# 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
The same research group optimized the semi-circular fiber reinforced actuator in [50], and improved the rehabilitation gloves by using a better rectangular actuator design. In the preliminary clinical evaluation, patients showed a 40 percents increase in picking blocks by using soft robotic gloves, and the accuracy and precision of the participant's grasp are significantly improved. In 2015, [PERSON] et al. proposed a method for rapid design of soft fingers made of light hyperelastic material (Figure 3c) [53]. This method is suitable for various sizes and lengths of fingers. The part is designed by SolidWorks, and the mould is printed by 3D laser rapid prototyping. However, this work only made a single soft finger, which needs further study if it is to be applied to rehabilitation robots. In the same year, [PERSON] et al. proposed a new actuator made of liquid silicone (Ecoflex 30) and carried out the simulation and bending characteristic curve test of the actuator [54]. They found that the silicone-only structure was prone to be excessively deformed, and then solved the problem by utilizing fiber reinforced structures. They tested five actuators tied to the back of their hands but did not integrate them into a whole rehabilitation glove. In this system, five actuators were actuated by only one pump at the same time, which reduces the flexibility of each actuator. Multy-pump system can solve this problem, but the system would become heavier and more complex either. In 2016, [PERSON] et al. proposed a linearly extending artificial muscle with fixed unilateral sleeve length. Based on this pneumatic muscle, a soft wearable rehabilitation glove which can be grasped and pinched repeatedly and a rehabilitation wrist exoskeleton were designed (Figure 3d,e) [55; 56]. Gloves solve the challenge of releasing motion under electric assistance by not setting assistive muscles at the little finger, which is the main achievement of this work. In the same year, [PERSON] et al. proposed a low-cost and easy-to-use upper extremity exoskeleton robot, RUPERT (Figure 3f), which has 5 degrees of freedom [57]. RUPERT is driven by compliant and safe pneumatic muscles. Compared with their previous work, this manipulator has been expanded and improved in safety and feasibility. In the clinical trials of patients with chronic stroke, it was proved that RUPERT exoskeleton robot was safe, and Rupert could enhance the motor function of the palsy arm of moderate or severe stroke patients for six months or more. Besides, [PERSON] et al. proposed a flexible orthosis with integrated curvature sensor (Figure 3g) [58]. The rehabilitation is purely polymeric and highly compliant. The main body of the composite glove is made of silicone elastomer. Gloves provide little resistance to natural movement without pressure. When inflated, the fingers of gloves bend and harden. The force test of the actuator shows that the output tip force ranges from 0 to 5 N, and the applied pressure ranges from 0 to 270 kPa [59; 60]. The output force is not large enough to carry out many daily activities and needs to be improved. In 2017, [PERSON] et al. proposed flexion and extension actuators that could be inserted into actuator bags separately, which alleviates the problem of slow dynamics in previous work on soft mechanical gloves [50; 61]. Based on this, a bidirectional soft mechanical glove, which is completely based on fabric, was designed (Figure 3h) [62]. Compared with the previously developed soft actuator, the fabric-based flexible actuator can achieve smaller bending radius and higher force output under lower pressure. The motion range and grip force of gloves were tested and evaluated. The results showed that the actuator could generate 11.3 \(\pm\) 2.5 N (tested with a cylinder with a diameter of 75 mm) and 7.9 \(\pm\) 3.0 N (tested with a cylinder with a diameter of 50 mm) friction. The glove-assisted finger motion range was larger than the average functional range of motion of the hand.