Research ArticleAPPLIED SCIENCES AND ENGINEERING

Miniaturized, light-adaptive, wireless dosimeters autonomously monitor exposure to electromagnetic radiation

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Science Advances  13 Dec 2019:
Vol. 5, no. 12, eaay2462
DOI: 10.1126/sciadv.aay2462
  • Fig. 1 Ultralow-power, light-adaptive, wireless blue light dosimeter.

    (A) Photograph of a blue light dosimeter with BLE communication capabilities on the tip of an index finger. The insets show bottom and side views. (B) Circuit and block diagrams that illustrate accumulation mode, adaptive operation, and wireless interface to smartphones (BLE radio). The ADM, PD, SC, MOSFET, and low-power comparator (LPCOMP) are labeled ADM, PD, SC, MOS, and LPCOMP, respectively. VSC and VREF denotes the accumulated voltage on SC and the reference voltage of LPCOMP, respectively. ADC, analog-to-digital converter. (C) Illustration of VSC as a function of time during no light, weak light, and intense light exposure conditions and activity of central processing unit (CPU) and BLE radio at corresponding times. (D) Schematic, exploded view illustration of the constituent layers and components: BLE SoC, battery, MOSFET (MOS), SC, blue light photodiode (PD), copper interconnects [Cu/PI (polyimide)/Cu], and chip antenna. (E) Photographic image of three ultralow-power blue light dosimeters, next to respective batteries of capacities 140, 40, and 5.5 mA·hour (left to right). (F to H) Photographs of encapsulated sensors mounted on a pair of glasses, an earring, and a smart watch. Insets in (H) show top and bottom views of the unencapsulated device. Photo credit: Seung Yun Heo, Northwestern University.

  • Fig. 2 Outdoor characterization and power consumption of blue light dosimeters.

    (A) Voltage outputs and current consumptions of an ultralow-power, blue light dosimeter (n = 1) exposed to blue light over time with constant intensity at four different intensities corresponding to low and moderate blue light conditions outdoors. The time intervals (Twake) to “wake” the devices from a sleep state when exposed to blue light with constant intensity of different levels are indicated. (B) Average current consumption assuming continuous use (Iavg) and average current consumption assuming use corresponding to 50% of available daylight (Iavg,50%) as a function of Twake. (C) Projected lifetime as a function of Twake for batteries of capacities of 140, 40, and 5.5 mA·hour assuming use corresponding to 50% of available daylight: lifetime = battery capacity/Iavg,50%.

  • Fig. 3 Indoor characterization of light-powered, accumulation mode detection blue light dosimeters.

    (A) Photograph of an indoor blue light dosimeter held between the fingertips. (B) Schematic, exploded view illustration of the constituent layers and components: BLE SoC, battery, a MOSFET (MOS), SCs (×3), blue light PDs (×10), copper interconnects (Cu/PI/Cu), and chip antenna. (C) Circuit and block diagrams of the system and its wireless interface to BLE-enabled devices for blue light monitoring indoors. (D to G) Voltage output and wake-up time interval of an indoor blue light dosimeter (n = 1) placed at a distance of 50, 100, and 150 cm from a white light phototherapy lamp (D), at a distance of 50 cm from artificial light sources (E), at a distance of 10 cm from display screens (F), and at a distance of 5 cm away from a tablet display equipped with 0, 30, 50, and 70% blue light blocking filter (G). The Twake values are labeled. Photo credit: Seung Yun Heo, Northwestern University.

  • Fig. 4 Outdoor/indoor dual-use blue light dosimeters with an automated, wireless sensitivity switching scheme.

    (A) Photographic image of a blue light dosimeter with an automated sensitivity switching scheme to allow monitoring of low-intensity blue light indoors and high-intensity blue light outdoors. (B) Circuit and block diagrams of the system with wireless switching scheme between outdoor and indoor sensing circuits based on the presence or absence of UVA irradiation. Blue light PD, MOSFET, SC, MUX, selection signal, the anode voltage of a UVA PD, and WuS are labeled BL PD, MOS, SC, MUX, S, VUVA, and WuS, respectively. (C) Voltage and 1-bit flag (0 for indoor and 1 for outdoor) outputs as a function of time without UVA exposure (blue) and with UVA exposure (yellow). (D) Voltage and 1-bit flag outputs as a function of time with daylight outdoors (yellow) and with a 60-LED ring light source (blue). Photo credit: Seung Yun Heo, Northwestern University.

  • Fig. 5 Multichannel system: Dosimeters with capabilities for simultaneous measurements in the UVA, blue, and IR.

    (A) Photograph of an ultralow-power, three-channel, UVA/blue/IR light dosimeter held between the fingertips. (B) Schematic, exploded view illustration of the constituent layers and components: the BLE SoC, battery, MOSFETs (×3 MOS), SCs (×3 SC), UVA photodiode (UVA PD), blue light PD, IR PD, copper interconnects (Cu/PI/Cu), and chip antenna. (C) Circuit and block diagrams of the adaptive, accumulation mode of detection, and wireless interface to a remote BLE radio (i.e., smartphones). (D) Photographs of a multichannel sensor mounted on earphones. (E to G) Measurements obtained from a UVA/blue/IR light dosimeter (n = 1) as a function of time during morning (E), noon (F), and afternoon (G) hours in Evanston, IL on April 2019. Photo credit: Seung Yun Heo, Northwestern University.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/12/eaay2462/DC1

    Fig. S1. EQE of the blue light PD.

    Fig. S2. Flow diagram of BLE blue light sensing system using ultralow-power sleep/wake-up capability.

    Fig. S3. Measured time intervals (Twake) between wake-up events as a function of exposure intensity.

    Fig. S4. Real-time current measurements of BLE blue light dosimeters.

    Fig. S5. Power consumption and expected lifetime of BLE dosimeters in connected mode.

    Fig. S6. Blue light dosimeters with high detection sensitivity for monitoring short-wavelength blue light from indoor lighting and display systems.

    Fig. S7. EQE of UVA and IR PDs.

    Fig. S8. Daily outdoor exposure over two cloudy days (25 July to 26 July; Evanston, IL) and two sunny days (31 July to 1 August; Evanston, IL) from 5:30 a.m. to 1:30 p.m. using a two-channel blue/UVA dosimeter.

  • Supplementary Materials

    This PDF file includes:

    • Fig. S1. EQE of the blue light PD.
    • Fig. S2. Flow diagram of BLE blue light sensing system using ultralow-power sleep/wake-up capability.
    • Fig. S3. Measured time intervals (Twake) between wake-up events as a function of exposure intensity.
    • Fig. S4. Real-time current measurements of BLE blue light dosimeters.
    • Fig. S5. Power consumption and expected lifetime of BLE dosimeters in connected mode.
    • Fig. S6. Blue light dosimeters with high detection sensitivity for monitoring short-wavelength blue light from indoor lighting and display systems.
    • Fig. S7. EQE of UVA and IR PDs.
    • Fig. S8. Daily outdoor exposure over two cloudy days (25 July to 26 July; Evanston, IL) and two sunny days (31 July to 1 August; Evanston, IL) from 5:30 a.m. to 1:30 p.m. using a two-channel blue/UVA dosimeter.

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