Recognition: unknown
Droplet-LNO: Physics-Informed Laplace Neural Operators for Accurate Prediction of Droplet Spreading Dynamics on Complex Surfaces
Pith reviewed 2026-05-10 01:02 UTC · model grok-4.3
The pith
A physics-informed Laplace neural operator learns to predict droplet spreading dynamics on varied surfaces by embedding exponential transient behavior directly into its architecture.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
Through the Laplace integral transform serving as a learned physics-informed functional basis, PI-LNO natively represents the exponential transient dynamics of droplet spreading. When trained with a physics-regularized loss that combines data fidelity terms (MSE, MAE, RMSE) and constraints drawn from the Navier-Stokes and Cahn-Hilliard equations plus causality conditions, the architecture produces predictions that remain consistent with the underlying multiphysics on complex surfaces.
What carries the argument
The Laplace integral transform function, used as a learned physics-informed functional basis that directly encodes the exponential time-domain decay and transient response of the spreading process.
If this is right
- Droplet morphology and contact-line motion can be obtained in seconds rather than hours for each new surface condition.
- Physical consistency with fluid dynamics and phase-field equations holds across the full range of tested contact angles without separate correction steps.
- Rapid exploration of spreading behavior becomes feasible for applications such as inkjet printing and spray cooling on varied substrates.
- The same operator architecture can be retrained on additional CFD datasets to extend coverage to new surface textures or fluid properties.
Where Pith is reading between the lines
- The same Laplace-basis construction could be applied to other transient multiphysics problems that exhibit exponential relaxation, such as certain heat-transfer or viscoelastic flows.
- If inference remains stable, the model might support real-time feedback loops in microfluidic control systems where full CFD is too slow.
- Operator learning that incorporates integral transforms may offer a route to respect causality and decay properties in a wider class of physical systems without explicit time-stepping.
Load-bearing premise
That embedding Navier-Stokes, Cahn-Hilliard, and causality constraints inside a single composite loss is sufficient to enforce physical consistency and generalization across surfaces without hidden data-specific biases or post-training corrections.
What would settle it
Generate a new CFD simulation for an unseen surface geometry with contact angle inside the training range, run the trained PI-LNO forward pass, and check whether the predicted velocity and pressure fields satisfy the Navier-Stokes equations to within discretization error; repeated large violations would falsify the claim of enforced physical consistency.
read the original abstract
Spreading of liquid droplets on solid substrates constitutes a classic multiphysics problem with widespread applications ranging from inkjet printing, spray cooling, to biomedical microfluidic systems. Yet, accurate computational fluid dynamic (CFD) simulations are prohibitively expensive, taking more than 18 to 24 hours for each transient computation. In this paper, Physics-Informed Laplace Operator Neural Network (PI-LNO) is introduced, representing a novel architecture where the Laplace integral transform function serves as a learned physics-informed functional basis. Extensive comparative benchmark studies were performed against five other state-of-the-art approaches: UNet, UNet with attention modules (UNet-AM), DeepONet, Physics-Informed UNet (PI-UNet), and Laplace Neural Operator (LNO). Through complex Laplace transforms, PI-LNO natively models the exponential transient dynamics of the spreading process. A TensorFlow-based PI-LNO is trained on multi-surface CFD data spanning contact angles $\theta_s \epsilon [20,160]$, employing a physics-regularized composite loss combining data fidelity (MSE, MAE, RMSE) with Navier-Stokes, Cahn-Hilliard, and causality constraints.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript introduces the Physics-Informed Laplace Neural Operator (PI-LNO), a neural operator architecture that employs the Laplace integral transform as a learned physics-informed functional basis for predicting the transient spreading dynamics of liquid droplets on solid substrates with varying contact angles. The model is trained on multi-surface CFD data for contact angles in [20,160] using a composite loss that combines data-fidelity terms (MSE, MAE, RMSE) with constraints from the Navier-Stokes and Cahn-Hilliard equations plus causality. It is benchmarked against UNet, UNet-AM, DeepONet, PI-UNet, and LNO, with the central claim that complex Laplace transforms allow PI-LNO to natively capture the exponential transient behavior of the spreading process.
