Electromagnetic radiation (EMR) exposure to the sun and artificial lighting systems represents modifiable risk factors for various health conditions, including skin cancer, skin aging, sleep and mood disorders, and retinal damage. Personalized EMR dosimetry technology can guide lifestyles toward behaviors that ensure healthy exposure levels. Here, we report a millimeter-level ultra-low-power digital dosimeter platform that can simultaneously provide continuous EMR dosimetry in an autonomous mode at one or more wavelengths, and time with standard consumer equipment Managed wireless remote communication. By combining the cumulative detection mode using optical power supply and the ultra-low power circuit design of light adaptation, a single small button battery can support a life span of many years. Field studies have demonstrated this type of single-peak and multi-peak dosimetry platform, focusing on monitoring the short-wavelength blue light emitted by indoor lighting and display systems and the ultraviolet/visible/infrared radiation emitted by the sun.
Electromagnetic radiation (EMR) from the sun and indoor lights, luminous displays, and other man-made sources have specific wavelength and dose-dependent effects on the basic life processes that determine health conditions. The adverse effects of overexposure or underexposure on EMR will accumulate over time, and the consequences may be potential (1). Specifically, excessive exposure to ultraviolet radiation (UVR) and blue light by the sun or emission sources (such as those in tanning beds and cell phones) has various associated risks. Repetitive keratinocyte damage caused by long-term exposure to ultraviolet radiation is the main cause of skin cancer, which is the most commonly diagnosed form of cancer in the United States (2-4). The shorter wavelengths of the visible spectrum (VIS) produce reactive oxygen species in the skin, which can cause DNA damage, causing inflammation and pigmentation, and enhancing the degradation of collagen and elastin, leading to photoaging and skin wrinkles (5-7) . Beyond certain thresholds, blue light can cause photochemical damage to retinal tissues and accelerate age-related macular degeneration (8-12). Other effects can regulate the control of human circadian rhythm by the retina, including inhibition of melatonin secretion (13). On the other hand, the right amount of UVR and VIS is essential for the production of vitamin D and immune regulation. Underexposure can also cause seasonal affective disorder (SAD), which is usually treated with bright light therapy.
Through technology, you can easily and quickly obtain personalized information for specific wavelengths of EMR exposure. These technologies can guide behaviors to prevent adverse health consequences, from sunburns and skin cancers to mood swings and sleep disorders. The previously reported methods are almost entirely focused on UVR measurements using color-changing chemicals (14) or the digital sampling output of UVR photodiodes (15). The former provides semi-quantitative information in platforms that cannot be reused. The latter is susceptible to sampling errors, and its service life is limited by battery capacity. The latest proposal involves a miniaturized, high-precision dosimeter that uses a continuous detection mode of photodynamic force and battery-less operation (16). Here, the current from the photodiode accumulates on the storage capacitor, so that the resulting voltage directly corresponds to the dose by the calibration factor. In the reported system, the small loop antenna supports the Near Field Communication (NFC) protocol as a digital wireless interface for the phone for data collection. The main disadvantage of these millimeter-level NFC (mm-NFC) devices is that they require active user involvement to perform data collection and device reset (capacitor discharge) by “swiping” the phone.
The ideal platform would provide automatic and remote wireless updates while retaining many other attractive attributes of the cumulative mode mm-NFC method. This article introduces this technology, which is based on a combination of advanced optical adaptive electronic control circuits with an accumulative detection module (ADM) for dosimetry and an on-chip Bluetooth low energy (BLE) system for wireless communication. Here, even some of the smallest button batteries (MS621F) can run continuously for more than 1.2 years in “always on” mode, which can run automatically without any form of user involvement. The total size of the final device is only slightly larger than the recently launched commercial mm-NFC dosimeter system, which supports a variety of personal use options, such as installation on glasses, earphones, shoelaces, straps, bracelets, pendants, or other accessories. The lack of interface ports and mechanical switches, and no need to replace the battery, so the device can be fully sealed, so as to achieve waterproof, sweat and wear resistance.
