Synthesis and Nanomechanical Characterization of Piezoelectric Nanocomposite Films for Applications in Energy Harvesting MEMS Devices

Abstract

Autonomous micro-devices are micro-sensors and micro-actuators that can operate independently and fulfill their energy-requirements from their ambient environments. It is envisioned that such truly autonomous microdevices can revolutionize numerous applications and technologies, including smart implantable microdevices, smart cities, and the internet of things (IoT). To obtain truly autonomous microdevices, it is necessary to make sure that these microsystems have components that allow them to harvest energy from ambient sources. One of the most ubiquitous sources of energy is ambient mechanical/vibrational energy. Piezoelectric materials like Lead Zirconate Titanate (PZT) and Aluminium Nitride (AlN) have been used in energy harvesting microsystems. However, the brittleness of these ceramic films has limited their applications. newlinePiezoelectric polymer nanocomposites can be a viable alternative to these piezoelectric ceramics. Piezoelectric polymer nanocomposites usually consist of one or more piezoelectric ceramic nanomaterial(s) distributed in a matrix of the compliant polymer matrix, which can either be piezo-active or passive. However, the application of piezoelectric nanocomposites as structural and functional components requires knowledge of the material properties of the nanocomposites as functions of the nanomaterial content and process parameters. This thesis presents the synthesis and characterization of Pb-free piezoelectric polymer nanocomposite films that are compatible with well-established microfabrication process-flows. newlineThe first study considers a nanocomposite where the matrix is a commonly used negative photoresist, SU8-2015, and the nano-scale reinforcement is piezoelectric zinc oxide (ZnO). Integration of ZnO nanoparticles with SU8 in the form of photo-patternable nanocomposite films can lead to the development of a new generation of energy-harvesting microdevices.