Significance. If the accuracy and generalization claims are substantiated with quantitative evidence, the work could meaningfully accelerate multiphysics simulations of droplet dynamics that currently require 18-24 hours per CFD run, with relevance to inkjet printing, spray cooling, and microfluidics. The integration of a Laplace-based functional basis with physics constraints represents a potentially useful direction for operator learning on transient nonlinear PDE systems, though the manuscript does not yet demonstrate that this basis independently encodes the target dynamics.
major comments (3)
- [Abstract and §1] Abstract and §1 (central claim): The assertion that 'Through complex Laplace transforms, PI-LNO natively models the exponential transient dynamics of the spreading process' is not supported by any derivation showing how the Laplace integral transform produces exponential solutions for the nonlinear coupled Navier-Stokes + Cahn-Hilliard system. The exponential character could arise from the data term or the composite loss rather than the transform layer itself; a concrete mapping from the learned Laplace basis to the transient form of the droplet equations is required.
- [Abstract and benchmark section] Abstract and benchmark section: The manuscript states that 'extensive comparative benchmark studies' were performed against five baselines yet supplies no quantitative error metrics (e.g., L2 errors, relative errors, or convergence rates), no tables of performance numbers, and no mention of training/validation splits or generalization across surfaces. Without these data it is impossible to verify that PI-LNO supports the accuracy claims or outperforms the baselines in a load-bearing way.
- [Training and loss description] Training and loss description: The physics-regularized composite loss is described as combining data fidelity with Navier-Stokes, Cahn-Hilliard, and causality constraints, but no explicit weighting schedule, enforcement mechanism, or ablation study is provided to demonstrate that the physics terms enforce consistency independently of the CFD training data. This leaves open the possibility that outputs reduce to data-driven fits rather than independent physics-informed predictions.
minor comments (1)
- [Abstract] Notation: The contact-angle range is written as '$θ_s ε [20,160]$'; this should be corrected to the standard set notation '$θ_s ∈ [20,160]$'.
Simulated Author's Rebuttal
We thank the referee for their thorough and constructive review of our manuscript on the Physics-Informed Laplace Neural Operator (PI-LNO) for droplet spreading dynamics. We address each major comment point by point below, providing clarifications and committing to revisions that strengthen the substantiation of our claims without misrepresenting the work.
read point-by-point responses
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Referee: [Abstract and §1] Abstract and §1 (central claim): The assertion that 'Through complex Laplace transforms, PI-LNO natively models the exponential transient dynamics of the spreading process' is not supported by any derivation showing how the Laplace integral transform produces exponential solutions for the nonlinear coupled Navier-Stokes + Cahn-Hilliard system. The exponential character could arise from the data term or the composite loss rather than the transform layer itself; a concrete mapping from the learned Laplace basis to the transient form of the droplet equations is required.
Authors: We acknowledge that the manuscript would benefit from a more explicit explanation of how the complex Laplace transform serves as a functional basis for the exponential transients in this nonlinear system. The transform is chosen because it maps decaying exponential behaviors to algebraic forms in the s-domain, enabling efficient representation of the spreading dynamics; for the coupled nonlinear PDEs this is realized through the learned operator combined with the physics loss. To address the concern directly, we will revise the abstract slightly for precision and add a new paragraph in the methods section with a step-by-step rationale, including the linearised droplet equation case where the mapping is exact, while noting the role of data and loss in the full nonlinear setting. revision: yes
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Referee: [Abstract and benchmark section] Abstract and benchmark section: The manuscript states that 'extensive comparative benchmark studies' were performed against five baselines yet supplies no quantitative error metrics (e.g., L2 errors, relative errors, or convergence rates), no tables of performance numbers, and no mention of training/validation splits or generalization across surfaces. Without these data it is impossible to verify that PI-LNO supports the accuracy claims or outperforms the baselines in a load-bearing way.
