Here, recent significant developments are reviewed in manipulating soft matter systems through the use of magnetic torque. Magnetic torque enables the orientation, assembly, and manipulation of thermally fluctuating systems in broad material fields including biomaterials, ceramic and composite precursor suspensions, polymer solutions, fluids, foams, and gels. Magnetism offers an effective, safe, and massively parallel manufacturing approach. By exploiting magnetic torque, leading soft matter researchers have demonstrated new technologies in rheology, life sciences, optics, and structural materials. Specifically, magnetic torque has been used to assemble particle suspensions, to fabricate and actuate composite materials, and to control and manipulate biological materials. In each of these applications, there are energetic limitations to magnetic torque that need to be understood and characterized. However, magnetic torque offers a promising remote‐controlled approach to creating and enabling new soft matter technologies.

Magnetic concentration of drug-laden magnetic nanoparticles has been proven to increase the delivery efficiency of treatment by 2-fold. In these techniques, particles are concentrated by the presence of a magnetic source that delivers a very high magnetic field and a strong magnetic field gradient. We have found that such magnetic conditions cause even 150 nm particles to aggregate significantly into assemblies that exceed several micrometers in length within minutes. Such assembly sizes exceed the effective intercellular pore size of tumor tissues preventing these drug-laden magnetic nanoparticles from reaching their target sites. We demonstrate that by using dynamic magnetic fields instead, we can break up these magnetic nanoparticles while simultaneously concentrating them at target sites. The dynamic fields we investigate involve precessing the field direction while maintaining a field gradient. Manipulating the field direction drives the particles into attractive and repulsive configurations that can be tuned to assemble or disassemble these particle clusters. Here, we develop a simple analytic model to describe the kinetic thresholds of disassembly and we compare both experimental and numerical results of magnetic particle suspensions subjected to dynamic fields. Finally we apply these methods to demonstrate penetration in a porous scaffold with a similar pore size to that expected of a tumor tissue.

We present computer simulations and experiments on dilute suspensions of superparamagnetic particles subject to rotating magnetic fields. We focus on chains of four particles and their decay routes to stable structures. At low rates, the chains track the external field. At intermediate rates, the chains break up but perform a periodic (albeit complex) motion. At sufficiently high rates, the chains generally undergo chaotic motion at short times and decay to either closely packed clusters or more dispersed, colloidal molecules at long times. We show that the transition out of the chaotic states can be described as a Poisson process in both simulation and experiment.

Utilization of post-consumer waste plastics as fuels is of technological interest because their energy contents (heating values) are comparable to those of premium fuels. Pyrolytic gasification of these solid polymers yields a mixture of predominately gaseous hydrocarbons and hydrogen. This gaseous fuel mixture can then be suitably blended with air and burned in well-controlled premixed flames. Such flames are much less polluting than diffusion flames, which would have been generated had the polymers been burned in their solid state. In this work, an apparatus was designed and built to continuously process polymers, in pelletized form, and to pyrolytically gasify them at temperatures in the range of 800−900°C in N 2 -or CO 2 -containing environments. Subsequently, the gaseous pyrolyzates were mixed with air, ignited, and burned in a Bunsen-type burner in a manner similar to natural gas. Polyethylene and polypropylene pyrolyzates burned with blue-tint flames akin to those of natural gas. The flames were fairly steady and nearly stoichiometric, generating effluents with low CO/CO 2 ratios. The combustion reactions released heat in a small water boiler coupled to a miniature steam engine, which produced electricity, illustrating the feasibility of "clean" power generation from waste plastics. Because pyrolysis of polyolefins requires a nominal heat input that amounts to only a minuscule fraction of the heat released during their combustion, large-scale implementation of this technique is deemed to be technologically viable and economically favorable.

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