publications
publications by categories in reversed chronological order.
2026
- Need for Speed: Gait-Agnostic Tendon-Routing Optimization for Terrestrial Tendon-Actuated Soft RobotsIn 2026 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), 2026
Low locomotive speed remains a primary barrier to real-world deployment of terrestrial soft robots. Locomotion fundamentally results from manipulating frictional contact with the environment. This makes makes terrestrial soft robots, with low force-to-mass ratios, highly sensitive to surface variability. Beyond robot control, the actuator design - specifically how forces are transmitted through the soft robot body to the robot-environment interface - largely determines the achievable contact forces and resulting locomotion. This work presents a gait-agnostic actuator path design optimization framework for motor-tendon-actuated soft limbs that improves speed without prescribing target deformation shapes. Based on first principles, the objective function uses the mean nodal displacement magnitude along the limb’s ground-contact edge as a tractable proxy for increasing contact forces. Tendon paths are parameterized as planar cubic Hermite splines, with spline control-point coordinates and spline-plane inclination angles as design variables. Using an ABAQUS/Explicit finite-element forward model, a custom Multi-Generation Random Search with Radius Decay (modified basin-hopping) optimizes the objective subject to linear and nonlinear constraints that encode limb geometry and hexahedral meshability requirements. The optimized actuator path design yields a 56.7% improvement in simulated contact-edge displacement over the baseline design. Coupled with a data-driven gait synthesis framework, optimal actuation sequences for each robot were identified for three surfaces of increasing roughness - whiteboard, rubber mat, plywood. The optimized tendon path design delivers an average locomotion speed increase of 80.6% - demonstrating substantial and surface-robust gains due to actuator design optimization. To the best of our knowledge, this is the first gait-agnostic tendon-path optimization framework for terrestrial motor-tendon soft robots that is experimentally validated across multiple surfaces.
@inproceedings{duttaIROS, author = {}, city = {Pittsburgh, Pennsylvania, USA}, doi = {}, isbn = {}, booktitle = {2026 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS)}, month = {}, publisher = {IEEE}, title = {Need for Speed: Gait-Agnostic Tendon-Routing Optimization for Terrestrial Tendon-Actuated Soft Robots}, volume = {}, year = {2026}, dimensions = {false} } - Inverse design framework for fabric-based soft inflatable actuatorsWang D Dutta S and Patiballa S KIn ASME International Design Engineering Technical Conferences & Computers and Information in Engineering Conference (IDETC), 2026
Soft inflatable actuators fabricated from inextensible fabric sheets offer a compelling platform for robotic grasping due to their low weight, minimal cost, and straightforward manufacturing. When two sheets are sealed together and pressurized, the sealed regions act as constraints that direct the inflated shape through buckling instability. This mechanism has been exploited in shape-morphing and reconfigurable systems; however, a systematic model-driven approach to designing seal patterns for prescribed grasping curvatures remains largely unexplored. In this work, we develop an inverse design framework for soft gripper appendages, each featuring two sealed joints that govern the bending upon inflation. A finite element forward model is coupled with a global optimizer to determine the joint geometries and inflation pressure required to achieve a target radius of curvature. We investigate two joint geometries–diamond and triangular–across multiple target radii. The diamond design matched targets with 1.85% average error in simulation and 5.48% in experiment, with deviations attributed to fabrication sensitivities. The triangular design achieved 5.49% average error in simulation and 2.61% in experiment. Across both geometries, the optimizer produced physically intuitive results: narrower joints for tighter curvatures and wider joints for gentler bending. A three-finger gripper assembled from the diamond design was evaluated on five objects from the Yale-CMU-Berkeley (YCB) benchmark object and model set, achieving an overall grasping success rate of 80%. Together, the proposed framework provides a FEA-based inverse design methodology for lightweight, easy-to-fabricate, inflatable-based soft robotic manipulation.
