Soft inflatable kirigami actuators for wearable applications

Advances in soft robotics technologies have led to the development of safer human-oriented designs such as soft exosuits and wearable rehabilitative devices. A core transduction mechanism for such applications is pneumatic actuation, which although offering advantages of light weight, flexibility and high force densities, have limited strain capacity. Recently, kirigami designs have been implemented in actuators that address the strain limit of pneumatic actuators. To fully exploit the potential of these actuators, detailed study of the performance of kirigami actuators with respect to geometrical parameters is needed.
In this paper, the effects of different geometrical parameters on strain capacity and actuation performance are evaluated using numerical simulations and experimental tests. These parameters include aspect ratio of unit cell, length of cut, width of air channels, and tessellation of the unit cells. The results illustrate a trade-off between strain capacity and output force by changing these geometrical parameters. In addition, tessellation number plays an important role in mechanical and actuation performance where a tessellation increases the actuation forces by 50% comparing to a single column of unit cells, which is important for enhanced performance at lower pressures. To demonstrate the performance of the kirigami inflatable actuator in rehabilitation applications, assistance in the adduction of the lower arm is studied in demonstration while the maximum pressure applied for actuation is below 40 kPa for safe operation.