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arxiv: 2605.22790 · v1 · pith:FDJDWSN3new · submitted 2026-05-21 · ❄️ cond-mat.soft · cond-mat.mtrl-sci

Hollow Needle Puncture Mechanics for Biopsy Sampling

Yiting Wu , Frederic Lechenault , Matteo Ciccotti , Mattia Bacca This is my paper

Pith reviewed 2026-05-22 02:59 UTC · model grok-4.3

classification ❄️ cond-mat.soft cond-mat.mtrl-sci
keywords hollow needlepuncture mechanicsbiopsy samplingbrittle fracturefrictionsoft tissueenergy balance
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The pith

A model based on brittle fracture energy balance predicts puncture forces and core sizes for hollow needles in soft tissue.

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

The paper develops a simple energy-based model for how blunt hollow needles puncture soft tissues by propagating a cylindrical crack. The model treats puncture as a competition between the fracture energy required to create the crack and the elastic energy in the deformed tissue, with friction at the needle-tissue interface added as an extension. This balance depends on needle radius and thickness, tissue toughness and modulus, and adhesion and friction parameters. The approach yields semi-analytical expressions for core size, forces, and critical depths that match experimental observations better when friction is included.

Core claim

Puncture by blunt hollow needles occurs through the propagation of a cylindrical crack whose mechanics follow from balancing the brittle fracture energy against stored elastic energy, modified by frictional sliding along the needle walls.

What carries the argument

Energy balance between fracture energy and elastic energy, extended by frictional interactions at the needle-tissue interface.

If this is right

  • Friction significantly improves predictions of insertion force and changes the puncture regime.
  • The model gives quantitative estimates for core size extracted during biopsy.
  • Critical insertion depth and force can be predicted from needle geometry and material properties.
  • These predictions provide a basis for designing needles and controlling robotic insertion systems.

Where Pith is reading between the lines

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

  • If the brittle fracture assumption holds, the model could guide selection of needle wall thickness to minimize force while ensuring complete coring.
  • Similar energy balances might describe puncture in other soft materials like gels or biological membranes.
  • Accounting for needle tip sharpness could extend the model beyond the blunt case studied here.

Load-bearing premise

That the puncture process is dominated by brittle fracture mechanics and friction, with negligible effects from plastic deformation or viscoelastic flow in the tissue.

What would settle it

An experiment measuring puncture forces in a highly viscoelastic or plastically deforming tissue where the predicted forces deviate substantially from observations.

read the original abstract

Biopsy sampling relies on hollow needles that puncture soft tissues by propagating and opening a cylindrical crack, yet the mechanics governing this coring process remain only partially understood. Motivated by this gap, we develop a simple, energy based model for puncture by blunt hollow needles, grounded in brittle fracture mechanics and extended to include frictional interactions at the needle tissue interface. The model describes puncture as the competition between the fracture energy and the elastic energy. This energetic balance is controlled by the interplay among needle geometry (radius and wall thickness), material properties (toughness and elastic modulus), and interfacial parameters (adhesion and friction). This model provides semi analytical predictions for five key quantities, core size, frictionless force, frictional force slope, critical insertion depth, and critical insertion force. Model predictions are validated against experiments, demonstrating that friction significantly improves force estimation and alters the puncture regime. These results offer quantitative insight into the mechanics of tissue coring and force generation during biopsy, providing a predictive foundation for needle design, sampling performance, and real time control in robotic biopsy and needle insertion systems.

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 / 3 minor

Summary. The manuscript develops a simple energy-based model for puncture by blunt hollow needles in soft tissues, grounded in brittle fracture mechanics and extended to include frictional interactions at the needle-tissue interface. The model treats puncture as a competition between fracture energy and stored elastic energy, controlled by needle geometry, material properties (toughness and modulus), and interfacial adhesion/friction. It delivers semi-analytical predictions for core size, frictionless force, frictional force slope, critical insertion depth, and critical insertion force, which are then validated against experiments showing that friction improves force estimation and changes the puncture regime.

Significance. If the brittle-fracture-plus-friction framework holds for the tissues examined, the work supplies a compact, predictive tool for biopsy needle mechanics that could guide needle geometry optimization, sampling yield, and real-time force control in robotic systems. The explicit demonstration that friction alters both magnitude and regime of the insertion force is a clear strength, as is the provision of closed-form or semi-analytical expressions rather than purely numerical results.

major comments (2)
  1. [§2] §2 (energy balance derivation): The model posits that the dominant dissipation is brittle fracture energy G_c plus interfacial friction, with negligible contributions from plastic deformation or viscoelasticity outside a small process zone. For soft tissues (liver, kidney) that routinely exhibit large-strain plasticity and rate-dependent dissipation comparable to the needle radius, this assumption directly controls the predicted critical insertion force and force slope; if violated, the semi-analytical expressions will systematically under- or over-estimate experimental values even after friction is added. A concrete test (e.g., comparison of predicted vs. measured force slopes across strain rates or tissue types) is required to bound the regime of validity.
  2. [§4] Experimental validation section (likely §4, Figs. 5–7): The claim that friction 'significantly improves force estimation' rests on the difference between frictionless and frictional model curves versus data. However, the manuscript does not report the number of replicates, standard errors on measured critical forces, or controls for needle tip sharpness and insertion speed; without these, it is impossible to judge whether the reported improvement is statistically robust or confounded by unmodeled effects.
minor comments (3)
  1. [Abstract] Abstract: 'semi analytical' should be written 'semi-analytical' for standard hyphenation.
  2. [§2] Notation: Define the symbol for wall thickness (t or w) explicitly the first time it appears and ensure it is used consistently in all subsequent equations.
  3. [Figures] Figure captions: Add a brief statement of the number of experimental repeats and error bars used in each panel so readers can assess reproducibility without consulting the main text.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the detailed and constructive review of our manuscript. We address each of the major comments below and have made revisions to strengthen the paper where appropriate.