The key feature of ADM is that it can continuously and directly measure exposure dose without consuming any power. In contrast, conventional digital methods use a series of short intensity measurements to approximate the dose by calculating a time integral, each of which is performed using active battery-powered electronics. Here, increasing the sampling frequency can improve accuracy, but it will reduce battery life. ADM eliminates this trade-off and can achieve high-precision dosimetry even when the interval between two effective measurements is very long. The active, adaptive optical circuit design introduced here will automatically adjust the time and frequency used to query ADM, depending on the radiation intensity. In the absence of light, the device remains in an ultra-low power sleep mode (~0.4μA) while continuously monitoring the dose through ADM. When the dose exceeds the set threshold, the device will wake up briefly (about 10μA), use the BLE protocol to wirelessly transmit the exposure information, reset the ADM, and then quickly return to sleep mode. The result is an outstanding energy-efficient dosimeter that can automatically adjust its operation and communication with the mobile phone as needed to achieve millimeter-level dimensions and multi-year battery life, which corresponds to both devices and is always effective and long-lasting without user involvement. . The following sections describe the circuit design, working principle, and key factors that determine life and accuracy. The application focuses on the dosimetry of blue light and multispectral measurement in the UVR, blue and infrared (IR) regions of the spectrum, some examples of which are in field test studies.
The device in Figure 1A utilizes the unique design features described above for blue light dosimetry and has an estimated service life of 1.2 years. The width (w), length (l), thickness and weight are 8.1mm, 10.9mm, 3.2mm and 0.36g respectively. Two subsystems (Figure 1B) are the keys to high-efficiency, ultra-low power operation and long life in this miniaturized form: (i) ADM, as a photodynamic sensing system, continuously measures exposure dose in a cumulative mode, and (A) ii) The BLE SoC is equipped with an optical adaptive circuit design to automatically switch between two operating states (“running” and “sleeping”) in response to changing irradiation conditions. ADM includes photodiodes (PD), super capacitors (SC) and metal oxide semiconductor field effect transistors (MOSFET). The PD generates photocurrent continuously and passively, and the magnitude of the photocurrent is linearly proportional to the light intensity of the exposure. The SC arranged in parallel with the PD captures and stores the accumulated charge generated. The corresponding voltage (VSC) on the SC can be calibrated to the total exposure dose within the wavelength range defined by the external quantum efficiency (EQE) of the PD (Figure S1). In order to prevent excessive accumulation of charge on the SC, the gate of the MOSFET is connected to the general-purpose input/output (GPIO) of the BLE SoC to programmatically control the current flow between the source and drain of the MOSFET and the discharge of the SC.
(A) A photo of the blue light dosimeter with BLE communication function on the tip of the index finger. The illustration shows a bottom view and a side view. (B) The circuit diagram and block diagram illustrate the accumulation mode, adaptive operation, and wireless interface (BLE radio) of the smartphone. ADM, PD, SC, MOSFET and low-power comparator (LPCOMP) are marked as ADM, PD, SC, MOS and LPCOMP respectively. VSC and VREF represent the cumulative voltage on SC and the reference voltage of LPCOMP, respectively. ADC, analog to digital converter. (C) The relationship between time and time of VSC under no light, low light and strong light conditions, and the activities of the central processing unit (CPU) and BLE radio at the corresponding time. (D) Schematic diagram of decomposition of constituent layers and components: BLE SoC, battery, MOSFET (MOS), SC, blue photodiode (PD), copper interconnection [Cu / PI (polyimide) / Cu] and chip antenna. (E) Photographic images of three ultra-low-power blue light dosimeters, located next to batteries with capacities of 140, 40, and 5.5 mA·hour (from left to right). (From F to H) Photos of encapsulated sensors mounted on a pair of glasses, earrings and smart watches. The illustrations in (H) show top and bottom views of unpackaged equipment. Image source: Seung Yun Heo, Northwestern University.
In optical adaptive operation, when the device is in ultra-low-power sleep mode, the BLE SoC’s low-power comparator (LPCOMP) monitors the VSC. When VSC exceeds the pre-programmed reference voltage (VREF), LPCOMP will generate a “wake-up” event, which puts the BLE SoC in operating mode for about 6.5 s, and the average current consumption is about 10.22μA. Here, the central processing unit (CPU) wirelessly transmits the input voltage of the analog-to-digital converter (ADC) connected to the SC, activates the MOSFET to discharge the SC, and then returns the system to sleep mode. The time required to sample the ADC input voltage, transmit BLE data packets, and discharge the SC (for example, 5 s) determines the running time. Unless the voltage on SC exceeds VREF, the device will remain in sleep mode. In this mode, the CPU and all peripherals except LPCOMP will be disabled, thereby reducing the average current consumption to ~0.43μA, which is approximately equal to 20 times the average current associated with the operating mode.
