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Textile technology has opened the door to innovative and multidisciplinary research. A wide range of areas are approaching this sector to develop new products, taking advantage of textiles' physical and mechanical properties. There is no doubt that textiles can be used for everything, from products that improve medical care, such as protecting wounds to jackets with embedded controllers for Virtual Reality. However, there are still bridges to strengthen between disciplines. For example, Electrical Engineering and Fashion Design, where these two areas need to work even closer together to produce high-quality e-textiles. Electronic Textiles (e-textiles) have been receiving much attention in the past two decades. But even though textiles offer an extensive range of advantages, their structure and fibre composition are also considered a big challenge as they are 3D porous materials, making it challenging to embed electronics. Literature has flagged different gaps that we should address as researchers to continue improving the manufacturing and testing of e-textiles. These include poor communication and linguistic barriers between disciplines, lack of production and performance testing standards, and limited end-user involvement in the design process. This research uses experimental methods to determine the most suitable printing and materials for conductive track by exploring both Screen and Inkjet printing on different substrates (natural and synthetic) with two basic textile structures (plain weave and weft knit). It also highlights the importance of the materials' properties, their interaction and adaptability with other materials and their role in garment design. This multidisciplinary research involves chemistry, material science, product design, fashion design, and electrical engineering. The present work's original contribution to knowledge is the development of a multidisciplinary methodology, replicable and easy to follow for different disciplines to manufacture and test functional printed e-textiles. Thus, guiding non-experts in the field through a step-by-step process to understand, characterise, print, test and replicate the manufacturing of printed e-textiles. The results presented in this research support the textile, fashion and engineering community to enhance the quality of new developments by building bridges between disciplines.

Functional printing is a tried and tested method of low-cost and high-throughput production. Combining 2d materials with printing is an emerging, cost-effective and large-scale fabrication strategy of their devices. However, successful scale-up and adoption of printing as an ubiquitous fabrication method has been limited due to the lack of diversity in the available printing methods and materials. Since 2012, the majority of the 2d material printing demonstrations have been with inkjet. Methods such as blade coating, screen printing and flexography have received less attention despite having notable advantages. Also, the majority of 2d material printing research has focused on conducting (e.g. graphene) and semiconducting (e.g. black phosphorus) 2d materials and less emphasis has been placed on dielectric layers using wide bandgap 2d materials like hexagonal boron nitride (h-BN), which represent an important material in printed electronics applications, for example, in parallel plate capacitors and thin film transistors. Similarly, 2d material printing has thus far been demonstrated on flat surfaces, and little work has been done to print on conformal 3d objects. Conformal printing is an attractive and emerging field, which can enable the deposition of specific electronic features, such as sensors and circuits, directly on to 3d objects. Functional ink deposition on 3d structures is not a trivial process due to uneven and sometimes, complex topography. My PhD dissertation focuses on these key aspects of 2d material inks, I first present the formulation of conductive 2d material inks for screen printing. I begin to tackle the issues outlined above by using the screen inks to fabricate simple devices. I then combine screen printing with a water-based technique utilising a sacrificial layer that is capable of printing on to 3D objects. Next, I demonstrate and evaluate the feasibility of using flexographic printing as a means of large-scale fabrication via the high-speed printing of graphene-modified flexographic ink on a commercial press. Lastly, I investigate the use of h-BN as a dielectric nanofiller to enhance the dielectric properties of an existing dielectric polymer, polyurethane (PU). The work I present on conformal printing and in the formulation of dielectric inks in my thesis is my novel contribution to the research field. My research, therefore, addresses existing shortcomings of 2d material inks towards their large-scale exploitation.

Electronics in different applications, such as in medical imaging devices, radar systems, communication transmitters, and optical drives, often require various power and signal lines to be integrated at board level. In such cases, different lines may cross over one another in three-dimensional space for efficient electronic integration. Crossovers are usually achieved by adding additional layers to a PCB. However, these additional layers increase the cost, weight, and complexity of the component. By creating a process and structure to offer board-level heterogenous integration, these factors may be reduced. RF-DC crossovers were designed and additively manufactured using an aerosol jet printer. Benzocyclobutene (BCB), a thermally curable dielectric material, and Norland Electronic Adhesive 121 (NEA), a UV curable dielectric ink, were printed as crossover materials on boards containing an RF transmission line. Electroninks 615 (EI-615), a conductive silver ink, was printed on the crossover’s surface to complete the DC circuit trace. Two different toolpath designs were explored to serve for the digital printing of the crossover structure. A network analyzer was used to measure the scattering parameters (S12 and S21) across the RF transmission line in X-band (8-12 GHz). A thermal camera was used to capture the heat spread across the crossover region. The printed ramp design resulted in a more gradual slope as expected, requiring a single print of the conductive trace while the steep pad design required tilting of the crossover and multiple printing sessions. The NEA 121 and BCB showed no significant changes in the S21 parameter as DC power increased; however, slight coupling occurred in both. The largest S21 difference recorded at 10 GHz was 0.339 dB. The BCB crossovers exhibited higher power handling than the NEA 121 crossovers, reaching up to 6.93 W. The maximum breakdown temperature occurred at 273.0°C in the NEA 121 and at 248.6°C in the BCB crossovers.

This thesis presents the implementation of some of the basic concepts of digital logic design in a fun and creative way with the help of paper electronics. This involves circuit building on paper using conductive tape or conductive ink and circuit components as electronics craft materials. Paper electronics toolkit called circuit sticker microcontroller which is deployed by a company named Chibitronics and AT89C51 microcontroller were used for the computational functioning of the circuits built on paper. This can be used to teach the fundamentals of digital logic design to the students in their early stage of studies in an attractive way and can help them them gain a better understanding. This thesis can also be helpful in grabbing the attention of high school students and motivate them towards choosing the engineering discipline for their higher studies.

The layer-by-layer nature of additive manufacturing (AM) allows for access to the entire build volume of a component during manufacture including the internal structure. Voids are accessible during the build process and allow for components to be embedded and sealed with subsequently printed layers. This process, in conjunction with direct write (DW) of conductive materials, enables the direct manufacture of parts featuring embedded electronics, including interconnects and sensors. The scope of previous works in which DW and AM processes are combined has been limited to single material AM processes. The PolyJet process is assessed for hybridization with DW because of its multi-material capabilities. The PolyJet process is capable of simultaneously depositing different materials, including rigid and elastomeric photopolymers, which enables the design of flexible features such as membranes and joints. In this work, extrusion-based DW is integrated with PolyJet AM technology to explore opportunities for embedding conductive materials on rigid and elastomeric polymer substrates. Experiments are conducted to broaden the understanding of how silver-loaded conductive inks behave on PolyJet material surfaces. Traces of DuPont 5021 conductive ink as small as 750?m wide and 28?m tall are deposited on VeroWhite+ and TangoBlack+ PolyJet material using a Nordson EFD high-precision fluid dispenser. Heated drying at 55°C is found to accelerate material drying with no significant effect on the conductor's geometry or conductivity. Contact angles of the conductive ink on PolyJet substrates are measured and exhibit a hydrophilic interaction, indicating good adhesion. Encapsulation is found to negatively impact conductivity of directly written conductors when compared to traces deposited on the surface. Strain sensing components are designed to demonstrate potential and future applications.