# A Novel Soft Robotic Exoskeleton System for Hand Rehabilitation and Assistance Purposes
## 2 Development of the SEG Device  
### Requirments and Technical Specifications  
Before setting the requirements for an SEG device, it is essential to track down the clinical conditions that require the use of SEG devices. As aforementioned, this device facilitates rehabilitation after a medical condition (injury, stroke, etc.). Regardless of the medical issues that led to the disability, the cases of monoplegia and hemipleggia (Figure 2a) are the medical conditions in which SEG devices could be useful in terms of rehabilitation and assistance [21]. It is worth mentioning that according to the literature, these cases contribute a percentage of around 40% of total disability cases [21]. The main idea for the functionality of SEG is the widespread rehabilitation method of mirror therapy (MT). In detail, MT utilizes specific configurations with mirrors in order to create the illusion of the movement of the affected limb; with this technique, the sections of the brain that are related to the motion of the affected limb are activated, and the rehabilitation process is accelerated [22; 23]. In traditional MT, the whole process of therapy is performed physically with the healthy limb; this offers only optical stimulus for the patient's brain. On the other hand, the SEG device proposed in this study enables advanced MT. In detail, the utilization of the control glove on the healthy hand combined with the SEG device on the affected hand provides both optical and physical stimulus for the patient's brain resulting in the activation of more brain sections and avoiding muscle ankyloses due to the physical movement of the affected limb [24; 25]. For these reasons, the proposed SEG device appears to accelerate even more the rehabilitation process. Figure 2b depicts an indicative image of traditional MT configuration [26]. Having analyzed the medical conditions and the working principles of an SEG device, the next step is to set the main requirements and technical specifications for both the software and the hardware configuration. The first design requirement for the SEG is to be easy to use with regard to the application and its operation. For this reason, the device should be compatible with the majority of human hands, according to anthropometrics data [27]. Furthermore, both the software and the hardware should be user-friendly and harmless for the patient and healthcare professionals. Thus, the hardware was made with human-friendly and soft materials, and all electrical parts (wires, Printed Circuit Board/ PCBs, etc.) were covered with plastic cases. It is worth mentioning that in order to improve the user-friendly aspect and the rehabilitation efficiency of the device, the control of SEG could be performed via two different methods. The first method is to control the SEG through the developed software platform and the second method requires a second control glove, which is applied to the healthy hand. Then, the SEG imitates the motion of the healthy hand, stimulating the patient's brain and offering a more realistic  
Figure 2: (**a**) Illustration of monoplegia and hemipleggia medical conditions; (**b**) Indicative image of a traditional MT configuration for hand rehabilitation [26]. and physical movement for the affected limb. Moreover, the graphical user interface (GUI) of the software was designed with simple and clear graphics for each step of the procedure. One of the most important aspects of the SEG is its kinematics; the developed actuators of the SEG were designed to imitate the motion of a human finger in terms of angular range, motion speed, and physiology. In addition, in the designed SEG, the applied force of the actuators could be controlled through the working median pressure (i.e., pressurized air) in order to meet the patient's needs. Other requirements for the developed SEG are to be lightweight (<5 kg) and easy to carry for patients and healthcare professionals.