ADDITIVE MANUFACTURING AND CHARACTERIZATION OF NEXT GENERATION SENSORS

Md Taibur Rahman

Nanoparticle based additive printing, also called Microscale Additive Manufacturing (MAM), has emerged as a versatile technique where nanoparticles are deposited on a substrate and sintered to create films of functional materials for different applications. This method allows the fabrication of electronic devices and other systems on arbitrary surfaces with an excellent control over the film microstructure, opens up material choices for fabrication, and creates less waste; thus, overcoming several shortcomings of conventional manufacturing methods such as lithography. Amongst the different MAM techniques, Aerosol Jet (AJ) based additive method can create feature sizes down to 10 μm and can print nanoparticles dispersed in solvents having a viscosity as high as 1000 cP. This allows AJ method to print any material in the nanoparticle form at microscale and opens up the possibility of fabrication of miniature devices at high spatial densities. While the applicability of emerging AJ technique can bring many benefits, understanding the behavior of printed films at room temperature (RT) and at high temperatures (HT) is critical to their usage in various applications. This dissertation focuses on fundamental characterization of films fabricated by additive printing and exploring their novel applications as sensors operating at RT and HT. Sensor fabrication was performed using an AJ-based additive printing method where several novel printing approaches were explored. Four different materials, namely, silver (Ag), nickel (Ni), nickel-chromium (NiCr) alloy, and carbon nanotubes (CNTs) were evaluated as sensor films. The sensor films were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), x-ray diffraction (XRD), and x-ray photoelectron spectroscopy (XPS). We correlated the film microstructure with the sensor electrical and mechanical behavior at different temperatures (24-500 °C) and frequencies (0.02 - 300 kHz). This knowledge was used to fabricate and characterize several high-performance sensor devices such as highly sensitive touch sensors, customizable biosensors, and high gauge factor HT strain sensors. We also demonstrated 3-D metal-dielectric structures that can be used for antenna applications. The work carried out in this dissertation adds to our knowledge of additive manufacturing and opens up the possibility of realizing low-cost high-performance sensor devices using environmentally benign fabrication techniques.

ADDITIVE MANUFACTURING AND CHARACTERIZATION OF NEXT GENERATION SENSORS

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