About

Ellen Arruda is a Professor of Mechanical Engineering at the University of Michigan and serves as the Tim Manganello/BorgWarner Department Chair in Mechanical Engineering. Her research focuses on the mechanical behavior of materials including polymers, elastomers, and soft tissue, as well as tissue engineering of tendon and muscle constructs. She is involved in constitutive modeling of growth, remodeling, and functional adaptation in soft tissue, along with deformation mechanisms in polymers and crystal transformation mechanisms in semi-crystalline polymers. Her work also includes high strain rate testing of polymers and elastomers for crashworthiness applications in automotive engineering. Arruda holds a Ph.D. in Mechanical Engineering from the Massachusetts Institute of Technology, earned in 1992, and has a background in engineering mechanics and engineering science from Pennsylvania State University. Her research contributions have been recognized through numerous awards and honors, including membership in the College of Fellows of the American Institute for Medical and Biological Engineering, the A.C. Eringen Medal from the Society of Engineering Science, and the Nadai Medal from ASME. She has been distinguished for her outstanding career in biomechanics, materials, and engineering, and has been actively involved in advancing manufacturing education and space structures research.

Research topics

• Medicine
• Materials science
• Engineering
• Anatomy
• Composite material
• Computer Science
• Data Mining
• Artificial Intelligence
• Structural engineering
• Biology
• Nanotechnology
• Biological system
• Mathematics
• Physics
• Optics
• Cell biology

Selected publications

• Interpretable data-driven modeling of pixelated linear viscoelastic metamaterials under impact loadings

  Computer Methods in Applied Mechanics and Engineering · 2026-04-10

  articleOpen accessSenior author
  PublisherDOI

• Combined Cartilage Thickness and Mechanical Property Mismatch Drives Local Strain Amplification at the Patellar Osteochondral Allograft Interface

  bioRxiv (Cold Spring Harbor Laboratory) · 2026-05-17

  articleOpen access

  Abstract Patellar osteochondral allograft (OCA) transplantation is widely used to treat large full-thickness cartilage defects, yet long-term failure and reoperation rates remain high. Although surface congruity and osseous integration are emphasized clinically, cartilage thickness and mechanical compatibility between donor and recipient are not considered. Our previous work suggests that cartilage thickness mismatch can amplify local deformation at the graft boundary, potentially compromising graft longevity. This study investigates how combined mismatches in cartilage thickness and mechanical properties influence the local strain environment at the patellar OCA interface. Simplified two-dimensional axisymmetric finite element models of patellar OCA repair were developed in ABAQUS. Donor-to-recipient cartilage thickness ratios ranging from 0.33 to 3.25 were evaluated together with donor-recipient Young’s modulus mismatches (2.5-7.0 MPa). Cartilage was modeled using homogeneous linear elastic and functionally graded material formulations to account for depth-dependent stiffness. A compressive pressure of 1.0 MPa was applied to represent patellofemoral joint loading, and peak compressive and shear strains were quantified at the graft boundary. Cartilage thickness mismatch produced localized high-strain regions (HSR) of compressive and shear strain at the donor-recipient interface that were absent in thickness-matched constructs. Strain amplification increased with both thickness and mechanical property mismatch. Compressive strain exhibited directional asymmetry, with donor-side-thicker configurations producing greater amplification than recipient-side-thicker configurations. Incorporating depth-dependent cartilage stiffness reduced peak strain magnitudes but did not eliminate mismatch-driven strain amplification. These findings demonstrate that cartilage thickness and mechanical disparity can create HSR at the patellar OCA graft boundary that may predispose grafts to impaired integration and long-term failure.

  PublisherOA PDFDOI

• Constitutive parameter inference using physics-based data-driven modeling in full volume datasets of intact and torn rotator cuff tendons

  arXiv (Cornell University) · 2026-01-14

  preprintOpen accessSenior author

  In this work, we characterized the material properties of an animal model of the rotator cuff tendon using full volume datasets of both its intact and injured states by capturing internal strain behavior throughout the tendon. Our experimental setup, involving tension along the fiber direction, activated volumetric, tensile, and shear mechanisms due to the tendon's complex geometry. We implemented an approach to model inference that we refer to as variational system identification (VSI) to solve the weak form of the stress equilibrium equation using these full volume displacements. Three constitutive models were used for parameter inference: a neo-Hookean model, a modified Holzapfel-Gasser-Ogden (HGO) model with higher-order terms in the first and second invariants, and a reduced polynomial model consisting of terms based on the first, second, and fiber-related invariants. Inferred parameters were further refined using an adjoint-based partial differential equation (PDE)-constrained optimization framework. Our results show that the modified HGO model captures the tendon's deformation mechanisms with reasonable accuracy, while the neo-Hookean model fails to reproduce key internal features, particularly the shear behavior in the injured tendon. Surprisingly, the simplified polynomial model performed comparably to the modified HGO formulation using only three terms. These findings suggest that while current constitutive models do not fully replicate the complex internal mechanics of the tendon, they are capable of capturing key trends in both intact and damaged tissue, using a homogeneous modeling approach. Continued model development is needed to bridge this gap and enable clinical-grade, predictive simulations of tendon injury and repair.

