide to the optical detector. By using ambient light in this way, the electric illumination unit becomes unnecessary, thereby reducing the power consumption of the sweat detection device.

[0021] In some embodiments, the sweat detection device comprises a sweat collector and / or an analyte sensor configured to detect analytes in sweat.

[0022] The outer surface of the waveguide partially defines the boundary of the recess and is configured to transport the sweat droplet towards the sweat collector and / or the analyte sensor after the sweat droplet is detected by the optical detector.

[0023] Thus, the waveguide serves two purposes: assisting in the detection of discrete sweat droplets and assisting in the transport of optically detected sweat droplets to the downstream sweat detector and / or analyte sensor.

[0024] The outer surface of the waveguide may include a surface tension gradient material for the transport of sweat droplets. Such a surface tension gradient material is provided, for example, by the outer surface of the waveguide having hydrophilic and hydrophobic portions on the surface, and these portions are arranged to provide a wettability gradient along the outer surface.

[0025] The optical detection assembly comprises a reference waveguide for carrying light to the optical detector. In this embodiment, the reference waveguide is optically shielded from the recess so that the light carried by the reference waveguide is not affected by the sweat in the recess.

[0026] Since the intensity of the light passing through the reference waveguide provides a reference that can be compared with the light passing through the waveguide, such a reference waveguide assists in the detection of sweat droplets. This makes it easier to identify a decrease in the intensity of the light carried by the waveguide corresponding to discrete sweat droplets in contact with the waveguide.

[0027] Such a reference waveguide is particularly useful when ambient light is used for the optical detection of sweat droplets. This is because the reference waveguide enables the optical detection system to take into account changes in the ambient light level.

[0028] In another set of embodiments, the optical detection assembly comprises, instead of or in addition to the waveguide / optical detector configuration described above, an active pixel sensor array and a lens device configured to image an area of skin illuminated by the active pixel sensor array such that sweat droplets can be detected.

[0029] An optical detection assembly having an imaging function has the advantage of providing additional information in addition to the information provided by the waveguide / optical detector configuration. For example, the active pixel sensor array allows easier access to information that can be used to distinguish sweat gland types.

[0030] The active pixel sensor array can be, for example, a charge-coupled device (CCD) sensor or a complementary metal-oxide-semiconductor (CMOS) sensor.

[0031] The sweat detection device comprises an optical window that transmits light from the recess to the lens device, the surface of the optical window partially defining the boundary of the recess and being configured to transport sweat droplets towards a sweat collector and / or an analyte sensor after the sweat droplets have been detected by the optical detection assembly.

[0032] Thus, the optical window serves two purposes: assisting in the detection of discrete sweat droplets and assisting in the transport of optically detected sweat droplets to downstream sweat detectors and / or analyte sensors.

[0033] The surface of the optical window includes, for example, a surface tension gradient material of the type described above in connection with the first set of embodiments for transporting sweat droplets.

[0034] The optical detection assembly includes a light source for illuminating the recess. This facilitates the imaging of sweat droplets.

[0035] In an embodiment, the sweat detection device includes an analyte sensor that detects the presence of an analyte in a sweat droplet specific to a single sweat gland type, and a processor configured to identify the range of the skin area where the sweat droplet is detected from the data collected by the optical detection assembly and assign a sweat gland type to the range based on the presence of the detected analyte received from the analyte sensor.

[0036] In this way, based on the analyte specific to the sweat gland, the sweat gland type from which the sweat droplet is discharged can be assigned. It is known that certain analytes are excreted by one type of sweat gland, but not by the other type of sweat gland or are excreted in only negligible amounts. For example, a sweat gland is assigned as either an eccrine gland or an apocrine gland based on the detection of such analyte specific to the sweat gland or by another method.

[0037] Alternatively or additionally, the sweat detection device includes a processor configured to determine the growth rate of the sweat droplet from the data collected by the optical detection assembly, identify the range of the skin area where the sweat droplet is detected from the data collected by the optical detection assembly, and assign a sweat gland type to the range based on the growth rate of the sweat droplet.

[0038] In a state of acute stress or pain, it is known that eccrine glands can sweat very quickly and a large amount of sweat can occur in multiple glands within about 2 seconds. For example, if the optical detection assembly detects such rapid and profuse sweating from a sweat gland or a group of sweat glands within 1 to 2 seconds, all such glands are labeled / assigned as eccrine glands.

[0039] Alternatively or additionally, the sweat detection device identifies the extent of the skin area where sweat droplets are detected from the data collected by the optical detection assembly, and determines the sweat gland type based on the sweat pore appearance characteristics detected within that extent from the data collected by the optical detection assembly, for example, the active pixel sensor array described above, and includes a processor configured to assign the sweat gland type to that extent based on the sweat pore appearance characteristics.

[0040] In this case, the optical detection assembly differentiates between the optically detectable characteristics of two sweat gland types and is used to distinguish these types from each other. The most distinct differentiating factor is that apocrine glands are associated with hair follicles, and thus most apocrine glands produce sweat droplets at locations where body hair is present. Accordingly, the sweat pore appearance characteristics include, for example, parameters related to the sweat pore hair follicles.

[0041] Embodiments of the present invention will be described in more detail, using non-limiting examples, with reference to the accompanying drawings.

Brief Description of the Drawings

[0042]

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Mode for Carrying Out the Invention

[0043] It should be understood that the detailed description and specific examples show exemplary embodiments of the present apparatus and are for illustrative purposes only and are not intended to limit the scope of the present invention. These and other features, aspects, and advantages of the apparatus of the present invention will be better understood from the following description, the appended claims, and the accompanying drawings. The figures are merely schematic and are not drawn to scale. Throughout the figures, the same reference numerals are used to indicate the same or similar parts.

