Nature Materials

When migratory cells move from one stiffness niche to another in vivo, they are exposed to highly confined spaces imposed by dense extracellular matrix (ECM) networks and inter-tissue boundaries. Cells that originate from one niche possess distinct mechanosensitive adaptations that influence their response to their new niche, a concept known as mechanical memory. However, the mechanisms by which this memory is acquired, and the degree to which it influences migratory potential and decision-making processes in confinement remain poorly understood. Here, we combine stiffness priming using polyacrylamide hydrogels with a confinement platform to screen mechanical memory across healthy and transformed cells. Using a dose-and- passage approach, we find that in stiffness-sensitive cells primed on soft substrates navigate confinement more efficiently. Bulk RNA sequencing identifies NFATC2 as a transcription factor that mediates mechanical memory by reprogramming gene expression in stiffness-sensitive cells. siRNA-induced knockdown of NFATC2 in memory-sensitive cells confirmed its necessity for mechanical memory acquisition and subsequent confined migration enhancement. Interestingly, highly invasive cancer cells exhibit minimal sensitivity to prior mechanical priming, suggesting differential adaptation strategies. These findings reveal mechanical memory as a cell-intrinsic property shaped by past mechanical environments and highlight potential implications for controlling migration in wound repair, fibrosis, and disease progression.

The mechanical properties of the extracellular matrix (ECM) determine cell differentiation, proliferation and migration through mechanoresponsive proteins including YAP. However, how different mechanical signals cooperate, synergize or compete to steer cell behavior remains poorly understood. Here, we have examined competition between the two major ECM mechanical cues, i.e. rigidity, which activates cell mechanosensing, and viscous energy dissipation, which reduces stiffness blunting cell mechanotransduction. To trigger competition, we have engineered protein hydrogels allowing concomitant modulation of stiffness and viscosity by mechanisms characteristic of native ECM. Culturing cells on these hydrogels, we have found that substrate energy dissipation attenuates YAP mechanosensing prevailing over stiffness cues. Hampered YAP activation on more dissipative substrates correlates with faster actin flow and smaller focal adhesions. Mechanistically, inhibition of actomyosin contractility reverses the outcome of the competition between rigidity and energy dissipation. Our results highlight the dominating contribution of substrate viscosity to the biology of the cell.

Cells in load-bearing tissues experience both solid deformation and interstitial fluid flow during physiological loading, but the mechanisms by which they integrate these biphasic mechanical signals remain poorly understood. Here, we develop a porous, nanoarchitected 3D scaffold that allows simultaneous delivery and control of matrix strain and fluid shear stress. We validated the platform through fatigue loading experiments and simulations of fluid-structure interactions. In static culture, osteoblast-like cells adopted shapes, cytoskeletal architectures, and focal adhesion patterns templated by scaffold geometry. Under cyclic compression, the combined influence of matrix deformation and induced fluid flow disrupted this alignment, producing disordered actin structures and reduced focal adhesion eccentricity. These changes emerged even under low-frequency loading, within the drained poroelastic regime, indicating a high sensitivity of cytoskeletal organization to fluid-solid coupling. Our findings establish a tractable and tunable platform to investigate how cells sense and respond to dynamic biphasic mechanical environments in 3D. Significance StatementCells in tissues such as bone experience mechanical inputs from both matrix deformation and interstitial fluid flow. However, existing in vitro systems often isolate one type of input or lack the ability to control both independently. We engineered a nanoarchitected 3D scaffold that delivers tunable biphasic mechanical inputs by combining structural compression and fluid flow. Without external loads, cells align their cytoskeleton and focal adhesions to the scaffold geometry. When subjected to dynamic loading, they transition to disordered morphologies and less mature focal adhesions, suggesting a transition to migratory states. These results highlight the sensitivity of cells to even subtle biphasic cues and provide a new platform to study how cells integrate multiple mechanical signals in 3D environments.

