## 5 Soft Robotic Exoskeletons for Hand Rehabilitation
### Functional Features  
* _Actuated movements_. Most soft robot gloves with pneumatic actuation are designed to move all five fingers [74; 75; 89] so that the entire hand can be opened and closed. Soft gloves can allow the activation of only flexion, only extension, or both. The most important option is the movement of three fingers, namely the thumb, index, and middle finger. The movement of these three fingers allows the execution of a large number of important ADLs and gestures. Very few devices allow the actuation of one or two fingers, and in those cases where this is the case, it is performed to demonstrate the feasibility of the actuation system. There is a clear trend in the literature toward solutions in which both flexion and extension are activated, but flexion is often activated actively and extension passively. The proportion of gloves in which only one of the two actions is triggered also shows this preference for flexion over extension. Moving the thumb presents a more complex challenge than the other fingers. The most common choice is to implement only flexion and extension movements with an actuator similar to the actuator used for the other fingers, of course with smaller dimensions. In some cases, solutions have been proposed that also implement the adduction movement [79; 82] with specially developed actuators. * _ROM of actuated movements._ For the range of motion, some authors give the results obtained in general terms, without distinguishing between the fingers and the finger joints; others give the ranges for the different joints, again without distinguishing between the fingers; still others give precise data for the joints, distinguishing between the thumb and the other fingers. Table 4 summarizes the data on the ROM of some devices presented in the literature. Very often, the design features of the soft actuators used in soft exoskeletons allow the actuation of one degree of freedom for each finger without allowing the control of interphalangeal movements. In some cases, which are much rarer, the appropriately designed geometries of the soft actuators also allow motion control of the different phalanges. From the ROM analysis given by some authors and summarized in Table 4, it appears that for the proximal metacarpophalangeal joint of the finger (PIP), there is a considerable uniformity of values (between about 80\({}^{\circ}\) and 85\({}^{\circ}\)), whereas for the other joints, there are considerable differences between the values obtained with the different devices. For example, for the proximal finger joint, there are values below 30\({}^{\circ}\), above 80\({}^{\circ}\), or around 58\({}^{\circ}\). The values obtained for PIP correspond to those of a normal hand; for the other joints, the values are comparable in some cases and much lower in others. * _Forces developed by the devices._ In Table 5, the values of the maximum forces/maximum loads given by the authors of the analyzed publications in relation to the soft exoskeletons for the hand are listed. As can be seen from the large number of columns, there is great heterogeneity in the characterization of the devices in terms of the forces and load capacity. Some authors have characterized the device in terms of the maximum force that can be developed at the tip of a single finger. Others have used the maximum total force that can be developed at the fingertips, i.e., the maximum grip force. In other cases, they refer to the performance of the device in relation to the activity to be performed, i.e., the maximum value of the mass that can be lifted, gripped, or pinched. The range in which these quantities vary with the variations of the device is very large. The maximum force that can be developed by the fingers as a whole is 148.36 N, and this was obtained with textile actuators with TPE. Values of about 40 N can be achieved with fabric-reinforced soft actuators.