Lower limb exoskeletons enable paraplegic patients to stand-up and walk again. However, the weight and overall functional performance of the exoskeleton prevents them from being widely used. To reduce the weight and increase the performance, pneumatic actuators can be used as an alternative to the commonly used electromechanical actuators. This thesis presents a new pneumatic actuator design to power a lower limb exoskeleton in daily life activities. The goal of this thesis is to take a step towards the design and development of exoskeletons with reduced weight, increased compliance and that enable paraplegic patients to perform daily life activities. Out of several concepts, a single vane rotary actuator is worked out in more detail and a prototype is manufactured. This actuator is able to generate a peak torque of 96 ± 2 [Nm] at an operating pressure of 12 [bar], has a range of motion of 132 ± 1 [°] and is able to generate a peak angular velocity of 430 ± 5 [°/s] and a peak power of 252 ± 3 [W]. The designed actuator has a width of 165 [mm], a length of 135 [mm], a dept of 54 [mm] and a total mass of 2.3 [kg], but with small changes can be decreased to below 1.6 [kg]. This is the first known pneumatic actuator able to generate sufficient dynamics to power a full mobilization lower limb exoskeleton in daily life activities. It can be concluded that this new design is a promising actuator to be used in lower limb exoskeletons. In further work, the bandwidth of the actuator must be determined accurately.