Microtubules (MTs) and their motor proteins collectively harness chemical energy to generate mechanical work, driving some of the most coordinated self-organized dynamics in living cells. The unique properties of these molecules also make them versatile building blocks of cytoskeletal active matter and biomimetic nanomachines that recapitulate cellular motility, emergent pattern formation, and motor-driven transport. However, these canonical systems use MTs of fixed length and do not incorporate the natural ability of MTs to grow and regenerate. Here, we go beyond these limits by using dynamic self-amplifying branched MT networks. Driven by kinesin-1 and cytoplasmic dynein activity, surface-gliding branched MT bundles undergo swarming that yields large-scale collective MT architectures with several sought-after features. They are polar and orientationally aligned, dense, span millimeter scales, and persist over hours. We then show that these features enable molecular transport along the swarm at unprecedented capacities, with up to six million motor complexes walking in parallel across millimeter-scale distances over hours. Our results introduce a new regime in cytoskeletal active matter in which the interplay between motor-driven activity and filament generation via branching leads to emergent polar order in proliferating swarms. Such emergent polarity makes these swarms suitable for engineering scalable transport nanotechnologies and programmable soft materials.

Governing thermal transport in engineered materials creates opportunities to redirect and recover the excess heat generated in electronic and energy-conversion devices. Materials that pair low cross-plane thermal conductivity with high in-plane thermal conductivity are particularly valuable because they confine heat and channel it away from sensitive regions, preventing localized device failure. Two-dimensional crystals are efficient building blocks for such anisotropic thermal conductors, but they are brittle, and the polymer composites used to toughen them usually forfeit much of the intrinsic anisotropy: in conventional percolation-based design, filler fraction is the only handle available, and it governs both in-plane and cross-plane conduction. Here we report a composite of Ti3C2Tx (MXene) nanosheets and squid ring teeth (SRT) inspired recombinant tandem-repeat (TR) proteins in which the protein serves as a molecular template and bridge, setting the spacing between nanosheets with angstrom-level precision through the number of tandem-repeat units and independently of the filler fraction. This structural handle provides a second, independent design parameter. At a fixed MXene loading, the number of repeats tunes the cross-plane conductivity (0.30 to 0.93 W/mK) and, with it, the thermal anisotropy ratio over a wide range (from about 70 down to 17), while the in-plane conductivity stays high (16 to 21 W/mK). We rationalize these trends with a Gaussian Network Model (GNM) of the protein embedded in a two-phase layered medium, which reproduces the measured directional conductivities from a single structural parameter and identifies the protein gallery as the cross-plane bottleneck. Extending the model to a mechanically loaded five-period stack, we find that the anisotropy is robust to reversible compression and twist, changing by only a few percent, so the number of tandem repeats, not the applied strain, is the dominant design handle. Because anisotropy is tuned structurally rather than volumetrically, these protein-MXene composites decouple thermal anisotropy from filler content, pointing toward flexible thermal materials that are not bound by the rules of mixture and percolation.

Tissue morphogenesis and repair, as well as organ homeostasis, require cells to constantly monitor their 3D microenvironment and adapt their behaviors in response to local biochemical and mechanical cues1-6. In vitro studies have shown that substrate stiffness and stress relaxation are important mechanical parameters in the control of cell proliferation and differentiation, stem cell maintenance, cell migration 7-11, as well as tumor progression and metastasis12,13. Yet, the mechanical parameters of the microenvironment that cells perceive in vivo, within 3D tissues, remain unknown. In complex materials with strain- and time-dependent material properties, the perceived mechanical parameters depend both on the strain and timescales at which the material is mechanically probed14. Here, we quantify in vivo and in situ the mechanics of the cellular microenvironment that cells probe during vertebrate presomitic mesoderm (PSM) specification. By analyzing the magnitude and dynamics of endogenous, cell-generated strains, we show that individual cells preferentially probe the stiffness associated with deformations of the supracellular, foam-like tissue architecture. We reveal how stress relaxation leads to a perceived microenvironment stiffness that decreases over time, with cells probing the softest regime. While stress relaxation timescales are spatially uniform in the tissue, most mechanical parameters, including those probed by cells, vary along the anteroposterior axis, as mesodermal progenitors commit to different lineages. Understanding the mechanical parameters that cells probe in their native 3D environment is important for quantitative studies of mechanosensation in vivo2-4,6,15 and can help design scaffolds for tissue engineering applications16-18.

