Surface structured sensor for temperature measurement

Abstract

Estimating a core body temperature (CBT) of a user using a thermopile formed using a surface structured manufacturing process is disclosed. Surface structured fabrication processes may use materials having lower thermal conductivity than conventional trace materials (e.g., copper) to form thermopile traces and thermocouples while still producing the desired Seebeck effect. One thermocouple cluster may be located at a location expected to contact the skin of a user at a temperature T1, and the other thermocouple cluster may be located at a location having thermal acceptance to the ambient environment at a temperature T2. By measuring the voltage across the surface structured thermopile, gradients T1-T2 across the first position and the second position can be estimated. T1-T2 gradients along with measurements of T1 or T2 using absolute temperature sensors and some predetermined coefficients of a CBT prediction model may be used to estimate CBT.

Description

Technical Field

[0001] The present invention relates generally to temperature sensing systems and methods, and more specifically to temperature measurement using thermopile formed by surface structuring manufacturing processes. Background Technology

[0002] Core body temperature (CBT) can be an important parameter for monitoring a user's health. The ability to view an individual's CBT on demand, retrieve statistics about CBT from historical CBT estimates, or receive alerts when a user's current CBT exceeds preferred limits can provide valuable information about a user's current or recent health status. Summary of the Invention

[0003] Some examples of this disclosure relate to using thermopile within an electronic device to estimate a user's core body temperature (CBT), the thermopile being formed using a surface-structured fabrication process. The surface-structured fabrication process can use different materials to form thermopile traces and thermocouples within a device housing. These materials have lower thermal conductivity than conventional trace materials (e.g., copper) while still possessing a Seebeck coefficient, which generates a sufficient voltage across the two junctions (e.g., hot and cold junctions) formed by the different materials in each thermocouple when a temperature difference exists between the hot and cold junctions. In some examples, thermopiles formed using a surface-structured fabrication process can be integrated into wearable devices that contact a user's skin or into other devices that can be touched by a user. However, because the eardrum can couple more tightly to a user's core body temperature than other body parts, in some examples, surface-structured thermopiles can be integrated into wearable devices that contact a user's ear, such as earplugs, headphones, and smart glasses. The two junctions of each thermocouple within the surface-structured thermopile can be formed at two locations. One end of each thermocouple (e.g., the hot junction) may be located at or near a first position within the device housing where it is expected to contact the user's skin at temperature T1, and the other end of the thermocouple (e.g., the cold junction) may be located at or near a second position within the device housing where it is expected to have heat-receiving capacity to the surrounding environment at temperature T2. Additionally, an absolute temperature sensor may be placed near one or both of the first and second positions. By measuring the voltage across the surface-structured thermopile, the gradient T1-T2 at the first and second positions can be estimated. The T1-T2 gradient, along with measurements of T1 or T2 using the absolute temperature sensor and some predetermined coefficients of the CBT prediction model, can be used to estimate the CBT. Conversely, if the user's CBT is known and T1 is known from the absolute temperature sensor, those values, plus the T1-T2 gradient and predetermined coefficients of the CBT prediction model, can be used to estimate the ambient temperature. Attached Figure Description

[0004] Figures 1A to 1JExample electronic devices according to some examples of this disclosure are illustrated, which may include a surface-structured thermopile temperature sensing system for estimating core body temperature and optionally for estimating temperatures inside and / or outside the device (e.g., ambient temperature).

[0005] Figure 2 A block diagram of a computing system of an exemplary electronic device including a surface-structured thermopile temperature sensing system according to some examples of the present disclosure is shown.

[0006] Figure 3 Symbolic illustrations of surface-structured thermopiles and circuit diagrams of thermopile measurement circuits are shown in some examples according to this disclosure.

[0007] Figure 4A The following are examples of earplugs according to this disclosure, illustrating several different possible locations of the first and second temperature sensing positions of the surface-structured thermopile.

[0008] Figure 4B Examples of earbuds according to this disclosure are shown, illustrating channels Ch5 and Ch4 for a first temperature sensing position and a second temperature sensing position, respectively.

[0009] Figure 4C Examples of earbuds according to this disclosure are shown, illustrating channels Ch7 and Ch1 for a first temperature sensing position and a second temperature sensing position, respectively.

[0010] Figure 5 Symbolic illustrations of surface-structured thermopile according to some examples of this disclosure are shown.

[0011] Figure 6A and Figure 6B A 1-D heat flux model for a pair of earplugs is illustrated according to some examples of this disclosure.

[0012] Figure 7 A flowchart illustrating some examples of the present disclosure for fabricating a surface-structured thermopile on a polymer structure of an electronic device, the polymer structure having an embedded conductive seed material therein.

[0013] Figure 8 A flowchart illustrating an example of estimating the core body temperature (CBT) in an electronic device having a surface-structured thermopile comprising a plurality of thermocouples at a first temperature sensing location and a second temperature sensing location is shown. Detailed Implementation

[0014] The accompanying drawings, which form part of the following description of the examples and illustrate specific examples of optional implementations by way of example, will be referenced in the description. It should be understood that other examples and structural changes may be optionally used without departing from the scope of the disclosed examples.

[0015] Some examples of this disclosure relate to using thermopile within an electronic device to estimate a user's core body temperature (CBT), the thermopile being formed using a surface-structured fabrication process. The surface-structured fabrication process can use different materials to form thermopile traces and thermocouples within a device housing. These materials have lower thermal conductivity than conventional trace materials (e.g., copper) while still possessing a Seebeck coefficient, which generates a sufficient voltage across the two junctions (e.g., hot and cold junctions) formed by the different materials in each thermocouple when a temperature difference exists between the hot and cold junctions. In some examples, thermopiles formed using a surface-structured fabrication process can be integrated into wearable devices that contact a user's skin or into other devices that can be touched by a user. However, because the eardrum can couple more tightly to a user's core body temperature than other body parts, in some examples, surface-structured thermopiles can be integrated into wearable devices that contact a user's ear, such as earplugs, headphones, and smart glasses. The two junctions of each thermocouple within the surface-structured thermopile can be formed at two locations. One end of each thermocouple (e.g., the hot junction) may be located at or near a first position within the device housing where it is expected to contact the user's skin at temperature T1, and the other end of the thermocouple (e.g., the cold junction) may be located at or near a second position within the device housing where it is expected to have heat-receiving capacity to the surrounding environment at temperature T2. Additionally, an absolute temperature sensor may be placed near one or both of the first and second positions. By measuring the voltage across the surface-structured thermopile, the gradient T1-T2 at the first and second positions can be estimated. The T1-T2 gradient, along with measurements of T1 or T2 using the absolute temperature sensor and some predetermined coefficients of the CBT prediction model, can be used to estimate the CBT. Conversely, if the user's CBT is known and T1 is known from the absolute temperature sensor, those values, plus the T1-T2 gradient and predetermined coefficients of the CBT prediction model, can be used to estimate the ambient temperature.

[0016] While the various examples of this disclosure presented herein can be described primarily in the context of using surface-structured thermopile located near the user's ear to estimate the user's CBT, it should be understood that the examples of this disclosure are not limited thereto, but extend to estimating temperatures at other locations on the user's body, estimating temperatures within objects other than the user's body, or using surface-structured thermopile located in both wearable and non-wearable devices to estimate temperatures in the user's surrounding environment.

[0017] Figures 1A to 1JExample electronic devices according to some examples of this disclosure are illustrated, which may include a surface-structured thermopile temperature sensing system for estimating core body temperature and optionally for estimating temperatures inside and / or outside the device (e.g., ambient temperature). As described herein, the thermopile temperature sensor measures a temperature difference (temperature gradient measurement) corresponding to a temperature difference or gradient between two locations within the electronic device. When a user's skin comes into contact with the electronic device including the surface-structured thermopile temperature sensing system, the user's core body temperature can influence the temperatures at both locations, and a relationship can be established between the core body temperature and the temperatures at the two locations. Therefore, the measured temperature gradient can be used to estimate the core body temperature. In some examples, the system described herein may use measurements from the thermopile temperature sensor to estimate an external temperature (e.g., ambient air temperature, etc.).

