Disposable micro stir bars by photodegradable organic encapsulation of hematite-magnetite nanoparticles

Development of high-throughput microfluidic systems requires engineering of novel miniaturized stirring concepts that can overcome diffusion-limited mixing in micro-vessels. Here, we present the facile and scalable fabrication of disposable magnetic micro stir bars by one-step photodegradable encapsulation of magnetically aligned iron oxide nanoparticle agglomerates with polylysine. The resulting superparamagnetic nanocomposites have a tunable aspect ratio and a nano-rough surface. Optimal composition and morphologies are determined over a broad set of self-assembly conditions leading to flexible elongated structures with excellent mixing performance. Rapid disassembly is demonstrated by in situ photo-degradation of the coating under UV light providing a simple means for their safe disposal.