Invisible photonic prints shown by water

Invisible photonic prints have been prepared on a siloxane-containing photonic paper by creating a contrast of crosslinking or degree of hydrophobization with lithographical methods. When the invisible prints are soaked in water for several minutes, the small difference in reflection wavelength (λ) between the pattern and the background is significantly amplified due to their different swelling speeds, which leads to a visible image in the end. It is fully reversible and accessible to show and hide the patterns through soaking and drying. Photonic prints with multi-stopband can also be prepared by carefully controlling the crosslink or modification level in each lithographical procedure.