[0018] Figure 1A An example earplug 100 is illustrated according to some examples of the present disclosure. The example earplug may include a surface-structured thermopile temperature sensing system for estimating core body temperature. Figure 1B An example watch 102 is illustrated according to some examples of the present disclosure. The example watch includes a touch surface 104 and may include a surface-structured thermopile temperature sensing system for estimating core body temperature. Figure 1C Example earphone 106 is illustrated according to some examples of the present disclosure. The example earphone may include a surface-structured thermopile temperature sensing system for estimating core body temperature. Figure 1D An example smart speaker 108 is illustrated according to some examples of the present disclosure. The example smart speaker includes a touch surface 104 and may include a surface-structured thermopile temperature sensing system for estimating core body temperature. Figure 1E An example mobile phone 110 is illustrated according to some examples of the present disclosure. The example mobile phone includes a touch surface 104 and may include a surface-structured thermopile temperature sensing system for estimating core body temperature.

[0019] Figure 1F An example tablet computing device 112 is illustrated according to some examples of the present disclosure. The example tablet computing device includes a touch surface 104 and may include a surface-structured thermopile temperature sensing system for estimating core body temperature. Figure 1G An example mouse 114 is illustrated according to some examples of the present disclosure. The example mouse includes a touch surface 104 and may include a surface-structured thermopile temperature sensing system for estimating core body temperature. Figure 1H An example remote or game control 116 is illustrated according to some examples of the present disclosure. The example remote or game control includes a touch surface 104 and may include a surface-structured thermopile temperature sensing system for estimating core body temperature. Figure 1IAn example personal computer 118 is illustrated according to some examples of the present disclosure. The example personal computer includes a touch surface 104 and a touchpad 120 and may include a surface-structured thermopile temperature sensing system for estimating core body temperature. Figure 1J An example digital media player 122 is illustrated according to some examples of the present disclosure. The example digital media player includes a touch surface 104 and may include a surface-structured thermopile temperature sensing system for estimating core body temperature.

[0020] It should be understood that Figures 1A to 1J The example device shown is provided by way of example; other types of devices may include surface-structured thermopile temperature sensing systems for estimating core body temperature and optionally, the temperature inside or outside the device. For example, the device may include one worn on or placed in contact with the user's face, head, ears, or fingers (or at another location on the user's body). The device may include over-ear headphones, glasses, headbands, chest straps, wristbands, rings, etc. For example, glasses worn on a user's face may include a surface-structured thermopile temperature sensing system to estimate the user's core body temperature. In some examples, the glasses may include one or more absolute temperature sensors and one or more thermopiles terminating at or near the location of interest for estimating core body temperature. Similarly, headbands, chest straps, or rings may include one or more absolute temperature sensors and / or thermopiles for estimating core body temperature.

[0021] As described in this article, the surface-structured thermopile temperature sensing system can be incorporated into... Figures 1A to 1J The illustrated electronic device adds internal and / or external temperature sensing capabilities to the device. Specifically, the use of thermopile as described herein enables more accurate estimations because the thermopile reduces the influence of thermal interference sources (e.g., heat sources within the device, such as heat-generating components within the device) and also reduces the overall drift or other errors in temperature estimation (e.g., temperature sensor processes, voltage and / or temperature variations, influences from thermal interference sources, etc.). For example, a thermopile can be considered a dual-ended (or dual-sided) device whose output corresponds to a temperature difference or gradient measurement corresponding to the temperature difference between a first end (or side) of the thermopile and a second end (or side) of the thermopile. A surface-structured thermopile temperature sensing system can be configured such that it measures the temperature gradient or temperature difference between one location inside or outside the device and another location inside or outside the device.

[0022] In some examples, the absolute temperature sensor can be placed in a location separate from the location or area where the temperature is measured. The absolute temperature sensor can be placed in a first location, and a thermopile can be used to estimate the temperature at a second, different location. Therefore, the absolute temperature sensor can be integrated into a device remote from sources of temperature disturbance and / or provides flexibility for integrating the temperature sensor at locations remote from the location or area of ​​interest. In some cases, the thermopile may have a first end coupled to a first location within the device (e.g., near the absolute temperature sensor) and a second end coupled to a second location within the device (e.g., at the location or area of ​​interest). Based on a temperature gradient measurement of such a thermopile, a model (e.g., an equation with empirically determined coefficients) can be used to estimate the temperature at a third location (e.g., a user's core body temperature). In some cases, the same temperature gradient can also be used with the model to estimate the ambient temperature outside the device.

[0023] In some examples, surface-structured thermopile temperature sensing systems can continuously estimate core body temperature or ambient temperature during device operation. For instance, systems including the surface-structured thermopile temperature sensing system described herein can be used to estimate a user's core body temperature and / or track a user's core body temperature (when authorized by the user). Specifically, wearable electronic devices that are close to a user's body throughout the day and / or at night can provide seamless measurement of core body temperature.

[0024] Figure 2 A block diagram of a computing system comprising an exemplary electronic device including a surface-structured thermopile temperature sensing system, according to some examples of this disclosure, is shown. It should be noted that... Figure 2 Some functional blocks in the computing system are optional and may not be found in every device that includes a surface-structured thermopile temperature sensing system. Although described primarily as wearable devices herein, the computing system may alternatively be implemented partially or entirely in non-wearable devices. For example, the sensors and / or processing described herein may be implemented partially or entirely in non-wearable devices such as mobile phones, media players, tablets, personal computers, servers, etc. In some examples, temperature sensors (e.g., absolute temperature sensors or heat flux sensors comprising thermopiles fabricated using improved laser direct structuring (LDS)) may be implemented in wearable devices (e.g., earplugs), and the processing of temperature data may be performed in non-wearable devices (e.g., mobile phones). The processing and / or storage of temperature data in a separate device can enable devices including physiological sensors (e.g., earplugs) to be space and power efficient, which can be an important feature of portable / wearable devices.

[0025] The computing system 200 can correspond to, for example Figures 1A to 1JThe illustrated devices include earbuds 100, watches 102, headphones 106, smart speakers 108, mobile phones 110, tablet computing devices 112, mice 114, remote or game controls 116, personal computers 118, or digital media players 122 (or may be implemented in other wearable or non-wearable electronic devices). The computing system 200 may include a processor 210 (or more than one processor) programmed (configured) to execute instructions and perform operations associated with the computing system 200. For example, using instructions retrieved from program storage device 202, processor 210 may control the reception and manipulation of input and output data between components of the computing system 200. Processor 210 may be a single-chip processor (e.g., an application-specific integrated circuit) or may be implemented using multiple components / circuits. For example, Figure 2 The processor 210 is shown to include a relatively low-power processor 211-1 and a relatively high-power processor 211-2, as described in more detail herein.

[0026] In some examples, processor 210, together with an operating system, is operable to execute computer code and generate and / or use data. The computer code and data may reside within a program storage device 202 operatively coupled to processor 210. Program storage device 202 typically provides a location for holding data used by computing system 200. Program storage device 202 can be any non-transitory computer-readable storage medium. By way of example, program storage device 202 may include read-only memory (ROM), random access memory (RAM), hard disk drive, etc. Computer code and data may also reside on removable storage media and be loaded or mounted onto computing system 200 when needed. Removable storage media include, for example, CD-ROM, DVD-ROM, Universal Serial Bus (USB), Secure Digital (SD), Compact Flash (CF), memory sticks, Multimedia Card (MMC), and / or network components.

[0027] As described herein, in some examples, host processor 210 may represent multiple processors, such as a lower-power processor 211-1 and a higher-power processor 211-2. The lower-power processor 211-1 and the higher-power processor 211-2 may represent separate processing chips, each with independent timing and power requirements. For example, the lower-power processor 211-1 may operate using a first clock signal and at a first power level, allowing processor 211-1 to remain operational (“on”) in most or all operating modes of system 200 (e.g., sleep mode, wake-up mode, idle mode, etc.). In contrast, the higher-power processor 211-2 may operate using a second clock signal (e.g., a high-frequency clock) different from the first clock signal and at a second power level higher than the first power level. Due to the higher power requirements of the higher-power processor 211-2, host processor 210 (e.g., the operating system on processor 210) may selectively disable or power down the higher-power processor 211-2 or otherwise limit its power consumption during certain operating modes of system 200 (e.g., power-saving mode, sleep mode, etc.). In some examples, as described herein, the higher power processor 211-1 may be powered down or otherwise limited in its power consumption to achieve temperature measurement without errors introduced by the power dissipation of the higher power processor 211-1.

