# Variation: Morphology

#### Cross-section type

Three common cross-sectional shapes seen in soft actuators are rectangular, circular, and semi-circular. Assuming identical wall thicknesses and cross-sectional areas, we have found the following:

• The circular actuator is capable of applying the most bending torque for a given pressure, but it also has a high resistance to bending, making it the least efficient of the three shapes.
• The rectangular and semi-circular shapes have roughly similar efficiency. However, the rectangular cross-section deforms into a quasi-circular shape when pressurized, while the other two cross-section types maintain their original shapes.
• The sharp corners of the rectangular actuator may also increase the potential for stress concentrations and resulting fatigue/failure.