Magneto driven smart materials for sensing and actuation
Abstract
Magnetic field responsive, colloidal and particle systems provide an emerging tool to manipulate samples in miniaturised systems. Biomolecule sensing is one of the main functionalities integrated in Lab-on-a-Chip technologies, being the properties of the sensor scaffold that determine the efficiency of the sensor. Therefore, the incorporation of magnetic properties to the scaffold would facilitate non-invasive handling and programming of the sensor. In this regard, in the first half of the thesis, the effect of the ionic density in ex-situ and in-situ Fe3O4 magnetic nanoparticle phase nucleated alginate hydrogel is discussed. Then, the development of a novel TiO2 nanotubes/ alginate hydrogel optical biosensor platform, and the incorporation of magnetic properties with multiple functionalities such as optical biosensing, actuation and size exclusive filter is presented. The second section of this work discusses the possibilities brought by novel low surface energy magnetic particle systems in the microfluidic field. A floating superhydrophobic magnetic nanoparticles colloid layer is able to float on the water-air interface, easily bending downwards, under an externally applied gradient magnetic field, creating a stable twister-like structure with a flipped conical shape, under controlled water levels. As a proof of principle, three implementations of this structure in real scenarios are showed, the cargo and transport of water droplets in aqueous media, the generation of magneto controllable plugs in open surface channels, and the removal of floating micro-plastics from the air-water interface. As well, a flexible and easily adaptable strategy to efficiently collect, transport, and evacuate the underwater deposited air bubbles in microfluidic channels by low surface energy magnetic particles is discussed. The generated fundamental knowledge in magnetic hydrogels and the introduced novel sensing and actuation systems contribute to upstanding the development of materials and microfluidics field.