  PublisherDOI

• Experimental Realization of an Optimized Visco-elastic Auxetic Metamaterial for Enhanced Impact Mitigation

  SSRN Electronic Journal · 2026-01-01

  preprintOpen accessSenior author
  PublisherDOI

• Constitutive parameter inference using physics-based data-driven modeling in full volume datasets of intact and torn rotator cuff tendons

  ArXiv.org · 2026-01-14

  articleOpen accessSenior author

  In this work, we characterized the material properties of an animal model of the rotator cuff tendon using full volume datasets of both its intact and injured states by capturing internal strain behavior throughout the tendon. Our experimental setup, involving tension along the fiber direction, activated volumetric, tensile, and shear mechanisms due to the tendon's complex geometry. We implemented an approach to model inference that we refer to as variational system identification (VSI) to solve the weak form of the stress equilibrium equation using these full volume displacements. Three constitutive models were used for parameter inference: a neo-Hookean model, a modified Holzapfel-Gasser-Ogden (HGO) model with higher-order terms in the first and second invariants, and a reduced polynomial model consisting of terms based on the first, second, and fiber-related invariants. Inferred parameters were further refined using an adjoint-based partial differential equation (PDE)-constrained optimization framework. Our results show that the modified HGO model captures the tendon's deformation mechanisms with reasonable accuracy, while the neo-Hookean model fails to reproduce key internal features, particularly the shear behavior in the injured tendon. Surprisingly, the simplified polynomial model performed comparably to the modified HGO formulation using only three terms. These findings suggest that while current constitutive models do not fully replicate the complex internal mechanics of the tendon, they are capable of capturing key trends in both intact and damaged tissue, using a homogeneous modeling approach. Continued model development is needed to bridge this gap and enable clinical-grade, predictive simulations of tendon injury and repair.

  PublisherOA PDF

• Preliminary evaluation of full volume strain measurement in patellar cartilage following osteochondral allograft transplantation using magnetic resonance imaging

  Frontiers in Bioengineering and Biotechnology · 2026-01-07

  articleOpen access

  Introduction Articular cartilage (AC) defects of the patellofemoral joint (PFJ) are clinically challenging and mechanically demanding. Osteochondral allograft (OCA) transplantation is the standard treatment for large cartilage injuries; however, little is known about intra-tissue mechanics after transplantation. Computational models suggest that cartilage thickness mismatch concentrates stresses at donor–recipient interfaces in OCA-treated patella, but direct experimental evidence is scarce. Local cartilage strain is closely linked to tissue health; therefore, the goal of this work was to provide a preliminary, full volume assessment of patellar cartilage mechanics before and after OCA transplantation. Methods A displacement-encoded MRI sequence was used to quantify full volume displacement and strain fields in human patellar AC before and after OCA transplantation under controlled indentation. Intact cadaveric patellae (n = 4) were prepared, with three serving as recipients and one as donor. Samples were cyclically compressed in a custom-built rig using nominal displacements of 1 and 2 mm. The complex phase data were unwrapped and converted to displacements; the Green–Lagrange strain tensor was computed using a finite element framework in FEniCS. Minimum principal strain ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m1"> <mml:mrow> <mml:msub> <mml:mi>E</mml:mi> <mml:mi mathvariant="italic">min</mml:mi> </mml:msub> </mml:mrow> </mml:math> ) and maximum shear strain ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m2"> <mml:mrow> <mml:msub> <mml:mi>E</mml:mi> <mml:mrow> <mml:mi>m</mml:mi> <mml:mi>a</mml:mi> <mml:mi>x</mml:mi> <mml:mi>s</mml:mi> <mml:mi>h</mml:mi> <mml:mi>e</mml:mi> <mml:mi>a</mml:mi> <mml:mi>r</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:math> ) were analyzed. Donor–recipient step-off distance, representing cartilage-level geometric mismatch, was measured at the graft interface. Results Global displacement fields were similar between intact and OCA samples, with spherical indentation exhibiting through-thickness compression and lateral displacement in longitudinal and transverse directions. <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m3"> <mml:mrow> <mml:msub> <mml:mi>E</mml:mi> <mml:mi mathvariant="italic">min</mml:mi> </mml:msub> </mml:mrow> </mml:math> localized beneath the indenter, while <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m4"> <mml:mrow> <mml:msub> <mml:mi>E</mml:mi> <mml:mrow> <mml:mi>m</mml:mi> <mml:mi>a</mml:mi> <mml:mi>x</mml:mi> <mml:mi>s</mml:mi> <mml:mi>h</mml:mi> <mml:mi>e</mml:mi> <mml:mi>a</mml:mi> <mml:mi>r</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:math> concentrated near the articular surface. OCA-transplanted samples exhibited localized changes in strain distribution near portions of the graft rim, though these features varied across samples. Top-view percentile maps highlighted redistributed high-strain regions in some OCA samples. Exploratory step-off plots showed sample-specific directional trends between geometric mismatch and donor-recipient strain differences, though these trends were not consistent across all samples. Discussion This exploratory study provides the first experimental full volume displacement and strain distributions of patellar cartilage after OCA transplantation. The localized strain variations observed after transplantation should be interpreted descriptively, given the single-donor design and sub-physiological loading. These results establish an experimental foundation for validating computational models of the donor-recipient cartilage interaction and geometric mismatch following OCA transplantation and work investigating OCA mechanics under physiological loading.

