Research ArticleBiosensors

Wireless, battery-free, flexible, miniaturized dosimeters monitor exposure to solar radiation and to light for phototherapy

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Science Translational Medicine  05 Dec 2018:
Vol. 10, Issue 470, eaau1643
DOI: 10.1126/scitranslmed.aau1643
  • Fig. 1 Millimeter-scale, battery-free, wireless sensors of UVA radiation.

    (A) Photographic images of a dosimeter for measuring UVA exposure dose in a continuous accumulation mode, bent between the thumb and index finger. The diameter, thickness, and weight of the device are 8 mm, 1.5 mm, and 110 mg, respectively. Images of the other three dosimeters show the front and back of the device. (B) Circuit diagram of the system and its wireless interface to a smartphone. The NFC chip, the MOSFET, the SC, and the photodetector are labeled NFC, MOS, SC, and PD, respectively. GND indicates ground. (C) Schematic, exploded view illustration of the constituent layers: the RF antenna (Cu coil), the NFC chip (NFC), the passive components, the UVA photodetector (PD), the SC (SC), and the insulating film (PI). (D to I) Photographic images demonstrating the flexibility of the sensor on various body parts, materials, and form factors. Insets in (F) and (I) show higher-magnification images.

  • Fig. 2 Indoor characterization of millimeter-scale, battery-free UVA dosimeters.

    (A) EQE of the UVA PD (n = 1). a.u., arbitrary units. (B) Mean photocurrent from the UVA PD (n = 3) as a function of the intensity of UVA exposure. The error bars represent SDs. (C) Mean system-level leakage current of dosimeter (n = 3) at increasing SC voltage in the dark. Measured leakage current is the current needed to maintain a constant voltage across SC. The error bars represent the SD. (D) Current-voltage response of the UVA diode (n = 1) measured in the dark. The inset is the circuit diagram of the system with an arrow indicating the UVA diode. (E) Drain current of the MOSFET (n = 1) at ON (1.5 V) and OFF (~0 V) gate biases as a function of voltage. The inset is the circuit diagram of the system with an arrow indicating the MOSFET. (F) Mean leakage current associated with the SC (n = 3). The error bars represent the SD. The inset is the circuit diagram of the system with an arrow indicating the SC. (G) Mean voltage output as a function of cumulative dose of UVA exposure. Dosimeter (n = 3) was irradiated with constant intensity over time at six different intensities. The error bars represent the SD. (H) Voltage output as a function of time of UVA exposure with constant intensity, as the device (n = 1) submerged in water is cooled from 50°C to room temperature over 50 min. Voltage and temperature readouts were wirelessly obtained every 5 min with an NFC reader antenna.

  • Fig. 3 Outdoor characterization of millimeter-scale, battery-free UVA dosimeters.

    (A) Comparison of mm-NFC UVA dosimeter measurements to those of a standard commercial dosimeter from Scienterra. The graph includes a linear fit and a 95% confidence interval (shading). The measurements are from a field trial in Rio, Brazil on 10 March 2016. Participants (n = 8) wore one mm-NFC UVA dosimeter on the thumbnail or the middle fingernail, and one commercial dosimeter on the right wrist (inset). Participants collected data every hour while engaging in recreational activities of their preference on a roof top from 8 a.m. to 3 p.m. (B) mm-NFC dosimeter measurements from participants (n = 12) in Rio, Brazil engaged in water activities at a pool. (C) Schematic illustration of study participants wearing four mm-NFC UVA dosimeters as skin-mounted devices on LBH, LOA, LIA, and RBH and one commercial dosimeter on the right wrist. (D) Map of a ~6.44-km predetermined path in St. Petersburg, Florida. Participants performed wireless measurements with a smartphone after walking north (N), east (E), west (W), and south (S) in the morning (sun in the east), in the afternoon (sun at zenith), and in the evening (sun in the west). (E) Mean dosimetry measurements using mm-NFC UVA devices as a function of time during a trial in St. Petersburg, Florida (August, 2016). Participants acquired wireless measurements from four mm-NFC UVA dosimeters on the LBH, LIA, LOA, and RBH as in (C) every 30 min (shading) with a smartphone during morning (purple; n = 13), afternoon (green; n = 9), and evening (yellow; n = 11) exercise sessions. Morning and afternoon exercise took place on the same day, and the evening exercise occurred 4 days later. The presented data omit four measurements from failed devices taken from an afternoon exercise. The error bars correspond to SDs. (F) Box-and-whisker plot with minimum, maximum (25%, 75% percentile) and mean of mm-NFC dosimeter measurements from RBH and LBH of participants (n = 13) taken from a morning exercise. (G) Box-and-whisker plot with minimum, maximum (25%, 75% percentile) and mean of mm-NFC dosimeter measurements from the RBH and LBH of participants (n = 9) captured during an afternoon exercise. Comparison of measurements collected outdoors during (H) morning (n = 13), (I) afternoon (n = 9), and (J) evening (n = 11) exercises using mm-NFC dosimeters to those obtained with a commercial dosimeter. Graphs show averages of measurements acquired after walking north, east, west, and south and linear fits of collected data. The error bars represent SDs.

