Wet shape memory alloy actuators for active vasculated robotic flesh

A new type of actuator is presented where shape memory alloy (SMA) wires are embedded within artificial "blood vessels." Fluid flowing through vessels allows the SMA wires to be rapidly cooled by convection, resulting in greater bandwidth than ordinarily possible. Combinations of electric, fluidic, and thermal inputs can be used to control the contraction/extension of the SMA wires within the compliant vessels. These wet vascular SMA actuators can be used as robotic muscle or even embedded in a compliant rubber material to create an active vasculated robotic flesh. This paper begins by proposing a type of biomimetics where robots and machines are imbued with a vasculature or network of blood vessels. The concept of a wet SMA actuator is then introduced as an immediate application of a vasculated robot. A wet SMA actuator is then designed and implemented. Initial prototypes are 3 mm in diameter and are capable of 2% strain at 2 Hz by pulsing 2 A of current and 3 mL/s of water. Reservoirs of hot and cold water are also used to recycle the thermal energy and allow the actuators to exert static force with no electric current. Finally, multiple vascular SMA actuators are imbedded within a 4 mm thick rubber sheet to implement the active vasculated robotic flesh.