ABSTRACT This research investigates the influence of thermal radiation on the bioconvective flow of Casson‐type nanofluids over a stretching sheet, incorporating diffusion effects governed by the Cattaneo–Christov double‐diffusion model and activation energy. The nanofluid dynamics account for thermophoretic and Brownian motion, while the governing boundary‐layer equations are expressed as coupled partial differential equations with appropriate boundary conditions. Through a similarity transformation, these equations are reduced to an ordinary differential system, which is then solved numerically using the shooting technique and MATLAB's BVP4C solver to ensure high accuracy. The results provide detailed insight into how key parameters affect velocity, temperature distribution, nanoparticle concentration, and the spatial behavior of motile microorganisms, illustrated through comprehensive graphical and tabular analyses. Beyond its theoretical contribution, the study holds practical significance for a range of engineering and biotechnological processes in which heat transfer, nanoparticle transport, and microbial activity are simultaneously important. Such applications include advanced biomedical procedures like targeted drug delivery and controlled thermal therapies, the optimization of bioreactors and fermentation systems where microorganism growth occurs under radiative heat conditions, the development of microfluidic and lab‐on‐chip devices for efficient cooling and mixing of bio‐nano flows, improved thermal management and energy harvesting in solar collectors and photothermal systems, and environmentally focused technologies such as bio‐nanofluid‐based wastewater treatment where microorganisms aid in pollutant degradation. By integrating the effects of activation energy, thermal radiation, and the Cattaneo–Christov model into a single computational framework, this work provides both fundamental understanding and design guidance for next‐generation bio‐nanofluid systems in medical, industrial, and energy‐related fields.
Abid et al. (Wed,) studied this question.