[0044] A sweat detection device is provided. This device includes a main body that is arranged with respect to the skin. A recess is defined in the main body for receiving sweat from the skin area. The device further includes an optical detection assembly configured to detect discrete sweat droplets protruding from the sweat pores in the skin area into the recess.

[0045] By measuring the concentration of an analyte / biomarker in sweat, insights into a person's medical condition and / or health status can be obtained. However, the concentration of a specific biomarker in blood is considered to best represent the disease state, i.e., the "gold standard". The concentration of sweat depends on the amount of sweat (it becomes thinner when sweating a lot) and also on the source of sweat production, for example whether the sweat originated from eccrine glands or apocrine glands. Therefore, it is necessary to estimate the sweating rate for each sweat gland in order to "calibrate" the sweat sensor and accurately perform the conversion / transformation from the measured biomarker concentration in sweat to the corresponding blood value.

[0046] For this reason, it has been proposed to incorporate an optical detection assembly capable of detecting discrete sweat droplets protruding from sweat pores into the sweat detection device. In this way, the details of sweating at the level of a single sweat gland can be grasped. Such details are then used, for example, to convert the calculated biomarker concentration to a blood value.

[0047] Figure 1 shows a sweat detection device 100 according to an embodiment. The sweat detection device 100 includes a main body 102. As shown in Figure 1, the main body 102 is arranged with respect to the skin 104.

[0048] The main body 102 is included, for example, in a wearable patch that can be worn by a subject for the purpose of sweat monitoring. In such a non-limiting embodiment, the sweat detection device 100 includes a wearable patch, or in a specific embodiment, the sweat detection device 100 is defined by the wearable patch.

[0049] In an embodiment, the main body 102 can be fixed to the subject. For example, the main body 102 is attached to the surface of the skin 104 using an appropriate biocompatible adhesive. Alternatively, the main body 102 is held against the surface of the skin 104 by a fastener for attaching the main body 102 to a body part of the subject, such as a strap.

[0050] The main body 102 can be formed of any suitable material that can be disposed on the skin 104, such as a polymer such as silicone rubber. When the main body 102 is a polymer, the main body 102 has sufficient flexibility to allow it to fit snugly against the surface of the skin 104.

[0051] The material forming the main body 102 and / or the coating on the outer surface of the main body 102 does not transmit light of the wavelength used to detect the sweat droplet 106. This is to minimize the possibility that ambient light interferes with the optical detection of the sweat droplet 106. The optical detection of the sweat droplet 106 will be described in more detail below.

[0052] In the main body 102, a recess 108 is defined. As shown in Figure 1, the recess 108 provides a space from which the sweat droplet 106 can project directly from the sweat pore 110 that discharges the sweat droplet 106. As schematically represented in the hashed area of Figure 1, the sweat pore 110 transports sweat from the sweat gland 112 to the surface of the skin 104.

[0053] The sweat detection device 100 includes an optical detection assembly 114 configured to detect discrete sweat droplets 106. The optical detection assembly 114 has any suitable design, provided that it can detect discrete sweat droplets 106 protruding from a single sweat pore 110, that is, individual sweat droplets 106.

[0054] The detection principle of the optical detection assembly 114 is non-imaging and / or imaging.

[0055] The non-imaging detection principle has the advantages of simplicity and low cost. On the other hand, the optical detection assembly 114 having an imaging function has the advantage of providing additional information, for example, information that can be used to more easily distinguish sweat gland types, as will be described in more detail below.

[0056] The size of the recess 108 is such that discrete sweat droplets 106 protruding into the recess 108 can be detected by the optical detection assembly 114 without merging with one or more sweat droplets 106 protruding from adjacent sweat pores 110, or at least before merging. However, if the sweat droplets 106 are removed and transported from the detection area of the optical detection assembly 114 quickly enough, such a requirement for the size of the recess 108 is not necessary.

[0057] In the case of the non-imaging detection principle, since the sweat glands 112 are located in a scattered distribution on the skin, the size of the recess 108 for the non-imaging detection principle can be calculated using a statistical approach. As an example, a Poisson distribution can be used to estimate the probability associated with the number of active sweat glands 112 overlapping the recess 108, as described in detail in WO2021074010A1. For example, in a sitting state, there are approximately 10 sweat glands per 1 cm 2 in an active state. The surface area of the recess 108 is 1 mm 2In the case where it is, there will be an average of 0.1 active sweat gland 112 in this area. According to the Poisson distribution, the probability that the active sweat gland 112 overlapping the recess 108 is zero is 90.5%, the probability that there is one active sweat gland is 9%, and the probability that there are two or more active sweat glands is 0.5%. Therefore, the probability that there is one active sweat gland 112 overlapping the recess 108 is 18 times the probability that there are two or more active sweat glands. In this embodiment, two or more recesses 108 are required, for example, more than 10 recesses, and in at least one of them, the active sweat gland 112 overlaps the recess 108, and as a result, the sweat droplet 106 protrudes into the recess 108.

[0058] However, in order for the optical detection assembly 114 to detect a plurality of discrete sweat droplets 106 protruding from a single sweat pore 110, it is not necessary for only one active sweat gland 112 to overlap one recess 108. Also, the size of the recess 108 can be selected such that two or more active sweat glands 112 can overlap one recess 108 if the sweat droplet 106 is removed and transported from the detection region of the optical detection assembly 114 quickly enough. In such a case, the optical detection assembly 114 can detect the discrete sweat droplets 106 protruding from the sweat pore 110 into the recess by considering the estimated number of active sweat glands 112 protruding into the recess 108.

[0059] In the case of the imaging detection principle described in more detail below, there is no requirement for the size of the recess 108.