Authors: We agree that the benchmark results require clearer quantitative presentation to allow verification. Although the abstract references the studies against UNet, UNet-AM, DeepONet, PI-UNet, and LNO, specific error metrics, tables, data splits, and generalization details were not included in the main text. We will revise the manuscript to add a dedicated results table reporting L2 errors, relative errors, and other metrics for all methods across the contact angle range [20,160], explicitly describe the training/validation/test splits, and include generalization performance on held-out surfaces. revision: yes
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Referee: [Training and loss description] Training and loss description: The physics-regularized composite loss is described as combining data fidelity with Navier-Stokes, Cahn-Hilliard, and causality constraints, but no explicit weighting schedule, enforcement mechanism, or ablation study is provided to demonstrate that the physics terms enforce consistency independently of the CFD training data. This leaves open the possibility that outputs reduce to data-driven fits rather than independent physics-informed predictions.
Authors: We thank the referee for highlighting this gap in the loss description. The composite loss combines the data terms (MSE, MAE, RMSE) with the physics residuals from the Navier-Stokes and Cahn-Hilliard equations plus a causality penalty, but we agree that explicit weights, enforcement details, and an ablation are needed to demonstrate the physics contribution. We will revise the training section to specify the weighting schedule (e.g., data fidelity weight of 1.0 and physics terms at 0.05–0.1), clarify enforcement via automatic differentiation on the predicted fields, and add an ablation study comparing the full PI-LNO to a data-only variant. revision: yes
Circularity Check
No significant circularity in derivation chain
full rationale
The provided manuscript text introduces PI-LNO with the Laplace integral transform as a learned functional basis, trained on external multi-surface CFD data using a composite loss that includes data terms (MSE/MAE/RMSE) plus Navier-Stokes, Cahn-Hilliard, and causality constraints. The central claim that complex Laplace transforms 'natively model the exponential transient dynamics' is asserted as an architectural property but is not accompanied by any quoted equations or steps that reduce the claim to a fitted input, self-definition, or self-citation chain by construction. No uniqueness theorems, ansatzes smuggled via prior self-work, or renamings of known results are exhibited. The approach is benchmarked against independent baselines (UNet, DeepONet, etc.), and the physics constraints serve as regularization rather than forcing the output to equal the input data term. The derivation remains self-contained against external CFD benchmarks.
Axiom & Free-Parameter Ledger
free parameters (1)
- Contact angle training range =
[20,160]
axioms (1)
- domain assumption Navier-Stokes and Cahn-Hilliard equations plus causality constraints govern droplet spreading dynamics
invented entities (1)
-
Laplace integral transform function as learned physics-informed functional basis
no independent evidence
Reference graph
Works this paper leans on
-
[1]
Chakraborty, Microfluidics and Microscale Transport Processes
S. Chakraborty, Microfluidics and Microscale Transport Processes. CRC Press, 2012
2012
-
[2]
REVIEW PDMS microfluidics: A mini review,
R. M. Kiran and S. Chakraborty, “REVIEW PDMS microfluidics: A mini review,” 2020, doi: 10.1002/app.48958
-
[3]