[0028] The lower-power processor 211-1 and / or the higher-power processor can connect to various sensor interfaces of the system 200, including a touch sensor panel and / or touchscreen 220 (via touch and display controller 216), a motion and / or orientation sensor 230, an optical sensor 211 (via optical sensor controller 212), and a temperature sensor 250 (via temperature sensor controller 240). In some examples, the lower-power processor 211-1 can operate in sleep mode or power-saving mode while the higher-power processor 211-2 is powered down. In some examples, the lower-power processor 211-1 can alter the operating mode of the system 200 or otherwise cause the higher-power processor 211-2 to be powered on (e.g., when a wake-up condition is detected).

[0029] The computing system 200 may also include power management circuitry 209 and / or power dissipation monitoring circuitry 213. Host processor 210 (e.g., lower-power processor 211-1 and / or higher-power processor 211-2) may be coupled to power management circuitry 209 and / or power dissipation monitoring circuitry 213. Power management circuitry 209 may regulate power delivery from power supply circuitry (e.g., the battery or other power source of system 200) to various components of system 200 (e.g., sensors, processors, antennas, displays, etc.). As an example, power management circuitry 209 may interrupt or limit power delivery to components that generate heat within system 200 (e.g., sources of thermal interference), especially during temperature measurements that may be sensitive to heat from such components. Power management circuitry 209 may monitor temperatures within and / or outside the housing of system 200 (e.g., ambient temperature, user skin / core temperature). As an example, power management circuitry 209 can monitor these temperatures to detect unsafe operating conditions of system 200 and can selectively interrupt or limit power delivery to certain heat-generating components to bring system 200 into a safe operating state. In some examples, power management circuitry 209 provides control signals to in-line switches coupled between the system's power supply circuitry and various components of system 200, wherein the control signals determine the amount of current or power that can be delivered to the respective components. As an example, power management circuitry 209 can provide a first control signal to a switch inserted between the battery power supply of system 200 and touchscreen 220, such that the first control signal limits the amount of power or current delivered from the battery power supply to the touchscreen. As another example, power management circuitry 209 can provide a second control signal to a switch inserted between the battery power supply of system 200 and the system's antenna circuitry (not shown), such that the second control signal interrupts power delivery or current flow between the battery power supply and the antenna circuitry.

[0030] Power dissipation monitoring circuit 213 can monitor the power supply circuit (not shown) of system 200 and can regulate power transfer from the power supply circuit to various components of system 200 (e.g., by sending instructions to power management circuit 209). In some examples, power dissipation monitoring circuit 213 includes a sensor coupled to the power supply circuit (e.g., a battery) of system 200. The sensor can measure the power drawn by components of system 200 from the power supply circuit (e.g., the battery of system 200). In some examples, the power draw of components of the system can be estimated based on the current draw from the power supply circuit. In some examples, the power drawn can be estimated based on the device (e.g., the estimated current drawn from the battery). In some examples, the power drawn can be estimated on a per-component basis for some (e.g., known sources of thermal interference) or all of the components. In some examples, power dissipation monitoring circuit 213 includes at least one resistor (e.g., having a resistance greater than 10 MOhm, 20 MOhm, etc.) coupled between the power supply circuit or battery of system 200 and the power-drawing components of system 200. The current through a resistor can be measured by determining the voltage across the resistor (e.g., periodically or in response to a trigger) and converting the voltage to resistance (e.g., using Ohm's law).

[0031] In some examples, computing system 200 (e.g., processor 210, power management circuitry 209, and / or power dissipation monitoring circuitry 213) may include a power dissipation model that correlates current / power draw from the power supply or battery of system 200 with temperature or heat dissipation within the device. Additionally or alternatively, computing system 200 may include models for estimating power consumption and / or resulting temperature variations of different components in different operating modes of system 200 (e.g., power consumption of touchscreen 220 in idle mode, low brightness mode, high brightness mode, etc.). The impact of power consumption of certain components or thermal disturbances in system 200 can be determined using laboratory characterization of the components (e.g., rise time, fall time, and amplitude measured for each thermal disturbance at various corresponding power levels). Therefore, computing system 200 may dynamically model the temperature within system 200 based on the power dissipation model and one or more current / power draw measurements at the system's power supply circuitry or battery. In some examples, power management circuitry 209 may limit or interrupt power delivery to certain components based on information from power dissipation monitoring circuitry 213, such as during measurement intervals associated with temperature sensor 250 (e.g., intervals in which sensor data is collected from temperature sensor 250). For example, when a power dissipation model indicates that the amount of power drawn by components of system 200 corresponds to a temperature within the device that is outside the range required for accurate and / or reliable operation of temperature sensor 250, power management circuitry 209 limits or interrupts power to components of system 200 such that the total power drawn by the components is reduced to a level corresponding to the temperature within the range required for accurate and / or reliable operation of temperature sensor 250. In some examples, power dissipation monitoring circuitry 213 and / or power management circuitry may cause host processor 210 to delay the execution of certain functions or operations to limit or interrupt power to components of system 200. As an example, the host processor 210 may defer the operation (or modify the operation to reduce power consumption) of other components involving the touchscreen 220, GPS circuitry (not shown), wireless communication chip (not shown), antenna (not shown), or system 200 that could be sources of thermal interference, until after a measurement interval associated with the temperature sensor 250 (e.g., an interval during which one or more components receive less power).

[0032] Additionally or alternatively, component characterization (e.g., rise time, fall time, and amplitude measured for each thermal disturbance source at various corresponding power levels) can be used for temperature compensation. For example, host processor 210 can use a temperature compensation model to adjust sensor measurements or sensor data based on the temperature within the device or the temperature contribution of thermal disturbance sources (e.g., heat-generating components of system 200). As an example, the power draw of components of system 200 can be measured by power dissipation monitoring circuitry 213. The measured power draw can be used to correct for heat from thermal disturbance sources within the device. In some examples, compensation can be applied when the power draw corresponds to temperature variations outside the range required for accurate and / or reliable operation of temperature sensor 250. Thus, (e.g., temperature sensor controller 240) can use a temperature compensation model (e.g., corresponding to temperature variations in the power drawn by components) to adjust sensor data from temperature sensor 250 to account for temperature increases within the device caused by thermal disturbance sources.

[0033] The computing system 200 may also include one or more input / output (I / O) controllers operatively coupled to the processor 210. The I / O controllers may be configured to control interaction with one or more I / O devices, such as touch sensor panels, displays, touchscreens, physical buttons, dial pads, slider switches, joysticks, or keyboards. The I / O controllers operate by exchanging data between the processor 210 and the I / O devices that wish to communicate with the processor 210. The I / O devices and the I / O controllers may communicate via a data link. The data link may be unidirectional or bidirectional. In some cases, I / O devices may be connected to the I / O controller via a wireless connection. For example, the data link may correspond to any wired or wireless connection, including but not limited to PS / 2, Universal Serial Bus (USB), FireWire, Thunderbolt, Wireless Direct, IR, RF, Wi-Fi, Bluetooth, etc.

[0034] The computing system 200 may include a temperature sensor controller 240 operatively coupled to a processor 210 and one or more temperature sensors 250. As described herein, in some examples, the temperature sensor controller 240 may be coupled to an optical sensor controller 212. The temperature sensor 250 may include one or more absolute temperature sensors 254, one or more heat flux sensors 256 (which include surface-structured thermopile), and corresponding sensing circuitry 252 (e.g., analog and / or digital circuitry for measuring signals at sensors 254 / 256, providing processing (e.g., amplification, filtering, level shifting), and converting analog signals into digital signals). As an example, the one or more absolute temperature sensors 254 and the one or more heat flux sensors 256 (surface-structured thermopile) may be configured to measure temperatures at various locations within the system 200, including at least one location or region within or outside the wearable device that differs from the location or region of the system 200 where the absolute temperature sensors are located. These temperature and / or heat flux measurements can be used to measure the temperature characteristics of the device in various operating modes (e.g., to estimate when the temperature inside the device approaches unsafe or unsustainable levels), estimate the ambient temperature outside the device, or estimate physiological signals associated with the user (e.g., the user's core body temperature). Raw data from measurements of the absolute temperature sensor 254, heat flux sensor 256, and sensing circuitry 252 can be transferred to processor 210 (via temperature sensor controller 240), and processor 210 can perform the signal processing described herein to estimate internal or external temperatures and / or estimate physiological signals (e.g., body temperature associated with the user). Processor 210 and / or temperature sensor controller 240 can operate temperature sensor 250 to measure temperature values ​​associated with system 200 and estimate temperature values ​​associated with the environment outside the system. In some examples, temperature sensor controller 240 may include signal processor 242 to sample, filter, and / or convert (from analog to digital) signals generated by various temperature sensors 250, which may be located at different locations within the housing of system 200. Signal processor 242 may be a digital signal processing circuit, such as a digital signal processor (DSP). Analog data measured by temperature sensor 250 may be converted into digital data by an analog-to-digital converter (ADC). In some examples, digital data from the temperature sensor may be stored for processing in a buffer (e.g., FIFO) or other volatile or non-volatile memory (not shown) in temperature sensor controller 240. In some examples, data from the temperature sensor is used as input to a thermal model of the device and for estimating the temperature outside the enclosure of system 200 (e.g., the temperature of an object or user in contact with a part of the device, or the ambient temperature).In some examples, processor 210 and / or temperature sensor controller 240 may store raw data and / or processed information in memory (e.g., ROM or RAM) for historical tracking or for future diagnostic purposes.