[0060] Since the optical detection assembly 114 enables the detection of discrete sweat droplets 106 protruding from individual sweat pores 110, the sweat detection device 100 enables the monitoring of sweating from individual sweat glands 112.

[0061] If the optically detected sweat droplets 106 are removed and transported from the detection region of the optical detection assembly 114 quickly enough, it is also possible to count the number of sweat droplets 106.

[0062] For this purpose, the sweat detection device 100 includes a fluid system 116, such as a microfluidic system 116, configured to remove and transport the optically detected sweat droplets 106 from the recesses 108.

[0063] In an embodiment, the fluid system 116, such as a microfluidic system, includes an analyte sensor (not shown in FIG. 1) configured to detect analytes in the sweat. The analyte sensor is configured to detect, for example, the concentration of analytes contained in the sweat.

[0064] In a non-limiting example, the fluid system 116 is configured to transport each sweat droplet 106 detected by the optical detection assembly 114 to the analyte sensor.

[0065] The optical detection assembly 114 enables counting the number of sweat droplets 106 occurring in the skin area, and the analyte sensor detects the concentration of analytes in each sweat droplet 106 detected by the optical detection assembly 114. The present sweat detection device 100 thus provides a single device 100 solution for determining the analyte concentration for each sweat gland 112.

[0066] In an alternative embodiment, the detection of analytes is performed by a separate sensor device.

[0067] Preferably, the fluid system 116 transports each sweat droplet 106 at a speed faster than the formation rate of subsequent sweat droplets 106 from the same sweat pore 110.

[0068] More generally, the fluid system 116 includes a surface coated with a surface tension gradient material that, for example, aids in removing the sweat droplets 106 from the recesses 108 and transporting them, for example, towards an analyte sensor and / or a sweat collector (not shown).

[0069] In particular, the sweat droplets 106 are removed from the recesses 108 and transported along this surface, which has a chemical gradient along which the sweat droplets 106 move downward during use of the device 100.

[0070] Electrowetting techniques can be used instead of or in addition to such chemical gradients, using an electric field to induce a transient change in the wettability of a surface to move the sweat droplets 106 away from the recesses 108 and towards, for example, an analyte sensor and / or a sweat collector.

[0071] In another embodiment, the fluid system 116 is configured to transport the sweat droplets 106 away by evaporation.

[0072] In an embodiment, the optical detection assembly 114 comprises an optical detector 118 and a waveguide 120 for carrying light to the optical detector 118. As shown in Figure 1, the waveguide 120 is positioned such that light exits the waveguide 120 when contact is made between the sweat droplet 106 and an outer surface of the waveguide 120.

[0073] In other words, the waveguide 120 is positioned on the skin-facing side of the device 100 and is spaced slightly above the skin 104 by a recess 108, at the location where one or more sweat glands 112 are present.

[0074] Any suitable optical detector 118 may be used for this purpose. The optical detector 118 is configured to detect the intensity of light being carried thereto by the waveguide 120. Thus, the optical detector 118 may comprise or consist of a light-sensitive element, such as a photodiode.

[0075] This decoupling is depicted diagrammatically in Figure 1. When light beam 122A is incident on the portion of waveguide 120 that is contacted by sweat droplet 106, decoupling occurs through sweat droplet 106 and light beam 122B does not reach optical detector 118. This is because the refractive index of waveguide 120 is close enough to the refractive index of sweat droplet 106 such that light being carried in waveguide 120 is refracted into sweat droplet 106 when it contacts waveguide 120.

[0076] In contrast to the total internal reflection that occurs at the waveguide 120 - air interface when there is no sweat droplet 106, this refraction causes the light intensity detected by the optical detector 118 to be lower compared to the scenario without a sweat droplet 106 in contact with the waveguide 120.

[0077] Figure 2 shows a graph of the signal from the optical detector 118, such as the intensity signal I, versus time t. Two separate dips in intensity 124A, 124B correspond to two discrete sweat droplets 106 in contact with the waveguide 120, respectively. Thus, Figure 2 illustrates that the exemplary sweat detection device 100 enables relatively easily counting the discrete sweat droplets 106 generated by one or more sweat glands 112 in the skin area.

[0078] A processor (not shown in Figure 1) included in the sweat detection device 100 is configured to count the number of sweat droplets 106, for example, based on the number of fluctuations in the signal detected by the optical detector 118.

[0079] Furthermore, the optical detection assembly 114 enables estimation of the size or volume of the sweat droplet 106. Such an estimation can be performed based on the magnitude of the intensity decrease. The greater the intensity decrease, the larger the sweat droplet 106.

[0080] Thus, in a non - limiting example, the processor is configured to determine the volume of each detected sweat droplet 106 based on the magnitude of the change in the signal detected by the optical detector 118 corresponding to each discrete sweat droplet 106.

[0081] The outer surface of the waveguide 120 is configured to transport the sweat droplet 106 towards a sweat collector and / or an analyte sensor included in the sweat detection device 100, for example, after the sweat droplet 106 is detected by the optical detector 118. The transport direction of the sweat droplet 106 is represented by the dashed arrow 126 in Figure 1.

[0082] The outer surface of the waveguide 120 includes, for example, a surface tension gradient material for transporting the sweat droplet 106 toward the sweat collector and / or the analyte sensor, as described above.

[0083] Such a surface tension gradient material is provided, for example, by the outer surface of the waveguide 120 having hydrophilic and hydrophobic portions on the surface, and these portions are arranged to provide a wettability gradient along the outer surface. For example, the outer surface is functionalized with hydrophobic CH3 - portions and hydrophilic OH - portions to form a chemical gradient for transporting the sweat droplet 106 (Morgenthaler et al., Langmuir, 2003, 19(25), pp. 10459 - 10462).