Figure 1C graphically illustrates the entire operation. In the absence of light, the device stays in sleep mode until the exposure dose determined by the ADM exceeds VREF. At this time, the CPU wakes up, transmits data wirelessly, discharges the ADM and returns to sleep. Within the wavelength range defined by the PD’s EQE, the wake-up frequency increases with the increase in irradiance. The purpose of this light-adaptive operation is twofold: (i) often remind users of their exposure dose under high-intensity irradiation conditions, and sleep for a long time under low or no irradiation conditions, and (ii) autonomously and effectively manage according to testing needs Power consumption. The flow chart of the system software is shown in Figure 2. S2. As another option to avoid accidental data loss due to interruption of the wireless connection to the mobile phone, the system can be programmed to write the dose data into the memory available on the BLE SoC, as described below.
These devices use a thin (112μm thick) copper clad polyimide sheet that is processed by a laser cutting tool to define interconnected copper traces and support pads to bond ready-made surface mounts by soldering Components, as shown in Figure 2. The one-dimensional battery is a key factor in determining the overall size and weight and service life. Figure 1E shows a blue light dosimeter equipped with coin-shaped batteries with capacities of 140, 40, and 5.5 mA·hour, respectively. The device diameter (d) is 16.6 and 13.5 mm, and the length and width (l×w) are 8.1 mm. 10.9 mm respectively. Assuming (i) blue light from the sun occurs at a constant intensity of 7.8 mW/cm2 (outdoor is at a moderate level), and (ii) exposure at this level occurs for a total of 6 hours in a typical day. The service life of the dosimeter (in descending order of size) is greater than 30.9, 8.8 and 1.2 years. The miniaturized form factor allows many options and ways of use. Examples include sunglasses clips (Figure 1F), earrings (Figure 1G), and wristband accessories (Figure 1H). Sealed enclosures of different designs (Figure 1, F to H) can enhance operational reliability under environmental and mechanical influences.
SAD is a relatively common disease in North America and can cause depression in winter. SAD treatment includes conventional light therapy using natural light or bright white or blue light-emitting diode (LED) lighting panels (17-19). Information from personal blue light dosimeters can help guide behaviors that meet the recommended daily exposure dose to prevent mood disorders. This section demonstrates the use of devices with the designs outlined in the previous sections. These devices are designed to monitor sunlight at different irradiance levels. Measurements of current consumption can estimate the battery life of these use cases. These devices use blue PD (peak response at 390 nm) (Figure S1) and SC (capacitance 11.5 mF).
Calibration involves exposing the device to sunlight on sunny days and exposing it to 80%, 63%, and 50% of sunlight through a neutral density filter, which corresponds to high and low radiation conditions. Commercial blue light radiometers (visible blue light meters, daylight meters) measure reference exposure intensity. The time integral of the reference exposure intensity with respect to Twake is the reference exposure dose. A BLE-enabled smartphone will wirelessly receive an alarm every time it wakes up. For constant reference exposure intensities of 7.8, 6.2, 4.9, and 3.9 mW/cm2, the time interval (Twake) between two wake-up events is 3.2, 4.1, 5.1, and 6.7 minutes, respectively (Figure 2A). As the reference radiation intensity decreases, Twake increases proportionally (Figure S3), so that the blue light exposure dose (Dtot) for each wake-up event is Dtot = intensity (W / cm2) ×Twake (s) = 1.5±0.03 Joules/ Square centimeter Twake is the determining factor for calculating the average current (Iavg) consumption of the device: Iavg = [Irun, avg×Trun + Isleep, avg×(Twake-Trun)] / Twake. The method of measuring real-time current consumption appears in “Materials and Methods” and Figure 2. S4. BLE dosimetry can be performed in two wireless BLE transmission modes: connection mode and advertising mode. The equipment measured here operates in advertising mode. The current measurement result in connection mode is shown in Figure 2. S5. The average current consumption in sleep mode (Figure S4) is Isleep, avg = 0.43μA, and the average current consumption in running mode is Irun, avg = 10.22μA. The running time after the wake-up event is Trun = TADC + TBLE + TDSC = 6.56 s, where TADC and TBLE are the time required to sample ADC input voltage and transmit sampled data via BLE, and TDSC is the pre-programmed time (for example, 5 s) ) Fully discharge SC. In light-adaptive operation, as the irradiation intensity increases, Twake decreases proportionally, while Iavg increases. For constant exposure intensities of 7.8, 6.2, 4.9, and 3.9 mW/cm2, Iavg was 0.76, 0.70, 0.63, and 0.59μA, respectively (Figure 2B). The average current of 365×6 hours per year (equivalent to 50% of available daylight) is Iavg, 50% = Iavg×6 (hours) / 24 (hours) + Isleep, avg × 18 (hours) / 24 (hours)). Under 50% exposure conditions, the life of the device is life (hours) = battery capacity (mA·hour)/average 50% (mA). As an illustrative example, a device powered by a coin battery with a capacity of 5.5 mA·hour, continuously exposed at a constant intensity of 7.8 mW/cm2, has an expected lifespan of 1.2 years (Figure 2C), and an average of 50% of available daylight Iavg, 50 % Current = 0.52μA. Assuming (i) blue light from the sun occurs at a constant intensity of 7.8 mW/cm2 (at a moderate level outdoors), and (ii) exposure at this level in a typical day occurs for a total of 6 hours, these dosimeters The service life of the product is over 30.9, 8.8 and 1.2 years in descending order of size.
