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arxiv: 1907.03286 · v1 · pith:2QHLGFEMnew · submitted 2019-07-07 · ⚛️ physics.flu-dyn · physics.app-ph

Leveraging viscous peeling in soft actuators and reconfigurable microchannel networks

Lior Salem , Benny Gamus , Yizhar Or , Amir D. Gat This is my paper

Pith reviewed 2026-05-25 01:23 UTC · model grok-4.3

classification ⚛️ physics.flu-dyn physics.app-ph
keywords viscous peelingsoft actuatorsmicrochannel networksreconfigurable microfluidicselastic-viscous modelsoft roboticsvalvesfluid-structure interaction
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The pith

Viscous peeling forms and activates soft actuators and reconfigurable microchannel networks including valves from millimeter-scale structures.

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

This paper shows how introducing pressurized viscous fluid at the interface between an embedded slender structure and an outer elastic solid peels the materials apart to form internal cavities. The gap size depends directly on the applied pressure, so the resulting channels and valves can be much smaller than the fabrication resolution and can change over time. A nonlinear model of the coupled elastic and viscous dynamics is derived to describe the flow and deformation. Experiments fabricate and test micron-scale valves, channel networks, and transient soft actuators, with data matching the model predictions closely. A sympathetic reader would care because this removes the need to fabricate tiny internal voids directly, simplifying creation of complex fluidic systems in soft robotics and microfluidics.

Core claim

Viscous peeling can be leveraged to create and activate soft actuators and microchannel networks, including complex elements such as valves, without the need for fabrication of structures with micron-scale internal cavities. Configurations composed of an internal slender structure embedded within another elastic solid are separated by pressurized viscous fluid at their interface. The gap between the solids is set by the externally applied pressure, allowing the characteristic size of the fluidic network to vary in time and to be much smaller than fabrication resolution. A model for the highly nonlinear elastic-viscous dynamics is presented, and experimental demonstrations of valves, networks

What carries the argument

Viscous peeling at the interface between two elastic solids, where pressurized viscous fluid creates internal cavities whose gap is controlled by the external pressure.

If this is right

  • Micron-scale valves and channel networks can be created from millimeter-scale structures.
  • The size of fluidic networks can change dynamically with pressure.
  • Transient dynamics of peeling-based soft actuators can be predicted by the elastic-viscous model.
  • Complex fluidic elements become feasible without high-resolution internal cavity fabrication.

Where Pith is reading between the lines

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

  • Adjusting pressure over time could allow the same physical device to switch between different channel configurations on demand.
  • The approach might extend to layered elastic materials beyond the slender-embedded geometry tested here.
  • Biological systems with fluid-driven separation of soft tissues could exhibit analogous peeling dynamics under pressure.

Load-bearing premise

The gap between the solids is determined solely by the externally applied pressure and the peeling dynamics are captured accurately by the nonlinear elastic-viscous model without dominant contributions from surface tension, adhesion hysteresis, or material inhomogeneities.

What would settle it

Direct measurement of channel gap versus applied pressure in a simple peeling test that shows systematic deviation from the model's predicted gap values, or functional failure of a fabricated valve due to unmodeled surface effects preventing reliable opening and closing.

Figures

Figures reproduced from arXiv: 1907.03286 by Amir D. Gat, Benny Gamus, Lior Salem, Yizhar Or.

Figure 1
Figure 1. Figure 1: FIG. 1. Viscous peeling of an embedded slender cylinder. [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2. Viscous peeling in microfluidic networks and valves. [PITH_FULL_IMAGE:figures/full_fig_p004_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3. Experimental illustration of a viscous peeling based soft actuator dynamics. [PITH_FULL_IMAGE:figures/full_fig_p006_3.png] view at source ↗
Figure 5
Figure 5. Figure 5: FIG. 5. Experimental setup for transient deformation [PITH_FULL_IMAGE:figures/full_fig_p007_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: FIG. 6. Experimental steady-state measurements of fluidic [PITH_FULL_IMAGE:figures/full_fig_p008_6.png] view at source ↗
read the original abstract

The research fields of microfluidics and soft robotics both involve complex small-scale internal channel networks, embedded within a solid structure. This work examines leveraging viscous peeling as a mechanism to create and activate soft actuators and microchannel networks, including complex elements such as valves, without the need for fabrication of structures with micron-scale internal cavities. We consider configurations composed of an internal slender structure embedded within another elastic solid. Pressurized viscous fluid is introduced into the interface between the two solids, thus peeling the two elastic structures and creating internal cavities. Since the gap between the solids is determined by the externally applied pressure, the characteristic size of the fluidic network may vary in time and be much smaller than the resolution of the fabrication method. This work presents a model for the highly nonlinear elastic-viscous dynamics governing the flow and deformation of such configurations. Fabrication and experimental demonstrations of micron-scale valves and channel-networks created from millimeter scale structures are presented, as well as the transient dynamics of viscous peeling based soft actuators. The experimental data is compared with the suggested model, showing very good agreement.

