We measured differential pressures on the wing of an ornithopter with different stiffness of veins in flapping motion. The pressure measurement was carried out by using a MEMS differential pressure sensor attached on the wing surface. The ornithopter was modeled after a hawkmoth. The wing length was 110 mm, and total mass was 7.3-7.7 g. We fabricated three types of wings which had veins of different cross-section. In the experiment, the ornithopter was propelled by an electric motor and flapped at 10-11 Hz. The result suggested that when a wing is flexible, the different pressure on the wing is small, but the passive deformation of the wing is large during takeoff, then the ornithopter can fly by being subjected to thrust during upstroke and lift during downstroke.
