@article{devi_kumar_nakshatrala_patrick_2023, title={A methodology for measuring heat transfer coefficient and self-similarity of thermal regulation in microvascular material systems}, volume={217}, ISSN={["1879-2189"]}, DOI={10.1016/j.ijheatmasstransfer.2023.124614}, abstractNote={Fluid transport through microvascular networks—a hallmark for homeostasis in living systems—has transcended to engineered materials, primarily made possible because of modern manufacturing advancements. Vascular-enabled multifunctionality, including thermal regulation and self-healing, holds great potential for extending the lifetime of structural materials and expanding the operational envelope. Prior studies on vascular-based active cooling use a “combined” heat transfer coefficient (HTC): a single parameter lumps convection and radiation effects. Although the resulting mathematical models are linear—an attractive feature for computational modeling, the combined coefficient approach may not be accurate or even applicable if the operating temperature is unknown, which is the case with many thermal regulation applications (e.g., space probes). In this paper, we illustrate the remarked limitations of the lumped approach and advocate the need to use a decoupled HTC by splitting convective and radiative heat transfer modes. We show the broad applicability of the proposed method by applying it to three material systems: glass and carbon fiber-reinforced polymer composites and an additive manufactured metal. We show, using numerical simulations, the differences in the predictions from the decoupled approach with that of the combined HTC; these differences are prominent at higher heat fluxes. Also, the decoupling has enabled us to establish a scaling law that allows transferring of solutions fields across material systems, strengthening further the validity and utility of our approach. This work's significance is two-fold. First, the research is fundamental, providing accurate measurement protocols for critical model parameters. Second, this work facilitates the development of mathematical models for vascular-based thermal regulation that are predictive even for hostile environments (which are often difficult to realize in laboratories), such as outer space.}, journal={INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER}, author={Devi, Urmi and Kumar, Sandeep R. and Nakshatrala, Kalyana B. and Patrick, Jason F.}, year={2023}, month={Dec} }
 @article{devi_pejman_phillips_zhang_soghrati_nakshatrala_najafi_schab_patrick_2021, title={A Microvascular-Based Multifunctional and Reconfigurable Metamaterial}, ISSN={["2365-709X"]}, DOI={10.1002/admt.202100433}, abstractNote={Nearly all‐natural and synthetic composites derive their characteristic attributes from a hierarchical makeup. Engineered metamaterials exhibit properties not existing in natural composites by precise patterning, often periodically on size scales smaller than the wavelength of the phenomenon they influence. Lightweight fiber‐reinforced polymer composites, comprising stiff/strong fibers embedded within a continuous matrix, offer a superior structural platform for micro‐architectured metamaterials. The emergence of microvascular fiber‐composites, originally conceived for bioinspired self‐healing via microchannels filled with functional fluids, provides a unique pathway for dynamic reconfigurable behavior. Demonstrated here is the new ability to modulate both electromagnetic and thermal responses within a single structural composite by fluid substitution within a serpentine vasculature. Liquid metal infiltration of varying density micro‐channels alters polarized radio‐frequency wave reflection, while water circulation through the same vasculature enables active‐cooling. This latest approach to control bulk property plurality by widespread vascularization exhibits minimal impact on structural performance. Detailed experimental/computational studies, presented in this paper, unravel the effects of micro‐vascular topology on macro‐mechanical behavior. The results, spanning multiple physics, provide a new benchmark for future design optimization and real‐world application of multifunctional and adaptive microvascular composite metamaterials.}, journal={ADVANCED MATERIALS TECHNOLOGIES}, author={Devi, Urmi and Pejman, Reza and Phillips, Zachary J. and Zhang, Pengfei and Soghrati, Soheil and Nakshatrala, Kalyana B. and Najafi, Ahmad R. and Schab, Kurt R. and Patrick, Jason F.}, year={2021}, month={Aug} }