The eukaryotic cytoskeleton consists of three filament types: actin filaments, microtubules and intermediate filaments (IFs). IF proteins are expressed in a cell-type specific manner, and keratins are found in epithelial cells. In certain cell types, keratin forms a layer close to the membrane which may be referred to as an "IF-cortex". It is hypothesized that this IF-cortex arranges with radial bundles in a "rim-and-spokes" structure in epithelia. Based on this hypothesis, IFs and actin filaments might add complementary mechanical properties to the cortex. It was previously shown that single IFs in vitro remain undamaged at high strains and display a non-linear stretching behavior. We now ask the question of whether this unique force-extension behavior of single IFs is also relevant in the context of a filament network within a cell. We show that keratin-deficient (KO) MDCK II cells readily form 2D cell layers and 3D cysts and withstand high equibiaxial strains. High-resolution imaging using STED microscopy reveals altered actin cortex structures in KO cells, presumably in response to the missing keratin. We investigate the influence of the equibiaxial strain on the viscoelastic properties of wild-type (WT) and KO cells using atomic force microscopy. We find that the KO cells exhibit a higher pre-stress than the WT cells, likely due to the change of the cortical structure. Interestingly, both the pre-stress and the fluidity of the KO cells are altered already at intermediate strains, whereas the WT cells show a response only at high strain. Similarly, the KO cysts are stretched more easily at low strains than the WT cysts during injection experiments. The compressibility modulus is analyzed in a spatially resolved manner and we find this modulus to be increased at the cell rim, compared to the inside region, due to the geometry of the cell layer. Our results indicate that KO cells compensate for the missing keratin, but are nevertheless very sensitive to external strain, whereas the intricate interplay between the actin and keratin cortices in WT cells preserves the mechanical state and cell stability.

Cancer cells breach the extracellular matrix (ECM) using both protease-driven degradation and force-driven physical remodeling, yet most anti-metastatic drug screens still rely on biochemical assays that overlook cell-matrix mechanical reciprocity. Here, we present a fully synthetic 3D invasion platform based on cellular force-responsive polyisocyanide (PIC) hydrogels that isolates biophysical invasion mechanisms. Cell-generated forces align and densify the PIC fibrous network, reproducing hallmark matrix remodeling seen in the tumor microenvironment. A constitutive model, parameterized by the critical stress for strain stiffening effect, links matrix nonlinear elasticity to pericellular stiffening, long-range mechanotransmission, and intercellular coupling. Using this system, we show that breast cancer cells invade by pulling and pushing the network even when matrix metalloproteinases are inhibited, revealing a physical bypass of protease blockade. Accordingly, broad-spectrum metalloproteinase inhibitors that suppress invasion in Matrigel fail to inhibit invasion here, exposing a limitation of current drug-evaluation pipelines. In co-culture, cancer-associated fibroblasts markedly accelerate invasion by generating aligned fiber tracks through higher contractility, implicating CAF-driven mechanical remodeling as a key route for breaching barriers during metastasis. The platform is thermoresponsive, compatible with standard Transwell formats, enables direct imaging of fiber architecture and invasion fronts, and decouples biophysical from biochemical cues for mechanism-aware, animal-free assessment of anti-metastatic therapies.