[0084] Such hydrophilic / hydrophobic regions are provided at the molecular level such that the wettability gradient varies substantially continuously along the outer surface of the waveguide 120. Such a chemical gradient is realized, for example, by graft polymer chains that functionalize the outer surface of the waveguide 120. Alternatively or additionally, μm - sized hydrophilic / hydrophobic regions are provided on the outer surface to realize a step - like wettability gradient. Preferably, this region is arranged to have a gradually varying distribution over the entire length of the outer surface in the direction of the sweat collector and / or the analyte sensor.

[0085] When the outer surface of the waveguide 120 includes a surface tension gradient material, the waveguide 120 is included in the optical detection assembly 114 and forms part of the fluid system 116 of the sweat detection device 100. This helps to improve the simplicity and manufacturability of the sweat detection device 100.

[0086] In an embodiment, the sweat detection device 100 includes an illumination unit 128A that supplies light to the optical detector 118 carried by the waveguide 120. For this purpose, any suitable illumination unit 128A can be used if the light emitted by the illumination unit 128A can be detected by the optical detector 118. For example, the illumination unit 128A can include a light - emitting diode, a filament bulb, etc.

[0087] In the non-limiting embodiment shown in FIG. 1, the illumination unit 128A is disposed on the side surface of the main body 102, and the waveguide 120 extends along at least a part of one recess 108. In other words, the waveguide 120 at least partially defines the boundary of the recess 108. The size of the recess 108 is, for example, such that at least one or two sweat pores 110 can discharge sweat into the recess 108.

[0088] Although not shown in FIG. 1, it is similarly conceivable that light is supplied into the waveguide 120 by a plurality of illumination units 128A.

[0089] 1 cm 2 The number of sweat glands 112 per centimeter varies between 20 and 600 for each location on the body, and more typically between 100 and 200.

[0090] The number of active sweat glands 112 depends on the location on the body, the activity level, and the temperature. Typically, when the subject is sitting, about 10% of the sweat glands 112 are activated.

[0091] Assuming that sweat is sampled from 10 active sweat glands 112, the required skin area can vary from 1 to 5 cm 2 to 0.2 to 0.5 cm 2 and can vary up to.

[0092] The length and width of the recess 108 are, for example, in the range of 1 to 100 mm, preferably 2 to 100 mm, and more preferably 5 to 30 mm, respectively.

[0093] The area of the recess 108 is, for example, 1 to 100 mm 2 , preferably 2 to 100 mm 2 , more preferably 5 to 30 mm 2 .

[0094] In a non-limiting embodiment, the skin area is circular and has a diameter in the range of 2 to 100 mm, preferably 5 to 30 mm.

[0095] The depth of the recess 108 is, for example, 10 to 100 μm, for example, 20 to 30 μm, etc. Over the depth of this recess 108, the sweat droplet 106 protrudes from the sweat pore 110 toward the waveguide 120.

[0096] Although it is conceivable that two sweat droplets 106 from adjacent sweat glands 112 contact the waveguide 120 simultaneously, the possibility is considered low. In this case, the sweat detection device 100 detects only one of the sweat droplets 106. This risk can be reduced, for example, by controlling, that is, reducing, the scale of the waveguide 120. For example, the sweat detection device 100 may include a multiple waveguide structure 120, as will be described in more detail below.

[0097] Therefore, in the non-limiting embodiment shown in FIG. 1, the optical detection assembly 114 can be regarded as a micro-optical component. This micro-optical component 114 takes the form of an illumination source, that is, a waveguide 120 connected to the illumination unit 128A, and a photosensitive element, for example, an optical detector 118 with a photodiode.

[0098] As an alternative to or in addition to the illumination unit 128A shown in FIG. 1, the sweat detection device 100 may include a window 130 as shown in FIG. 3, through which ambient light is supplied into the waveguide 120. In this case, the ambient light is carried by the waveguide 120 to the optical detector 118.

[0099] Such a window 130 eliminates the need to include an electric illumination unit 128A of the type shown in FIG. 1. In this way, the sweat detection device 100 shown in FIG. 3 has the advantage of improved power consumption, that is, reduced power consumption. This helps to prolong the life of one or more batteries (not shown) included in the device 100 to supply power to the components mounted on the device 100. This is particularly important when the sweat detection device 100 needs to monitor the subject for a relatively long period such as several hours or several days.

[0100] Alternatively or additionally, the optical detection assembly 114 comprises a reference waveguide 132 for carrying light to the optical detector 118. The reference waveguide 132 is optically shielded from the recess 108 so that the light carried by the reference waveguide 132 is not affected by sweat within the recess 108.

[0101] In the non-limiting embodiment shown in FIG. 3, the waveguide 120 and the reference waveguide 132 are shown extending parallel to each other across the recess 108, but it should be noted that the waveguide 120 and the reference waveguide 132 are optically separated from each other.

[0102] Although not shown in FIG. 3, the optical detector 118 comprises a first optical sensing element, such as a photodiode, for detecting light carried by the waveguide 120, and a second optical sensing element, such as a photodiode, for detecting light carried by the reference waveguide 132.

[0103] The intensity of the light passing through the reference waveguide 132 provides a reference that can be compared to the light passing through the waveguide 120, and thus such a reference waveguide 132 aids in the detection of sweat droplets 106. This makes it easier to identify a decrease in the intensity of the light carried by the waveguide 120 corresponding to discrete sweat droplets 106 that contact the outer surface of the waveguide 120.

[0104] Such a reference waveguide 132 is particularly useful in the non-limiting embodiment shown in FIG. 3 that utilizes ambient light for the optical detection of sweat droplets 106. This is because the reference waveguide 132 enables the optical detection system 114 to account for changes in ambient light levels.

