But Zhang emphasizes that his polymer is not yet practical. One drawback is that it requires 120 volts, much more than the few volts available in portable devices.
He remains optimistic, though, and feels that the approach could scale up beyond microelectronics. The development of larger refrigerators based on the polymers depends on finding various other substances that exhibit the effect at adjacent temperature ranges. That way the right combination could operate as a “temperature cascade,” rejecting heat progressively. Says Zhang: “This could be the first step in the development of an electric-field refrigerator”—one with no bulky coils or noisy compressors. Someday chilling a picnic cooler might mean flipping a switch rather than loading up on ice.
Chilling with Crystals
Other mobile dipolar molecules might offer solid-state cooling superior to that of polyvinylidene fluoride co-polymers, Pennsylvania State University engineer Qiming Zhang says. Especially promising are the molecules that form images on flat-panel liquid-crystal displays (LCDs). Liquid crystals contain rodlike dipoles that align with an electric field and revert to their original arrangement when the field is removed. Zhang is as yet unsure if the electric charges on the ends of the rods will respond strongly enough to applied electric fields.
Note: This story was originally printed with the title, "Plastic Coolers".