  • Fig. 4 mm-NFC dosimeters with dual, independent operation in the UVA and UVB ranges.

    (A) Photographic image of a dosimeter capable of independent measurements of UVA and UVB, bent between a thumb and index finger. (B) Circuit diagram of the device. The configuration follows that of the UVA dosimeter but using two separate ADCs on a single NFC chip, two SCs (SC1, SC2), two MOSFETs (MOS2), and single GPIO for reset, and separate UVA PD (PD2) and UVB PDs (PD1 × 4). (C) EQE spectrum of a UVB PD (n = 1). (D) Output of the UVB dosimeter channel as a function of total dose of UVB (305 nm) exposure. Measurements show results for dosimeter that incorporate 10 UVB PDs (PDs), 4 PDs, and 1 PD to illustrate the scaling of the response (n = 1). (E) Photocurrent as a function of intensity of UVB (305 nm) exposure for dosimeters with 10 PDs, 4 PDs, and 1 PD (n = 1). (F) System-level leakage current of the dosimeter (n = 1). Measured leakage current is the current to maintain constant voltage. (G) Output voltages from the UVA and UVB channels (n = 1) as a function of time of exposure to a combination of UVA (365 nm) and UVB (305 nm), only UVA, or only UVB. The UVA intensity is 2.2 mW/cm2, and the UVB intensity is 0.16 mW/cm2.

  • Fig. 5 mm-NFC dosimeters for blue light phototherapy in the NICU.

    (A) Circuit diagram of the device. The configuration uses ADC1 and ADC2 on a single NFC chip to feature cumulative and instantaneous sensing, respectively. The cumulative sensing circuit follows that of the UVA dosimeter, using an SC (SC1), a MOSFET (M1), and a GPIO for reset and a blue light PD (D1). The instantaneous sensing circuit couples an Amp powered by VDDH to a blue light PD (D2). The amplified voltage response of the PD passes to the gate of M2, which has a threshold voltage of 850 mV. The sensitivity of the blue light dosimeter is optimized to correspond to threshold blue light phototherapy intensity of 30 μW/cm2. For exposure intensities 30 μW/cm2 or higher, M2 is switched to an ON state to activate a read indicator LED connected in series. Activation of the sensor by a reader antenna leads to wireless transmission of the digital output from the ADC through the NFC communication link. (B) Image of a blue light dosimeter/photometer with visual indicator of intensity threshold designed for monitoring blue light phototherapy exposures in the NICU. The diameter, thickness, and weight of this encapsulated device are 16 mm, 1.2 mm, and 0.3 g, respectively. (C) Image of a device without a visual indicator (inset) on the chest of a jaundiced infant undergoing phototherapy treatment. (D) EQE spectrum of blue PD (n = 1) with and without a layer of PI (5 μm) and absorbance spectrum profile of bilirubin. (E) Voltage measurements of blue sensor (n = 1) as a function of total dose blue light phototherapy. Dosimeter (n = 1) was irradiated with constant intensity for 60 min at 30.0 and 9.3 μW/cm2. (F) Voltage measurements of blue sensors (n = 3) as a function of blue light phototherapy intensity. Error bars represent the SD. (G) Measurements of instantaneous intensity and cumulative dosimetry from an mm-NFC device (n = 1) on the chest of a jaundiced infant throughout the course of a 20-hour phototherapy session.

  • Fig. 6 mm-NFC dosimeters with separate, independent operation at IR to the UV wavelengths.

