| 摘要 |
<p>A time delay messaging device and methods for making the device are described. The device contains at least five layers. These layers are: (1) a clear film, (2) an indicator, (3) a diffusion barrier, (4) an activator, and (5) a backing. p.H-sensitive inks, volatile acids and bases, and iodine vapors can be used to display the message. The device may include additional layers to form a selectively activated device.</p> |
