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This thesis investigates the feasibility of applying design-led approaches to influence user behaviour to reduce the negative social impacts of products during use. A review of the literature revealed a distinct lack of design-led research in this area. Three promising approaches from other disciplines, however, were found; ecofeedback, behaviour steering and intelligence. The majority of product examples identified did not use a singular approach, but combined two or more approaches. Most of the examples were concepts and focused on the end result. Few commented on the research and development processes undertaken to generate the final design. These limitations reinforced the need for case studies detailing these processes. To this end, two design studies were carried out; a preliminary study using a range of products and a further, more in-depth study on the use of mobile phones. The results of these studies led to the development of a framework of attributes for 'behaviour changing' devices. In response to these findings, two design resources were developed; a detailed design project to reduce the social impacts of mobile phone use in public and a short film on texting whilst on the move. Evaluation by design professionals provided analysis of the effectiveness of these resources and wider reflections on designer's perceived responsibilities for use and the ethics of designing for behavioural change. Collectively, the findings indicated that resources for designing behavioural change should; be explorative not prescriptive, focus on problem solving, be tailored to meet the needs of the intended recipient and ideally be applied in the early 'ideation' stages of the design process. Additionally, the findings indicated that designer's involvement in, and responsibility for, lifecycle impacts must be extended beyond point-of-purchase. Designers, however, are reportedly often unable to influence product development at a strategic level. Prior work, therefore, is needed to engage those at a senior level. Furthermore, the findings strongly indicate that 'behaviour changing' devices must be prototyped and subjected to rigorous consumer testing not only to establish their effectiveness but also to determine their acceptability.

A human centric approach to the design of products and workplaces is essential to ensure the appropriate accommodation of the people who interact with such designs. Digital human models (DHM) in ergonomic simulation are commonly used within design and development to ensure product suitability. DHM for ergonomic simulation has improved in terms of its reliability and appearance in recent years. However, there appears to be a need to improve how the flesh of the DHM deformsaround the joint to support improved ergonomics simulations. Supported by data acquired through the use of a 3D body scanner, this PhD research aimed to address this need by developing a methodology to simulate body deformation due to joint movements that suited the needs of ergonomics simulation. To anticipate the large scope of the research, this research focused on modelling a single joint: the elbow. To ensure the suitability of the proposed flesh deformation method a literature review and user study was performed to derive a set of DHM specifications. Six DHM specifications were proposed i.e. accuracy, realism, minimum user intervention, accommodating different body types and sizes, real time, and whole body modelling. An existing flesh deformation method (FDM) which had the potential to conform to the DHM specifications was determined and chosen to be developed further so that it matched the requirements of DHM for ergonomics simulation. The development resulted in a new FDM which required the provision of several elements to create a surface flesh deformation at the elbow. These were: five cross sections and their locations from four key postures (full extension, 135ᵒ flexion, 90ᵒ flexion and maximum flexion); the carrying angle; and perpendicular profiles from all of the four key postures. To avoid having to obtain these elements for every person for whom the elbow was to be modelled, a supporting data framework was developed. The framework utilised a database and a limited number of inputs (race, gender, BMI and a 3D scan data of a fully extended arm) to predict the FDM s elements from which flesh deformation at the elbow was created. The database stored five key cross sections, profiles, a parameter for the carrying angle and a parameter of the locations of UAF, UAM, LAM for two race groups i.e., Caucasian and Asian. A total of 23 subjects (11 males and 12 females) were carefully chosen to represent a variety of height and body type for each race and gender. The algorithm for the new FDM and the framework is supplied in the accompanying CD. DHM specifications were utilised to review the suitability of the new FDM for ergonomics simulation. The review results showed that the new FDM had a level of error < 3mm and was able to recreate flesh deformation around the elbow joint with a representative level of surface realism when compared to the 3D scan data. The review result also showed that the new FDM was able to accommodate different body types and sizes with a slightly larger error, < 4mm. The new FDM also demonstrated that it could be used to create flesh deformation with limited user intervention. A retrospective analysis for real time modelling and whole body modelling showed that the new FDM had a potential to conform to these two specifications. The overall result of the review demonstrated that the new FDM and framework had the potential to suit ergonomics simulation. The thesis has made a contribution to the field of DHM research for ergonomics simulation by proposing a flesh deformation approach for the elbow that allows the integration of carrying angle; and was built based on specification for the use of DHM s in ergonomics simulation and the utilisation of 3D scan data.

How do you know if the chair you are sitting on is comfortable or not?", is a question I asked my young son ol)e day, to which he replied, "just sit on it and see if it's comfortable!" Counting on his fingers, he ended with "Seriously, Dad, I could have done your PhD in 9 words!" Although measuring sitting comfort using subjective measures (comfort rating questionnaires) appears to be an intuitive, practical and cost effective method, it does have some limitations. For example, with purely subjective feedback it is difficult to reliably distinguish and rank well designed chairs with subtle design differences in terms of their comfort rating. From a chair designer or user perspective, if an objective, valid, sensitive and reliable method was available to assist in the design of the most comfortable seat, it would allow for better informed decisions to-be made about chair design factors that may in turn impact on innovation and ultimately user health. In terms of possible objective measures that warranted further investigation, in-chair movement (or lack thereof), temperature and humidity appeared to show most potential due to their roles within the current models of comfort and discomfort. For example, in-chair movements are understood to be a subconscious action performed to prevent or minimize the perception of discomfort. A lack of in- chair movements in a healthy unrestrained person may therefore be consistent with the existence of comfort. The studies presented in Chapters 2, 3, 4 focuses on the effects of specific chair design factors (legroom, cushion firmness, cushion contour) on in-chair movement and the subjective appreciation of comfort and discomfort. A high temperature or humidity at the user seat interface may result in the softening of the tissues in contact with the seat with the potential for macerative damage, skin or deeper tissue nociceptor stimulation and discomfort. In order to study the possible relationships between such physical modalities and the subjective domains of comfort and discomfort, it is therefore important to determine the number of sensors needed and the location for their placement in order to accurately measure these variables at the user-seat interface. The studies presented in Chapters 5 and 6 focus on the minimum number of sensors required and their placement, in orderto accurately assess temperature and humidity at the user-seat interface.

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