In this thesis, new all-printed capacitors are developed for the applications of energy storage, filter, and resonant circuits by using new dielectric material and an advanced technology. The innovative devices provide satisficing electrical performances with high breakdown voltages and capacitance densities.
The main body of this thesis is divided in three parts. The first part is to introduce the fundamental background of printing technologies, electrical capacitors and printable materials. Among all the printing technologies, direct writing family is the most advantageous in the small-scale and fast production of printed electronics due to the properties of masterless processing, digital control, and print-on-demand. Both inkjet printing and ultrasonic fluid dispensing applied in this work are grouped into the direct writing family. A cross-linkable dielectric material poly(methyl methacrylate)84/(4-benzoylphenyl methacrylate)16 [P(MMA84/BPMA16)] exhibits the optimized chemical and mechanical stabilities in comparison with uncross-linked poly(methyl methacrylate) (PMMA). Poly(vinylidene fluoride-co-trifluoro ethylene) [P(VDF-TrFE)] exhibits a high dielectric constant of 16. The great advantages of both polymeric dielectrics make them ideal for printed electronics. The second part is devoted to the preparation of printed thin-film capacitors by providing four different layouts and architectures for multiple electronic applications. The printing setup, process setting and steps are summarized in detail.
The following part which is the major content of this thesis is divided into two aspects: in the first aspect, the intriguing new form of continuous solution dispensing technology, ultrasonic fluid dispensing, is demonstrated as an alternative printing technology for the commonly applied ones. In comparison with the widely-used inkjet printing, continuous solution dispensing is the most advantageous in thin-film capacitor processing with metal nanoparticle and polymer dielectric inks. It enables precise pattern transfers with low surface roughness, small feature size (as small as 5 μm), and accurate positioning (5 μm resolution).
Most importantly, problems due to discrete droplets and nozzle clogging in inkjet printing are avoided in continuous solution dispensing. All the inks applied for printed capacitors in this work are printed successfully with this innovating technology. Direct printing on demand and rapid switching among different inks are some other attributes of this printing technology that enable high throughput. The second aspect of this part is to characterize and evaluate the fabricated capacitors. The measured values include capacitor dimension, dielectric strength, capacitance density, energy density, charge/discharge behavior and so on.
In summary, this work provides not only the use of the advantageous materials P(MMA84/BPMA16) and P(VDF-TrFE) in high-performance capacitors, but also paves the way of developing thin-film capacitors with a new continuous solution dispensing technology which makes the low-cost and high-quality manufacture of printed devices possible