(A) Ultra-low power blue light dosimeter exposed to blue light (n = 1) The voltage output and current consumption of the time-varying, constant intensity, corresponding to the outdoor medium and low blue light conditions at four different intensities. Indicates the time interval (Twake) to “wake up” the device from sleep when exposed to constant intensity blue light with different intensities. (B) It is assumed that the average current consumption (Iavg) of continuous use and the average current consumption of the assumed use correspond to 50% (Iavg, 50%) of the available daylight as a function of Twake. (C) Assuming the life expectancy of batteries with lifespans of 140, 40 and 5.5 mA·hours as a function of Twake, assuming that the usage is equivalent to 50% of the available daylight: life = battery capacity / Iavg, 50%.
The on-chip data retention function can be used to prevent data loss after losing the wireless connection with the mobile phone. The BLE SoC (nRF5283, Nordic Semiconductor) supports 4 kilobytes of static random access memory (SRAM) that can be used for this purpose. As a specific example of this mode of operation, the device can be programmed to store the latest 10 measurement events (10×2 bytes) in SRAM. Then, every time a wake-up event occurs, the entire data set is transmitted. When the phone is within the communication range of the device, the application compares the read data array with the data history stored on the phone and performs updates with any new data as needed. By using SRAM in this way, the average current consumption in sleep mode increases to Isleep, avg = 0.788μA, which is approximately twice the current consumption when SRAM is not used. In order to transmit the data set, the average current consumption in the running mode is Irun, avg = 10.459μA, and the running time after the wake-up event is Trun = 7 s. The average current consumed by the device that maintains SRAM data at an intensity of 7.8 mW/cm2 under 50% exposure conditions is Iavg, 50% = 0.88μA, which is about 1.7 times the operating current when SRAM is not used; therefore, the corresponding lifetime is shortened By 0.59 times.
Traditional BLE dosimeters digitally integrate intensity values ​​measured on a fixed schedule (for example, once every 30 s), which balances accuracy and power consumption in the aforementioned manner. Between the two measurements, the CPU remains powered on, but in an “idle” mode (light sleep mode) that does not involve any instruction execution. Here, the average current (Iidle, avg) is ~2.14μA (Figure S4D), which is approximately five times the current associated with sleep mode. At the intensity of 7.8mW/cm2, the device design with SRAM data retention function under 50% exposure conditions (as described in the previous paragraph), using a 5.5mA·hour battery can provide 0.72 years of working life, while in other cases, Only 8.02 weeks the device has a traditional instantaneous operating mode, the typical value is Twake = 30 s.
As an alternative to the previously described ADM’s “analog” accumulation mode sensing, the BLE device can be programmed to operate in an equivalent “digital” accumulation mode, which involves frequent sampling of the intensity from the PD and calculating the corresponding dose , And then store this information locally in SRAM. When the digital cumulative dose exceeds a certain level, wireless transmission occurs. Between measurement and transmission, the device will remain in idle mode until the sampling timer expires. In the run mode, the average current consumption of data sampling/storage and BLE transmission is Irun, data = 2.64μA and Irun, BLE = 4.89μA, and the running time is Trun = 5.28 s. The average current consumed by Twake = 30 s and TBLE = 3.2 min (under exposure to sunlight at a constant intensity of 7.8 mW/cm2) is Iavg, 50% = 2.21μA. The expected life span is 14.8 weeks, which is about twice that of traditional instantaneous mode equipment under the traditional value of Twake = 30 s, but it is still far below the life allowed by the ADM and optical adaptive modes highlighted in this article.