J. M. Acosta-Cuevas, M. A. García -Ramírez, G. Hinojosa-Ventura, Á. J. Martínez -Gómez, V. H. Pérez -Luna, and O. González -Reynoso, “Surface Roughness Analysis of Microchannels Featuring Microfluidic Devices Fabricated by Three Different Materials and Methods,” Coatings, vol. 13, no. 10, p. 1676, Sep. 2023, doi: 10.3390/coatings13101676
-
[4]
Effect of wall roughness on performance of microchannel applied in microfluidic device,
J. Jia, Q. Song, Z. Liu, and B. Wan g, “Effect of wall roughness on performance of microchannel applied in microfluidic device,” Microsyst. Technol., vol. 25, no. 6, pp. 2385– 2397, Jun. 2019, doi: 10.1007/s00542-018-4124-7
-
[5]
Roughness Induced Boundary Slip in Microchannel Flows,
C. Kunert and J. Harting, “Roughness Induced Boundary Slip in Microchannel Flows,” Phys. Rev. Lett., vol. 99, no. 17, p. 176001, Oct. 2007, doi: 10.1103/PhysRevLett.99.176001
-
[6]
Influence of surface roughness on the fluid flow in microchannel,
Y. Li, Z. Zhang, Y. Ji, L. Wang, and D. Li, “Influence of surface roughness on the fluid flow in microchannel,” J. Phys. Conf. Ser. , vol. 27 40, no. 1, p. 012059, Apr. 2024, doi: 10.1088/1742-6596/2740/1/012059
-
[7]
D. Quéré, “Wetting and Roughness,” Annu. Rev. Mater. Res., vol. 38, no. Volume 38, 2008, pp. 71–99, Aug. 2008, doi: 10.1146/annurev.matsci.38.060407.132434
-
[8]
Surface Roughness - Hydrophobicity Coupling in Microchannel and Nanochannel Flows,
M. Sbragaglia, R. Be nzi, L. Biferale, S. Succi, and F. Toschi, “Surface Roughness - Hydrophobicity Coupling in Microchannel and Nanochannel Flows,” Phys. Rev. Lett. , vol. 97, no. 20, p. 204503, Nov. 2006, doi: 10.1103/PhysRevLett.97.204503
-
[9]
Simra: Using crowdsourcing to identify near miss hotspots in bicycle traffic,
J. Huang, L. J. Segura, T. Wang, G. Zhao, H. Sun, and C. Zhou, “Unsupervised learning for the droplet evolution prediction and process dynamics understanding in inkjet printing,” Addit. Manuf., vol. 35, p. 101197, Oct. 2020, doi: 10.1016/j.addma.2020.101197
-
[10]
Detached Eddy Simulation (DES) of Co-Current Spray Dryer,
Muhammad Noor Intan Shafinas, M. N. I. Shafinas, Jolius Gimbun, and G. Jolius, “Detached Eddy Simulation (DES) of Co-Current Spray Dryer,” Jan. 2013
2013
-
[11]
Development and future of droplet microfluidics,
L. Nan, H. Zhang, D. A. Weitz, and H. Cheung Shum, “Development and future of droplet microfluidics,” Lab. Chip, vol. 24, no. 5, pp. 1135–1153, 2024, doi: 10.1039/D3LC00729D
-
[12]
X. Wang, B.-B. Wang, B. Deng, and Z.-M. Xu, “Superior droplet bouncing, anti-icing/anti- frosting and self-cleaning performance of an outstanding superhydrophobic PTFE coating,” Cold Reg. Sci. Technol. , vol. 224, p. 104229, Aug. 2024, doi: 10.1016/j.coldregions.2024.104229
-
[13]
Design of Anti-Icing Coatings Using Supercooled Droplets As Nano-to-Microscale Probes | Langmuir
“Design of Anti-Icing Coatings Using Supercooled Droplets As Nano-to-Microscale Probes | Langmuir.” Accessed: Apr. 07, 2026. [Online]. Available: https://pubs.acs.org/doi/10.1021/la2034565
-
[14]
Atomization characteristics and instabilities in the combustion of multi -component fuel droplets with high volatility differential | Scientific Reports
“Atomization characteristics and instabilities in the combustion of multi -component fuel droplets with high volatility differential | Scientific Reports.” Accessed: Apr. 07, 2026. [Online]. Available: https://www.nature.com/articles/s41598-017-09663-7
2026
-
[15]
A. Heydari, M. Zabetian Targhi, I. Halvaei, and R. Nosrati, “A novel microfluidic device with parallel channels for sperm separation using spermatozoa intrinsic behaviors,” Sci. Rep., vol. 13, no. 1, p. 1185, Jan. 2023, doi: 10.1038/s41598-023-28315-7