Biohybrid robots combining compliant synthetic support structures with biological actuators could enable future applications ranging from precision microsurgery to unmanned exploration. Machines actuated by living skeletal muscles are capable of adaptive behaviors, such as sensing and responding to environmental stimuli in real-time, offering functional advantages over non-biological actuators. However, typical skeletal muscle-powered biohybrid robots depend on 3D tissues which require large cell volumes and offer limited control of muscle fiber alignment, thus reducing efficiency of force generation and transduction. Here, we present a locomotive biohybrid robot powered by 2D monolayers, or thin films, of precisely aligned skeletal muscle fibers on a micropatterned hydrogel skeleton. We demonstrate how varying skeleton design parameters, ranging from material stiffness to microscale topology, impacts muscle fiber alignment and resultant actuation strains, generating forces 10X higher than previous 2D skeletal muscle actuators, improving untethered actuation longevity by [~]4500X from < 10 minutes to > 30 days, and increasing efficiency of muscle force output (force per unit volume of muscle) by 20X as compared to 3D muscles. Utilizing our optimized design for skeletal muscle thin films, we create a multi-limbed robot composed of independent muscle-powered fins capable of on/off control and frequency-dependent speed control. With these control inputs, we achieve steered multi-directional locomotion at speeds up to 4 body lengths per minute in straight movement and 1200 degrees per minute in rotational movement, highlighting potential for such actuators to be transformed into long-lasting functional soft robots.

High-grade serous ovarian cancer, the most common and aggressive form of ovarian cancer, generally metastasises to visceral adipose tissues. In these tissues, the extracellular matrix through which ovarian cancer cells adhere and migrate is confined by the presence and preponderance of adipocytes. How cells migrate in this unique environment is not known, yet critical to understanding metastatic progression. To study these processes, we develop biomimetic organo-hydrogels that recreate structural and mechanical properties of human visceral adipose tissues. We show that ovarian cancer cells present invasive tropism towards organo-hydrogels, replicating the behaviour observed in native adipose tissues. This migration is facilitated by the mechanical anisotropy and microstructure of organo-hydrogels and adipose tissues, allowing the formation of cell force-induced migratory tracks, a process regulated by TGF{beta} in an MMP degradation-independent manner. These results highlight the contribution of adipocytes to tissue biophysical features as a key regulatory factor of ovarian cancer cell migration.

Granular scaffolds have emerged as promising platforms for tissue regeneration, offering injectability and cell-scale porosity that support robust cell infiltration and tissue formation. However, the isotropic pore structure of spherical building blocks does not provide the directional cues needed to guide organized tissue formation. Addressing this requires asking not just whether granular scaffolds can be made anisotropic, but whether directional cues persist across the pore network at scales relevant to cell behavior. Using high aspect ratio GelMA hydrogel fibers as building blocks, we demonstrate that spherical granular materials lose orientational coherence at the cellular scale, confirming that isotropic building blocks are fundamentally incapable of providing structural guidance beyond individual pore neighborhoods. In contrast, fibrous building blocks extend persistence into the multicellular range, occupying an intermediate architectural regime exhibiting locally coherent but globally variable organization, rather than simple isotropic or uniaxial alignment, that has previously been inaccessible to granular scaffold design. We show this regime is functionally meaningful: myotubes undergo contact guidance through locally persistent but globally variable pore structure, and greater persistence is associated with increased myotube elongation and multinucleation in primary human muscle progenitor cells. Together these results expand the design space for granular scaffolds beyond pore size and porosity, and establish persistence as a variable linking granular scaffold architecture to organized tissue formation.

Embryogenesis, tissue repair and cancer metastasis rely on collective cell migration (CCM). In vitro studies propose that migrating cells are stiffer when exposed to stiff substrates, known to allow CCM, but softer when plated in compliant non-permissive surfaces. Here, by combining in vivo atomic force microscopy (iAFM) and modelling we reveal that to collectively migrate in vivo, cells require to dynamically decrease their stiffness in response to the temporal stiffening of their native substrate. Moreover, molecular and mechanical perturbations of embryonic tissues uncover that this unexpected cell mechanical response is achieved by a new mechanosensitive pathway involving Piezo1-mediated microtubule deacetylation. Finally, lowering microtubule acetylation and consequently cell stiffness was sufficient to allow CCM in soft non-permissive substrates, suggesting that a fixed value of substrate stiffness is not as essential for CCM as it is reaching an optimal cell-to-substrate stiffness value. These in vivo insights on cell-to-substrate mechanical interplay have major implications to our re-interpretation of physiological and pathological contexts.

