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arxiv: 2606.12625 · v1 · pith:4CRVE6THnew · submitted 2026-06-10 · ❄️ cond-mat.mtrl-sci · physics.app-ph· physics.ins-det

Lock-In Infrared Thermography: Phase Analysis for Rapid, Wide-Range Thermal Conductivity Measurements

Ethan A. Scott , Jeffrey L. Braun , Jessica Reyes , Bruce Bolliger , Terrence Soares , John T. Gaskins , Marko J. Tadjer , Patrick E. Hopkins This is my paper

Pith reviewed 2026-06-27 08:46 UTC · model grok-4.3

classification ❄️ cond-mat.mtrl-sci physics.app-phphysics.ins-det
keywords lock-in thermographythermal conductivityinfrared imagingphase analysisnon-contact measurementmultilayer thermal modelwide-range conductivity
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The pith

Phase analysis of lock-in infrared thermography extracts thermal conductivity across three orders of magnitude from non-contact front-side measurements.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper establishes a method that monitors the spatial phase lag in a material's temperature response to a modulated laser using an infrared camera locked to the laser frequency. This phase distribution is then fit to a multilayered thermal model to determine thermal conductivity as a fit parameter. The approach supports non-contact measurements on the front side of samples and remains insensitive to surface roughness. It applies to bulk materials and layered structures and has been demonstrated on samples ranging from approximately 1 W/m/K to more than 2000 W/m/K. A reader would care because the technique reduces the need for contact probes or permanent transducer layers while covering a broad conductivity range in one setup.

Core claim

The spatial distribution of thermal phase is captured by an infrared camera synchronized to a modulated laser heat source and is fit to a multilayered thermal model to extract thermal conductivity, enabling non-contact front-side measurements that are insensitive to surface roughness for materials spanning approximately 1 W/m/K to greater than 2000 W/m/K.

What carries the argument

The spatial phase distribution from the infrared camera fitted to a multilayered thermal model to extract thermal conductivity as a parameter.

If this is right

  • The method works for thermal conductivities spanning more than three orders of magnitude.
  • Non-contact front-side data collection is possible and remains insensitive to surface roughness.
  • Measurements apply to both bulk materials and layered structures.
  • A removable adhesive layer can be used optionally as a near-surface absorber but is not required.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • Automated scanning of the laser spot could enable spatial mapping of conductivity variations across a single sample.
  • The fitting procedure might be extended to extract thermal boundary resistance in addition to bulk conductivity.
  • The non-contact nature could support measurements on delicate or high-temperature samples where physical contact is impractical.

Load-bearing premise

The phase distribution observed by the camera matches the predictions of the multilayered thermal model without major unmodeled contributions from optical properties or surface effects.

What would settle it

A measurement on a reference material with independently known thermal conductivity yields a fitted value outside the reported uncertainty range when all other inputs are held fixed.

Figures

Figures reproduced from arXiv: 2606.12625 by Bruce Bolliger, Ethan A. Scott, Jeffrey L. Braun, Jessica Reyes, John T. Gaskins, Marko J. Tadjer, Patrick E. Hopkins, Terrence Soares.

Figure 1
Figure 1. Figure 1: FIG. 1. Schematic of experimental setup. [PITH_FULL_IMAGE:figures/full_fig_p001_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2. Example thermal phase images, as monitored by the IR camera, for 2 Hz laser modulation. The corresponding radial average of the [PITH_FULL_IMAGE:figures/full_fig_p002_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3. Fitted phase data from a bare Si wafer (a), Si wafer with PET on the polished side (b), and a Si wafer with PET on the unpolished side [PITH_FULL_IMAGE:figures/full_fig_p003_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4. Measurement parameter effects on fitted thermal conductivity. (a) Shows the effect of fit cutoff radius. (b) and (c) show the effect of [PITH_FULL_IMAGE:figures/full_fig_p004_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: FIG. 5. Comparison of measured thermal conductivity values with [PITH_FULL_IMAGE:figures/full_fig_p005_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: FIG. 6. Sensitivity, [PITH_FULL_IMAGE:figures/full_fig_p006_6.png] view at source ↗
read the original abstract

We report on a phase-based lock-in thermography approach, combined with a multilayered thermal model (often employed in thermoreflectance analysis), to measure the thermal conductivity of bulk materials and layered structures. The spatial distribution of the material's thermal phase is monitored with an infrared camera, which is locked into the frequency of a modulated laser used to heat the material. This phase distribution is then fit with a thermal model, in which properties such as thermal conductivity are extracted as fit parameters. This approach enables non-contact, front-side measurements, which are insensitive to surface roughness. The technique does not strictly require the application of a transducer layer, but we highlight the practical benefits of applying a removable adhesive layer to serve as a near-surface absorber. We demonstrate the efficacy of the method by measuring materials with thermal conductivities that span over three orders of magnitude (approximately 1 W/m/K to > 2000 W/m/K).

