Surfaces with wettability patterns are of great technological importance in industrial applications such as heat transfer, water collecting and particle separation. Traditional methods of fabricating such surfaces rely on technologies such as photolithography and microcontact printing, which have limitations on cost-effective scaling up and are difficult to be implemented on curved surfaces. By taking advantage of a mechanical instability, we show that spatial wettability patterns on both flat and curved surfaces can be spontaneously generated via a simple one-step dip coating process. Through variations in dipping time, pre-stress and chemical treatment, the domain size, morphology and wettability contrast of the heterogeneous surface can be controlled independently. We characterize the wettability contrast by capillary breakup. Further, such heterogeneous surfaces show potential for harvesting water from thin moistured air and generating microreactors in a high throughput.