[0035] A heat flux sensor 256 (such as a surface-structured thermopile) includes multiple thermocouples coupled in series. Each thermocouple may include two (or more) different conductive materials, characterized by different corresponding Seebeck coefficients or otherwise associated with different corresponding Seebeck coefficients. A first end of the heat flux sensor 256 may include a first set of contacts between two different conductive materials, and a second end of the heat flux sensor 256 may include a second set of contacts between two different conductive materials. When these two ends of the heat flux sensor 256 are positioned at corresponding first and second locations within the system 200, the heat flux sensor 256 can generate a voltage signal proportional to the temperature gradient or temperature difference between the first and second locations within the system 200. When one end of the heat flux sensor 256 is positioned or mechanically coupled to a location or region within the housing of the system 200, the temperature sensor controller 240 can use the temperature gradient generated by the heat flux sensor to estimate the temperature of an object (e.g., a user's core body temperature) in contact with the outer surface of the system 200.

[0036] To accurately model the environment outside system 200, in some examples, a heat flux sensor 256 (e.g., a surface-structured thermopile) may be used in conjunction with an absolute temperature sensor 254. In some examples, the temperature sensor controller 240 may use measurements from multiple individual absolute temperature sensors 254 located at well-defined locations ideally within the housing of system 200 to estimate the heat flux through the device (e.g., without using one or more dedicated heat flux sensors). In some examples, the absolute temperature sensor may include a negative temperature coefficient (NTC) temperature sensor, a resistance temperature detector (RTD), or a diode-based temperature sensor.

[0037] The computing system 200 may optionally include an optical sensor controller 212 operatively coupled to the processor 210 and one or more optical sensors 211. The optical sensors may include a light emitter 204, a light detector 206, and corresponding sensing circuitry 208 (e.g., analog circuitry for driving signals at the emitter and measuring the detector, providing processing (e.g., amplification, filtering), and converting analog signals into digital signals). As an example, the light emitter 204 and light detector 206 may be configured to generate light and emit it into the user's skin and detect reflected light (e.g., reflection and / or scattering) to measure physiological signals (e.g., vascular volumetric imaging or PPG signals). Absorption and / or return of light at different wavelengths may also be used to determine user characteristics (e.g., oxygen saturation, heart rate) and / or the contact status between the light emitter 204 / light detector 206 and the user's skin. Raw data from measurements taken from light emitter 204, photodetector 206, and sensing circuitry 208 can be transferred to processor 210, which can perform the signal processing described herein to estimate user characteristics (e.g., oxygen saturation, heart rate, etc.) based on physiological signals. Processor 210 and / or optical sensor controller 212 can operate light emitter 204, photodetector 206, and / or sensing circuitry 208 to measure data from the optical sensors. In some examples, optical sensor controller 212 may include timing generation for light emitter 204, photodetector 206, and / or signal processor 214 to sample, filter, and / or convert (from analog to digital) signals measured for light at different wavelengths. Optical sensor controller 212 can process data from signal processor 214 and report outputs (e.g., PPG signal, relative modulation ratio, perfusion index, heart rate, wrist / extra-wrist status, etc.) to processor 210. Signal processor 214 may be digital signal processing circuitry, such as a digital signal processor (DSP). Analog data measured by optical sensor 211 can be converted into digital data by an analog-to-digital converter (ADC), and the digital data from physiological signals can be stored for processing in a buffer (e.g., FIFO) or other volatile or non-volatile memory (not shown) in optical sensor controller 212. In some examples, for instance, some light emitters and / or photodetectors can be activated, while others can be deactivated (by power management circuitry 209) to save power, for example, or for time multiplexing (e.g., to avoid interference between channels). In some examples, processor 210 and / or optical sensor controller 212 can store raw data and / or processed information in memory (e.g., ROM or RAM) for historical tracking or for future diagnostic purposes.

[0038] In some examples, some light emitters and / or light detectors have operating characteristics that vary based on the temperature of the light emitter and / or light detector. As an example, some light emitters can output light at a wavelength that varies based on the temperature of the light emitter. In some examples, optical sensor controller 212 and / or processor 210 (higher power processors 211-2 and / or lower power processors 211-1) can receive temperature information associated with the light emitter (e.g., from temperature sensor controller 240) and adjust the wavelength of the optical sensor and / or the processing of signals associated with the light emitter and / or corresponding light detector based on the received temperature information. For example, estimations of physiological characteristics (e.g., oxygen saturation, heart rate) can be sensitive to the wavelength of the light used to measure the optical signal. In some examples, optical sensor controller 212 and / or processor 210 can use the received temperature information to estimate the wavelength of the light generated by the optical sensor and compensate for the estimation of physiological characteristics based on the estimated wavelength of the light.

[0039] The computing system 200 may also optionally include one or more motion and / or orientation sensors 230, such as accelerometers, gyroscopes, inertial measurement units (IMUs), etc. In some examples, the motion and / or orientation sensors 230 may include multi-channel accelerometers (e.g., 3-axis accelerometers).

[0040] In some examples, the computing system 200 may optionally include a touch and display controller 216 operatively coupled to the processor 210 and the touchscreen 220. For example, the touchscreen 220 may be configured to display visual output in a graphical user interface (GUI). The visual output may include text, graphics, video, and any combination thereof. In some examples, the visual output may include a textual or graphical representation of a physiological signal (e.g., a PPG waveform) or characteristics of a physiological signal (e.g., oxygen saturation, heart rate, etc.). The touchscreen may be any type of display, including liquid crystal displays (LCDs), light-emitting polymer displays (LPDs), electroluminescent displays (ELDs), field emission displays (FEDs), light-emitting diode displays (LEDs), organic light-emitting diode displays (OLEDs), etc. The processor 210 may send raw display data to the touch and display controller 216, and the touch and display controller 216 may send signals to the touchscreen 220. The data may include voltage levels for multiple display pixels in the touchscreen 220 to project an image. In some examples, the processor 210 may be configured to process raw data and send signals directly to the touchscreen 220. The touch and display controller 216 can also detect and track touch or proximity touches (and any movement or release of the touch) on the touchscreen 220. For example, the touch processor 218 can process data representing touch or proximity touches on the touchscreen 220 (e.g., location and magnitude) and recognize touch or proximity gestures (e.g., tap, double tap, swipe, clamp, reverse clamp, etc.). The processor 210 can translate the detected touch input / gesture into an interaction with a graphical object (such as one or more user interface objects) displayed on the touchscreen 220, or perform other functions (e.g., to initiate device wake-up or power on one or more components).

[0041] In some examples, touch and display controller 216 may be configured to send raw touch data to processor 210, and processor 210 may process the raw touch data. In some examples, touch and display controller 216 may process the raw touch data itself (e.g., in touch processor 218). The processed touch data (touch input) may be transferred from touch processor 218 to processor 210 to perform a function corresponding to the touch input. In some examples, a separate touch sensor panel and display may be used instead of a touchscreen, via corresponding touch controller and display controller.