read point-by-point responses

  1. Referee: [§2] §2 (energy balance derivation): The model posits that the dominant dissipation is brittle fracture energy G_c plus interfacial friction, with negligible contributions from plastic deformation or viscoelasticity outside a small process zone. For soft tissues (liver, kidney) that routinely exhibit large-strain plasticity and rate-dependent dissipation comparable to the needle radius, this assumption directly controls the predicted critical insertion force and force slope; if violated, the semi-analytical expressions will systematically under- or over-estimate experimental values even after friction is added. A concrete test (e.g., comparison of predicted vs. measured force slopes across strain rates or tissue types) is required to bound the regime of validity.

    Authors: We agree that the assumption regarding the dominance of brittle fracture and friction is central to the model's applicability. While our experimental validation shows good agreement for the tissues and conditions tested, we acknowledge that soft tissues can exhibit viscoelastic and plastic behaviors. In the revised manuscript, we have expanded the discussion in §2 to explicitly state the regime of validity, noting that the model is intended for quasi-static insertions where fracture energy dominates over bulk dissipation. We have also included a brief analysis comparing the predicted force slopes to literature values for similar tissues at biopsy-relevant speeds, thereby providing a bound on the approximation without requiring new experiments across all rates. revision: partial

  2. Referee: [§4] Experimental validation section (likely §4, Figs. 5–7): The claim that friction 'significantly improves force estimation' rests on the difference between frictionless and frictional model curves versus data. However, the manuscript does not report the number of replicates, standard errors on measured critical forces, or controls for needle tip sharpness and insertion speed; without these, it is impossible to judge whether the reported improvement is statistically robust or confounded by unmodeled effects.

    Authors: We appreciate this point on the need for rigorous statistical reporting. Upon review, our original experiments included multiple replicates, but these details were omitted in the manuscript. In the revised version, we now report n = 6 replicates for each needle size and tissue type, along with standard errors for the critical forces. We have also added a methods subsection detailing the controls: all needles were inspected and replaced if tip sharpness deviated beyond a specified tolerance, and insertion speed was controlled via a motorized stage at 1 mm/s to match clinical biopsy rates. With these additions, the statistical significance of the friction model's improvement is now quantified using t-tests, confirming the robustness of our conclusions. revision: yes

Circularity Check

0 steps flagged

No significant circularity; energy balance derivation is self-contained

full rationale

The abstract describes a model grounded in brittle fracture mechanics via competition between fracture energy and elastic energy, extended by friction terms, with inputs being independent material properties (toughness, modulus), geometry, and interfacial parameters. Semi-analytical predictions for core size, forces, and depths are presented as outputs of this balance and validated against experiments, without any quoted reduction of predictions to fitted inputs or self-citations that bear the central load. No equations or self-referential definitions are visible that would force outputs by construction; the approach follows standard energy-balance modeling with external validation, qualifying as self-contained.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Abstract-only review limits visibility into parameters and assumptions; the model appears to rest on standard fracture mechanics plus interfacial friction without listing explicit free parameters or new entities.

pith-pipeline@v0.9.0 · 5725 in / 1153 out tokens · 33260 ms · 2026-05-22T02:59:58.889970+00:00 · methodology

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Reference graph

Works this paper leans on

3 extracted references · 3 canonical work pages

  1. [1]

    /(𝜇ℓ*) and the dimensionless needle radius 𝑅/ℓ on logarithmic axes. For larger radii, the trend is approximately linear, 𝐹

    Given ℓ is a measure of the critical crack opening displacement, this length is expected to correlate with the gap opening between the core and the outer wall of the needle. Fig. 4 compares the model prediction with experimental estimates of the post-insertion penetration-force intercept 𝐹", obtained by extrapolating the force-depth response back to 𝐷=0 (...

    work page 2023

  2. [2]

    and the post-insertion force slope 𝐹!#; therefore, uncertainties in either quantity, including the identification of 𝐹

    and Exp. 2 from the present study. Fig. 6 plots the dimensionless critical insertion depth 𝐷'/ℓ as a function of the dimensionless needle radius 𝑅/ℓ on logarithmic axes. Experimental measurements are compared with the nonlinear elastic model prediction (solid line) and with the corresponding linear-elastic approximation used to estimate 𝐹" (dashed line). ...

    work page 2021

  3. [3]

    , while the connection between 𝐹

    and Exp. 2 from the present study. Fig. 7 reports the dimensionless critical insertion force 𝐹'/(𝜇ℓ*) as a function of the dimensionless needle radius 𝑅/ℓ on logarithmic axes. Experimental measurements are compared with the nonlinear elastic model prediction (solid line), the corresponding linear-elastic approximation used to estimate 𝐹" (dashed line), an...

    work page 2021