e-labels are labels containing electronics or electrics. They are likely to appeal to many human senses instead of just sight as with conventional printed labels. E-labels will variously exhibit recording, speech, texture change, RFID, self-adjusting use-by dates and other functions and energy harvesting is likely to be used extensively in e-labels within ten years. Possible construction processes are shown below.
Possible production sequence for e-labels and e-packaging
Clearly the resulting products will sell in hundreds of billions yearly and energy harvesting will be an essential part of the design. What form this may take also needs careful consideration and a range of products will result.
Electroactive polymers EAPs have been proposed for harvesting energy by movement including vibration. These polymers have a large strain, elastic energy density, and high energy conversion efficiency. The total weight of systems based on EAPs is expected to be much lower than those based on piezoelectric materials but they will not have the heat tolerance and maybe not the life of established inorganic piezoelectrics. However, large areas will be practicable.
Electroactive polymers change dimensions when a voltage is applied across them. This is an ionic effect and it may be slow. Micromuscle AB in Sweden commercialises these for guiding surgeon's tools, for example. Closely allied to this is the use of multiply deformable polymers in a capacitor like structure which causes them to deform when a voltage is applied. In short, the capacitor tries to become thinner under the electrostatic force which makes it occupy a larger area reversibly. Artificial Muscle Inc makes these. In principle, both could work in reverse to generate electricity. Artificial Muscle has power generation as part of its business plan, intending that others develop this under license. Artificial Muscle is keen to partner with other companies on dielectric film development (high permittivity and dielectric strength, low Young's modulus) and roll to roll printing/manufacturing development. CNRS, Matsushita and others are also researching electroactive polymers for energy harvesting.