Millikelvin-resolved ambient thermography

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Science Advances  09 Dec 2020:
Vol. 6, no. 50, eabd8688
DOI: 10.1126/sciadv.abd8688
  • Fig. 1 Thermal imaging sensitized by MIT.

    (A) Schematic illustration of boosted temperature resolution of thermography by the thermal imaging sensitizer (TIS) and its working mechanism. As the object (covered with TIS) is heated up across the MIT, the TIS switches from a reflector (hence, low absorbance and low emissivity) in the insulating (I) phase to a resonator (hence, high absorbance and high emissivity) in the metallic (M) phase for mid-IR waves. (B) In contrast to conventional materials or black body, the sharp increase in thermal emissivity (ε) at the MIT of WxV1−xO2 introduces a high amplification (>15) of ΔT to ΔTIR and thus reduction in NEDT. (C) Representative temperature resolution required for ambient thermography in various applications with paradigmatic feature sizes (details in the Supplementary Materials). TIS pushes boundaries of these applications and generates new markets.

  • Fig. 2 Characterization of the TIS.

    (A) Optical image of a fabricated TIS, showing high flexibility. (B) False-colored cross section of the TIS film imaged by scanning electron microscopy (SEM) before transfer. (C) IR temperature and temperature amplification as a function of actual temperature for TIS with three selected compositions (fractions of W in the WxV1−xO2 layer). (D) Schematics and directly captured IR images of two closely placed (1-mm gap) small heaters imaged without and with TIS. (E) Calibrated temperature profiles along the dashed lines in (D). The twin-heater feature is distinctly resolved in the TIS-assisted imaging because of the ~15 times improvement of the experimental thermal sensitivity. Photo credit: Kechao Tang, University of California, Berkeley.

  • Fig. 3 TIS applied to oEA.

    (A) Enhancement of thermographic contrast on a central processing unit (CPU) by TIS, allowing differentiation of various working modes. (B) Optical and IR mappings of temperature rise because of currents flowing in adjacent circuit traces on a printed circuit board (PCB), imaged without and with TIS. (C) Extracted current versus real current in the traces. The dashed line and the shadow correspond to the ideal current extraction and ±10% deviation, respectively. The experimental error bars for the data points are comparable to the size of the points. The model used to extract currents is detailed in the Supplementary Materials. Photo credit: Kechao Tang, University of California, Berkeley.

  • Fig. 4 TIS applied to medical thermography.

    (A) RMA cells were injected at two adjacent spots to initiate the tumor growth in mice, which was then tracked by optical imaging, IR imaging without TIS, and with TIS. (B) TIS imaging reveals the two tumors in early stage after the injection when they are not yet detectable visibly or by conventional thermography. The white curves are temperature profiles across the center of the two tumors in each IR image, labeled with the amplitude of TIR variation in each curve. Photo credit: Kechao Tang, University of California, Berkeley.

Supplementary Materials

  • Supplementary Materials

    Millikelvin-resolved ambient thermography

    Kechao Tang, Kaichen Dong, Christopher J. Nicolai, Ying Li, Jiachen Li, Shuai Lou, Cheng-Wei Qiu, David H. Raulet, Jie Yao, Junqiao Wu

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    • Figs. S1 to S19
    • Table S1
    • References

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