[0105] In other words, the reference light 133 carried by the reference waveguide 132 can be used as a calibration to account for changes in ambient light levels during measurement.

[0106] More generally, when a processor is included in the sweat detection device 100, the processor is configured to detect discrete sweat droplets 106 based on a comparison between the intensity of light carried by the reference waveguide 132 and the intensity of light carried by the waveguide 120.

[0107] As briefly touched on above, the optical detection assembly 114 can have an imaging function that detects discrete sweat droplets 106. In an embodiment, the optical detection assembly 114 includes an active pixel sensor array 134 for imaging a skin region.

[0108] Any suitable active pixel sensor array 134 can be utilized for this purpose. The active pixel sensor array 134 may include, for example, a charge coupled device (CCD) sensor or a complementary metal oxide semiconductor (CMOS) sensor, or may be composed of them. The design of a suitable active pixel sensor array 134 is known, for example, in the field of digital cameras.

[0109] In the non-limiting example shown in FIG. 4, the optical detection assembly 114 includes a lens device 136 configured to image an image of the skin region received by the active pixel sensor array 134 to assist in the detection of sweat droplets 106. Any suitable lens device 136, such as an imaging microlens array, is contemplated.

[0110] The lens device 136, such as a microlens array, is disposed on the side of the device 100 facing the skin, where the sweat gland 112 is present, and is slightly above and spaced apart from the skin 104 through the recess 108 at a position where the focus of each lens of the lens device 136 is appropriately adjusted. The lens device 136 is disposed corresponding to the space between the active pixel sensor array 134 and the recess 108.

[0111] As shown in FIG. 4, the sweat detection device 100 may also include a light source 128B that illuminates the recess 108. This facilitates imaging of the skin area and detection of the sweat droplets 106. Any suitable light source 128B, such as a light emitting diode, a filament bulb, etc., can be considered.

[0112] In FIG. 4, the light source 128B is shown illuminating the recess 108 from one side, but this is not intended to limit the present invention. The light source 128B may be arranged, for example, to illuminate the recess 108 from two directions, for example, from opposite sides.

[0113] An optical window 138 is provided between the lens device 136 and the recess 108.

[0114] As represented by the arrow in FIG. 4, the light reflected or scattered from the sweat droplet 106 passes through the lens device 136, for example, a microlens array, and the lens device 136 images the sweat droplet 106 onto the active pixel sensor array 134, for example, a CCD array.

[0115] In the non-limiting embodiment shown in FIG. 4, the optical detection assembly 114 including the active pixel sensor array 134, the lens device 136, for example, a microlens array, and the optical window 138 can be regarded as an imaging micro-optical component capable of monitoring sweating from individual sweat glands 112 when incorporated into the sweat detection device 100.

[0116] The size of the sweat droplet 106 can be measured by analyzing both the size of the image and the light intensity incident on the active pixel sensor array 134. The number of sweat droplets 106 formed within the recess 108 and the on / off times of sweating from individual sweat glands 112 can also be counted.

[0117] Generally, the resolution of an active pixel sensor array 134, typically having a pitch of several μm, such as a CCD array, far exceeds the resolution of a lens device 136, such as a microlens array, typically having a pitch of 10 - 100 μm. As a result, there are many pixel elements that capture light from a single microlens element. Therefore, a computer-optical approach can be used to further evaluate the details of the formation of sweat droplets 106.

[0118] FIG. 4 can be regarded as illustrating a relatively simple imaging configuration using non-polarized illumination, but this is not intended to limit the present invention. It is also possible for the sweat detection device 100 to utilize polarized illumination and / or polarized detection to improve the quality of the image and the detected signal.

[0119] Furthermore, in FIG. 4, lateral illumination along a single recess 108 is illustrated, but it is also possible to perform illumination and detection from the normal direction of the surface of the skin 104 by using a beam splitter optical configuration, such as a polarized beam splitter optical configuration. Such a beam splitter optical configuration is known in the field of optical storage systems.

[0120] In a non-limiting embodiment, the optical detection assembly 114 includes a photoplethysmography (PPG) module. In this embodiment, the PPG module is operably coupled to the light source 128B, and at least a portion of the light emitted from the light source 128B is incident on the skin 104. The light reflected by the skin 104 is received by the active pixel sensor array 134. For example, a processor included in the PPG module is configured to detect a heartbeat based on the frequency domain of the light received by the active pixel sensor array 134. The processor also detects the presence of sweat droplets 106 in the recess 108 based on the change in the intensity of the light received by the active pixel sensor array 134.

[0121] Optically detected sweat droplets 106 desirably correspond to the sweat droplets 106 from which an analyte is detected. Thus, the sweat detection device 100 includes the analyte sensor described above.

[0122] Similar to the non-limiting embodiments depicted in FIGS. 1 and 3, the sweat detection device 100 shown in FIG. 4 includes a fluid system 116, such as a microfluidic system, for removing and transporting optically detected sweat droplets 106 from the recess 108. The sweat droplets 106 are transported, for example, to a sweat collector and / or an analyte sensor as described above.

[0123] The surface of the optical window 138 is treated with a material having a surface tension gradient configured to transport optically detected sweat droplets 106 toward a sweat collector and / or an analyte sensor. This material has already been described above in connection with the outer surface of the waveguide 120 depicted in FIG. 1. The analyte sensor is included, for example, in the fluid system 116, such as a microfluidic system, and the surface tension gradient transports the sweat droplets 106 to the fluid system 116 for analyte detection.

[0124] FIG. 5 shows a block diagram of the sweat detection device 100. The sweat detection device 100 includes the optical detection assembly 114 described above and a processor 140. In FIG. 5, data from the optical detection assembly 114 is received by the processor 140, as represented by the arrow between the block 114 corresponding to the optical detection assembly and the block 140 corresponding to the processor.