The intensity of blue light emitted by artificial light and electronic displays is much lower than that produced by outdoor sunlight (20-21). Nevertheless, the distance between the screen and the eyes is very close, and long-term exposure to the screen late at night and late at night, there are still health risks. The blue light dosimeter used indoors (Figure 3, A and B) adopts a similar design to that outdoors, but has 10 blue PDs connected in parallel and three collectors of 7.5 mF SC connected in series (Figure 3C) to increase light Current and reduce storage capacitance to increase sensitivity (Figure S6, A and B). The off-the-shelf blue PD for indoor monitoring dosimeters has a peak response at 390 nm and is higher than the effective PD for outdoor applications (Figure S1). The final device is powered by a standard button battery with a capacity of 40 mA·hour, and its diameter and thickness are 13.5 and 3.9 mm, respectively.
(A) A photo of an indoor blue light dosimeter held between fingertips. (B) Schematic diagram of decomposition of the constituent layers and components: BLE SoC, battery, MOSFET (MOS), SC (×3), blue PD (×10), copper interconnection (Cu / PI / Cu), and chip antenna. (C) The circuit and block diagram of the system, and the wireless interface for indoor blue light monitoring with BLE-enabled devices. (D to G) The voltage output and wake-up time interval of indoor blue light dosimeters (n = 1) at a distance of 50, 100, and 150 cm from the white light phototherapy lamp (D) is 50 cm from the artificial light source (E), and the display screen (F) ) 10 cm, 5 cm (G) from flat panel displays equipped with 0%, 30%, 50% and 70% blue blocking filters. The Twake value is marked. Image source: Seung Yun Heo, Northwestern University.
Figure 3 (D to G) are representative results of exposure to various indoor light sources including white light phototherapy lamps, different types of artificial light bulbs and various electronic displays. The measured values ​​at the distance (d) 50, 100, and 150 cm from the white light source used to treat SAD (Figure S6C) indicate the Take value of 1.38, 4.24, and 8.47 minutes, respectively (Figure 3D). According to the inverse square law of light propagating from a point light source, the exposure intensity is roughly inversely proportional to d2. The graph that varies with the inverse square of d is shown in Figure 5. S6D. The measured exposure dose is equivalent for each Twake, so Twake has a linear relationship with the exposure intensity. The change in linearity in the graph. S6D occurs because the light source is composed of an LED array in this case, so it cannot be accurately approximated as a point light source. The wake-up time of the device 50 cm away from the LED, fluorescent and incandescent light sources is 12.72, 22.48, and 43.63 minutes, respectively (Figure 3E). These results are consistent with the relative emission spectra of LEDs, fluorescent lamps, and incandescent lamps near the blue region of the spectrum. The Twake values ​​of devices 10 cm away from TVs, computer monitors, laptop screens, tablet monitors, and smartphone monitors were 23.75 minutes, 26.73, 30.07, 34.19, and 51.78 minutes, respectively (Figure 7). 3F). During the exposure, all computers displayed the same white screen. As expected, the results showed that TVs with the largest displays emit the most blue light, while smartphones with the smallest displays emit the least blue light. Flat panel displays (Figure 3G) equipped with blue light filters set to 0%, 30%, 50%, and 70% produced Take values ​​of 30.60, 36.32, 49.00, and 94.62 minutes, respectively. The graph of Twake as a function of percentage of attenuation is shown in Figure 2. S6E. The mismatch between the detection spectrum of the PD and the filtering spectrum of the tablet partially caused the deviation of the linearity in FIG. 2. S6E. Additional exposure experiments with and without commercial anti-blue film are shown in Figure 2. S6F. Take with and without anti-blue film film is 69.91±0.06 and 57.66±0.24 minutes respectively. Experiments show that the commercial blue film (ZOVER) can block about 17.52% of the radiation near 390 nm.