Aligned extracellular matrix fibers enable fibroblasts to undergo myofibroblastic activation and lead to elongated cell morphology. The fibroblasts in turn contract to cause alignment of the extracellular matrix. This feedback process is critical in pathological occurrences such as desmoplasia and is not well understood. Using engineered fiber networks that serve as force sensors, we identify lateral protrusions with specific functions and morphology that are induced by elongated fibroblastic cells and which apply extracellular fiber-deflecting contractile forces. Lateral projections, named twines, produce twine bridges upon interacting with neighboring parallel fibers. These mature into \"perpendicular lateral protrusions\" (PLPs) that enable cells to spread laterally and effectively contract. Using quantitative microscopy, we show that the twines originate from the stratification of cyclic actin waves traversing the entire length of the cell. The primary twines swing freely in 3D and engage neighboring extracellular fibers. Once engaged, a lamellum extends from the primary twine and forms a second twine, which also engages with the neighboring fiber. As the lamellum fills in the space between the two twines, a sheet-like PLP is formed to contract effectively. By controlling the geometry of extracellular networks we confirm that anisotropic fibrous environments enable PLP formation, and these force-generating PLPs are oriented perpendicular to the parent cell body. PLP formation kinetics indicated mechanisms analogous to other/known actin-based structures. Our identification of force-exerting PLPs in anisotropic fibrous environments suggests an explanation for cancer-associated desmoplastic expansion at single-cell resolution, providing possible new clinical intervention opportunities.

As collective cell migration is essential in biological processes spanning development, healing, and cancer progression, methods to externally program cell migration are of great value. However, problems can arise if the external commands compete with strong, pre-existing collective behaviors in the tissue or system. We investigate this problem by applying a potent external migratory cue--electrical stimulation and electrotaxis--to primary mouse skin monolayers where we can tune cell-cell adhesion strength to modulate endogenous collectivity. Monolayers with high cell-cell adhesion showed strong natural coordination and resisted electrotactic control, with this conflict actively damaging the leading edge of the tissue. However, reducing pre-existing coordination in the tissue by specifically inhibiting E-cadherin-dependent cell-cell adhesion, either by disrupting the formation of cell-cell junctions with E-cadherin specific antibodies or rapidly dismantling E-cadherin junctions with calcium chelators, significantly improved controllability. Finally, we applied this paradigm of weakening existing coordination to improve control to demonstrate accelerated wound closure in vitro. These results are in keeping with those from diverse, non-cellular systems, and confirm that endogenous collectivity should be considered as a key, quantitative design variable when optimizing external control of collective migration.

Cell alignment is a fundamental process in tissue morphogenesis. While density-dependent collective cell alignment has been widely observed, its underlying mechanisms remain poorly understood. Here, using C2C12 myoblasts, we demonstrate that static uniaxial mechanical stretch induces collective cell alignment in a density-dependent manner: densely populated cultures align robustly, whereas sparse populations do not. We reveal a biphasic alignment process, comprising an initial passive phase and a subsequent active phase. The passive phase, driven by substrate deformation, transiently biases cell orientation along the stretch axis regardless of density. In the active phase, initial alignment progressively dissipates in low-density cultures, but is sustained and reinforced in high-density cultures. Supported by coarse-grained agent-based simulations, we propose that self-generated cellular forces facilitate kinetic transitions between orientations, enabling cells to explore orientational states, whereas cell-cell interactions provide a thermodynamic bias that stabilizes the locally aligned state. In dense cultures, strong intercellular interactions promote this stabilization, enabling persistent alignment. In contrast, sparse cultures lack sufficient cell-cell interaction, leading to alignment dissipation. Within this C2C12 system, our findings highlight the cooperative roles of cellular forces and intercellular interactions in orchestrating multicellular ordering, offering new insights into mechanobiology of tissue morphogenesis.

