substrates while maintaining the properties of the structure. This allows fabrication of functional devices directly on to previously-inert surfaces. To demonstrate this, we conformally-print devices, including joule heaters on glassware, conductive patterns on small gummy candies for capacitive based proximity sensing and deformation sensors on marshmallows and candies. We also demonstrate the ability of this method to conformally print multi-layered devices by demonstrating the fabrication of a graphene/PU/graphene thin film parallel plate capacitor and subsequent water transfer on to soft and hard substrates.

![Applications of water assisted conformal printing. **a** Temperature evolution curves of conformally printed spiral heater under constant voltages of 10 V, 15 V, 20 V, 25 V and 30 V. **b** Photograph of a spiral pattern functioning as a joule heater on a round bottom flask with the corresponding IR image. **c** Photograph of a spiral pattern on a glass beaker with a corresponding IR image. **d** Conformally printed square pattern functionalising green heart-shaped candies for capacitive touch sensing. **e** Circuit discharge time before and after proximity capacitive sensing of the candy. **f** Conductivity response of the deformation of a marshmallow’s surface. **g** Deformation sensor printed on two-toned white/pink candies with corresponding $\Delta R/R$ responses when applied 