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 1 minor

Summary. The manuscript presents a phase-based lock-in infrared thermography technique that monitors the spatial phase distribution via IR camera under modulated laser heating and fits it to a multilayer thermal model (standard in thermoreflectance) to extract thermal conductivity as a parameter. It claims non-contact front-side measurements insensitive to surface roughness, applicability to bulk and layered structures, optional use of a removable adhesive layer as near-surface absorber, and experimental demonstration across k spanning ~1 to >2000 W/mK.

Significance. If the central extraction is shown to be robust, the method would offer a potentially rapid, wide-range, non-contact route to thermal conductivity that leverages existing multilayer models and IR imaging hardware. The claimed span over three orders of magnitude would be a notable practical strength for materials screening if supported by quantitative validation.

major comments (2)
  1. [Abstract] Abstract and method description: the central claim that the observed IR phase map is described to high accuracy by the multilayer heat-transport solution (with k as dominant free parameter) requires explicit demonstration that emissivity variations, near-surface absorption, and lateral-flow effects remain negligible or correctly parameterized across the full claimed range; this is load-bearing for k > 2000 W m^{-1} K^{-1} where the thermal diffusion length becomes large even at modest lock-in frequencies.
  2. [Abstract] Abstract: the statement that the optional adhesive layer serves as a near-surface absorber without introducing unknown interface resistance or thickness variation is asserted but not quantified; any unmodeled thermal boundary resistance would systematically bias the extracted k for all samples and must be bounded experimentally.
minor comments (1)
  1. [Abstract] The abstract would benefit from naming the specific materials measured and reporting fit residuals or uncertainty estimates to allow readers to assess the claimed accuracy.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their thorough review and valuable feedback on our manuscript. We respond to each major comment below and agree to revise the manuscript accordingly to address the concerns raised.

read point-by-point responses

  1. Referee: [Abstract] Abstract and method description: the central claim that the observed IR phase map is described to high accuracy by the multilayer heat-transport solution (with k as dominant free parameter) requires explicit demonstration that emissivity variations, near-surface absorption, and lateral-flow effects remain negligible or correctly parameterized across the full claimed range; this is load-bearing for k > 2000 W m^{-1} K^{-1} where the thermal diffusion length becomes large even at modest lock-in frequencies.

    Authors: The full manuscript provides experimental validation across the claimed range, with phase maps fitted to the multilayer model yielding consistent results. We recognize the need for more explicit checks on potential confounding effects. In the revised version, we will include additional analysis, such as frequency-dependent measurements and model sensitivity studies, to demonstrate that emissivity variations are accounted for via calibration, near-surface absorption effects are localized and avoided in fitting, and lateral heat flow is properly modeled in the 3D solution even for high-k materials where diffusion lengths are longer. revision: yes

  2. Referee: [Abstract] Abstract: the statement that the optional adhesive layer serves as a near-surface absorber without introducing unknown interface resistance or thickness variation is asserted but not quantified; any unmodeled thermal boundary resistance would systematically bias the extracted k for all samples and must be bounded experimentally.

    Authors: We agree that quantification is necessary. The adhesive layer is optional and the paper shows results both with and without it. To bound any thermal boundary resistance, we will add experimental comparisons on reference materials in the revision, providing upper limits on the interface resistance based on the fit quality and consistency with known thermal conductivity values. revision: yes

Circularity Check

0 steps flagged

No circularity: standard parameter fitting to established model

full rationale

The paper presents an experimental measurement technique that acquires spatially resolved phase data via lock-in IR thermography and fits it to a pre-existing multilayer thermal model (commonly used in thermoreflectance) to extract thermal conductivity as a fit parameter. This is inverse modeling, not a first-principles derivation or prediction that reduces to the input by construction. Validation occurs through direct experimental demonstration on materials spanning >3 orders of magnitude in k, with no self-referential equations or load-bearing self-citations that collapse the central claim. The approach is self-contained against external benchmarks.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The claim depends on the standard assumptions of heat transport modeling in layered structures and the practical implementation of locking the camera to the laser frequency.

