microrods

Microrods are rod-shaped micro-objects with typical dimensions from 1 to tens of micrometers in length and sub-micrometer to a few micrometers in diameter. Their elongated geometry gives them anisotropic mechanical, optical, magnetic, and transport properties, which can be exploited in imaging, sensing, and actuation. Microrods can be crystalline or amorphous and may be standalone inorganic particles, organic polymers, or composite assemblies. They are used in laboratories as model systems for anisotropic diffusion and rheology, and in applied contexts for microrobotics and targeted delivery.

Synthesis methods include template-based approaches using hard templates such as anodic aluminum oxide or track-etched membranes, followed by electrodeposition or sol-gel filling; hydrothermal or solvothermal growth of rod-like crystals; lithography and etching to define micro-rod geometries; electrospinning to produce fibrous mats subsequently cut into rods; and self-assembly methods that yield rod-like colloids.

Material platforms include silica microrods, polymer microrods (e.g., polystyrene, PMMA), and magnetic microrods based on nickel, iron oxide, or cobalt ferrite, among others. Magnetic microrods can align with external magnetic fields and be steered or actuated; silica and polymer rods are often used in optical and biocompatible contexts. Surface functionalization enables biomolecule conjugation and targeted interactions.

Applications include microrobotics and actuated assemblies, micromixing in microfluidics, as contrast agents and tracers in imaging, and in biosensing where anisotropic geometry enhances signal or binding specificity. They also serve as model systems to study anisotropic diffusion, rheology, and self-assembly.

Challenges include achieving uniform size and aspect ratio, scalable production, controlling surface chemistry, preventing aggregation, and biocompatibility for in vivo use.