## 5 Survey of Sensing Systems for Haptic Interface  
A large number of perspectives on intelligent wearable systems such as HMIs can be expected thanks to the outstanding advancements in emerging technologies such as 5G/6G communication, the Internet of things (IoT) [90; 91; 92], tactile Internet [93], machine learning, image processing [94; 95], and neural data processing [96; 97]. Hand gestures are commonly involved in every form of human-computer interaction [98; 99]. The preponderance of HMI systems relies on touch, audio, and visual modalities. Using two-way tactile communication is crucial since sensory feedback alone is insufficient for productive conversation. Most VR/AR systems mainly offer visual and audio feedback but do not give consumers immersive experiences. Innovative implantable and wearable devices having flexible and elastic form factors and characteristics such as wearability, non-obtrusiveness, and biocompatibility have also been made possible thanks to advances in material sciences [100; 101]. To monitor tiny movements, pressure changes, or physiological signals, these latter must be conformally applied to the body [102; 103]. These advancements in sensing technologies have expanded the possibilities to develop intelligent, user-friendly glove-based HMIs. Technology advancements are making interactive gadgets quicker; therefore, it's important to investigate the modalities to enhance the user experience and accommodate several users, including deafblind persons with compromised visual and audible modalities. Realizing a robust tactile communication system that offers genuine emotions requires understanding the physiological and emotional aspects of human touch [104]. [PERSON] et al. considered these factors while integrating interdisciplinary inputs from several disciplines, including electronics, mechanics, communications, informatic, material science, and robotic systems. They mainly concentrated on haptic smart gloves that use feedback and tactile sensing [93]. Human contact largely relies on visual, audio, and tactile interactions, as already mentioned; however, deafblind persons cannot use these senses. Nevertheless, impaired \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Device**} & \multirow{2}{*}{**Application**} & \multirow{2}{*}{**N. of** **Actuators/Sensors**} & **Actuators or Sensors** & **Feedback** & **Future Applications** \\  & & & **Technology** & **Typology** & **Fure Applications** \\ \hline \multirow{2}{*}{Vi-Hab band [56]} & Rehabilitation systems & (5) Vibrational coin & \multirow{2}{*}{Vibrotactile} & Kinesthetic Feedback (independent and simultaneous) & Force control on active prosthesis or exoskeleton \\  & (biomedical) & & & & \\ \hline \multirow{4}{*}{Smart Glove [34]} & VR surgical & (8) Triboelectric & Triboelectric tactile & \multirow{2}{*}{Vibrotactile} & Remote home-care; Self-powered system; Intelligence \\  & training, VR social & sensors & & & \\ \cline{1-1}  & network & (1) PZT stimulator & & & \\ \cline{1-1}  & & & & & \\ \hline \multirow{4}{*}{Ungrounded [69]} & \multicolumn{4}{c}{(1) Piezo actuator} & \multirow{4}{*}{Piezoelectric} & \multirow{4}{*}{Force Feedback} & Portable haptic device; Reduced mobile parts by implementing ball bearing \\  & & & & & \\ \cline{1-1}  & & & & & \\ \cline{1-1}  & & & & & \\ \cline{1-1}  & & & & & \\ \hline \multirow{4}{*}{PPTs [76]} & \multirow{4}{*}{Haptic devices} & Printed polymer & \multirow{4}{*}{Piezoelectric} & Vibrotactile and acoustic haptic feedback based on ultrasound \\  & & & & & \\ \cline{1-1}  & & & & & \\ \cline{1-1}  & & & & & \\ \cline{1-1}  & & & & & \\ \hline \multirow{4}{*}{Vibrotactile [69]} & VR object & \multirow{4}{*}{(4) Piezoelectric actuators} & \multirow{4}{*}{Piezoelectric} & Vibrotactile Feedback & \multirow{4}{*}{3D VR interaction} \\ \cline{1-1}  & & & & & \\ \cline{1-1}  & & & & & \\ \cline{1-1}  & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Characteristics and technical specifications of all the analyzed devices.