  PublisherOA PDFDOI

• Viscoelastic Topological Mechanical Metamaterial for Broadband Vibration Isolation

  Journal of the Mechanics and Physics of Solids · 2026-05-01

  articleOpen accessCorresponding
  PublisherDOI

• Constitutive parameter inference using physics-informed full volume inverse modeling of intact and torn rotator cuff tendons

  Journal of the Mechanics and Physics of Solids · 2026-05-05

  articleOpen accessSenior author

  In this work, we characterized the material properties of an animal model of the rotator cuff tendon using full volume datasets of both its intact and injured states by capturing internal strain behavior throughout the tendon. Our experimental setup, involving tension along the fiber direction, activated volumetric, tensile, and shear mechanisms due to the tendon's complex geometry. We implemented an approach to model inference that we refer to as variational system identification (VSI) to solve the weak form of the stress equilibrium equation using these full volume displacements. Three constitutive models were used for parameter inference: a neo-Hookean model, a modified Holzapfel-Gasser-Ogden (HGO) model with higher-order terms in the first and second invariants, and a reduced polynomial model consisting of terms based on the first, second, and fiber-related invariants. Inferred parameters were further refined using an adjoint-based partial differential equation (PDE)-constrained optimization framework. Our results show that the modified HGO model captures the tendon's deformation mechanisms with reasonable accuracy, while the neo-Hookean model fails to reproduce key internal features, particularly the shear behavior in the injured tendon. Surprisingly, the simplified polynomial model performed comparably to the modified HGO formulation using only three terms. These findings suggest that while current constitutive models do not fully replicate the complex internal mechanics of the tendon, they are capable of capturing key trends in both intact and damaged tissue, using a homogeneous modeling approach. Continued model development is needed to bridge this gap and enable clinical-grade, predictive simulations of tendon injury and repair.

  PublisherDOI

• Realization of a Theoretically Optimized Visco-elastic Auxetic Metamaterial for Impact Mitigation

  SSRN Electronic Journal · 2026-01-01

  preprintOpen accessSenior author
  PublisherDOI

• Viscoelastic Topological Mechanical Metamaterial for Broadband Vibration Isolation

  SSRN Electronic Journal · 2026-01-01

  preprintOpen access
  PublisherDOI

Recent grants

• Virtual Fields Methods for Soft Musculoskeletal Tissue Characterization and Model Validation

  NSF · $429k · 2015–2018

Frequent coauthors

• Krishna Garikipati

  43 shared

• Anthony M. Waas

  University of Michigan–Ann Arbor

  40 shared

• Sofía D. Merajver

  University of Michigan–Ann Arbor

  35 shared

• Lisa M. Larkin

  University of Michigan–Ann Arbor

  34 shared

• Alejandra C. Ventura

  33 shared

• Silvia Escudero

  32 shared

• Devin T. Rosenthal

  31 shared

• Zhifen Wu

  Fujian Medical University

  30 shared

Labs

• Arruda GroupPI

Awards & honors

• Member, College of Fellows, American Institute for Medical a…
• A.C. Eringen Medal, Society of Engineering Science (2021)
• Nadai Medal, ASME (2019)
• James R. Rice Medal, Society of Engineering Science (2018)
• Member, National Academy of Engineering (2018)