    (A) Circuit diagram of the device and wireless communication to a smartphone. The configuration uses three separate ADCs on a single NFC chip, three SCs (SC1, SC2, and SC3), three MOSFETs (M1, M2, and M3), a single GPIO for reset and three separate photodetectors (PD1, PD2, and PD3). (B) EQE spectrum of broadband red and IR PDs (n = 1). (C) Voltage measurements from an mm-NFC sensor (n = 1) operating in the IR/red as a function of exposed energy at each corresponding wavelength range. (D) Image of an mm-NFC dosimeter with operation in the UVA/UVB/IR configured as a ring. Inset shows higher magnification. (E) Image of an mm-NFC dosimeter with operation in the UVB/red/blue as a shirt-worn badge in front of a white light phototherapy lamp. (F) Results of cumulative dosimetry using a UVB/red/blue mm-NFC device (n = 1) during exposure with different light sources, illustrating stable, separate operation across corresponding regions of the spectrum.

Supplementary Materials

  • www.sciencetranslationalmedicine.org/cgi/content/full/10/470/eaau1643/DC1

    Fig. S1. Screenshots of the smartphone application.

    Fig. S2. Millimeter-scale, battery-free, wireless sensors of UVA/UVB radiation.

    Fig. S3. Electrical characterization and simulation.

    Fig. S4. Field study results involving human participants outdoors in Rio, Brazil.

    Fig. S5. Field study results from outdoor exercise involving human participants in St. Petersburg, Florida.

    Fig. S6. Field study results from a morning exercise involving human participants in St. Petersburg, Florida.

    Fig. S7. Field study results from an afternoon exercise involving human participants in St. Petersburg, Florida.

    Fig. S8. Field study results from an evening exercise involving human participants in St. Petersburg, Florida.

    Fig. S9. UVA dosimetry measurements performed with Scienterra and an mm-NFC UVA device during time-dependent simulated shading.

    Fig. S10. Demonstration of the use of mm-NFC dosimeters with dual operations in the UVA and UVB spectrums in a clinical phototherapy unit.

    Fig. S11. Clinical utility of blue light mm-NFC dosimeters in a NICU.

    Table S1. mm-NFC dosimeters with dual operation in the UVA and UVB spectrums after UVA phototherapy in clinical phototherapy unit.

    Table S2. mm-NFC dosimeters with dual operation in the UVA and UVB spectrums after UVB phototherapy in clinical phototherapy unit.

    Table S3. Spatiotemporal map of clinical UVA phototherapy unit measured with mm-NFC dosimeters with dual operation in the UVA and UVB spectrums.

    Table S4. Spatiotemporal map of clinical UVB phototherapy unit measured with mm-NFC dosimeters with dual operation in the UVA and UVB spectrums.

  • This PDF file includes:

    • Fig. S1. Screenshots of the smartphone application.
    • Fig. S2. Millimeter-scale, battery-free, wireless sensors of UVA/UVB radiation.
    • Fig. S3. Electrical characterization and simulation.
    • Fig. S4. Field study results involving human participants outdoors in Rio, Brazil.
    • Fig. S5. Field study results from outdoor exercise involving human participants in St. Petersburg, Florida.
    • Fig. S6. Field study results from a morning exercise involving human participants in St. Petersburg, Florida.
    • Fig. S7. Field study results from an afternoon exercise involving human participants in St. Petersburg, Florida.
    • Fig. S8. Field study results from an evening exercise involving human participants in St. Petersburg, Florida.
    • Fig. S9. UVA dosimetry measurements performed with Scienterra and an mm-NFC UVA device during time-dependent simulated shading.
    • Fig. S10. Demonstration of the use of mm-NFC dosimeters with dual operations in the UVA and UVB spectrums in a clinical phototherapy unit.
    • Fig. S11. Clinical utility of blue light mm-NFC dosimeters in a NICU.
    • Table S1. mm-NFC dosimeters with dual operation in the UVA and UVB spectrums after UVA phototherapy in clinical phototherapy unit.
    • Table S2. mm-NFC dosimeters with dual operation in the UVA and UVB spectrums after UVB phototherapy in clinical phototherapy unit.
    • Table S3. Spatiotemporal map of clinical UVA phototherapy unit measured with mm-NFC dosimeters with dual operation in the UVA and UVB spectrums.
    • Table S4. Spatiotemporal map of clinical UVB phototherapy unit measured with mm-NFC dosimeters with dual operation in the UVA and UVB spectrums.

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