A pneumatic artificial muscle (PAM) actuator body can be formed from an elastic material that includes an inflatable chamber and a restraining component, such as flexible, but inextensible fibers, that causes the actuator to contract when the chamber is inflated with fluid (e.g., air or water). The actuator body can be cylindrical or flat. The actuator body can include a sensor layer formed of an elastic material including a microchannel filled with a conductive fluid to sense the expansion of the actuator body. The sensor layer can be configured to expand when the actuator body is inflated causing the electrical resistance of the conductive fluid to change. A sensor layer between the actuator body and restraining component can be used to measure changes in the contraction force of the actuator and a sensor layer outside of the restraining component can be used to measure changes in the length of the actuator.