arXiv subjects

Manu Sebastian

Publications and source records attributed to Manu Sebastian.

4 recordsLinked to original sources

arXiv2026

Design and modelling of compliant mechanisms with invertible Poisson's ratio effect for growing biological cells

The behaviour of biological cells depends on the mechanical properties, such as Elastic Modulus and Poisson's ratio, of the substrate they adhere to. Tunable materials such as polyacrylamide gels and hydrogels were previously used as substrates to understand this dependence. However, these substrates do not facilitate changing their elastic properties in situ while cells are growing on them. This work presents an alternate approach that enables this--substrates based on tunable compliant micro mechanisms. In particular, the mechanism proposed here has an invertible Poisson's ratio effect. In the first configuration, the effect is positive, and in the second, it is negative, with any desired magnitude. We achieve this by changing the stiffness between two internal points of a mechanism with the shape of a re-entrant structure. An increase in stiffness causes the direction of deformation along the lateral axis to reverse for a given reference load along the horizontal axis. We derive analytical expressions that relate the geometric parameters to the ratio of input and output displacements for both mechanism configurations. The analytical modelling is verified with finite element analysis and experiments on mesoscale design prototypes of both configurations.

cond-mat.soft↗

arXiv2026

Potential Role of Agentic Artificial Intelligence in Toxicologic Pathology

As the volume and complexity of nonclinical toxicology studies continue to increase, toxicologic pathology reporting faces persistent challenges, including fragmented sources of data (e.g., histopathology images, clinical pathology and other study data, adverse effects database, mechanistic literature), variable reporting timelines and heightened regulatory expectations. This white paper examines the emerging role of agentic artificial intelligence (AI) in addressing these issues through coordinated workflow orchestration, data integration, and pathologist-in-the-loop report generation. Based on a closed-door roundtable held during the 2025 Society of Toxicologic Pathology (STP) Annual Meeting and follow-on discussions, this paper synthesizes the perspectives of leading toxicologic pathologists, toxicologists, and AI developers. It outlines the key pain points in current reporting workflows, identifies realistic near-term use cases for agentic AI, and describes major adoption barriers including requirements for transparency, validation, and organizational readiness. A phased adoption roadmap and pilot design considerations are proposed to help support responsible evaluation and deployment of agentic AI system in nonclinical settings. The paper concludes by emphasizing the need for coordinated efforts across pharmaceutical organizations, CROs, academia, and regulators to establish shared standards, benchmarks, and governance frameworks that will lead to safe, transparent, and trustworthy integration of AI into toxicologic science.

cs.CY↗

arXiv2025

Compliant Mechanisms for Invertible Poisson's Ratio and Tunable Stiffness in Cell Culture Substrates

The mechanical environment of a substrate plays a key role in influencing the behavior of adherent biological cells. Traditional tunable substrates have limitations as their mechanical properties cannot be dynamically altered in-situ during cell culture. We present an alternate approach by using compliant mechanisms that enable realization of tunable substrate properties, specifically, invertible Poisson's ratio and tunable stiffness. These mechanisms transition between positive and negative Poisson's effects with tunable magnitude through a bistable Engaging-Disengaging Compliant Mechanism (EDCM). EDCM allows stiffness between two points of the substrate to switch between zero and theoretically infinite. In the stiffened state, lateral deformation reverses under a constant axial load, while in the zero-stiffness state, the deformation direction remains outward as that of re-entrant structure. EDCM in conjunction with an offset mechanism also allows tuning of the effective stiffness of the entire mechanism. We present analytical models correlating geometric parameters to displacement ratios in both bistable states and through illustrative design cases, demonstrate their potential for designing dynamic and reconfigurable cell culture substrates.

cond-mat.soft↗

arXiv2025

Design of an engaging-disengaging compliant mechanism by using bistable arches

Compliant mechanisms utilise elastic deformation of their segments to transmit motion or force. The utility and behaviour of specific compliant mechanisms can be enhanced by introducing an engaging and disengaging ability with its elastic segments. Towards this, we present an engaging-disengaging compliant mechanism (EDCM) that can switch its stiffness between infinite and zero. The design of the EDCM is based on bistable arches and a locking mechanism. We describe its working, identify its design parameters, and use analytical expressions to arrive at its dimension. The design is verified by detailed finite element analysis and experiments on a 3D-printed prototype. Three alternate designs that lead us to the final mechanism are also briefly discussed.

cond-mat.soft↗