substrattransport

Substrattransport is a general term used to describe the movement of substrate molecules within, across, or along a substrate medium. It encompasses transport through membranes and interfaces, diffusion within porous solids and films, and the delivery of substrates to active sites. The concept is relevant in biology, chemistry, and materials science, and it covers passive processes driven by gradients as well as active processes driven by energy input.

Mechanisms of substrattransport include diffusion driven by concentration or chemical potential differences, advection or convective transport in fluid systems, and active transport through carrier proteins or pumps. In solids and porous media, transport can occur by pore diffusion, surface diffusion, or capillary action. In electrically active systems, electromigration or electroosmotic flow can also contribute. Surface interactions at interfaces can accelerate, impede, or selectively favor certain substrates, a phenomenon often described as surface-mediated transfer.

Contexts and applications of substrattransport span several fields. In biology, it underpins nutrient uptake and metabolite export across cell membranes. In chemical engineering and catalysis, substrate transport determines reaction rates by controlling how quickly reactants reach active sites. In materials science and microfabrication, it affects dopant distribution, film growth, and permeation through membranes or porous layers. Controlling substrattransport is essential for optimizing drug delivery, tissue engineering, sensing, and energy storage systems.

Measurement and modeling of substrattransport typically employ diffusion theories, such as Fick’s laws for neutral species and the Nernst-Planck framework for charged substrates, alongside pore-scale models for porous materials. Experimental methods include tracer diffusion studies, fluorescence or radiolabeling, and electrochemical tests to quantify permeation and uptake.

See also: diffusion, mass transfer, permeation, substrate diffusion.