Magnetic Polymer Composite Transducers for Integrated Systems

Abstract

Compact, autonomous computing systems with integrated transducers are imperative to deliver advances in healthcare, navigation, livestock monitoring, point of care diagnostics, remote sensing, internet-of-things applications, smart cities etc. Reflecting this need, there has been sustained growth in the market for transducers. Polymer based transducers, which meld highly desirable properties such as low cost, light weight, high manufacturability, biocompatibility and flexibility, are quite attractive. Doping polymers with magnetic materials results in the formation of magnetic composite polymers, enhancing the attractive traits of polymer transducers with magnetic properties. This dissertation is dedicated to the development of magnetic polymer transducers, which are suitable for energy harvesting and saline fluid transduction. The first-ever magnetic composite energy harvester capable of converting vibrations from the practically relevant low-frequency range into electrical energy was fabricated and tested. The harvester was realized by fabricating an array of PDMS-iron nanowire nanocomposite cilia on a planar coil array and exhibits a linear frequency response.

This energy harvester design was further improved by increasing the doping concentration of the composite, adding a composite proof mass and improving the microfabricated coil. These changes manifest in an energy harvester that not only increases the power density by 4 orders of magnitude over the previous design but also possesses large operational bandwidth. The composite structure, comprising of the cilia and the proof mass has a frequency response comprised of two closely spaced resonant peaks facilitating the desirable broadband behavior at low frequency.A polymer-based magneto hydrodynamic pump prototype capable of actuating saline fluids was developed. The benefit of this pumping concept to operate without any moving parts is combined with simple and cheap fabrication methods and a magnetic composite material, enabling a high level of integration together with the advantages of mechanical flexibility. The pump electrodes are created by laser printing of graphene on polyimide, while the permanent magnet is molded from an NdFeB powder - polydimethylsiloxane (PDMS) composite. These materials were leveraged to fabricate an integrated, low profile magneto hydrodynamic pump, suitable for deployment in lab on chip systems.