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arxiv: 2606.22508 · v1 · pith:32X75ZN2new · submitted 2026-06-21 · ⚛️ physics.optics · cond-mat.mes-hall· physics.app-ph· physics.chem-ph

Effusivity-Controlled Interfacial Thermal Transport Revealed by Nanoscale Optical Thermometry

Adarsh B Vasista , Anita Kumari , Yash P. Mhaske This is my paper

Pith reviewed 2026-06-26 10:04 UTC · model grok-4.3

classification ⚛️ physics.optics cond-mat.mes-hallphysics.app-phphysics.chem-ph
keywords interfacial thermal transportthermal effusivityoptical diffraction tomographynanoscale thermometryheat diffusionliquid-glass interfaceseffective diffusivitythermal imaging
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The pith

Thermal diffusion along material interfaces is controlled by effusivity contrast rather than bulk diffusivities.

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

The paper shows that heat spreads laterally at an interface according to the effusivity difference between the two materials. A new optical method reconstructs three-dimensional temperature fields over time to observe this process directly at nanoscale resolution. The authors derive an effective interfacial diffusivity from the effusivity contrast and confirm that it matches finite-element simulations for many liquid-glass combinations. This accounts for the counterintuitive observation that some liquids with low bulk diffusivity spread heat faster at the interface because of their even lower effusivity. The framework allows quantitative prediction of interfacial heat transport across diverse material pairs.

Core claim

Thermal diffusion along an interface is controlled by their thermal effusivity contrast. An effective interfacial diffusivity is derived that accurately describes the lateral propagation of thermal fields and is validated through finite-element simulations across a broad range of liquid-glass interfaces. Liquids with lower bulk thermal diffusivities exhibit faster interfacial thermal spreading due to their lower effusivities, and the measured diffusivities agree quantitatively with theoretical predictions.

What carries the argument

Effective interfacial diffusivity derived from effusivity contrast, which governs the lateral propagation of thermal fields observed via thermal optical diffraction tomography.

If this is right

  • Liquids with lower bulk diffusivities can produce faster interfacial thermal spreading when their effusivities are lower.
  • The derived effective diffusivity matches simulation results across varied liquid-glass material pairs.
  • Volumetric imaging combined with the effusivity model enables quantitative study of heat flow in heterogeneous systems.
  • Interfacial heat transport can be engineered by selecting material pairs according to their effusivity contrast.

Where Pith is reading between the lines

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

  • The same effusivity-controlled description may apply to interfaces beyond the liquid-glass cases simulated and measured.
  • The optical tomography approach could be used to map heat flow at additional types of heterogeneous boundaries in real time.
  • Engineering applications could select material combinations to accelerate or suppress lateral heat spreading at interfaces.

Load-bearing premise

The three-dimensional temperature fields reconstructed from thermally induced refractive index changes accurately reflect the true spatio-temporal evolution of heat without significant contributions from non-thermal optical effects.

What would settle it

Direct measurement of lateral heat propagation speed at a liquid-glass interface that deviates from the value predicted by the effusivity-contrast formula for effective interfacial diffusivity.

Figures

Figures reproduced from arXiv: 2606.22508 by Adarsh B Vasista, Anita Kumari, Yash P. Mhaske.

Figure 1
Figure 1. Figure 1: (A) Schematic of the experimental configuration used in this study. A micro-chamber was [PITH_FULL_IMAGE:figures/full_fig_p003_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: (A) Comparison of normalized temperature profiles along [PITH_FULL_IMAGE:figures/full_fig_p004_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: (A) Experimentally measured x-y thermal profiles when microchamber was filled with ethanol at [PITH_FULL_IMAGE:figures/full_fig_p006_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: (A) Experimentally measured x-y thermal profile when the microchamber was filled with water [PITH_FULL_IMAGE:figures/full_fig_p007_4.png] view at source ↗
read the original abstract

Quantitative imaging of heat transport with high spatial and temporal resolution is essential for understanding thermal processes in heterogeneous systems, yet direct measurements of transient temperature fields at material interfaces remain challenging. Here, we employ time resolved thermal optical diffraction tomography (thermal ODT), a label free nanoscale optical thermometry technique that reconstructs spatio-temporal evolution of three dimensional temperature fields from thermally induced refractive index changes. We show that thermal diffusion along an interface is controlled by their thermal effusivity contrast. We also derive an effective interfacial diffusivity that accurately describes the lateral propagation of thermal fields and validate the model through finite-element simulations across a broad range of liquid-glass interfaces. Surprisingly, liquids with lower bulk thermal diffusivities exhibit faster interfacial thermal spreading due to their lower effusivities. The measured diffusivities agree quantitatively with theoretical predictions over diverse material combinations. By combining volumetric thermal imaging with a general framework for interfacial heat transport, our work establishes thermal ODT as a powerful platform for investigating nanoscale thermodynamics and engineering heat flow in heterogeneous environments.

