Implications of Fabrication Processes

This section discusses the implications of the fabrication approaches proposed in this thesis. It also details how these approaches have been iteratively refined and adapted based on technical evaluations as well as the design process for developing behind them.

Laser Cutting

The initial fabrication approach proposed in this thesis utilised the rapid nature of laser cutters for high fidelity prototyping of shape-changing displays, PolySurface (chapter 4). Laser cutters were used for initial fabrication explorations as they are easily accessible and can be commonly found in maker-spaces, design studios, and FAB labs [29]. The initial fabrication process is based around the idea of semi-solid surfaces: surfaces that consist of solid components (laser cut polypropylene) fused onto a flexible sub-surface (spandex).

Though this fabrication approach was rapid (e.g. two days for prototype development), there were still high assembly requirements. The laser cut parts each had to be manually glued onto the Spandex material by hand. Though not highly technical, this tedious manual assembly still increases labour cost. Though technical developers have the necessary skills to operate laser cutters, those who do not have the necessary maker experience with digital fabrication would struggle initially to independently design and fabricate their own surfaces.

The key design implications of using laser cutters are focused on their utility for rapid high-fidelity prototyping of shape-changing displays. Particularly, for large scale implementations that go beyond the dimensions of a 3D printer’s building plate. For rapid and iterative designing, laser cutters show a promising direction for prototyping shape-changing displays. The cheaper material costs (e.g. Perspex sheets) compared to 3D printing filaments also narrow the accessibility and adoption barrier for fabrication with laser cutters. The 2D design environments used for laser cutters (e.g. Adobe Illustrator) also simplify the initial design process compared to CAD 3D modelling.

155 Though there is a greater level of assembly required with the 2D pattern designs fabricated with laser cutters that is an issue for complex hardware systems.

The material properties of the sheets used for laser cutting should also be taken into consideration during the design process. Though Polypropylene (PP) 0.8mm sheets used for PolySurface (chapter 4) are thinner and more flexible than Perspex, when laser cut small segments in close proximity to each other would fuse together with PP. This meant that particularly small laser cut segments with PP were difficult to fabricate precisely compared to traditional Perspex material.

3D Printing with SLA and FDM

The high assembly requirements for the laser cutting approach might limit adoption to a wider range of domains beyond initial prototyping of shape-changing displays. From a convenience perspective, 3D printing supports personal fabrication much easier than laser cutters. Especially as most users can become skilled using 3D printers through open access content and tutorials online. Unlike with laser cutters, that use CO2 lasers, no additional supervision or health and safety precautions are usually needed with FDM printers. To reduce assembly requirements alternative fabrication approaches were established using two 3D printing methods; Stereolithography (SLA) in chapter 5 and multi-material Fused Deposition Modeling (FDM) in chapter 6.

With SLA 3D printing, the design process focused on interlinking each of the solid parts of the surface together during the printing process to reduce manual assembly. The intricate nature of the 3D printed interlinked surface CAD designs required the creation of accurate and repeatable dimensions on a small scale. This was not possible using the more commonly available Fused Deposition Modeling (FDM) machines as the scale of links caused multiple print errors with a filament extruder.

SLA 3D printers support a multitude of different resin types that have a wider range of material properties, such as flexible and clear. The clear and translucent materials used supported under the surface visualisation with a projector. The core issue with SLA is that it does not yet support multi-material 3D printing. Instead, multi-material parts have to be individually printed and can only be assembled manually after each part is printed and post-processed. This can also further complicate the design process. The interlink design could be "templated" to allow novices to simply tweak parameters (perhaps

156 through a GUI rather than a CAD programme) to help them design a custom-made surface.

One of the core advantages of FDM printers is their ability to support multi-material 3D printing. FDM printing was adopted (chapter 6) for refining the final fabrication approach to support 3D printing circuitry for integrated surfaces. In terms of multi- material applications, this is particularly prominent with the introduction of 4D printing. Using the same core premise of extruder based FDM processes, the smart materials used during printing can also achieve actuation as well as sensing of external stimuli. The future of shape-changing displays can fully utilize the use of smart and active materials for designing and developing a new generation of dynamic displays that can be printed as one. The reduction of electronic components and mechanical actuation, through 3D/4D printing smart dynamic surfaces, can further minimalize the technical barrier of adoption for shape-changing displays. Essentially, by creating a singular actuated surface, with integrated interaction and visualisation capabilities, that can be designed and fabricated as one without the need for external mechanical actuators.

This premise is already demonstrated within the field of soft robotics and smart material sciences. The shape-changing interfaces and HCI community, as a whole, could benefit greatly with closer collaborations with these fields for technically focused developments.