axioms (1)
  • domain assumption Multilayered thermal diffusion model from thermoreflectance analysis accurately describes the phase response in the lock-in setup.
    The paper explicitly combines this model with the phase data fitting.

pith-pipeline@v0.9.1-grok · 5728 in / 1163 out tokens · 27302 ms · 2026-06-27T08:46:38.553330+00:00 · methodology

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Works this paper leans on

33 extracted references · 33 canonical work pages

  1. [1]

    author author T. W. \ Pfeifer , author H. B. \ Schonfeld , author E. A. \ Scott , author H. T. \ Aller , author J. T. \ Gaskins , author D. H. \ Olson , author J. L. \ Braun , author S. Graham ,\ and\ author P. E. \ Hopkins ,\ https://doi.org/10.1146/annurev-matsci-080423-010435 journal journal Annu. Rev. Mater. Res. \ ,\ pages 37 ( year 2025 ) NoStop

    work page doi:10.1146/annurev-matsci-080423-010435 2025

  2. [2]

    author author J. L. \ Braun , author B. N. \ Baines , author J. T. \ Gaskins ,\ and\ author P. E. \ Hopkins ,\ journal journal Rev. Sci. Instrum. \ volume 96 ,\ https://doi.org/10.1063/5.0267492 10.1063/5.0267492 ( year 2025 ) NoStop

    work page doi:10.1063/5.0267492 2025

  3. [3]

    author author A. J. \ Schmidt , author R. Cheaito ,\ and\ author M. Chiesa ,\ https://doi.org/10.1063/1.3212673 journal journal Rev. Sci. Instrum. \ volume 80 ,\ pages 094901 ( year 2009 ) NoStop

    work page doi:10.1063/1.3212673 2009

  4. [4]

    author author J. L. \ Braun , author D. H. \ Olson , author J. T. \ Gaskins ,\ and\ author P. E. \ Hopkins ,\ journal journal Rev. Sci. Instrum. \ volume 90 ,\ https://doi.org/10.1063/1.5056182 10.1063/1.5056182 ( year 2019 ) NoStop

    work page doi:10.1063/1.5056182 2019

  5. [5]

    author author A. U. \ Gaitonde , author A. A. \ Candadai , author J. A. \ Weibel ,\ and\ author A. M. \ Marconnet ,\ https://doi.org/10.1063/5.0149659 journal journal Rev. Sci. Instrum. \ volume 94 ,\ pages 074904 ( year 2023 ) NoStop

    work page doi:10.1063/5.0149659 2023

  6. [6]

    Bedoya , author E

    author author A. Bedoya , author E. Mar \' n , author J. J. \ Puld o \' o n ,\ and\ author C. Garc \' a-Segundo ,\ https://doi.org/10.1007/s10765-022-03138-2 journal journal Int. J. Thermophys. \ volume 44 ,\ pages 27 ( year 2023 ) NoStop

    work page doi:10.1007/s10765-022-03138-2 2023

  7. [7]

    Bedoya , author A

    author author A. Bedoya , author A. Salazar , author A. Mendioroz ,\ and\ author E. Mar \' n ,\ journal journal J. Appl. Phys. \ volume 135 ,\ https://doi.org/10.1063/5.0198882 10.1063/5.0198882 ( year 2024 ) NoStop

    work page doi:10.1063/5.0198882 2024

  8. [8]

    Salazar \ and\ author A

    author author A. Salazar \ and\ author A. Mendioroz ,\ https://doi.org/10.1016/j.ijthermalsci.2025.109928 journal journal Int. J. Therm. Sci. \ volume 214 ,\ pages 109928 ( year 2025 ) NoStop

    work page doi:10.1016/j.ijthermalsci.2025.109928 2025

  9. [9]

    Cifuentes , author A

    author author A \' A . Cifuentes , author A. Mendioroz ,\ and\ author A. Salazar ,\ https://doi.org/10.1016/j.ijthermalsci.2017.07.023 journal journal Int. J. Therm. Sci. \ volume 121 ,\ pages 305 ( year 2017 ) NoStop

    work page doi:10.1016/j.ijthermalsci.2017.07.023 2017

  10. [10]

    Kaneko , author R

    author author Y. Kaneko , author R. Fujita , author T. Ishizaki ,\ and\ author H. Nagano ,\ https://doi.org/10.1007/s10765-025-03523-7 journal journal Int. J. Thermophys. \ volume 46 ,\ pages 50 ( year 2025 ) NoStop

    work page doi:10.1007/s10765-025-03523-7 2025

  11. [11]