-
[16]
Recent advances of droplet -based microfluidics for engineering artificial cells,
S. Fasciano and S. Wang, “Recent advances of droplet -based microfluidics for engineering artificial cells,” SLAS Technol. , vol. 29, no. 2, p. 100090, Apr. 2024, doi: 10.1016/j.slast.2023.05.002
-
[17]
O. Arjmandi-Tash, N. M. Kovalchuk, A. Trybala, I. V. Kuchin, and V. Starov, “Kinetics of Wetting and Spreading of Droplets over Various Substrates,” Langmuir, vol. 33, no. 18, pp. 4367–4385, May 2017, doi: 10.1021/acs.langmuir.6b04094
-
[18]
H. Tran, Z. He, P. Pirdavari, and M. Y. Pack, “Interp lay of Drop Shedding Mechanisms on High Wettability Contrast Biphilic Stripe-Patterned Surfaces,” Langmuir, vol. 39, no. 48, pp. 17551–17559, Dec. 2023, doi: 10.1021/acs.langmuir.3c03042
-
[19]
S. K. Sethi, R. Gogoi, A. Verma, and G. Manik, “How can the geo metry of a rough surface affect its wettability? - A coarse-grained simulation analysis,” Prog. Org. Coat., vol. 172, p. 107062, Nov. 2022, doi: 10.1016/j.porgcoat.2022.107062
-
[20]
Wettability of porous surfaces,
A. B. D. Cassie and S. Baxter, “Wettability of porous surfaces,” Trans. Faraday Soc., vol. 40, no. 0, pp. 546–551, Jan. 1944, doi: 10.1039/TF9444000546
-
[21]
Two types of Cassie -to-Wenzel wetting transitions on superhydrophobic surfaces during drop impact,
C. Lee et al. , “Two types of Cassie -to-Wenzel wetting transitions on superhydrophobic surfaces during drop impact,” Soft Matter, vol. 11, no. 23, pp. 4592–4599, 2015
2015
-
[22]
E. Ezzatneshan and A. Khosroabadi, “Droplet spreading dynamics on hydrophobic textured surfaces: A lattice Boltzmann study,” Comput. Fluids, vol. 231, p. 105063, Dec. 2021, doi: 10.1016/j.compfluid.2021.105063
-
[23]
Injection continuous liquid interface production of 3D objects,
G. Lipkowitz et al., “Injection continuous liquid interface production of 3D objects,” Sci. Adv., vol. 8, no. 39, p. eabq3917, Sep. 2022, doi: 10.1126/sciadv.abq3917
-
[24]
An Experimental Method for Three-Dimensional Dynamic Contact Angle Analysis,
D. Baptista, L. Muszyński, D. J. Gardner, and E. Atzema, “An Experimental Method for Three-Dimensional Dynamic Contact Angle Analysis,” J. Adhes. Sci. Technol., vol. 26, no. 18–19, pp. 2199–2215, Oct. 2012, doi: 10.1163/156856111X610135
-
[25]
J. Chen, F. Yang, K. Luo, Y. Wu, C. Niu, and M. Rong, “Study on contact spots of fractal rough surfaces based on three-dimensional Weierstrass-Mandelbrot function,” in 2016 IEEE 62nd Holm Conference on Electrical Contacts (Holm) , Oct. 2016, pp. 198 –204. doi: 10.1109/HOLM.2016.7780032
-
[26]
X. Hu, Q. Ma, P. Zhao, and X. Wang, “Physics-aware neural operator for high-fidelity fluid dynamics modeling with geometric and spectral priors,” Phys. Fluids , vol. 37, no. 11, p. 115111, Nov. 2025, doi: 10.1063/5.0299765
-
[27]
J. He, S. Kushwaha, J. Park, S. Koric, D. Abueidda, and I. Jasiuk, “Sequential Deep Operator Networks (S -DeepONet) for predicting full -field solutions under time -dependent loads,” Eng. Appl. Artif. Intell., vol. 127, p. 107258, Jan. 2024, doi: 10.1016/j.engappai.2023.107258
-
[28]
Fourier Neural Operator for Parametric Partial Differential Equations
Z. Li et al., “Fourier Neural Operator for Parametric Partial Differential Equations,” May 17, 2021, arXiv: arXiv:2010.08895. doi: 10.48550/arXiv.2010.08895
work page internal anchor Pith review doi:10.48550/arxiv.2010.08895 2021
-
[29]
Prediction of turbulent channel flow using Fourier neural operator-based machine-learning strategy,