An automatic wireless scheme can be used to track indoor and outdoor exposure scenes in the blue light dosimeter, which can switch between parallel sensing circuits according to the presence (outdoor) or absence (indoor) of UVA radiation, as shown in Figure 4A. When using a 40 mA.hour battery, the width (w), length (l), thickness and weight are 12.32 mm, 14.78 mm, 4.21 mm and 1.09 g, respectively. The circuit (Figure 4B) consists of independent ADMs configured to monitor outdoor (one blue PD, one SC and one MOS) and indoor (10 blue PD, three SC and one MOS) paired with UVA PD and MOS. The BLE SoC is configured to automatically switch between the two ADMs to achieve low (outdoor) and high (indoor) detection based on the voltage input from the UVA PD (VUVA) through a 2:1 multiplexer (MUX) based on the selection signal Sensitivity (S). In the presence or absence of UVA radiation, the GPIO connected to the UVA PD is set to HIGH (“1″) or LOW (“0″) respectively. The GPIO read value is used as a selection signal. Under sunlight, VUVA is high, S is 1, 2:1 MUX output is switched to outdoor ADM, and outdoor ADM is connected to LPCOMP and ADC to use VREF for light adaptive operation, as described above. In this state, the MOS paired with the UVA PD will continuously discharge the indoor ADM to prevent excessive charge accumulation on the corresponding SC. In the absence of UVA radiation (VUVA = LOW, S = 0), 2:1 MUX output is switched to indoor ADM. The edge detector monitors the GPIO value and generates a wake-up signal (WuS) when the edge is rising (when the input is from 0 to 1) or falling (when the input is from 1 to 0) (corresponding to indoor to outdoor). Outdoor and outdoor to indoor switch. At each indoor/outdoor switch, the GPIO wake-up event will cause the CPU to release two ADMs to update the 1-bit flag value (indoor is 0, outdoor is 1), as an activation instruction to the user interface indoor or outdoor ADM, and then again Enter sleep mode. When an LPCOMP wake-up event occurs, the CPU operates in the same manner as described in the previous sections, and additionally sends the first bit of the flag value to the user interface. The user interface checks whether the most significant bit (MSB) of the received BLE data is 0 or 1, and projects the exposure dose to indoor (MSB = 0) and outdoor (MSB = 1) respectively.
(A) An image of a blue light dosimeter with an automatic sensitivity switching scheme to allow monitoring of low-intensity blue light indoors and high-intensity blue light outdoors. (B) Circuit and block diagram of a system with wireless switching scheme between outdoor and indoor sensing circuits with or without UVA radiation. Blue PD, MOSFET, SC, MUX, select signal, UVA PD anode voltage and WuS are marked as BL PD, MOS, SC, MUX, S, VUVA and WuS respectively. (C) The voltage and the 1-digit flag (0 for indoor and 1 for outdoor) are output as a function of time, with no exposure to UVA (blue) and UVA (yellow). (D) Under outdoor daylight (yellow) and 60-LED ring light (blue), the voltage and 1-bit marker output are a function of time. Image source: Seung Yun Heo, Northwestern University.
With no UVA exposure and with UVA exposure, the voltage and MSB as a function of time are shown in Figure 4C. Here, the dosimeter uses the same blue PD for both outdoor and indoor circuits (Figure S1) to illustrate the switching operation between ADMs with high or low detection sensitivity. In these experiments, a blue light (Giraffe Blue Spot PT, GE Healthcare) exposed the device to a constant intensity with and without UVA light (UVL-26, Analytik Jena). In the time period without UVA, when the output voltage of the indoor ADM (VSC0) exceeds 175.77±0.58 mV (the flag value is 0) and the Twake is 59.21±1.44 min, the device will wake up. With the introduction of UVA, the device will wake up and update the flag value 1 to the user interface. During UVA exposure, when the output voltage of the indoor ADM (VSC1) exceeds 175.95±1.06 mV (the flag value is 1) and the Twake is 2.07 min, the device will wake up. Compared with outdoor ADM, the sensitivity of indoor ADM for this operation is 29 times higher. Figure 4D shows a blue light dosimeter with automatic switching function under actual exposure conditions. Here, since BLE-enabled mobile phones obtain VSC0 or VSC1 and 1-bit flag output wirelessly, outdoor sunlight and indoor 60-LED ring lights are exposure sources. The blue/UVA intensity from the sun and the blue/UVA intensity from the LED measured with a photometer were 9.8/3.6 and 2.5/0 mW/cm2, respectively. During outdoor testing, when VSC1 exceeds 183.13±0.38 mV and the flag value is 1, and the constant Twake of 853 mJ/cm2 is 1.45 minutes, the device wakes up. When indoors, there is no UVA, and the device will wake up and update the flag value to 0. During the indoor test, when VSC0 exceeds 174.57±2.19 mV (the flag value is 0), the device will wake up, and for TSC, its Twake value is 29.67±0.58 s. The exposure dose is 74 mJ/cm2. The results show that the sensitivity of indoor ADM is 11.5 times that of outdoor ADM. This difference is due to the huge difference in emission spectra around 390 nm between the two exposure sources.
