Evaluation of a Fabric Channel Cooling Apparatus for Twisted Coiled Actuators

Wearable robotic systems have the potential to help many individuals with rehabilitation and to support activities of daily living. Unfortunately, these systems are not widespread due to their cost, limited portability, and size. Twisted Coiled Actuators (TCA), novel artificial muscles made from nylon thread, are inexpensive, lightweight, and slim. However, the natural cooling time of these thermally activated muscles is too slow to support rehabilitation or voluntary motions. This paper presents and assesses the feasibility of a novel cooling apparatus for the TCA. The cooling method involves a flexible fabric channel and a miniature air pump to cool the TCA with forced convection. The channel is lightweight, flexible, and can easily be sewn onto other materials to allow easy fabrication of wearable devices. ANSYS Fluent simulations were performed to determine the relationship between the input air velocity and the cooling time constant of the system. The results indicate that the miniature air pumps currently available are not powerful enough to cool the TCA at the required frequencies. There was a 13.2% difference between the cooling time constant predicted by the model and the time constant found experimentally for an input of 1 m/s.