[0042] In some examples, touch sensing of the optional touchscreen 220 may be provided by capacitive touch sensing circuitry (e.g., based on mutual capacitance and / or self-capacitance). For example, the touchscreen 220 may include touch electrodes arranged as a matrix of small, individual conductive material plates or as drive and sensing lines, or arranged in another pattern. The electrodes may be formed of a transparent conductive medium (such as ITO or ATO), but other partially or completely transparent and opaque materials (e.g., copper) may also be used. In some examples, the electrodes may be formed of other materials, including conductive polymers, metal meshes, graphene, nanowires (e.g., silver nanowires), or nanotubes (e.g., carbon nanotubes). The electrode may be configured for mutual capacitance or self-capacitance sensing, or a combination of mutual capacitance and self-capacitance sensing. For example, in one operating mode, the electrode may be configured to sense the mutual capacitance between the electrodes; in other operating modes, the electrode may be configured to sense the self-capacitance of the electrodes. During self-capacitance operation, an AC waveform may be used to excite the touch electrodes, and the self-capacitance of the touch electrodes to ground may be measured. When an object approaches a touch electrode, the self-capacitance of the touch electrode to ground may change (e.g., increase). This change in the self-capacitance of the touch electrode can be detected and measured by a touch sensing system to determine the location of one or more objects when one or more objects touch or approach the touchscreen without touching it. During mutual capacitance operation, the first touch electrode can be stimulated with an AC waveform, and the mutual capacitance between the first and second touch electrodes can be measured. When an object approaches the overlapping or adjacent area of ​​the first and second touch electrodes, the mutual capacitance between them may change (e.g., decrease). This change in mutual capacitance can be detected and measured by a touch sensing system to determine the location of one or more objects when multiple objects touch or approach the touchscreen. In some examples, some of the electrodes may be configured to sense the mutual capacitance between them, and some of the electrodes may be configured to sense their self-capacitance.

[0043] It should be noted that one or more functions described herein, including estimating the temperature within an electronic device (e.g., core body temperature) or outside an electronic device (e.g., ambient temperature) according to some examples of this disclosure, may be executed by firmware stored in memory (or program storage device 202) and executed by temperature sensor controller 240, optical sensor controller 212, touch and display controller 216, or processor 210. This firmware may also be stored and / or transmitted in any non-transitory computer-readable storage medium for use or in conjunction with an instruction execution system, apparatus, or device (such as a computer-based system, a processor-containing system, or other system capable of retrieving and executing instructions from and from an instruction execution system, apparatus, or device). In the context of this document, "non-transitory computer-readable storage medium" may be any medium (excluding signals) that may contain or store programs for use or in conjunction with an instruction execution system, apparatus, or device. Computer-readable storage media may include, but are not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, devices, or equipment; portable computer disks (magnetic); random access memory (RAM) (magnetic); read-only memory (ROM) (magnetic); erasable programmable read-only memory (EPROM) (magnetic); portable optical discs such as CD, CD-R, CD-RW, DVD, DVD-R, or DVD-RW; or flash memory such as compact flash memory cards, secure digital cards, USB storage devices, memory sticks, etc.

[0044] The firmware may also be propagated in any transmission medium for use by or in conjunction with an instruction execution system, apparatus, or device, such as a computer-based system, a processor-based system, or other system capable of retrieving and executing instructions from and from an instruction execution system, apparatus, or device. In the context of this document, "transmission medium" can be any medium that can communicate, propagate, or transmit the program for use by or in conjunction with an instruction execution system, apparatus, or device. Such transmission medium may include, but is not limited to, electronic, magnetic, optical, electromagnetic, or infrared wired or wireless transmission media.

[0045] Figure 3 Symbolic illustrations of surface-structured thermopiles according to some examples of this disclosure and circuit diagrams of thermopile measurement circuitry are shown. The thermopile sensing system includes a surface-structured thermopile 358 electrically coupled to the thermopile measurement circuitry (sensing circuitry) 330 via trace 360, which in some examples can be implemented using a single electronic device (e.g., Figures 1A to 1J The device illustrated in the example is used to achieve this. The surface-structured thermopile 358 can correspond to... Figure 2The heat flux sensor 256 is shown, and the sensing circuit 330 may include components from the sensing circuit 252 and / or the signal processor 242. The surface-structured thermopile 358 may include a collection of thermocouples connected in series via thermopile traces 372. Each thermocouple is formed by two electrically coupled junctions 362 of two different conductors 364 and 366, which have different associated Seebeck coefficients suitable for generating the desired temperature gradient. Figure 3 In the example, three thermocouple junctions 362 are clustered at the first temperature sensing location 368, and two thermocouple junctions are clustered at the second temperature sensing location 370. However, it should be understood that different numbers of thermocouples can be used within each temperature sensing location to create thermopile of thermocouples with different numbers of series connections.

[0046] The surface-structured thermopile 358 can generate an output voltage between its two terminals 374 and 376, corresponding to the temperature difference or gradient between a first temperature sensing location 368 and a second temperature sensing location 370, thereby measuring the heat flux through its two ends when the thermal resistance is known. Compared to arrangements that estimate heat flux based on the difference between temperature readings from two different absolute temperature sensors whose locations are constrained within an electronic device (e.g., temperature sensor integration may be difficult due to given spatial constraints and may be limited to a specific PCB mounted at a distance from the location or area of ​​interest within the device), the thermopile 358 allows the first temperature sensing location 368 to be positioned close to the surface of interest (e.g., a user's skin), which improves coupling with the surface of interest and the repeatability of heat flux measurements. Furthermore, because the thermopile 358 directly measures the temperature gradient, the drift error, which can be doubled by using two absolute temperature sensors, can be eliminated or reduced, providing more accurate heat flux or temperature gradient measurements.

[0047] The use of surface-structured thermopile 358 can also simplify manufacturing and increase throughput. For example, absolute temperature sensors may require extensive characterization and calibration (e.g., during manufacturing) to produce accurate temperature readings. However, compared to absolute temperature sensors (especially when used in conjunction with another absolute temperature sensor for heat flux measurement), surface-structured thermopile 358 may require no factory calibration or may require significantly less factory calibration and characterization to produce accurate readings. Surface-structured thermopile 358 can also achieve higher accuracy than absolute temperature sensors (e.g., orders of magnitude improvement).

[0048] The surface-structured thermopile 358 can be connected to a sensing circuit 330, which may include a first stage 320, a second stage 322, and an analog-to-digital converter (ADC) 324. The first stage 320 may include an amplifier 321, such as an operational amplifier (op-amp). In some examples, the op-amp may have a positive input terminal biased at a specific voltage level (e.g., using a resistive voltage divider between power and ground or between high and low voltages), and a negative input terminal that can be coupled to the output of the op-amp. The output of the op-amp may be a bias voltage applied to a first terminal 376 of the thermopile 358 and coupled to the second stage 322 via an input resistor. In some examples, the first stage 320 may be referred to as a bias amplifier because it generates a bias voltage for both the thermopile 358 and the second stage 322.

[0049] The second stage 322 may include another amplifier 323 (e.g., an operational amplifier) ​​having an input resistor and a feedback resistor. The positive terminal of the operational amplifier in the second stage 322 may be connected to the second terminal 374 of the thermopile 358. An ADC 324 may be coupled to the outputs of the first stage 320 and the second stage 322. For example, the output of the first stage may be used as a reference voltage and the output of the second stage may be used as the input voltage of the ADC. The ADC 324 may be configured to generate a digital value corresponding to the voltage output by the surface-structured thermopile 358 (differential operation removing the reference bias voltage from the output). In some examples, the second stage 322 may be referred to as a differential amplifier because it amplifies the differential voltage between the two terminals 376 and 374 of the thermopile 358 (e.g., where the amplifier gain may be a function of the feedback resistor). As mentioned above, the voltage output by the surface-structured thermopile 358 can be proportional to the temperature difference between the second temperature sensing location 370 and the first temperature sensing location 368. The surface-structured thermopile includes multiple thermocouples connected in series, each optionally formed by a conductive path of metals with different Seebeck coefficients. The digital conversion of the voltage output by the first stage 320 and the second stage 322 can be based on the voltage generated by the surface-structured thermopile 358 and can be used by processing circuitry to estimate the temperature at the first temperature sensing location 368 based on absolute temperature sensor measurements at or around the second temperature sensing location 370 (e.g., the temperature at the first temperature sensing location is the temperature at the second temperature sensing location, plus the temperature difference between the first and second temperature sensing locations generated by the surface-structured thermopile 358).

[0050] Figure 4A An earpiece 400 according to some examples of this disclosure is illustrated, showing several different possible locations of a first temperature sensing location and a second temperature sensing location of a surface-structured thermopile. Figure 4AIn the example, the positions corresponding to channels 1 (Ch1) to 7 (Ch7) can be candidate positions for both the first and second temperature sensing positions. Generally, channels closer to the tip 478 of the earpiece 400 (such as Ch7 and Ch2) are candidates for the first temperature sensing position due to the possibility that the user's eardrum will be adjacent to the positions of Ch7 and Ch2. Channels further away from the tip (such as Ch1, Ch3, Ch5, and Ch4) are candidates for the second temperature sensing position due to the possibility that these positions will be more susceptible to environmental conditions and temperature.