@inproceedings{duttaIDETC, author = {Dutta S, Wang D and K, Patiballa S}, city = {Houston, Texas, USA}, doi = {}, isbn = {}, booktitle = {ASME International Design Engineering Technical Conferences & Computers and Information in Engineering Conference (IDETC)}, month = {}, publisher = {ASME}, title = {Inverse design framework for fabric-based soft inflatable actuators}, volume = {}, year = {2026}, dimensions = {false} } - Influence of Shear Stiffness on Static and Dynamic Performance of Auxetic Metamaterials (Under Review)Journal of Engineering Materials and Technology, 2026
Auxetic mechanical metamaterials exhibit a negative Poisson’s ratio, i.e., they contract laterally under longitudinal compression, which densifies the structure and enables superior energy absorption and impact resistance. This counterintuitive behavior is coupled to shear stiffness. However, the influence of shear stiffness in auxetics remains incompletely understood, owing to the highly nonlinear, geometry- and rate-dependent nature of shear. In this study, we address this by comparing two metamaterial geometries with varying shear stiffness: negative Poisson’s ratio low shear (NLS) and negative Poisson’s ratio high shear (NHS) lattices. The unit cell geometries were constructed via load flow-based design framework, and their bulk properties were computed using visco-hyperelastic finite element analysis (FEA) models. The structures were then characterized experimentally under quasi-static compression, cyclic compression, and drop-weight impact. Under quasi-static compression, the NHS lattice exhibited a 32.0% higher load-bearing capacity than the NLS lattice, and under cyclic loading, it dissipated 20.5% more energy. This behavior reversed under dynamic impact, where the NLS lattice absorbed 53.6% more energy than the NHS counterpart. Finite element models were developed and validated against experiments with average relative errors of 5.0% for quasi-static compression and 11.0% for drop-weight impact across all configurations. The results show that auxetic metamaterial lattices with different shear stiffness exhibit significant differences in static and dynamic performance. This research highlights the importance of shear stiffness in auxetic metamaterials for applications in protective barriers and debris-resistant structures.
@article{duttaJEMT, title = {Influence of Shear Stiffness on Static and Dynamic Performance of Auxetic Metamaterials (Under Review)}, author = {}, journal = {Journal of Engineering Materials and Technology}, publisher = {ASME}, volume = {}, number = {}, pages = {}, year = {2026}, doi = {}, dimensions = {false} } - A Design Framework for Compositional Hierarchical Mechanical Metamaterials via a Qualitative Unit-Cell Library (Under Review in ASME JMD)Krishnan G Dutta S and Patiballa S K2026
Hierarchically designed mechanical metamaterials involve nested levels of structural organization, mimicking natural structures (such as bones, wood, and bird feathers) to create advanced functional materials. Compositional hierarchy, a specific type of hierarchical strategy that involves the methodical assembly of discrete building blocks, offers unique advantages in engineering design due to its modular nature. This involves proper selection and spatial arrangements of distinct microstructures, as a result of which the desired macro-scale mechanical behavior can be achieved. Towards the design of such compositional hierarchical metamaterials, this paper presents a two-step design framework. First, material optimization of the design domain is performed using a parameterized elasticity matrix to obtain optimal conceptual designs. Second, building-block microstructure geometries are selected from a qualitative library and subjected to shape-size refinement to satisfy the desired kinematic or stiffness requirements. To construct the qualitative library, a novel parametrization scheme is initially introduced, which categorizes the planar orthotropic elasticity matrix into four distinct classes. Utilizing a kinetostatic load flow visualization technique, the candidate microstructure geometries are then populated within these four classes. The framework is validated for the design of a cantilever beam with a specified lateral stiffness requirement and the design of planar sheets that exhibit specified target deformation patterns. Thus, the present work provides a systematic and physically intuitive methodology applicable to arbitrary kinematic deformation and stiffness requirements.
@misc{duttaJMD-HMM2D, title = {A Design Framework for Compositional Hierarchical Mechanical Metamaterials via a Qualitative Unit-Cell Library (Under Review in ASME JMD)}, author = {Dutta S, Krishnan G and K, Patiballa S}, journal = {Journal of Mechanical Design}, volume = {}, number = {}, pages = {}, year = {2026}, eprint = {2605.20219}, doi = {10.48550/arXiv.2605.20219}, archiveprefix = {arXiv}, primaryclass = {cond-mat.soft}, url = {https://arxiv.org/abs/2605.20219}, dimensions = {true} }
2025
- Development and Validation of Computational Modeling Framework for Tendon-based Soft RoboticsVikas V Dutta S and Patiballa S KJournal of Mechanisms and Robotics, 2025
Tendon-driven soft robotic systems are extensively recognized for their intrinsic flexibility, exceptional dexterity, potential for safe human interaction, and adaptability to unstructured environments. Modeling such systems is challenging because of their highly nonlinear continuum structure, coupled with complex tendon interactions and friction. Traditionally, modeling has been dominated by continuum Cosserat rods. While mathematically robust, the underlying assumptions of the Cosserat model restrict its use to simple, slender geometries. Moreover, the Cosserat rod models do not fully consider the complex tendon interactions in the system. Herein, we propose an alternative high-fidelity finite element model for tendon-driven soft robotics systems, incorporating a hyperelastic material model, contact definitions within and between the bodies, and frictional forces, to accurately capture the deformation of tendon-driven locomotion and manipulation systems, achieving a mean tip position error of less than 7.91%. In addition, the finite element modeling (FEM) is verified by comparing the complete shape of the actuators using curvature and torsion metrics. The efficacy of the proposed FEM is demonstrated through a parametric analysis of tendon-driven soft actuators and by modeling nonslender actuator geometries subjected to significant contact interactions. This research paves the way for scalable and generalizable computational models to enhance the practicality of tendon-driven soft robotics.
