# Additive Manufacturing in Bespoke Interactive Devices--A Thematic Analysis
## 4 Discussion  
Following the analysis of each theme, the relationship map shown in Figure 8 gives an overview of how the themes are related. This generates insights into the difficulties of designing for AM in future interactive devices. 1. Relationship between Additive Manufacturing and Measurement Devices for Data Acquisition  
3D Scanning is a common mode of data acquisition in AM, used to collect data that can be recreated in a digital environment. The generated 3D model is then used as a basis  
Figure 8: Relationship between the themes generated in the DEFINED workshop. for the product to be developed, and can also be used to simulate design concepts. From the workshop, the requirements for data collection systems include mobility, reliability, accuracy, compactness, lightweight, portability, and fast real-time processing speeds. The scanning systems discussed were stationary scanners, high- and low-end portable scanners, and depth cameras. In the literature, the main 3D scanning devices are MR and CT scans [78; 83]. Relationship between Measurement Devices for Data Acquisition and User-Centred Design  
Human body data can be easily measured using 3D scanning devices, which allows for user-specific data acquisition. This ensures that the interactive device conforms to the patient's body. Therefore, the device must be designed in such a way as to comfortably support the stationary and dynamic distribution of forces exerted on the limb [74]. Traditionally, bespoke interactive devices are casted, sculpted, moulded, and processed prior to being checked for fitting on the end-user's person. This is a laborious process, and would require multiple patient visits [77]. However, measurement devices for data acquisition facilitate this process, as interactive devices can be fabricated according to end-user requirements. A 3D model is generated from the 3D scans, which allows the designer to adjust it according to the end-user's needs [71; 79]. The workshops also discussed how end-user requirements influence the type of measurement device that can be used for data acquisition. Handheld scanners with fast real-time processing and single-shot data acquisition devices are best suited for patients with limited dexterity, as they are more prone to involuntary movements. Relationship between Additive Manufacturing and User-Centred Design  
The customisability aspect of AM is ideal for bespoke devices, since it enhances product differentiation by developing unique interactive devices with minimal post-processing. The rapid manufacturing nature of AM also facilitates user feedback integration, since the 3D digital model can be easily updated, and devices can be produced quickly for immediate user feedback. Both the workshops and literature emphasised that the end-user is involved in the design concept generation, implementation, and evaluation [28]. Furthermore, to prioritise patient requirements both workshops and literature mentioned that the design process of AM interactive devices is iterative [28], and requires a multidisciplinary approach [34; 35; 36; 37; 38]. Workshop 1.2 noted that ergonomics, usability, and functionality requirements are critical design challenges in interactive device design. Workshop 2.3 also mentioned that aesthetics and safety requirements also must be considered. Adherence to rehabilitation therapy was discussed in both workshops and in literature. Customised, effective, and usable interactive devices encourage participation by improving the satisfaction and quality of life of the end-user [71; 72; 73; 74; 78; 81]. Workshop 2.1 presented the strapping mechanism of the interactive device developed throughout PRIME-VR2 as a case study, as shown in Figure 7. The self-closing strap was designed to facilitate use, which will encourage user independence. In the workshops, the ability to print sensors was another capability of AM that was highlighted. This contributes to the customisability of interactive devices, since the user's physical activity throughout rehabilitation therapies can be monitored.