The basic design and operating principles can be easily extended to allow simultaneous dosimetry in up to seven different wavelength bands from ultraviolet to VIS and IR in the solar spectrum. The three-channel device shown in Figure 5A uses the same exposure assumptions as before and measures the exposure dose under UVA, blue, and IR. The estimated working life outdoors is 8.8 years. Here, the diameter and thickness are 13.5 and 3.92 mm, respectively. These components include UVA PD, blue PD, IR PD, three 11.5 mF SC, three MOSFETs, a BLE SoC and a 40 mA·hour battery (Figure 5B). The peak response wavelengths of UVA and IR PD are 380 and 940 nm, respectively (Figure S7). The circuit configuration (Figure 5C) utilizes three independent ADCs on the BLE SoC, each of which is connected to an independent ADM. Here, LPCOMP monitors the ADC associated with the blue light sensing system (CH1) so that when the VSC of CH1 exceeds VREF, the device enters the operating mode and wirelessly transmits all three ADC values. Select the blue light as the parameter to trigger the wake-up event. The gates of the three MOSFETs are connected to a single GPIO to allow all three SCs to discharge simultaneously after a wake-up event. An example of a three-channel dosimeter mounted on the earphone is in Figure 5D.
(A) A photo of an ultra-low power three-channel UVA/blue/IR light dosimeter held between fingertips. (B) Schematic diagram of decomposition of constituent layers and components: BLE SoC, battery, MOSFET (×3 MOS), SC (×3 SC), UVA photodiode (UVA PD), blue light PD, IR PD, copper interconnection (Cu / PI/Cu) and chip antenna. (C) Circuit diagram and block diagram of adaptive, cumulative detection mode and wireless interface with remote BLE radio (ie smart phone). (D) Photo of the multi-channel sensor installed on the headset. (E to G) The time obtained from the UVA/blue/infrared dosimeter (n=1) in Evanston, Illinois in April 2019 as a function of time, which is morning (E) and noon (F) And afternoon (G) time. Picture provided by: Northwestern University Seung Yun Heo
The data collected under these conditions and wirelessly transmitted to the smartphone is shown in Figure 5 (E to G). There were 9 wake-up events in the morning, and Twake was reduced from 12.28 to 4 minutes at sunrise. The blue and UVA doses measured during the morning exposure were 13.5 and 4.5 J/cm2, respectively. Measurements around noon involved 27 wake-up events, and Twake remained roughly constant at 2.16±0.07 minutes. The exposure doses for blue and UVA at noon were 40.5 and 11.8 J/cm2, respectively. There are 15 wake-up events in the afternoon. During sunset, Twake increased from 3.25 minutes to 5.45 minutes, and the total blue and UVA doses were 22.5 and 7.1 J/cm2, respectively. See picture. The S8 is a field test result of outdoor UVA and blue light exposure using a two-channel device for 4 days (July 25 to July 26 and July 31 to August 1; Illinois). The cumulative UVA/blue light doses on July 25, July 26, July 31 and August 1 from 5:30 am to 1:30 pm were 15.31/76.5, 13.02/61.5, 34.64/123.0 and 33.02/ 115.5 J/cm2.
The combined use of adaptive circuit design and cumulative detection scheme provides a basis for a compact wireless digital platform that can continuously monitor at a personalized level across one or more wavelengths in an autonomous mode that can be continuously adjusted to surrounding conditions EMR exposure. These highly accurate millimeter-level systems operate in an always-on state and have a life span of many years. In a practical sense, they will be permanent for most envisioned applications. The exposure data is automatically reported to standard consumer electronic devices via a long-distance wireless link, using it as the basis for information that can be used to guide healthy behavior. These technical functions and the negligible user burden related to data collection, power management, battery replenishment and wearability represent an ideal set of functions. Coincidence with low-cost, mass production suggests that large-scale deployment is possible to help prevent the risks of skin cancer, mood disorders, eye damage, and other conditions related to EMR exposure.