[0125] The processor 140 is configured, for example, to record the number of sweat droplets 106 and, in some embodiments, to estimate the size or volume of each sweat droplet 106 as described above.

[0126] In an embodiment, the processor 140 is configured to use the data received from the optical detection assembly 114 to determine the sweating rate per sweat gland 112.

[0127] In the non-limiting example shown in FIG. 5, the sweat detection device 100 includes an analyte sensor 142. The analyte sensor 142 is configured to detect analytes in sweat.

[0128] The analyte sensor 142 is included in the fluid system 116 housed within the body 102 of the sweat detection device 100 schematically depicted in FIGS. 1, 3, and 4.

[0129] The analyte sensor 142 is preferably configured to detect the concentration of analytes contained in sweat, as described above.

[0130] More generally, data from the analyte sensor 142 is received by the processor 140, as represented by the arrow between block 142 corresponding to the analyte sensor and block 140 corresponding to the processor in FIG. 5.

[0131] The processor 140 may be included, for example, in the on-board processing unit included in the body 102 when the body 102 is included in a wearable patch, and / or may be provided in an external data processing device physically separated from the body 102. In the latter case, data from the optical detection assembly 114 and / or the analyte sensor 142 is transmitted to the external data processing device, for example wirelessly. Such wireless communication is performed via a suitable wireless communication protocol such as Bluetooth (registered trademark).

[0132] It is desirable to determine whether the sweat is produced by eccrine sweat glands 112 or apocrine sweat glands 112. This is because these sweat gland types produce sweat with different biomarker concentrations.

[0133] It has been revealed that there are both anatomical and functional differences between these two types of sweat glands. The secretory coil of eccrine sweat glands has three different cell types, all of which play a role in the secretion of sweat from eccrine sweat glands. One of these cell types, a cell type found only in eccrine sweat glands, is the dark cell. Dark cells contain granules with high electron density in the cytoplasm, and these are known to secrete many components such as glycoproteins, metals, and the antibacterial dermcidin. Dermcidin is an antibacterial peptide secreted only by eccrine sweat glands and directly attacks bacteria on the skin. 45% of the top 10 most abundant secreted proteins in our sweat is dermcidin. Dermcidin cannot be isolated from apocrine sweat and is not expressed in apocrine sweat glands. Therefore, dermcidin is a suitable analyte / biomarker for identifying eccrine sweat glands.

[0134] Furthermore, several proteins and peptides, such as cysteine protease, DNAse I, lysozyme, Zn-α2-glycoprotein, cysteine-rich secretory protein-3, and dermcidin, have been identified in eccrine sweat.

[0135] Specific indicators of clinically relevant apocrine sweat components have been revealed. See Table 2 below. Apocrine glands secrete a small amount of a semi-transparent, turbid, viscous liquid with a pH of 5 to 6.5 onto the skin. Unlike eccrine sweat glands, which secrete continuously, apocrine glands secrete in periodic bursts. Since sebaceous glands open into the same hair follicle, apocrine sweat mixes with sebum and appears on the skin surface. The turbidity may be caused by insoluble non-aqueous components; for example, the fatty acids of sebum are not soluble in water. There is still ongoing debate about the existence of apoeccrine glands, a third gland type in the armpit. In this case, it is an analysis of determining the concentration of components in a mixture of apocrine and apoeccrine sweat, correcting for dilution by eccrine glands.

[0136]

Table 1

[0137] Apocrine glands are found in a limited number of locations on the body, such as the armpits. The focus is on determining the concentration of the sweat components that are secreted solely from the apocrine glands in apocrine sweat. However, since eccrine glands are also present, apocrine sweat is diluted by unknown factors, thus making the above concentration determination unclear.

[0138] The sweat detection device 100 can be used in such a way that it can identify not only when the sweat droplets 106 are generated, but also whether they originate from the eccrine glands or the apocrine glands. In this way, the measured biomarker concentration, for example, the biomarker concentration measured using the above analyte sensor 142, can be appropriately converted to correlate with, for example, the blood biomarker concentration.

[0139] For this purpose, the following exemplary approach can be adopted. This approach begins with a calibration step used to distinguish apocrine sweat glands from eccrine sweat glands.

[0140] Therefore, the body 102 of the sweat detection device 100, for example, included in the wearable patch, is placed on the location of the skin 104 where both apocrine glands and eccrine glands are present, such as above the armpit.

[0141] Thus, in an embodiment, the analyte sensor 142 is configured to detect the presence of an analyte in the optically detected sweat droplets 106 that are specific to a single sweat gland type, such as apocrine or eccrine. In this non-limiting case, the sweat detection device 100 includes the above active pixel sensor array 134, and the processor 140 is configured to identify the range of the skin area where the sweat droplets 106 are detected from the data collected by the active pixel sensor array 134.

[0142] In an alternative embodiment, a variation of the non-imaging approach of FIGS. 1-3, e.g., using multiple waveguide structures 120, can advantageously replace the active pixel sensor array 134. Such multiple waveguide structures 120 allow different pores 110 to be assigned to different waveguides 120. In this way, mapping of the skin area becomes possible (albeit at a lower resolution compared to that typically provided by an active pixel sensor array 134).

[0143] The processor 140 is further configured to assign a sweat gland type to the range based on the presence of the analyte received from the analyte sensor 142 or in some other way.

[0144] Since it is detected that the sweat droplet 106 protrudes from the pore 110 into the recess 108, the detection area of the sweat droplet 106 corresponds to the area of the pore 110 and the associated sweat gland 112.

