# Additive Manufacturing in Bespoke Interactive Devices--A Thematic Analysis
## 1 Introduction  
The ISO/ASTM 52900 terminology standard defines Additive Manufacturing (AM) as a bottom-up technique that fuses materials to build a physical product, starting from a virtual 3D model. Material is introduced to \"print\" the equivalent physical product layer upon layer, as opposed to subtractive and formative manufacturing processes. In recent years, AM has brought about advancements in manufacturing and product development. This is due to the various advantages of AM compared to conventional top-down fabrication techniques, including a shorter time-to-product, production on demand, low costs for small lot sizes, improvements in product functionality, and greater freedom in design [1; 2; 3; 4; 5]. AM provides opportunities for innovative designs of complex geometries, which are impossible to produce with traditional manufacturing processes [6; 7]. Additionally, a high degree of customisation in AM is feasible due to the fact that product-specific tooling is not required [6]. For these reasons, AM is no longer restricted to rapid prototyping, which until recently was its main application, but is being applied for the manufacturing of end-use products.  
One such potential application is in the design of highly bespoke devices meant for human-machine interaction. This application requires individual customisation [8; 9; 10], and AM meets the essential design and manufacturing requirements in the medical field [8; 9; 11; 12].  
Virtual Reality (VR) technology has existed for over thirty years, but in recent years it has gained popularity in various sectors due to its advantages, in particular enhancing the visualisation experience of the user. The dominant VR market is the entertainment world, notably in gaming. However, VR is being applied in other sectors including manufacturing, maintenance, cultural heritage, architecture, and healthcare. Regarding the latter, VR is being exploited for surgical intervention training and rehabilitation. Irrespective of the application, a device, similar to a gaming console, is required to enable users to play a \"serious\" game in an interactive and immersive VR environment. The primary purposes of a serious game goes beyond pure entertainment, such as to meet a rehabilitation purpose. However, most VR-based applications use an off-the-shelf controller, which for a certain category of end-users with limited hand and finger dexterity, may not be sufficiently comfortable to use.  
Within this context, the project titled \"Personalised Recovery through a Multi-User Environment: Virtual Reality for Rehabilitation\" (PRIME-VR2) aimed to deliver a VR controller, fabricated with AM, which is purposely designed according to the person's needs for rehabilitation purposes, rather than using an off-the-shelf device. The tailor-made wearable controller has been developed for three target users, namely, persons who have suffered a sports injury, post-stroke patients, and children with dystonia (suffering involuntary hand movements). The main reasons to adopt a VR-based rehabilitation approach are to reduce the duration of the therapy programme and to engage more the aforementioned user groups in the therapy, compared to the current traditional clinical practices.  
This paper presents the principal themes generated from a two-day workshop titled Design for Additive Manufacturing: Future Interactive Devices (DEFINED). This workshop aimed at discussing the design for AM issues encountered throughout PRIME-VR2.  
In the next section, the materials and methodologies used are discussed, followed by a review of the relevant literature, and results from the thematic analysis carried out are presented. These results are then discussed, and finally conclusions are drawn.