    Ishizaki \ and\ author H

    author author T. Ishizaki \ and\ author H. Nagano ,\ https://doi.org/10.1016/j.infrared.2019.04.023 journal journal Infrared Phys. Technol. \ volume 99 ,\ pages 248 ( year 2019 ) NoStop

    work page doi:10.1016/j.infrared.2019.04.023 2019

  12. [12]

    Jiang , author X

    author author P. Jiang , author X. Qian ,\ and\ author R. Yang ,\ journal journal J. Appl. Phys. \ volume 124 ,\ https://doi.org/10.1063/1.5046944 10.1063/1.5046944 ( year 2018 ) NoStop

    work page doi:10.1063/1.5046944 2018

  13. [13]

    author author D. J. \ Kirsch , author J. Martin , author R. Warzoha , author M. McLean , author D. Windover ,\ and\ author I. Takeuchi ,\ journal journal Rev. Sci. Instrum. \ volume 95 ,\ https://doi.org/10.1063/5.0213738 10.1063/5.0213738 ( year 2024 ) NoStop

    work page doi:10.1063/5.0213738 2024

  14. [14]

    author author D. G. \ Cahill ,\ https://doi.org/10.1063/1.1819431 journal journal Rev. Sci. Instrum. \ volume 75 ,\ pages 5119 ( year 2004 ) NoStop

    work page doi:10.1063/1.1819431 2004

  15. [15]

    author author J. L. \ Braun \ and\ author P. E. \ Hopkins ,\ journal journal J. Appl. Phys. \ volume 121 ,\ https://doi.org/10.1063/1.4982915 10.1063/1.4982915 ( year 2017 ) NoStop

    work page doi:10.1063/1.4982915 2017

  16. [16]

    Yang , author E

    author author J. Yang , author E. Ziade ,\ and\ author A. J. \ Schmidt ,\ https://doi.org/10.1063/1.4939671 journal journal Rev. Sci. Instrum. \ volume 87 ,\ pages 014901 ( year 2016 a ) NoStop

    work page doi:10.1063/1.4939671 2016

  17. [17]

    Xie , author D

    author author X. Xie , author D. Li , author T.-H. \ Tsai , author J. Liu , author P. V. \ Braun ,\ and\ author D. G. \ Cahill ,\ https://doi.org/10.1021/acs.macromol.5b02477 journal journal Macromolecules \ volume 49 ,\ pages 972 ( year 2016 ) NoStop

    work page doi:10.1021/acs.macromol.5b02477 2016

  18. [18]

    Yang , author E

    author author J. Yang , author E. Ziade ,\ and\ author A. J. \ Schmidt ,\ https://doi.org/10.1063/1.4943176 journal journal J. Appl. Phys. \ volume 119 ,\ pages 095107 ( year 2016 b ) NoStop

    work page doi:10.1063/1.4943176 2016

  19. [19]

    Wolf , author P

    author author A. Wolf , author P. Pohl ,\ and\ author R. Brendel ,\ https://doi.org/10.1063/1.1811390 journal journal J. Appl. Phys. \ volume 96 ,\ pages 6306 ( year 2004 ) NoStop

    work page doi:10.1063/1.1811390 2004

  20. [20]

    author author E. A. \ Scott , author S. W. \ Smith , author M. D. \ Henry , author C. M. \ Rost , author A. Giri , author J. T. \ Gaskins , author S. S. \ Fields , author S. T. \ Jaszewski , author J. F. \ Ihlefeld ,\ and\ author P. E. \ Hopkins ,\ journal journal Appl. Phys. Lett. \ volume 113 ,\ https://doi.org/10.1063/1.5052244 10.1063/1.5052244 ( year...

    work page doi:10.1063/1.5052244 2018

  21. [21]

    Ziade ,\ journal journal Rev

    author author E. Ziade ,\ journal journal Rev. Sci. Instrum. \ volume 91 ,\ https://doi.org/10.1063/5.0021917 10.1063/5.0021917 ( year 2020 ) NoStop

    work page doi:10.1063/5.0021917 2020

  22. [22]

    Paterson , author D

    author author J. Paterson , author D. Singhal , author D. Tainoff , author J. Richard ,\ and\ author O. Bourgeois ,\ https://doi.org/10.1063/5.0004576 journal journal J. Appl. Phys. \ volume 127 ,\ pages 245105 ( year 2020 ) NoStop

    work page doi:10.1063/5.0004576 2020

  23. [23]