Epithelial cells experience long lasting loads of different magnitudes and rates. How they adapt to these loads strongly impacts tissue health. Yet, much remains unknown about the evolution of cellular stress in response to sustained strain. Here, by subjecting cell pairs to sustained strain, we report a bimodal stress response, where in addition to the typically observed stress relaxation, a subset of cells exhibits a dynamic tensioning process with significant elevation in stress within 100s, resembling active pulling-back in muscle fibers. Strikingly, the fraction of cells exhibiting tensioning increases with increasing strain rate. The tensioning response is accompanied by actin remodeling, and perturbation to actin abrogates it, supporting cell contractilitys role in the response. Collectively, our data show that epithelial cells adjust their tensional states over short timescales in a strain-rate dependent manner to adapt to sustained strains, demonstrating that the active pulling-back behavior could be a common protective mechanism against environmental stress.

The development, maintenance and repair of epithelial tissues critically rely on adhesion complexes that ensure structural integrity while enabling dynamic remodeling. Such tissue remodeling underpins both physiological morphogenesis and pathological transformation. Central to these processes are mechanical forces, which tightly couple cytoskeletal organization to adhesion dynamics. Despite extensive investigations in two-dimensional (2D) systems, how these interactions are orchestrated within polarized three-dimensional (3D) epithelia remains largely unresolved. Here, we introduce a new, non-invasive strategy to probe localized force generation within 3D epithelial tissues. We engineered elastic polyacrylamide (PAAm) microbeads with cell-mimetic size and mechanical properties, enabling their seamless integration. In contrast to conventional bead injection approaches, these PAAm microbeads were spontaneously engulfed by the tissue, thereby establishing an intrinsic interface through which bead deformation can be directly correlated with local cytoskeletal architecture and adhesion organization, as visualized through high-resolution imaging combined with quantitative 3D computational reconstruction. Using this approach, we demonstrated that localized mechanical perturbations trigger pronounced cytoskeletal remodelling while preserving global tissue polarity. We further identified the extracellular matrix composition as key determinant of bead-tissue interactions, with collagen-I coating promoting robust adhesion and efficient incorporation. At the bead-cell interface, cells assembled tension-bearing focal adhesions and organized actin stress fibers, revealing the emergence of active cortical stress. Strikingly, quantitative analysis of bead deformation revealed a previously unrecognized mechanical duality: spatially segregated regions of pulling and pushing forces coexisted at the microscale, directly correlated with local cytoskeleton dynamics. This finding challenges the prevailing view of homogenous force application and instead supports a model in which cells deploy highly coordinated and spatially patterned force-generating strategies. Altogether, this integrative and non-invasive strategy offers a comprehensive pipeline for dissecting the dynamic interplay between cellular processes and tissue mechanics during morphogenesis in 3D model systems.

For tissue development, cells must generate contractile forces which are transmitted to their surrounding matrix or neighbouring cells via adhesion complexes. It is often envisaged that a simple linear counterbalance of cell generated stress with extracellular matrix (ECM) traction forces exists. However, experimental evidence indicates that modulating cell-ECM attachment does not necessarily lead to expected reciprocal changes in intercellular stresses. As ECM composition or mechanical properties are rarely uniform, it is important to understand the complexity of how focal adhesions alter stress transmission and the force-balance of a tissue. To address this, we confined monolayers on adhesive patterns altering focal adhesion distribution. Traction force microscopy and laser ablations of cell-cell junctions were used to examine stresses across epithelial monolayers whilst modulating substrate stiffness. We show that monolayers reach different force-balance states depending on focal adhesion distribution. Using an active matter model and confirmed experimentally, we reveal that a force-balance is generated by non-uniform patterns of cell contractility linked to adhesion patterning. This work highlights the importance of integrating the position of cell-ECM attachments into our vision of the mechanical landscape of living tissues. TeaserTo infer a tissues force-balance, positional information of focal adhesion distribution needs to be integrated due to the emergence of non-uniform patterns of cell contractility.