[0051] Figure 4B An earbud 400 according to some examples of this disclosure is illustrated, showing channels Ch5 and Ch4 for a first temperature sensing position 468 and a second temperature sensing position 470, respectively.

[0052] Figure 4C An earbud 400 according to some examples of the present disclosure is illustrated, showing channels Ch7 and Ch1 for a first temperature sensing position 468 and a second temperature sensing position 470, respectively.

[0053] Figure 5 Symbolic illustrations of surface-structured thermopiles according to some examples of this disclosure are shown. Surface-structured thermopile 558 may correspond to... Figure 2 The heat flux sensor 256 is shown. The surface-structured thermopile 558 may include a collection of thermocouples connected in series via thermopile traces 572. Each thermocouple is formed by two electrically coupled junctions 562 of two different conductors 564 and 566, which have different associated Seebeck coefficients suitable for generating the desired temperature gradient. Figure 5 In the example, three thermocouple junctions 562 are clustered at the first temperature sensing location 568, and two thermocouple junctions are clustered at the second temperature sensing location 570. However, it should be understood that different numbers of thermocouples can be used within each temperature sensing location to create thermopile structures with different numbers of thermocouples connected in series. In various examples, the first temperature sensing location 568 and the second temperature sensing location 570 can correspond to... Figure 4A Any one of the channel positions shown. Additionally, the first temperature sensing position 568 can correspond to... Figure 4B and Figure 4C Position 468 in the middle, and the second temperature sensing position 570 can correspond to Figure 4B and Figure 4C Position 470 in the middle.

[0054] The thermopile traces 572 of the surface-structured thermopile 358 can be manufactured starting from a polymer structure having an embedded conductive seed material (e.g., a metal). The polymer structure can be injection-molded plastic, thermoplastic, resin (e.g., ABS and polycarbonate), etc. By applying heat (such as from a laser) along multiple desired thermopile trace locations on the polymer, channels can be formed in the polymer, and the heat causes the conductive seed material to be extruded (extruded) from the polymer molecules to the surface of the newly formed channels. The heating process can be controlled so that the channels can be formed in straight lines or curves on a flat or curved surface of the housing. The conductive seed material in the channels can then be plated with another metal or alloy to form the thermopile traces 572. After the channels are plated, they can be covered with a protective material via injection molding or other processes.

[0055] As described herein, in some examples, LDS technology can be used to manufacture thermopile. For instance, LED manufacturing techniques utilize the activation of a laser applied to a plastic material containing additives, such as seed materials or particles. Laser activation induces a chemical reaction that produces thermopile traces, which can then be metallized.

[0056] As noted above, the thermopile trace 572 is formed by two distinct conductors 564 and 566, each with a different associated Seebeck coefficient suitable for generating the desired temperature gradient. In one example, the two distinct conductors 564 and 566 can be formed from copper and constantan (an alloy of 55% copper and 45% nickel). Copper can have a Seebeck coefficient of 6.5 μV / K, and constantan can have a Seebeck coefficient of -35 μV / K (relative to platinum at room temperature). This example can provide increased ductility, although the copper may need to be covered with a protective material. Copper can be plated first over the conductive seed material in one part of the channel, and then constantan can be plated in another part of the channel, but with some overlap with the plated copper, to form a thermoelectric coupling with the copper. In another example, the two distinct conductors 564 and 566 can be formed from a chromium-nickel alloy (an alloy of 90% nickel and 10% chromium) and constantan. Chromium-nickel alloys can have a Seebeck coefficient of 25 μV / K, while constantan can have a Seebeck coefficient of -35 μV / K (relative to platinum at room temperature). Constantan can be first plated over the conductive seed material in one part of the channel, and then the chromium-nickel alloy can be plated in another part of the channel, but overlapping some of the constantan plating to form a thermoelectric coupling with the constantan. Chromium-nickel alloys offer advantages over copper because they have lower thermal conductivity than copper, but a higher Seebeck coefficient (e.g., 25 μV / K compared to 6.5 μV / K for copper). The high thermal conductivity of copper causes a detrimental thermal short-circuit effect in the temperature gradient of interest, while chromium-nickel alloys produce less thermal short-circuit effect but generate a higher voltage (Seebeck effect) due to their higher Seebeck coefficient. In other words, while the high conductivity of copper may be desirable when forming conductive traces, chromium-nickel alloys have a different (e.g., higher) thermal resistance and higher voltage sensitivity than copper, which may be desirable when forming thermopile. The aforementioned surface-structured thermopile fabrication process may be advantageous when forming thermopile traces of materials such as copper, constantan, and chromium-nickel alloys on curved surfaces, as those materials may be less malleable and more difficult to form into foils, or to roll or bend on curved surfaces. While thermocouples formed from copper, constantan, and chromium-nickel alloys have been described in detail above, in other examples, thermocouples may be formed from other materials, including but not limited to iron and constantan, nickel / molybdenum and nickel / cobalt alloys, chromium-nickel alloys and nickel / aluminum / manganese / nickel alloys, palladium / platinum / gold and gold / palladium alloys, nickel / chromium / silicon and nickel / silicon alloys, gold and platinum, or platinum and palladium. In some examples, the material may have a Seebeck coefficient (relative to platinum at room temperature) in the range of 0 μV / K to ±100 μV / K. In some examples, the material may include one with a Seebeck coefficient in the range of 1.5 μV / K to 25 μV / K (relative to platinum at room temperature) and another with a Seebeck coefficient in the range of -10 μV / K to -40 μV / K (relative to platinum at room temperature).

[0057] In some examples, the surface-structured thermopile 558 may have a length of 5 mm 580, a thermopile trace width of 0.05 mm 582, and a spacing between thermopile traces 584 of 0.15 mm, such as... Figure 5 (Not drawn to scale) As shown. In addition, the thermopile traces can have a thickness of 11 micrometers (0.011 mm), a surface curvature radius of 30.3 mm to 2.6 mm, and a substrate area of ​​5 × 5 mm.

[0058] Figure 4B and Figure 4C The dashed line connecting the first temperature sensing location 468 and the second temperature sensing location 470 is a symbolic path for the thermopile trace 572. More specifically, in some examples, the above-described surface-structured thermopile manufacturing process can form the thermopile trace 572 on the inner or outer surface of the polymer housing or other structural component of the electronic device into which the seed is embedded. If formed on the outside of the device, in some examples, a protective covering can be applied for skin safety. In some examples, the thermopile trace 572 can be formed partially inside and partially outside the housing, including the formation of a surface-structured thermopile trace passing between the inner and outer surfaces of the housing. For example, the surface-structured thermopile trace 572 can be routed to a thermocouple located at the first temperature sensing location 568 inside the housing, as this location can provide a more stable environment for thermal coupling to the user's skin, and also routed to a thermocouple located at the second temperature sensing location 570 outside the housing, which can be a better location for thermal coupling to the ambient temperature around the device.

[0059] For reference Figure 4B and Figure 4C Conceptually, heat transfer typically occurs in one direction, from the user's body to the first temperature sensing location 468 and to the second temperature sensing location 470. In other words, power (in the form of heat) is dissipated from the user's body to the environment. However, it may be advantageous to create a certain amount of thermal isolation between the user's body and the environment. To achieve this, in one example, power can be applied to terminals 574 and 576 of the surface-structured thermopile 558 (see...). Figure 5 (V+ and V- in the diagram). By applying a voltage difference across terminals 574 and 576, a voltage difference is formed across the junction 562 of the thermocouple, and the resulting current generates heat at the thermocouple junction. In some examples, the thermopile measurement circuit (see...) Figure 3The voltage generator 325 (330) can be modified to switch between applying voltage to terminals 574 and 576 using voltage generator 325 and measuring the voltage on those terminals using sensing circuit 330. When the measured voltage on terminals 574 and 576 indicates that the temperature at the first temperature sensing location 568 is close to or equal to the temperature at the second temperature sensing location 570, this indicates that there is almost no heat flux at those locations, and therefore possibly almost no heat flux from the user's body to the first temperature sensing location. Under this condition, the accuracy of CBT estimation can be improved, and the application of voltage can be stopped. However, in some cases (e.g., cold environments), the temperature at the first temperature sensing location 568 may be close to or equal to the temperature at the second temperature sensing location 570, but far from the user's CBT. In those cases, an absolute temperature sensor can be used to determine whether the application of voltage should continue.