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 claims that viscous peeling, induced by introducing pressurized viscous fluid at the interface between an embedded slender structure and an elastic solid, can create and activate soft actuators and reconfigurable microchannel networks (including valves) without fabricating micron-scale internal cavities. The gap size is set by the applied pressure via a nonlinear elastic-viscous model whose predictions show very good agreement with experiments on millimeter-scale structures producing micron-scale features.

Significance. If the central claim holds, the approach would simplify fabrication of complex internal fluidic networks in soft robotics and microfluidics by allowing dynamically tunable channel sizes below fabrication resolution limits. The experimental demonstrations of functional valves and networks provide concrete evidence of utility, and the model-experiment comparison is presented as independent validation.

major comments (2)
  1. [Model derivation and assumptions] The central claim requires that the fluid gap (and thus microchannel size) is determined solely by externally applied pressure through the nonlinear elastic-viscous peeling model. At the micron scales shown in the demonstrations, surface tension, adhesion hysteresis, or material inhomogeneities could dominate the force balance or alter the peeling front, violating model closure. No analysis quantifying the relative magnitude of these effects versus the modeled terms is provided.
  2. [Experimental validation and comparison] The abstract states 'very good agreement' between model and experiment, but the manuscript does not report quantitative metrics (e.g., residuals, R², or error bars on the comparison plots), data exclusion rules, or raw measurement details. This prevents independent assessment of whether the agreement supports the predictive claim or is consistent with unmodeled effects.
minor comments (1)
  1. [Model section] Notation for the elastic and viscous parameters should be defined consistently in the model section and used uniformly in the figures.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their constructive comments, which have helped us improve the manuscript. We respond to each major comment below.

read point-by-point responses

  1. Referee: [Model derivation and assumptions] The central claim requires that the fluid gap (and thus microchannel size) is determined solely by externally applied pressure through the nonlinear elastic-viscous peeling model. At the micron scales shown in the demonstrations, surface tension, adhesion hysteresis, or material inhomogeneities could dominate the force balance or alter the peeling front, violating model closure. No analysis quantifying the relative magnitude of these effects versus the modeled terms is provided.

    Authors: We agree that a quantitative analysis of potential confounding effects such as surface tension and adhesion at micron scales is necessary to fully support the model assumptions. In the revised manuscript, we will include estimates of the capillary number and comparisons of capillary pressure to the applied pressures used in experiments, demonstrating that viscous and elastic forces dominate. We will also discuss experimental evidence regarding adhesion hysteresis. This addition will strengthen the justification for the model closure. revision: yes

  2. Referee: [Experimental validation and comparison] The abstract states 'very good agreement' between model and experiment, but the manuscript does not report quantitative metrics (e.g., residuals, R², or error bars on the comparison plots), data exclusion rules, or raw measurement details. This prevents independent assessment of whether the agreement supports the predictive claim or is consistent with unmodeled effects.

    Authors: The referee is correct that quantitative metrics for the model-experiment comparison are missing. We will revise the manuscript to report R² values, root-mean-square errors, and error bars from replicate experiments on the comparison plots. Additionally, we will provide details on data acquisition, processing, and any criteria for data inclusion or exclusion. This will allow readers to better evaluate the strength of the agreement. revision: yes

Circularity Check

0 steps flagged

No significant circularity; model and experiments are independent

full rationale

The paper derives a nonlinear elastic-viscous peeling model from first principles for the fluid-solid interaction, then validates it against separate fabrication and experimental demonstrations of valves and channel networks. No load-bearing step reduces to a fitted parameter renamed as prediction, a self-citation chain, or an ansatz smuggled via prior work by the same authors. The central claim (micron-scale channels created without micron-scale fabrication) rests on the experimental outcomes, which are described as independent of the model. The reader's provided circularity score of 2 reflects only the possibility of unmodeled effects, not any definitional or self-referential reduction in the derivation chain itself.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Based on abstract only; the nonlinear model is stated to govern the dynamics but no explicit free parameters, axioms, or invented entities are enumerated in the provided text.

pith-pipeline@v0.9.0 · 5724 in / 1108 out tokens · 22759 ms · 2026-05-25T01:23:02.111555+00:00 · methodology

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Reference graph

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