Summary ParagraphTissues and organs in living organisms represent centimeter-scale hierarchical architectures comprising nano-to microscale, uniaxially aligned extracellular matrix (ECM) fibres with high mechanical strength, integrated with cellular components, as exemplified in tendon, skin, cartilage, bone, and blood vessels1. Here, we present a liquid-liquid interfacial spinning method to produce highly uniaxially aligned, centimeter-scale collagen fibres. The dried fibres exhibit exceptional mechanical properties, with fracture strength of 280 MPa, Youngs modulus of 6 GPa, and toughness of 17 MJ m-3, comparable to spider silk and tendon collagen, and exceeding supramolecular and double-network hydrogels1. Incorporating living cells into the collagen solution yielded centimeter-scale, cell-laden aligned fibres, with densely adherent, uniaxially aligned cells and over 80% viability. Myoblast-laden fibres recapitulate biological features of fibrotic muscle tissues, as observed in type II diabetes2. Interfacial collagen assembly further enables fabrication of dimension-controlled constructs, like 2D sheets, 0D capsules, and 1D tubes, thus providing modular building blocks for centimeter-scale 3D tissues and organ-like structures. This approach offers a versatile platform to engineer mechanically robust, cell-laden tissues with controlled hierarchical architecture.

Fibrotic encapsulation around medical implants affects millions of patients annually. Current approaches targeting inflammation or implant material properties have failed clinically, but the mechanical origins of implant-induced fibrosis remain unexplored. Here, we demonstrate that directional imbalance of mechanical forces ("tension anisotropy") is the primary driver of fibroblast activation at implant-tissue interfaces, and that it can be eliminated through adhesive bonding strategies. Computational modeling reveals a mechanistic basis for successful adhesive anti-fibrotic interfaces: conventional sutured implants generate highly anisotropic stress fields between discrete suture anchor points that activate fibroblasts, while adhesive interfaces distribute forces isotropically, maintaining a mechanical environment that does not activate fibroblasts. In vivo experiments from the literature across multiple animal models confirm these predictions: as predicted, adhesive interfaces completely prevent fibrotic capsule formation for up to 12 weeks across diverse organs, while maintaining identical implant composition and geometry compared to sutured controls. Results establish tension anisotropy as a mechanical regulator of implant fibrosis and provide a mechanistic foundation explaining why adhesive interfaces succeed where all previous anti-fibrotic strategies have failed. By addressing the root mechanical cause of fibrosis, this mechanobiology-driven approach may enable a universal approach for preventing fibrosis across all categories of implantable medical devices. Significance statementMillions of patients suffer from medical device failure due to fibrotic encapsulation, in which a surgically implanted item such as pacemaker leads or a vascular graft loses function by becoming covered with scar tissue. Implants affixed to soft tissues by sutures are especially prone to this form of failure, but implants affixed with a recently invented adhesive are not. We present the discovery that directional imbalance of forces ("tension anisotropy") drives conversion of healing tissue into scar tissue. Conventional sutured implants create highly anisotropic stress fields between anchor points that activate fibroblasts, while adhesive interfaces distribute forces isotropically, attenuating scarring. This mechanistic insight explains why adhesive implant-tissue interfaces successfully prevent fibrotic capsule formation across multiple animal models and organ systems, where all previous anti-fibrotic approaches have failed. By addressing root mechanical causes of fibrotic remodeling, this discovery provides a pathway for clinical remediation of fibrotic encapsulation.