A desert beetle tilts its body forwards into the fog-laden wind to collect water by its hydrophilic patches on its superhydrophobic backs.In this study,the pinning and dewetting mechanism of a tilted drop pinned by a hydrophilic defect on a superhydrophobic surface with negligible contact angle hysteresis (CAH) is explored both experimentally and theoretically.The defect is designed in different shapes including square,rectangle and triangle.The uphill and downhill angles of the tilted drop vary with the inclined angle (α) of the plate.The drop remains pinned until the critical inclined angle (αc) is achieved.As α=αc,the uphill angle of the drop reduces to the receding angle of the defect.The magnitude of αc grows approximately linearly with the pinning length (ω),which is the contact line length on the defect and perpendicular to the sliding direction.For a square or rectangular defect,ω equals to the side-length perpendicular to the sliding direction and the side-length parallel to the sliding direction has insignificant effect on αc.While ω on square and rectangular defects remains unchanged before sliding,ω on the triangular defect grows with increasing α.The relation between ω and α for the triangular defect is consistent with that between ω and αc for square and rectangular defects.Surface Evolver simulations based on free energy minimization are performed to reproduce the wetting and dewetting behavior.The simulation outcomes agree quite well with the experimental results.