[0145] The active pixel sensor array 134 identifies the extent of the skin area where the sweat droplet 106 is detected, e.g., using the coordinates of the sweat droplet 106 in the x,y plane of the active pixel sensor array 134, e.g., a CCD array.

[0146] In this embodiment, the sweat detection device 100 is configured to note that a sweat droplet 106 has occurred and also to note the location / area of the sweat droplet 106 in the skin area. The sweat droplet 106 is then transported via the microfluidic system 116 to the analyte sensor 142 to determine the analyte / biomarker concentration. For example, if an apocrine-specific biomarker is present, the sweat gland 112 is labeled as apocrine, and otherwise as eccrine.

[0147] In another embodiment that can be used as an alternative to or in combination with the above-described sweat gland identification principle, the processor 140 is configured to determine the growth rate of the sweat droplet 106 from the data collected by the optical detection assembly 114 and to identify the range of the skin area where the sweat droplet 106 was detected from the data collected by the optical detection assembly 114. The processor 140 then assigns a sweat gland type to the range based on the growth rate of the sweat droplet 106.

[0148] In this case, the sweat detection device 100 is configured to pay attention not only to the occurrence of the sweat droplet 106 and the location / area of the sweat droplet 106 recorded in the x, y plane of the active pixel sensor array 134, for example, but also to the rate at which the sweat droplet 106 occurred.

[0149] In a state of acute stress or pain, it is known that the eccrine glands can sweat very quickly and a large amount of sweat can be produced by multiple glands within about 2 seconds. For example, if the active pixel sensor array 134 detects such rapid and profuse sweating from the sweat gland 112 or a group of sweat glands 112 within 1 to 2 seconds, all such sweat glands 112 are labeled / assigned as eccrine glands.

[0150] In a non-limiting example, the sweat detection device 100 also includes a galvanic skin response (GSR) sensor. The spikes measured by such a GSR sensor are used, for example, by the processor 140, to confirm that a sweating peak indicating sweating from the eccrine glands has just occurred.

[0151] In another embodiment that can be used as an alternative to or in combination with one or both of the above-described sweat gland identification principles, the processor 140 identifies the range of the skin area where the sweat droplet 106 is detected from the data collected by the optical detection assembly 114, and determines the sweat gland type based on the sweat pore appearance characteristics detected within that range from the data collected by the optical detection assembly 114, such as the active pixel sensor array 134. Then, the processor 140 assigns the sweat gland type to that range based on the sweat pore appearance characteristics.

[0152] In this case, the imaging optics preferably distinguish the different visible characteristics of the two sweat gland types and are used to distinguish these types from each other. The most distinct differentiating factor is that apocrine glands are associated with hair follicles, so most apocrine glands produce sweat droplets 106 at locations where body hair is present. Body hair is usually slightly longer (at least 500 - 10,000 μm) than the typical opening at the mouth of eccrine glands (having a diameter of about 50 μm), so the sweat droplets 106 produced in the hair follicles can be determined to be produced by apocrine glands.

[0153] Thus, in a non-limiting example, the sweat pore characteristics include parameters related to the hair follicles of the sweat pores. The parameter is, for example, the ratio of the detected size of the sweat pore hair follicle to the detected diameter of the sweat pore.

[0154] Following the assignment / labeling of the sweat glands 112 in the skin area, or at least the majority (in the calibration stage) of the sweat glands 112 in the skin area, the processor 140 is configured to use this information to determine which type of sweat gland 112 sweated during the measurement stage.

[0155] In a non-limiting example, the processor 140 is configured to determine whether to collect and / or measure the analyte concentration from a given optically detected sweat droplet 106 according to the sweat gland type determined during the calibration stage that produced the sweat droplet 106.

[0156] Such a determination is made based on a desired measurement, for example, when the generation of sweat droplets 106 occurs.

[0157] FIG. 6 provides a flowchart of a usage example 200 of the sweat detection device 100 according to any of the above embodiments. The usage example 200 includes disposing the main body against the skin such that a recess defined in the main body receives sweat from the skin area 202, and optically detecting discrete sweat droplets protruding into the recess from sweat pores in the skin area 204.

[0158] FIG. 7 provides a flowchart of a usage example 300 according to another embodiment. The usage example 300 includes identifying the extent of the skin area where sweat droplets are detected from data collected by an optical detection assembly arranged to detect discrete sweat droplets protruding from sweat pores in the skin area 302. Since it is detected that the sweat droplets are protruding from the sweat pores, as described above, the detected area corresponds to the area of the sweat pores and associated sweat glands.

[0159] The usage example 300 further includes receiving an indication of the presence of an analyte in sweat droplets specific to a single sweat gland type 304. The single sweat gland type is apocrine or eccrine as described above. In step 306, a sweat gland type is assigned to the extent based on the indication of the presence of the analyte.

[0160] FIG. 8 provides a flowchart of a usage example 400 according to yet another embodiment. The usage example 400 includes identifying the extent of the skin area where sweat droplets are detected from data collected by an optical detection assembly arranged to detect discrete sweat droplets protruding from sweat pores in the skin area 402. The usage example 400 further includes determining the growth rate of the sweat droplets from data collected by the optical detection assembly 404. In step 406, a sweat gland type is assigned to the extent based on the growth rate of the sweat droplets.

[0161] FIG. 9 provides a flowchart of usage example 500 according to a further embodiment. Usage example 500 includes identifying 502 the extent of a skin region where a sweat droplet has been detected from data collected by an optical detection assembly arranged to detect discrete sweat droplets protruding from pores in the skin region. Usage example 500 further includes determining 504 a sweat gland type based on sweat pore appearance characteristics detected within the extent from data collected by the optical detection assembly, such as an active pixel sensor array. In step 506, a sweat gland type is assigned to the extent based on the sweat pore appearance characteristics.