@article{duttaJMR, title = {Development and Validation of Computational Modeling Framework for Tendon-based Soft Robotics}, author = {Dutta S, Conzola J, Vikas V and K, Patiballa S}, journal = {Journal of Mechanisms and Robotics}, volume = {18}, number = {6}, pages = {1--37}, year = {2025}, doi = {10.1115/1.4069292}, dimensions = {true} } - Design Optimization for Uniform Stress Distribution in Mechanical Metamaterials Using a Maximum Material Utilization MetricDutta S and Patiballa S KJournal of Mechanical Design, 2025
Mechanical metamaterials have garnered considerable interest for their enhanced properties, such as high strength-to-weight ratios, remarkable resilience, and superior energy absorption capabilities. Despite their advantages, localized stress concentrations in additively manufactured metamaterial geometries remain a challenge. In this article, we propose a bioinspired design optimization framework to achieve metamaterials with uniformly distributed stresses. The framework uses the maximum material utilization (MMU) metric to quantify and uniformly distribute stresses in metamaterial geometries. Optimization begins with the selection of an initial conceptual design from a qualitative library of planar metamaterials previously developed by the authors. Once we have a conceptual design, we optimize it using the MMU metric for both size and shape. We assessed our optimization methods on two planar auxetic metamaterials: negative Poisson’s ratio microstructures with low shear (NPLS) and negative Poisson’s ratio microstructures with high shear (NPHS). The optimized designs achieved a uniform stress distribution across the entire topology, at both the microstructural and material levels. We highlight the efficacy of our design methodology by using numerical simulations and experiments. In addition, we demonstrate the utility of stress-optimized metamaterials by conducting numerical dynamic impact tests on optimized and unoptimized NPLS lattices. The optimized lattice absorbed more energy than its unoptimized counterpart. This study paves the way for computationally inexpensive, insightful, and stress-based design optimization of metamaterials.
@article{duttaJMD, title = {Design Optimization for Uniform Stress Distribution in Mechanical Metamaterials Using a Maximum Material Utilization Metric}, author = {S, Dutta and K, Patiballa S}, journal = {Journal of Mechanical Design}, volume = {148}, number = {1}, pages = {011702}, year = {2025}, doi = {10.1115/1.4068956}, dimensions = {true} }
2022
- Proposed auxetic cluster designs for lightweight structural beams with improved load bearing capacityEngineering Structures, 2022
Auxetic materials have gained popularity in engineering applications owing to their unique deformation response mechanism. However, they have not been exploited to their full potential in engineering load bearing applications. The current paper, therefore, is focused on exploring and improving the deflection behaviour of auxetic beam structures. Initially, a single re-entrant unit cell and an array of auxetic clusters are modelled using Finite Element Method (FEM). These numerical models are then verified for its Poisson’s ratio and deflection behaviour using theoretical formulations. Subsequently, in the next phase, a comparison of the deflection characteristics of the in-use common beams with that of the conventional auxetic beam design is carried out. Much overlooked factors such as orientation and placements of auxetic clusters are introduced in beam designs and are exploited to improve the deflection characteristics of conventional auxetic beams. Through this assessment, the paper proposes two novel design concepts of Oriented Re-entrant Structures (ORS) and Assorted Re-entrant Structures (ARS) for improved load bearing response. Novel designs of ORS and ARS beams are observed to perform significantly better than the conventional auxetic and honeycomb beams. The newly proposed beam designs exhibit a 64% reduction in mass in comparison to the homogeneous beam. The usefulness of these designs are brought out by introducing the ARS auxetic beams into a real-world lightweight foot bridge design. The bridge designs with ARS cross beams demonstrates a better behaviour in comparison to the bridge designs with conventional cross beams in terms of both deformation and material usage. This work highlights the potential use of unconventional mechanical metamaterial structures in engineering load bearing problems to address the demands of green engineering and sustainability without compromising on its structural integrity.
@article{menonES, title = {Proposed auxetic cluster designs for lightweight structural beams with improved load bearing capacity}, author = {}, journal = {Engineering Structures}, publisher = {Elsevier}, volume = {260}, number = {1}, pages = {114241}, year = {2022}, doi = {10.1016/J.ENGSTRUCT.2022.114241}, dimensions = {true} }