## 6 Hybrid Soft-Rigid Robotic Exoskeletons for Hand Rehabilitation
### Interactive Experience Features  
* _Wearability_. The wearability of exoskeletons is one of the most important factors to consider throughout a comparative examination of these devices. A major focus of these devices is their lightweight nature and ease of use. This approach is adopted with the objective of alleviating the degree of tiredness experienced by the user after extended periods of use. The implementation of a single actuator equipped with four fingers is a prevalent technique, presenting significant benefits in terms of its straightforwardness and effectiveness [120]. This methodology becomes beneficial as it enables the flexion and extension motions of the finger. In addition, the use of a Bowden cable system inside the wearable component of the exoskeleton facilitates weight reduction in such components, hence improving the overall comfort when using the device [16; 124]. The prioritization of ergonomic concerns places emphasis on individual flexibility and seeks to provide a comfortable fit by customizing the design to accommodate anthropometric characteristics [123]. This claim carries substantial significance. Several devices offer efficient danning features, allowing persons with less prior experience to utilize them effectively for ordinary chores [126; 127]. Furthermore, the water and dust resistance features of the devices, particularly in the region where the remote actuation unit is located, augment their practicality [126]. In the realm of extended activities, the attainment of comfort and safety is accomplished by incorporating many features, including but not limited to flexibility and mechanical safety components. Hybrid designs, characterized by integrating rigid components and flexible interfaces, effectively increase the scope of potential applications for these devices to aid in many activities pertaining to daily existence [128]. The proposed technique differentiates itself from other exoskeletons by enabling the active control of finger flexion and extension while also maintaining the inherent somatosensory sense in the palms and fingers [130]. This gives a significant advantage to wearable exoskeleton technologies. \begin{table}
\begin{tabular}{l l l l l l l l l l} \hline \hline
**Ref.** & **Actuator Type** & \(\mathbf{FF}\) & \(\mathbf{TF}\) & \(\mathbf{DIP_{f}}\) & \(\mathbf{PIP_{f}}\) & \(\mathbf{MCP_{f}}\) & \(\mathbf{CMC_{t}}\) & \(\mathbf{MCP_{t}}\) & \(\mathbf{IP_{t}}\) \\  & **[deg]** & **[deg]** & **[deg]** & **[deg]** & **[deg]** & **[deg]** & **[deg]** & **[deg]** & **[deg]** \\ \hline \hline
[120] & Sliding springs mechanism & & & 40.7 & 67.3 & 36.7 & & & \\ \hline
[121] & Pneumatic armor-covered & & & & & & & & \\ \hline
[16] & Spring blades tendon-driven & & 34.0 & 61.0 & 32.0 & & & & \\ \hline
[123] & Cable and spring mechanism & & 60.0 & 55.0 & 40.0 & & 65.0 & 50.0 \\ \hline
[124] & Bowden remote tendon-driven system & & & 95.0 & 75.0 & & & \\ \hline
[126] & Tendon-driven with sliding springs joints & \(-15\)-\(90\)* & \(-15\)-\(90\)* & \(-15\)-\(90\)* & \(-10\)-\(45\)** & \(-10\)-\(45\)** & \(-10\)-\(45\)** & \(-10\)-\(45\)** \\ \hline
[127] & Splint hybrid structure and cables & & 75.0 & 90.0 & 82.5 & & 50.0 & 70.0 \\ \hline
[128] & Fiber-reinforced pneumatic bending actuator & & 35.0 & 60.0 & 40.0 & & & \\ \hline
[129] & Bowden cable transmission & & 66.0 & 66.0 & 72.0 & & & \\ \hline
[130] & Remote chest-pack with tendon actuation & & 20 & & & & & \\ \hline \hline \end{tabular}  
* Overall range obtained from the sum of MCP, PIP, and DIP; ** overall range obtained from the sum of CMC, MCP, and IP.  
\end{table} 
Table 6: ROM achieved by devices presented in the literature. FF: finger flexion; TF: thumb flexion; DIP\({}_{f}\): DIP fingers; PIP\({}_{f}\): PIP fingers; MCP\({}_{f}\): MCP fingers; CMC\({}_{t}\): CMC thumb; MCP\({}_{t}\): MCP thumb; IP\({}_{f}\): IP thumb. * _Control possibilities._ There are several approaches to the implementation of hybrid exoskeleton control strategies.