[0060] In some examples, voltage can be automatically applied to terminals 574 and 576 upon startup. For example, in the earbud example, voltage can be applied when earbud insertion into the ear is detected, or when earbud pairing with another device is detected. Applying voltage immediately upon startup can help reduce the settling time for temperature measurements.

[0061] As mentioned above, the temperature gradient T1-T2 between the first temperature sensing position 568 (T1) and the second temperature sensing position 570 (T2), together with the measurement of T1 or T2 using an absolute temperature sensor and some predetermined coefficients of the CBT prediction model, can be used to estimate the CBT. The general equation or model used to estimate the CBT is:

[0062] CBT = a*T1 + b*(T1-T2) + c(1)

[0063] This model is based on the concept of heat flux or heat transfer.

[0064] Figure 6A and Figure 6B A 1-D heat flux model for a pair of example earbuds is illustrated according to some examples of this disclosure. In general,

[0065] (CBT - T1) / R C1 = (T1 - T2) / R 12 (2)

[0066] And therefore:

[0067] CBT = T1 + (R C1 / R 12 (T1 - T2)(3)

[0068] Where R C1It is the thermal resistance between the expected CBT location and the first temperature sensing location 668, and R 12 It is the thermal resistance between the first temperature sensing position 668 and the second temperature sensing position 670.

[0069] The coefficients a, b, and c of equation (1) can be determined empirically and depend on the placement of the surface-structured thermopile and thermocouple in the electronic device relative to their intended contact points with the user's skin. Coefficient b can depend on the thermal resistance of the material of the thermopile traces. In cases such as... Figure 4C In the example device shown, with surface-structured thermopile and thermocouple located at Ch7 and Ch1, a = 0.75, b = 0.98, and c = 9.42. In such a device... Figure 4A In another example device shown, with surface-structured thermopile and thermocouples located at Ch5 and Ch1, a = 0.29, b = 0.35, and c = 27. In such... Figure 4A In another example device shown, with surface-structured thermopile and thermocouples located at Ch7 and Ch2, a = 1.03, b = 0.99, and c = 1.24. In such... Figure 4A In another example device shown, with surface-structured thermopile and thermocouple located at Ch4 and Ch1, a=0.38, b=0.22, and c=24.

[0070] As shown in Equation (1), when the coefficients a, b, and c are known, the user's CBT can be estimated after determining the temperature gradient T1-T2 by measuring the voltage on the surface-structured thermopile and determining T1 or T2 by measurement using an absolute temperature sensor. Equation (1) also shows that when a voltage is applied to the surface-structured thermopile and T1=T2, the CBT temperature depends only on T1, and the desired thermal isolation between the user's body and the environment (T2) can be achieved.

[0071] The estimated CBT can be made available to the user as needed, and in some examples, the user can access statistics about the CBT from historical (previously obtained) estimates. Additionally, an alert can be issued to the user if the estimated CBT exceeds a threshold limit (e.g., too hot or too cold). In other examples, if the user's CBT is known and T1 is known from an absolute temperature sensor reading, those values, plus the T1-T2 gradient and predetermined coefficients of the CBT prediction model, can be used to estimate the ambient temperature and provide that information to the user.

[0072] Figure 7A flowchart illustrating some examples of the present disclosure for fabricating a surface-structured thermopile on a polymer structure of an electronic device, the polymer structure having an embedded conductive seed material therein. At 786, heat can be applied to the polymer structure along a plurality of intended thermopile trace locations to form a plurality of channels along the intended thermopile trace locations due to the applied heat, these channels including conductive seed material extruded from the polymer due to heat. In some examples, heat can be applied via a laser using LDS fabrication technology. At 788, a first conductive material and a second conductive material can be deposited over the conductive seed material in the plurality of channels to form a plurality of thermocouples at which the first and second conductive materials are in contact with each other.

[0073] Figure 8 A flowchart illustrating an example of estimating the core body temperature (CBT) in an electronic device having a surface-structured thermopile, comprising a plurality of thermocouple junctions having junctions at a first temperature sensing location and a second temperature sensing location, is shown. At 890, a thermal gradient T1-T2 on the surface-structured thermopile can be determined, where T1 is the temperature at the first temperature sensing location and T2 is the temperature at the second temperature sensing location. At 892, T1 can be determined from at least one absolute temperature sensor. At 894, CBT can be calculated as CBT = a*T1 + b*(T1-T2) + c, where a, b, and c are predetermined coefficients depending on the locations of the first and second temperature sensing locations.

[0074] Therefore, according to the foregoing, some examples of this disclosure relate to a method for fabricating a surface-structured thermopile on a polymer structure of an electronic device, the polymer structure having an embedded conductive seed material therein, the method comprising: applying heat to the polymer structure along a plurality of intended thermopile trace locations to form a plurality of channels along the intended thermopile trace locations due to the applied heat, the channels including conductive seed material extruded from the polymer due to the heat; and depositing a first conductive material and a second conductive material over the conductive seed material in the plurality of channels to form a plurality of thermocouples, the first conductive material and the second conductive material being in contact with each other at the plurality of thermocouples, wherein at least one of the first conductive material and the second conductive material is formulated to have a thermal resistance different from that of copper and a Seebeck coefficient higher than that of copper. In addition to or alternatively to one or more of the examples disclosed above, in some examples, at least one of the first conductive material and the second conductive material is constantan. In addition to or alternatively to one or more of the examples disclosed above, in some examples, at least one of the first conductive material and the second conductive material is a chromium-nickel alloy. In addition to or alternative to one or more of the examples disclosed above, in some examples, at least one of the first conductive material and the second conductive material is copper. Additionally or alternatively, in some examples, an electronic device including a surface-structured thermopile is manufactured according to one or more of the examples disclosed above. In addition to or alternative to one or more of the examples disclosed above, in some examples, the method further includes measuring voltages on at least two thermopile traces and calculating the core body temperature based on the measured voltages. In addition to or alternative to one or more of the examples disclosed above, in some examples, the method further includes applying voltages to at least two thermopile traces to generate heat at the thermoelectric junction and increase the accuracy of the core body temperature calculation. In some examples, the generated heat may specify operation of the thermopile in a temperature range of 22°C to 45°C. In some examples, the generated heat may specify operation of the thermopile in a temperature range of 30°C to 40°C. In some examples, the generated heat may specify operation of the thermopile in a temperature range of 35°C to 38°C. In addition to or as an alternative to one or more of the examples disclosed above, in some examples, applying heat to the polymer structure along multiple intended thermopile trace locations to form multiple channels includes activating a laser for direct laser structuring. The multiple channels are formed due to one or more chemical reactions between the seed material, the polymer, and the energy of the laser.

[0075] Some examples of this disclosure relate to an electronic device having a surface-structured thermopile formed thereon, the electronic device comprising: a first plurality of thermocouples formed at a first temperature sensing location on a polymer structure of the electronic device, each of the first plurality of thermocouples comprising a first conductive material and a second conductive material in contact with each other; a second plurality of thermocouples formed at a second temperature sensing location on the polymer structure of the electronic device, each of the second plurality of thermocouples comprising a first conductive material and a second conductive material in contact with each other; and a plurality of thermopile traces connecting the first plurality of thermocouples and the second plurality of thermocouples, the plurality of thermopile traces being formed of the first conductive material and the second conductive material, wherein at least one of the first conductive material and the second conductive material is formulated to have a thermal resistance different from that of copper and a Seebeck coefficient higher than that of copper. In addition to or alternatively to one or more of the examples disclosed above, in some examples, at least one of the first conductive material and the second conductive material is constantan. In addition to or alternative to one or more of the examples disclosed above, in some examples, at least one of the first conductive material and the second conductive material is a chromium-nickel alloy. In addition to or alternative to one or more of the examples disclosed above, in some examples, at least one of the first conductive material and the second conductive material is copper. In addition to or alternative to one or more of the examples disclosed above, in some examples, the electronic device further includes a thermopile measurement circuit electrically coupled to at least two of the plurality of thermopile traces, the thermopile measurement circuit being configured to measure the voltage on the at least two thermopile traces. In addition to or alternative to one or more of the examples disclosed above, in some examples, the electronic device further includes a voltage generator switchably coupled to at least two thermopile traces, the voltage generator being configured to apply a voltage to the at least two thermopile traces to generate heat at the thermoelectric junction. In addition to or alternative to one or more of the examples disclosed above, in some examples, the first temperature sensing location is located near a location in the electronic device intended for user contact. In addition to or alternative to one or more of the examples disclosed above, in some examples, the second temperature sensing location is located near a location intended for thermal coupling with the ambient temperature experienced by the electronic device. In addition to or alternative to one or more of the examples disclosed above, in some examples, a first set of multiple thermopile traces is formed on the exterior of the electronic device housing. In addition to or alternative to one or more of the examples disclosed above, in some examples, a second set of multiple thermopile traces is formed inside the electronic device housing.In addition to or alternative to one or more of the examples disclosed above, in some examples, a first portion of a first set of multiple thermopile traces is wired externally to the housing of the electronic device, and a second portion of the first set of multiple thermopile traces is wired internally to the housing. In addition to or alternative to one or more of the examples disclosed above, in some examples, a first portion of the thermopile traces wired externally to the housing is coupled to a thermopile junction selected for thermal coupling to ambient temperature, and a second portion of the thermopile traces wired internally to the housing is coupled to a thermopile junction selected for thermal coupling to the user's skin.