A flexible sheet (AP8535R, Pyralux) of copper (thickness of 18μm)/polyimide (thickness of 75μm)/copper (thickness of 18μm) was used as the substrate. The UV laser system (ProtoLaser U4, LPKF) ablated the copper to define conductive traces and vias. The electric pulse plating system (Contac S4, LPKF) creates a copper conductive plug between the two patterned copper layers through the via. In/Ag solder paste (Indalloy 290, Indium Corporation) heated to 90°C is used as solder joints for surface mount components (BLE, SC, UVA PD, UVB PD, blue PD and MOSFET). Polydimethylsiloxane (SYLGARD 184, Dow Corning Corporation) molded and cured at 70°C forms a robust package structure.
The calibration includes exposure to outdoor sunlight at a constant intensity on a sunny day on a sunny day, and there is no cloud during solar noon. Blue light (visible light blue light meter, daylight meter) and UVA photometer (sensitive UVA meter, daylight meter) measure the intensity of incident sunlight. The time integral of the measured intensity is the cumulative dose of blue light or UVA exposure. A BLE-enabled phone (iPhone 6) can wirelessly obtain the dosimeter voltage measurements for all wake-up events.
The Power Profiler Kit (PPK) board (NRF6707, Nordic Semiconductor) is used as a current measurement tool for the dosimeter. PPK supplies power to the BLE blue light dosimeter through an external device under the tested connector, and uses its ADC to measure the voltage drop across a series of measurement resistors. The real-time current consumed by the blue light dosimeter is I (A) = the measured voltage drop (V) / resistance value (ohm). PPK provides current measurement with resolution as low as 0.2μA and real-time display with resolution as low as 13μs for desktop applications. By installing PPK on the nRF52 Development Kit (DK) board (nRF52-DK, Nordic Semiconductor), nRF52-DK provides a connection between PPK and a computer with PPK applications. PPK software is an application running in nRF Connect, nRF Connect is a cross-platform development software for BLE. For more details, see the supplementary material.
In connection mode, the device must meet the connection rules provided by the user interface to establish a connection link. The connection parameters that comply with the Apple Device Accessories Design Guide (Release R8) are dependent delay = 3, and the maximum connection interval = 500 ms, so the maximum connection interval × (dependent delay + 1) ≤ 2 s. Devices based on these connection rules exchange data packets with the user interface every 2 seconds to maintain the connection state, even if there is no need to transmit user data. This operation will greatly reduce the overall power efficiency of the device. In the advertising mode, the BLE device sends data to any listening user interface that knows the device ID without establishing any connection. This mode can provide efficient BLE operation for low duty cycle applications such as those described here. For more details, see the supplementary material.
For supplementary materials for this article, please see http://advances.sciencemag.org/cgi/content/full/5/12/eaay2462/DC1
Figure S2 Flow chart of BLE blue light sensing system using ultra-low power sleep/wake-up function.
Figure S6. Blue light dosimeter with high detection sensitivity for monitoring short-wavelength blue light from indoor lighting and display systems.
Figure S8 5:30 am to 1:30 pm, using a two-channel blue/UVA dosimeter.
This is an open access article distributed under the terms of the Creative Commons Attribution-Non-Commercial License, which allows the use, distribution and reproduction in any medium, as long as the final use is not for commercial gain and the premise is that the original work is correct. Reference.
Note: We only ask you to provide an email address so that the person you recommend to the page knows that you want them to see the email and that the email is not spam. We will not capture any email addresses.
This question is used to test whether you are a human visitor and to prevent automatic spam.
By Kyeongha Kwon, Seung Yun Heo, Injae Yoo, Anthony Banks, Michelle Chan, Jong Yoon Lee, Jun Bin Park, Jimhyun Kim, John A. Rogers
A small wireless dosimeter with light adaptability and ultra-low power consumption, which can continuously monitor personalized exposure.
By Kyeongha Kwon, Seung Yun Heo, Injae Yoo, Anthony Banks, Michelle Chan, Jong Yoon Lee, Jun Bin Park, Jimhyun Kim, John A. Rogers
A small wireless dosimeter with light adaptability and ultra-low power consumption, which can continuously monitor personalized exposure.
©2020 American Association for the Advancement of Science. all rights reserved. AAAS is a partner of HINARI, AGORA, OARE, CHORUS, CLOCKSS, CrossRef and COUNTER. ScienceAdvances ISSN 2375-2548.