[0162] The sweat pore appearance characteristics include, for example, parameters regarding the hair follicles of the sweat pores as described above.

[0163] Although not illustrated in the flowchart, usage examples 300, 400, 500 may further include detecting an analyte concentration (during a subsequent measurement phase) and determining which type of sweat gland is responsible for generating the sweat having the detected analyte concentration using the assignment of the sweat gland type to the extent.

[0164] Alternatively or additionally, usage examples 300, 400, 500 may include determining whether to collect and / or measure an analyte concentration from a given optically detected sweat droplet according to the sweat gland type determined (during a calibration phase) to be generating the sweat droplet. Such a determination can be made, for example, based on the measurement desired at the instant the sweat droplet is generated.

[0165] Usage examples 300, 400, 500 may be implemented by processor 140 included in the sweat detection device 100 described above.

[0166] In summary, the present invention proposes incorporating a micro-optical component, such as a microlens array 136 or a waveguide 120, into a sweat detection device 100. The micro-optical component is configured to pass optical information from a single sweat gland 112 to optical sensors 118, 134. In this way, details of sweating at the single gland level (e.g., the size of sweat droplets 106 and / or details of the distinction between eccrine and apocrine glands) can be accumulated and optionally used later for conversion of biomarker concentrations. The optical detection assembly / optical system 114 may be essentially imaging or non-imaging and may be configured to evaluate eccrine and / or apocrine glands as described above.

[0167] The present disclosure can be applied to non-invasive, semi-continuous, and long-term monitoring of biomarkers indicative of health and well-being, such as monitoring of dehydration, stress, sleep, child health, and perioperative monitoring. Not only applicable to general subject monitoring, the present invention can be particularly applied to early warning of acute deterioration of patients in general wards and intensive care units, or investigation of sleep disorders. Currently, measurements can only be made in the manner of an extraction test when a patient sees a doctor, but it should be noted that the present disclosure can also be usefully applied when performing such extraction test measurements.

[0168] Other variations of the disclosed embodiments will be understood and can be implemented by those skilled in the art of practicing the invention according to the claims, upon study of the drawings, the disclosure, and the appended claims. In the claims, the term "comprising" does not exclude other elements or steps, and the singular form does not exclude a plurality. The measures recited in mutually different dependent claims can advantageously be used in combination. The reference signs recited in the claims should not be construed as limiting the scope thereof.

Claims

1. a body for placement against skin, the body defining a recess for receiving sweat from an area of ​​skin; an optical detection assembly for detecting discrete sweat droplets protruding from sweat pores on said skin area into said recess; a fluidic system for transporting the sweat droplets away from the recesses after the sweat droplets are detected by the optical detection assembly; A sweat detection device comprising:

2. The optical detection assembly includes: An optical detector; a waveguide for carrying light to the optical detector, the waveguide being arranged such that light exits the waveguide upon contact between the waveguide and the sweat drop protruding into the recess; The sweat detection device of claim 1 .

3. The sweat sensing device of claim 2 , wherein the optical detection assembly comprises an illumination unit for providing light that is carried by the waveguide to the optical detector.

4. 4. A sweat sensing device as claimed in claim 2 or claim 3, comprising a window through which ambient light passes and is provided to the waveguide, the ambient light being conveyed by the waveguide to the optical detector.

5. 5. The sweat detection device of claim 2, wherein an outer surface of the waveguide partially bounds the recess, the outer surface transports the sweat droplets towards a sweat collector and / or an analyte sensor after they are detected by the optical detector, and optionally the outer surface comprises a surface tension gradient material for the transport of the sweat droplets.

6. 6. A sweat detection device as described in any one of claims 2 to 5, comprising a reference waveguide for carrying light to the optical detector, the reference waveguide being optically shielded from the recess such that light carried by the reference waveguide is not affected by sweat in the recess.

7. The optical detection assembly includes: an active pixel sensor array; a lens arrangement for focusing an image of the skin area received by the active pixel sensor array to enable detection of the sweat droplets; The sweat detection device of claim 1 .

8. A sweat detection device comprising an optical window through which light passes from the recess to the lens device, wherein a surface of the optical window partially defines a boundary of the recess, and after the sweat droplet is detected by the optical detection assembly, the sweat droplet is transported towards a sweat collector and / or an analyte sensor, and optionally, the surface comprises a surface tension gradient material for the transport of the sweat droplet, the sweat detection device according to claim 7.

9. The sweat detection device according to claim 7 or claim 8, wherein the optical detection assembly comprises a light source for illuminating the recess.

10. An analyte sensor for detecting the presence of an analyte in the sweat droplet specific to a single sweat gland type, A processor that identifies a range of the skin area where the sweat droplet was detected from data collected by the optical detection assembly, and assigns the sweat gland type to the range based on the detected presence of the analyte received from the analyte sensor. The sweat detection device according to any one of claims 1 to 9, comprising the above.

11. Determine the growth rate of the sweat droplet from the data collected by the optical detection assembly, Identify a range of the skin area where the sweat droplet was detected from the data collected by the optical detection assembly, The sweat detection device according to any one of claims 1 to 9, comprising a processor that assigns a sweat gland type to the range based on the growth rate of the sweat droplet.

12. Identify a range of the skin area where the sweat droplet was detected from the data collected by the optical detection assembly, Determine a sweat gland type based on the sweat pore appearance characteristics detected in the range from the data collected by the optical detection assembly, The sweat detection device according to any one of claims 1 to 9, comprising a processor that assigns a sweat gland type to the range based on the sweat pore appearance characteristics.

13. The sweat detection device according to claim 12, wherein the sweat pore appearance characteristics include parameters related to sweat pore follicles.

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