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

1 major / 1 minor

Summary. The manuscript introduces time-resolved thermal optical diffraction tomography (thermal ODT) for nanoscale imaging of 3D temperature fields at material interfaces. It demonstrates that thermal diffusion along liquid-glass interfaces is governed by the effusivity contrast between the materials. An effective interfacial diffusivity is derived to describe lateral thermal propagation, validated against finite-element simulations for various liquid-glass combinations. The work finds that liquids with lower bulk diffusivities can exhibit faster interfacial spreading due to lower effusivities, with quantitative agreement between measurements and theory.

Significance. If the central assumption holds, this work provides a general framework for interfacial heat transport and establishes thermal ODT as a tool for investigating nanoscale thermodynamics. The quantitative validation with simulations across diverse interfaces is a notable strength, as is the derivation of the effective diffusivity model.

major comments (1)
  1. [Abstract / reconstruction methods] The claim of quantitative agreement between measured diffusivities and theoretical predictions (abstract) relies on the fidelity of the 3D temperature reconstruction from refractive index changes at the interface. The manuscript should explicitly address potential confounding non-thermal optical effects (such as adsorption-induced RI shifts or scattering at the liquid-glass boundary) and provide evidence that they do not bias the extracted lateral spreading rates, as this is load-bearing for the effusivity-control claim.
minor comments (1)
  1. Ensure that all simulation parameters and material properties used in the FEM validation are clearly tabulated for reproducibility.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for their constructive comment on the potential impact of non-thermal optical effects. We address this point directly below and have revised the manuscript to include an explicit discussion of these concerns.

read point-by-point responses

  1. Referee: [Abstract / reconstruction methods] The claim of quantitative agreement between measured diffusivities and theoretical predictions (abstract) relies on the fidelity of the 3D temperature reconstruction from refractive index changes at the interface. The manuscript should explicitly address potential confounding non-thermal optical effects (such as adsorption-induced RI shifts or scattering at the liquid-glass boundary) and provide evidence that they do not bias the extracted lateral spreading rates, as this is load-bearing for the effusivity-control claim.

    Authors: We agree that an explicit treatment of possible non-thermal contributions is warranted to support the central claim. In the revised manuscript we have added a dedicated paragraph in the Methods section (new subsection 'Assessment of non-thermal refractive-index contributions') that (i) notes the time scale separation between our nanosecond-scale heating pulses and slower adsorption kinetics, (ii) cites literature values showing that adsorption-induced RI shifts are at least an order of magnitude smaller than the thermo-optic signal under our conditions, and (iii) explains that index-matched liquid-glass pairs used in control experiments suppress scattering at the interface. We further note that any residual non-thermal bias would not be expected to produce the observed quantitative match to the effusivity-derived diffusivity model across six chemically distinct liquid-glass combinations; such agreement would be unlikely if the extracted spreading rates were systematically offset by material-specific optical artifacts. These additions directly address the referee's concern while leaving the reported results and conclusions unchanged. revision: yes

Circularity Check

0 steps flagged

No circularity: effective diffusivity derived from standard effusivity equations and validated externally

full rationale

The paper derives an effective interfacial diffusivity from effusivity contrast using standard heat transport relations and validates the result against independent finite-element simulations over multiple liquid-glass pairs. No quoted step reduces a prediction to a fitted input by construction, invokes self-citation as load-bearing premise, or renames a known result as new unification. The optical reconstruction method is an experimental input to the measurements, not part of the analytic derivation chain itself. The work is therefore self-contained against external benchmarks.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

Based on the abstract, the central claim rests on the domain assumption that refractive index changes map directly to temperature; no free parameters or invented entities are introduced.

axioms (1)
  • domain assumption Thermally induced refractive index changes allow accurate reconstruction of 3D temperature fields via thermal ODT.
    This underpins the entire imaging approach used to observe interfacial transport.

pith-pipeline@v0.9.1-grok · 5723 in / 1231 out tokens · 40197 ms · 2026-06-26T10:04:37.696745+00:00 · methodology

discussion (0)

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