In the age of smart systems, artificial intelligence, and personalized devices, the need for effective methods to facilitate multifunctionality integration has become a necessity. One of the fields that boosts the efforts of multifunctionality integration yet suffers from the current implementation methodologies is the field of microfluidics. Conventional fabrication methods of microfluidics, that rely on microfabrication technologies and soft lithography, are limited by high costs, labor-intensive procedures, and restricted material choices. In contrast, additive manufacturing (AM) offers a promising alternative capable of producing complex multi-material, multifunctional microfluidic devices. However, challenges such as limited printable materials and inherent process non-idealities need to be addressed for AM to be fully viable for multifunctional and on-demand microfluidic devices' fabrication.

This thesis addresses the above-mentioned challenges by focusing on the development of suitable printable material systems and the improvement of the specific printing non-ideality of surface roughness, to realize fully additive-manufactured microfluidic systems. For the realization of printed microactuators, a piezoelectric PZT ink was formulated for inkjet printing, achieving the required rheological properties and demonstrating excellent stability and jettability. Additionally, a soda-lime glass ink was developed for extrusion printing, exhibiting appropriate viscosity and shape retention properties for constructing structural components of microfluidic devices.

The practical utility of these materials was validated through the fabrication and testing of various printed devices. The characterization of PZT-based cantilever devices confirmed that our PZT films exhibit sufficient piezoelectric strain constant d31 (47.6 - 68.6 pm/V). PZT membrane actuators were simulated within the range of the d31 values obtained. The acquired results demonstrated high deflection in the order of tens of micrometers, verifying the feasibility of using our PZT in microfluidic applications such as micropumps.

The impact of AM processes on devices' surface quality and fluid flow within printed microfluidic structures was assessed. Through the use of Fused Filament Fabrication process, the relation between printing process parameters and surface roughness was established. An analytical model derived from experimental data showed a strong correlation between printing parameters and surface roughness. Computational fluid dynamics simulations demonstrated that increasing surface roughness (> 200 nm) led to significant degradation in fluid flow. High-efficiency 3D printed plastic valveless micropumps having a maximum working backpressure of 978 Pa, and water flow rate of 210 µl/min were achieved through the reduction of surface roughness (<200 nm). The soda-lime glass ink was utilized to 3D print high-efficiency micropumps through surface roughness control by fabrication process parameters. Soda-lime glass micropumps achieving a water flow rate of 140 µl/min were fabricated.

Based on the comprehensive findings presented in this thesis, we demonstrated the capability of AM technologies to produce high-performance functional microfluidic devices in polymer and glass material systems. This achievement marks a significant advancement toward the development of viable microfluidic platforms for customized multifunctional systems such as personalized medical devices.