# Soft Rehabilitation and Nursing-Care Robots: A Review and Future Outlook
## 2 Mechanical Design
### Soft Rehabilitation and Nursing-Care Robots Based on the Soft Intelligent Materials Actuation
#### 2.2.1 Pneumatic Fiber Braids and Elastomeric Polymers
Gloves are based entirely on fabric actuators, so they are lighter and cheaper than gloves in previous studies. In 2018, [PERSON] et al. proposed a new type of 3D-printed soft-pneumatic actuator [63]. This is a new soft pneumatic actuator's design scheme that allows customization of geometry-based bending modes. Inspired by the biological structure of fish bones, [PERSON] et al. proposed a novel fish-bone soft actuator with multi-degrees-of-freedom and designed a preliminary soft glove (Figure 3i) [64]. Fishbone actuators are manufactured by a method called lost-wax-inverse-flow-injection [65]. The actuator can execute three motion modes with only one chamber. Each finger of the fishbone-inspired soft robotic glove can achieve two degrees of freedom through a single chamber, and the glove can achieve multi-DoFs movement. Compared with the traditional fiber reinforced actuator, the fishbone-inspired actuator can exert 11.27 N force at 250 kPa, while the fiber reinforced actuator can exert 11.38 N force at the same pressure. The results show that besides realizing multi-DoFs motion, the actuator has similar force output characteristics as the fiber reinforced actuator. [PERSON] et al. proposed a new kind of fiber-reinforced pneumatic muscle and established a dynamic model of pneumatic muscle by using second-order differential equation [66]. The parameters in the model are identified by visual recognition experiments with a high-speed camera. The final results of simulation verified the reliability of this model. The results show that the pneumatic muscle can be used to make soft rehabilitation mechanical gloves. In 2017, [PERSON] et al. proposed a soft wearable shoulder joint robot consisting of a vest (Figure 3j) [67]. The vest is made of neoprene and is fitted with two fabric-based actuators. This robot is lightweight, low-profile, comfortable, and does not affect the patient's wearing other clothes, nor does it affect the patient's actions. Recently, [PERSON] et al. proposed a novel type of pneumatic muscle actuator, and based on this, they designed a soft robotic arm that can be used by individuals who suffer from lack of mobility due to stroke or other similar disabling illness (Figure 3k) [68]. This robotic arm is a portable rehabilitation device that is wear resistant and lightweight. Experimental results have shown that this portable exoskeleton can provide more effective intensive rehabilitation therapy at home without the need for a therapist and at a lower cost. In addition, [PERSON] et al. developed a soft elbow rehabilitation robot based on pneumatic muscles (Figure 3j) [69], which has two degrees of freedom. This soft robot is relatively simple to manufacture and its operation is easy and flexible. The experimental results show that the device can complete the rehabilitation process of the elbow joint under appropriate control. As for the rehabilitation robots designed for helping other body parts, including lower limbs, facial, and so on, there are some existing studies based on pneumatic fiber braids and elastomeric polymers actuation. In 2013, [PERSON] et al. proposed a concept of human-robot-interaction (HRI) control for orthosis and applied it to a pneumatic soft-actuators robot for lower limb rehabilitation [70]. The robot consists of two orthoses with two DOFs per orthosis (Figure 4a). A single actuator can provide movements from 0\({}^{\circ}\) (extension) to 45\({}^{\circ}\) (bending). In 2017, [PERSON] et al. proposed and evaluated a rehabilitation robot for soft ankle joint (Figure 4b) [71]. The rehabilitation device is driven by four parallel pneumatic muscles and enables three rotational degrees of freedom. In 2019, [PERSON] et al. proposed a lower-limb exoskeleton actuated by pneumatic muscle actuators (Figure 4c) [72]. The exoskeleton system consists of mechanical structure, a treadmill, and a weight support system. The mechanical mechanism of the exoskeleton system is optimized to achieve the wearing comfort for patients. In 2015, [PERSON] et al.