Screen-printed free-standing structures on textile and flexible substrate

Abstract

This thesis had demonstrated free-standing structures fabricated solely using screen-printing technique on textile and flexible substrate. Since the screen-printing method provides more flexibility in terms of design and fabrication, this method was employed as a method of choice for the fabrication process compared to knitting and weaving techniques. This thesis is intended to explore the fabrication of small scale (tens of microns to mm) three dimensional (3D) structures using standard printing process and the application of the 3D printing process on three different structures.

This research investigated in detail the comparison between two different removal sacrificial material which are thermal and water removed sacrificial materials. Both of these sacrificial materials are compatible with textile as the temperature process is lower than 200°C and the solvents used are not corrosive which will not alter the properties of the textile. However, because thermal sacrificial material has ragged edges and reacts with the structural layer, the water removed sacrificial layer is selected. The water removed sacrificial material is based on polyvinyl alcohol (PVA) and can be cured at 80°C for 3 minutes, providing a solid foundation for subsequent printed layers. This sacrificial layer can be removed in 90°C agitate water to form free-standing structure. Minico M 7000 Blue A is the thermally cured structural material used with the sacrificial material. The Minico had the highest mechanical properties (5523 MPa) compared to another four structural materials. This is important as this layer is the main structure of the design. Hence, the stiffest material will provide the most durable free-standing structure. The feasibility of the screen-printing process on textile had been demonstrated by fabricating three different free-standing structures which are cantilever, encastre beam and diaphragm structure. The cantilever structure was demonstrated as energy harvesting application on textile with power output of 27.9 nW excited at frequency of 201 Hz. A printed encastre beam was tested on one side of piezoelectric elements using the electromechanical shaker and the maximum output generated was 0.1545 volt at natural frequency of 3.835 kHz had also been demonstrated. The final structure which is the free-standing diaphragm was evaluated and had successfully demonstrated the sound pressure level of 74 decibel between 12 kHz to 19 kHz with 15mm microphone distance from circular diaphragm structure. These applications are the first of its kind being reported and fabricated directly on textile and flexible substrate.

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ORCID for Stephen Beeby: orcid.org/0000-0002-0800-1759

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