You pay a lot more for a piece of fresh salmon at the supermarket, so that it is, of course, of your interest to know if it is really fresh, i.e., always being kept at low temperature during transportation and storage (so called cold chain).

A small piece of label, which is able to tell you instantly if this piece of salmon has ever been over a particular temperature and if it has, how high the actual temperature was, is the right stuff for this, and many other applications in which monitoring the highest temperature in the thermal history is required.

We have developed a range of low cost (less than a half of US$ per piece of label) shape memory polymeric temperature labels to reveal the highest ever temperature in a small piece of item (food, medicine etc).

Figure 1 reveals that upon heating to different temperatures, the outer concentric circle disappears first, then the middle circle, and finally the central circle.

In Figure 2 (left column: optical image; right column: 3-D surface scanning), upon heating (from top to bottom) the surface impression changes continuously.

In addition, such a label can be used as an anti-counterfeit label. As shown in Figure 3, upon heating to different temperatures, the surface impression changes. Note that switch in surface pattern at different temperatures serves as watermark for high security.

A piece of polymeric label with integrated temperature sensing and anti-counterfeit functions is able to ensure that the piece of salmon is authentic and fresh, so that you can check it by yourself and then relax, and enjoy.