Y. Wang, Z. Li, Z. Yuan, W. Peng, T. Liu, and J. Wang, “Prediction of turbulent channel flow using Fourier neural operator-based machine-learning strategy,” Phys. Rev. Fluids, vol. 9, no. 8, p. 084604, Aug. 2024, doi: 10.1103/PhysRevFluids.9.084604
-
[30]
Confidence in Assurance 2.0 Cases
“UNet++: A Nested U -Net Architecture for Medical Image Segmentation | SpringerLink.” Accessed: Jul. 25, 2024. [Online]. Available: https://link.springer.com/chapter/10.1007/978- 3-030-00889-5_1
-
[31]
Z. ( 朱智杰) Zhu, G. ( 赵国庆) Zhao, and Q. ( 招启军) Zhao, “Fast and high -precision compressible flowfield inference method of transonic airfoils based on attention UNet,” Phys. Fluids, vol. 36, no. 3, p. 036111, Mar. 2024, doi: 10.1063/5.0188550
-
[32]
Lattice-Boltzmann-Driven Physics-Informed Neural Networks for Droplet Wettability on Rough Surfaces
G. S. Meshram, P. P. Chakrabarti, and S. Chakraborty, “Lattice-Boltzmann-Driven Physics- Informed Neural Networks for Droplet Wettability on Rough Surfaces,” Apr. 03, 2026, arXiv: arXiv:2604.03481. doi: 10.48550/arXiv.2604.03481
work page internal anchor Pith review Pith/arXiv arXiv doi:10.48550/arxiv.2604.03481 2026
-
[33]
Operator Learning: A Statistical Perspective
U. Subedi and A. Tewari, “Operator Learning: A Statistical Perspective”
-
[34]
Fourier neural operator with boundary conditions for efficient prediction of steady airfoil flows,
Y. Dai, Y. An, Z. Li, J. Zhang, and C. Yu, “Fourier neural operator with boundary conditions for efficient prediction of steady airfoil flows,” Appl. Math. Mech., vol. 44, no. 11, pp. 2019– 2038, Nov. 2023, doi: 10.1007/s10483-023-3050-9
-
[35]
L. Li, W. Zhang, Y. Li, C. Jiang, and Y. Wang, “An attention -enhanced Fourier neural operator model for predicting flow fields in turbomachinery Cascades,” Phys. Fluids, vol. 37, no. 3, p. 036121, Mar. 2025, doi: 10.1063/5.0254681
-
[36]
H. Qu, X. Zheng, L. Yang, and Z. Song, “Fourier neural operator for high -resolution fluid flow simulation based on low -resolution data: the vorticity equation as an example,” Acta Oceanol. Sin., vol. 44, no. 6, pp. 165–177, Jun. 2025, doi: 10.1007/s13131-024-2453-1
-
[37]
K. Kontolati, S. Goswami, G. Em Karniadakis, and M. D. Shields, “Learning nonlinear operators in latent spaces for real-time predictions of complex dynamics in physical systems,” Nat. Commun., vol. 15, no. 1, p. 5101, Jun. 2024, doi: 10.1038/s41467-024-49411-w
-
[38]
Operator Learning for Reconstructing Flow Fields from Sparse Measurements:
Q. Zhang, D. Krotov, and G. E. Karniadakis, “Operator learning for reconstructing flow fields from sparse measurements: An energy transformer approach,” J. Comput. Phys., vol. 538, p. 114148, Oct. 2025, doi: 10.1016/j.jcp.2025.114148
-
[39]
Q. Wang, L. Song, T. Liu, and Z. Guo, “Enhancing generalization in endwall film cooling prediction: Incorporating the superposition principle into transformer -based neural operators,” Phys. Fluids, vol. 36, no. 12, p. 126110, Dec. 2024, doi: 10.1063/5.0239483
-
[40]
S. K. Boya and D. Subramani, “A physics-informed transformer neural operator for learning generalized solutions of initial boundary value problems,” May 14, 2025, arXiv: arXiv:2412.09009. doi: 10.48550/arXiv.2412.09009
-
[41]
Scaling the predictions of multiphase flow through porous media using operator learning,
N. Jain, S. Roy, H. Kodamana, and P. Nair, “Scaling the predictions of multiphase flow through porous media using operator learning,” Chem. Eng. J., vol. 503, p. 157671, Jan. 2025, doi: 10.1016/j.cej.2024.157671
-
[42]
Géron, Hands-On Machine Learning with Scikit-Learn , Keras , and
A. Géron, Hands-On Machine Learning with Scikit-Learn , Keras , and. O’Reilly Media
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