    Liu \ and\ author M

    author author W. Liu \ and\ author M. Asheghi ,\ https://doi.org/10.1115/1.2130403 journal journal J. Heat Transfer \ volume 128 ,\ pages 75 ( year 2005 ) NoStop

    work page doi:10.1115/1.2130403 2005

  24. [24]

    Cancellieri , author E

    author author C. Cancellieri , author E. A. \ Scott , author J. Braun , author S. W. \ King , author R. Oviedo , author C. Jezewski , author J. Richards , author F. La Mattina , author L. P. H. \ Jeurgens ,\ and\ author P. E. \ Hopkins ,\ journal journal J. Appl. Phys. \ volume 128 ,\ https://doi.org/10.1063/5.0019907 10.1063/5.0019907 ( year 2020 ) NoStop

    work page doi:10.1063/5.0019907 2020

  25. [25]

    author author E. A. \ Scott , author J. L. \ Braun , author K. Hattar , author J. D. \ Sugar , author J. T. \ Gaskins , author M. Goorsky , author S. W. \ King ,\ and\ author P. E. \ Hopkins ,\ https://doi.org/10.1063/5.0038972 journal journal J. Appl. Phys. \ volume 129 ,\ pages 055307 ( year 2021 ) NoStop

    work page doi:10.1063/5.0038972 2021

  26. [26]

    Yang , author C

    author author J. Yang , author C. Maragliano ,\ and\ author A. J. \ Schmidt ,\ https://doi.org/10.1063/1.4824143 journal journal Rev. Sci. Instrum. \ volume 84 ,\ pages 104904 ( year 2013 ) NoStop

    work page doi:10.1063/1.4824143 2013

  27. [27]

    Mendioroz , author R

    author author A. Mendioroz , author R. Fuente-Dacal , author E. Api n \ n aniz ,\ and\ author A. Salazar ,\ https://doi.org/10.1063/1.3176467 journal journal Rev. Sci. Instrum. \ volume 80 ,\ pages 074904 ( year 2009 ) NoStop

    work page doi:10.1063/1.3176467 2009

  28. [28]

    Fabbri \ and\ author P

    author author L. Fabbri \ and\ author P. Fenici ,\ https://doi.org/10.1063/1.1146443 journal journal Rev. Sci. Instrum. \ volume 66 ,\ pages 3593 ( year 1995 ) NoStop

    work page doi:10.1063/1.1146443 1995

  29. [29]

    Cheaito , author J

    author author R. Cheaito , author J. T. \ Gaskins , author M. E. \ Caplan , author B. F. \ Donovan , author B. M. \ Foley , author A. Giri , author J. C. \ Duda , author C. J. \ Szwejkowski , author C. Constantin , author H. J. \ Brown-Shaklee , author J. F. \ Ihlefeld ,\ and\ author P. E. \ Hopkins ,\ https://doi.org/10.1103/PhysRevB.91.035432 journal jo...

    work page doi:10.1103/physrevb.91.035432 2015

  30. [30]

    author author H. T. \ Aller , author J. A. \ Malen ,\ and\ author A. J. H. \ McGaughey ,\ https://doi.org/10.1103/PhysRevApplied.15.064043 journal journal Phys. Rev. Appl. \ volume 15 ,\ pages 064043 ( year 2021 ) NoStop

    work page doi:10.1103/physrevapplied.15.064043 2021

  31. [31]

    Monachon , author L

    author author C. Monachon , author L. Weber ,\ and\ author C. Dames ,\ https://doi.org/10.1146/annurev-matsci-070115-031719 journal journal Annu. Rev. Mater. Res. \ ,\ pages 433 ( year 2016 ) NoStop

    work page doi:10.1146/annurev-matsci-070115-031719 2016

  32. [32]

    Jiang , author M

    author author F. Jiang , author M. Ryu , author V. Pachauri , author S. Ingebrandt , author X. T. \ Vu ,\ and\ author J. Morikawa ,\ https://doi.org/10.1063/5.0160602 journal journal Rev. Sci. Instrum. \ volume 94 ,\ pages 094903 ( year 2023 ) NoStop

    work page doi:10.1063/5.0160602 2023

  33. [33]

    Alasli , author R

    author author A. Alasli , author R. Iguchi , author K.-i. \ Uchida ,\ and\ author H. Nagano ,\ https://doi.org/10.1063/5.0245566 journal journal Appl. Phys. Lett. \ volume 126 ,\ pages 044102 ( year 2025 ) NoStop

    work page doi:10.1063/5.0245566 2025