# Design Methodology for Soft Wearable Devices--The MOSAR Case
## 1 Introduction  
In the last decade, soft robots have drastically expanded their domain in the medical field. Particularly, soft wearable devices (SWDs) are aid systems that merge robotics and wearable technology in order to overcome human disabilities [1]. These systems are manufactured with materials that are characterized for their flexibility, adaptability, lightness and increasingly large deformations [2]. These features allow comfortable structures that fit with the limbs and emulate joints motions. SWD rehabilitation and assistance tasks have been mainly focused on regaining joints range of motion (ROM) through exercise routines. Furthermore, SWDs help patients to recover self-esteem and independence to execute the activities of daily living and act as a supportive aid for therapists [3]. For example, Soft Exo-suits have been proposed for walking tasks [4; 5] and knee rehabilitation [6; 7]. Soft Exo-sleeves for shoulder [8; 9], elbow [10; 11], forearm [12; 13] and wrist [14] rehabilitation have been also reported. Moreover, soft exo-gloves (SEG) have been developed for hand rehabilitation and objects manipulation [15; 16]. On the generation of SWD, one of the most important challenges is the development of soft actuators. Among several options, cable-driven and fluid pressurization have been mostly selected [17; 18]. Important efforts have been made concerning the materials that improve the structure of soft actuators. For example, the use of elastomer [19], composite materials [20] or materials similarto human muscles [21] that offer variable stiffness. 3D printing is highly used as a manufacturing process for soft actuators since it reduces costs and time delays [22; 23]. During SWD evolution, several requirements have been attended to in order to enhance their efficiency, satisfy patients needs and guarantee their security. For instance, the authors of Reference [24] establish that SEG performance is determined by the operation and usability conditions which refer to several system attributes such as actuation, materials, degrees of freedom (DOF) and manufacture processes, among others. Furthermore, in Reference [15] a control unit is proposed to guarantee safe interactions between SWD, patient and environment. SWD fabrication procedures have been diversified but sequential approaches are the most employed as has been stated in Reference [24]. Overall, these methods are integrated by modeling, fabrication and validation (MFV) phases. In sequential approaches, based on general requirements, the engineering point of view prevails over the medical knowledge and experience. However, these approaches are not suitable for all patients since his/her clinical condition must be considered for SWD design, fabrication and implementation. This paper proposes a design methodology which comprises the conception and manufacturing of SWD oriented to a specific necessity based on bottom-top methodologies (BTM) [25; 26]. BTM principles have been already applied in automotive, military and aerospace industries [27]. Similar structures have been proposed in References [28; 29] for the design of manipulator robots. Therefore, this paper extends the application of BTM into the soft wearable devices field to produce a new methodology that goes from a particular solution to general cases. This extension of BTM represents the main contribution of this paper allowing the proposal of a modular technological platform for SWD diversification. The proposed design methodology seeks to unify medical, therapeutic and engineering guidelines for research, development and innovation of SWD. It is highlighted that the research aspect includes clinical support about patient's condition in order to identify his/her main necessity and define SWD constraints through concurrent engineering, instead of using general requirements as in MFV approaches. Concerning the development aspect, modeling and manufacturing tasks of EPM are addressed.