Rehabilitation is undoubtedly a difficult road for the patient with physical disabilities or limb injuries. Regularly going to institutions for rehabilitation has become routine. In general, rehabilitation equipment is usually designed with the goal of improving their health, with each new devices aimed at better treatment offering. Besides, a successful designer should understand the diverse and complex needs of people, and then design solutions and services to meet these needs [1]. However, sometimes this kind of equipment created to improving health can result in negative, even traumatic, emotional experiences in patients, for example, when operating cold rehabilitation equipment and the arduous rehabilitation process, they often feel uncomfortable. Besides, most patients don't want to be in the public eye when they are traumatized or failed in the rehabilitation process. As Kim opinions, the fundamental principle of human-centered design is premised on maintaining dignity [2]. Design for behaviour change (DfBC) should be considered at this moment, because it is viewed as an effective way to deal with some of the main problems in our society [3]. Brooker further proposed a concept of person-centered care, both healthcare professionals and administrators know that providing person-centered care is very important to patients [4]. Person-centered care should aim to create a positive social environment and enable people to experience wellbeing. Therefore, it is best practice to treat patients as individuals and thus assess and meet their individual needs. Patients are known to experience anxiety when interacting with the healthcare environment, and healthcare providers are slowly realizing that the services they provide often hard to meet the needs of their patients. In fact, if patients feel anxious during treatment or rehabilitation, it will definitely affect the quality of medical care. Anxiety must be taken seriously in the medical process today, since it has also been negatively associated with treatment, showing that anxiety can have far reaching consequences and it can undoubtedly impact quality of life in many different ways [5]. For example, it may lead to an increase in awareness and exacerbation of medical symptoms, and less effective medical decision-making. [6,7]. Mullaney also considers that it is necessary to reconsider the patient experience in healthcare, because human-centered design must look holistically at patient experience to find a new solution to mediate and prevent situational anxiety [8]. Therefore, when designing this functional physiotherapy rehabilitation equipment, the primary consideration is the user's psychological feelings. A successful product should be able to solve consumers' problems, or bring a more convenient life to the public, so designers and planners must identify problems and implement effective solutions when designing products, and strive to develop solutions that can bring consumers high-quality products with different benefits [9]. At present, most of the multi-functional rehabilitation hydrotherapy pools provided by rehabilitation institutions are large-sized products used by many people, while the personal rehabilitation hydrotherapy buckets take up little space but often have a single function. Considering that users may not be able to afford the huge cost of large-sized products and have too much space, this design case reduces the size of the multi-functional hydrotherapy bucket and modulates it for home use. In this way, the burden on the body, movement, and use of the rehabilitated person can be effectively reduced. At the same time, the developability and popularity of the product can be considered, and reduce production costs and product size as much as possible to benefit more users and perform personal rehabilitation with dignity. According to Cooper and Kleinschmidt, the key factors for the success of a product to be launched are the design of the product itself, the characteristics of the product, the production methods, and techniques aimed at producing a quality product, the implementation of collaborative production and design, and the benefits that the product brings to the user [10]. In addition, a good product should carefully evaluate every detail during the development phase. Therefore, to study the competitiveness of products, we should start from the market performance, analyze the direct factors such as cost, price and quality, and then analyze the indirect factors such as resources, materials, capital and technology, and finally find the specific reasons and ways to improve competitiveness. In this study, a concurrent design strategy was used as the main approach for the multifunctional hydrotherapy bucket, and different research methods were used to analyze and propose solutions for each problem in a clear box process, in the hope that the selected design solutions could effectively improve the problematic points of the product.

This research uses the concurrent design to solve the black box problem in design, and considers the practicality of the multi-functional hydrotherapy bucket, the storage capacity of the household type, and the safety during exercise. This research constructs a systematic, efficient, and fair design process.

Most of the users of the multi-functional hydrotherapy bucket are physically disabled or disabled. Therefore, in addition to the free entry and exit of the bucket, it is more important to include multiple rehabilitation functions without taking up space. In this case, products of different brands on the market were selected for analysis and comparison, and their problem points were summarized through functional analysis. The solution to the problem was found by TRIZ theory and the morphological chart method. Finally, the best design scheme was obtained by the PUGH method.

Before the outbreak of the epidemic, most people exercised outdoors, and most of the patient with physical disabilities were rehabilitated in rehabilitation institutions. However, in recent years, the spread of the Coronavirus Disease epidemic has led to changes in people's living habits. Designers must start confronting the importance of design for behavior change. For the patient with physical disabilities, if we can improve their behavior by design, or even reduce their anxiety during treatment by design, it will definitely bring them better quality of rehabilitation by design, it will definitely bring them better quality of life. Think from a different angle, if patients can rehabilitate in their own homes, in addition to reducing the risk of infection, they can also maintain patients’ self-esteem. Thus, in addition to behavioral change design, safety in use must also be considered. With these concepts, the concurrent design strategy is applied to the development and redesign process of the multi-functional hydrotherapy bucket. Pre-design of products with objectives tree method for decision making and design specifications. The TRIZ contradictions matrix and morphological diagram are used to find the problematic points and principles for solutions. Throughout the design process, the user experience and the PUGH method are used to select the best version of the design, and finally, the best one is presented in 3D by computer-aided design.

This study adopts a systematic design process, which can effectively save development and design time, and is also closer to the real needs of users. Overall, this design proposal uses various methodologies and data to select the best solution, and by compiling relevant data to build a user-oriented product as much as possible, but whether it can really achieve the effect of rehabilitation is still to be known after the test.