An actuator has a plurality of artificial muscle style hydraulic actuator elements forming a bundle with a bundle force density. Each artificial muscle style hydraulic actuator element has a first diameter. The bundle force density is at least two times greater than the force density of any single one of the artificial muscle style hydraulic elements if that single one artificial muscle style hydraulic actuator element had a second diameter. In illustrative embodiments, the second diameter is at least five times greater than the first diameter.