[0076] Some examples of this disclosure relate to a method for estimating core body temperature (CBT) in an electronic device having a surface-structured thermopile including a plurality of thermoelectric couplings at a first temperature sensing location and a second temperature sensing location. The method includes determining a thermal gradient T1-T2 on the surface-structured thermopile, where T1 is the temperature at the first temperature sensing location and T2 is the temperature at the second temperature sensing location; determining T1 from at least one absolute temperature sensor; and calculating CBT = a*T1 + b*(T1-T2) + c, where a, b, and c are predetermined coefficients depending on the locations of the first and second temperature sensing locations. In addition to or alternatively to one or more of the examples disclosed above, in some examples, the method further includes applying a voltage to the surface-structured thermopile to reduce the thermal gradient T1-T2 and improve the accuracy of the CBT calculation.

[0077] Some examples of this disclosure relate to a method for directly structuring a surface-structured thermopile on a polymer structure of an electronic device using a laser. The polymer structure may have an embedded conductive seed material. The method may include performing laser activation of the polymer structure along a plurality of intended thermopile trace locations to form a plurality of channels along the intended thermopile trace locations due to one or more chemical reactions between the seed material, the polymer structure, and the radiation energy of the laser activation. The channels include conductive seed material extruded from the polymer due to laser activation. The method may further include depositing a first conductive material and a second conductive material over the conductive seed material in the plurality of channels to form a plurality of thermocouples, the first conductive material and the second conductive material being in contact with each other at the plurality of thermocouples. At least one of the first conductive material and the second conductive material is formulated to have a thermal resistance different from that of copper and a Seebeck coefficient higher than that of copper.

[0078] While the disclosed examples have been fully described with reference to the accompanying drawings, it should be noted that various changes and modifications will become apparent to those skilled in the art. It should be understood that such changes and modifications are considered to be included within the scope of the disclosed examples as defined by the appended claims.

Claims

1. A method for fabricating surface-structured thermopiles on a polymer structure of an electronic device, the polymer structure having a conductive seed material embedded therein, the method comprising: applying heat to the polymer structure along a plurality of prospective thermopile trace locations to form a plurality of channels along the prospective thermopile trace locations due to the applied heat, the channels comprising the conductive seed material extruded from the polymer structure due to the heat; and plating over the conductive seed material in the plurality of channels with a first conductive material and a second conductive material to form a plurality of thermocouples, the first conductive material and the second conductive material contacting each other at the plurality of thermocouples; wherein at least one of the first conductive material and the second conductive material is formulated to have a thermal resistance different from that of copper and a Seebeck coefficient higher than that of copper.

2. The method of claim 1, wherein at least one of the first conductive material and the second conductive material is constantan.

3. The method of claim 1, wherein at least one of the first conductive material and the second conductive material is chrome-nickel alloy.

4. The method of claim 1, wherein at least one of the first conductive material and the second conductive material is copper.

5. The method of claim 1, further comprising: measuring voltage across at least two thermopile traces; and calculating core body temperature based on the measured voltage.

6. The method of claim 5, further comprising: applying voltage to the at least two thermopile traces to generate heat at the thermocouple junctions and improve accuracy of the core body temperature calculation.

7. The method of claim 1, wherein applying heat to the polymer structure along the plurality of prospective thermopile trace locations to form the plurality of channels comprises activating a laser for laser direct structuring (LDS), wherein the plurality of channels are formed due to one or more chemical reactions between the seed material, the polymer structure, and the energy of the laser.

8. An electronic device having surface-structured thermopiles formed thereon, the electronic device comprising: a first plurality of thermocouple junctions formed at first temperature sensing locations on a polymer structure of the electronic device, each thermocouple junction of the first plurality of thermocouple junctions comprising a first conductive material and a second conductive material contacting each other; a second plurality of thermocouple junctions formed at second temperature sensing locations on the polymer structure of the electronic device, each thermocouple junction of the second plurality of thermocouple junctions comprising the first conductive material and the second conductive material contacting each other; and a plurality of thermopile traces connecting the first plurality of thermocouple junctions and the second plurality of thermocouple junctions, the plurality of thermopile traces formed from the first conductive material and the second conductive material; wherein at least one of the first and second electrically conductive materials is formulated to have a thermal resistance different than that of copper and a Seebeck coefficient higher than that of copper.

9. The electronic device of claim 8, wherein at least one of the first and second electrically conductive materials is constantan.

10. The electronic device of claim 8, wherein at least one of the first and second electrically conductive materials is chromel.

11. The electronic device of claim 8, wherein at least one of the first and second electrically conductive materials is copper.

12. The electronic device of claim 8, further comprising a thermocouple measurement circuit electrically coupled to at least two of the plurality of thermopile traces, the thermocouple measurement circuit configured to measure voltage across the at least two thermopile traces.

13. The electronic device of claim 12, further comprising a voltage generator switchably coupled to the at least two thermopile traces, the voltage generator configured to apply a voltage to the at least two thermopile traces to generate heat at the thermocouple junctions.

14. The electronic device of claim 8, wherein the first temperature sensing location is proximate to a location of expected user contact in the electronic device.

15. The electronic device of claim 8, wherein the second temperature sensing location is proximate to a location of expected thermal coupling with an ambient temperature experienced by the electronic device.

16. The electronic device of claim 8, wherein a first set of the plurality of thermopile traces is formed on an exterior of a housing of the electronic device.

17. The electronic device of claim 16, wherein a second set of the plurality of thermopile traces is formed on an interior of the housing of the electronic device.

18. The electronic device of claim 8, wherein a first portion of a first set of the plurality of thermopile traces is routed on an exterior of a housing of the electronic device and a second portion of the first set of the plurality of thermopile traces is routed on an interior of the housing.

19. The electronic device of claim 18, wherein the first portion of the thermopile traces routed on the exterior of the housing are coupled to thermocouple junctions selected for thermal coupling to an ambient temperature and the second portion of the thermopile traces routed on the interior of the housing are coupled to thermocouple junctions selected for thermal coupling to a user's skin.

20. A method for estimating core body temperature (CBT) in an electronic device having a surface structured thermopile comprising a plurality of thermocouple junctions at a first temperature sensing location and a second temperature sensing location, the method comprising: determining a thermal gradient T1-T2 across the surface structured thermopile, where T1 is a temperature at the first temperature sensing location and T2 is a temperature at the second temperature sensing location; determining T1 from at least one absolute temperature sensor; and ​ calculating CBT = a*T1 + b*(T1-T2) + c, where a, b, and c are predetermined coefficients dependent on the location of the first temperature sensing location and the second temperature sensing location.

21. The method of claim 20, further comprising: applying a voltage across the surface structured thermopile to reduce the thermal gradient T1-T2 and improve accuracy of the CBT calculation.

22. A method for fabricating a surface structured thermopile on a polymer structure of an electronic device using laser direct structuring (LDS), the polymer structure having a conductive seed material embedded therein, the method comprising: performing laser activation of the polymer structure along a plurality of intended thermopile trace locations to form a plurality of channels along the intended thermopile trace locations due to one or more chemical reactions between the seed material, the polymer structure, and the laser activation’s radiant energy, the channels including the conductive seed material extruded from the polymer structure due to the laser activation; and plating over the conductive seed material in the plurality of channels with a first conductive material and a second conductive material to form a plurality of thermocouples, the first conductive material and the second conductive material contacting each other at the plurality of thermocouples; wherein at least one of the first conductive material and the second conductive material is formulated to have a thermal resistance different than that of copper and a Seebeck coefficient higher than that of copper.

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