would be no thicker than a standard, noninteractive greeting card, be priced similarly to standard cards, not require additional postage to mail, and be entirely recyclable. For this concept to reach the marketplace, however, there are a few barriers that need to be overcome in the areas of technology and infrastructure. One company that has developed a greeting card using printed electronics is PragmatIC Printing. Last year they collaborated with UK-based Tigerprint Ltd., a subsidiary of Hallmark, to produce a prototype card with flashing lights (Figure 2). Instead of a silicon chip, the card uses printed transistor logic to control the lights, which are small, surface-mount LEDs. Printed metal lines connect the logic circuit to the LEDs. The circuit is also connected to three printed batteries to provide power. According to Scott White, CEO of Pragmatic Printing, three batteries may be more than necessary to power this device, since a demo card still worked after at least six months of frequent use. It would be reasonable to assume that a greeting card would need to last up to a year on the shelf and a week of frequent use once purchased, so it may be possible to reduce the cost by using fewer batteries. Several companies produce printed batteries, which are suitable for a wide variety of applications including interactive greeting cards. The battery chemistry typically comprises a zinc anode, manganese dioxide cathode, and zinc chloride electrolyte. The anode and cathode terminals are printed with polymer-based conductive inks. Because they contain no toxic heavy metals, printed batteries are completely disposable. The in-plane dimensions of these batteries are usually between 4 and 6 cm, and they can be custom designed in specific shapes to fit the application. They are flexible and less than 1 mm thick. Barriers to implementation Do solutions exist today to produce an interactive card using only printed electronics that incorporate both light and sound? Using the design shown in Figure 1 as an example, the answer is “not yet.” Flexible, printed, organic LEDs (OLEDs) exist in concept but are not yet commonly available in the market. OLEDs would allow for reduced cost and more creativity regarding the size and design of lighted areas on a greeting card. While OLED manufactur-
Figure 2 Conventional electronics for greeting card with sound and light. ers are currently focused on large volume applications such as mobile phones, greeting cards do present a niche opportunity. The key difficulty in created a printed card with sound is the speaker. While thin, flexible speakers now exist for applications such as wall-mounting, the electronics required to power them makes them unsuitable for use in greeting cards. In theory, it would be possible to make a printed connection to standard greeting-card speakers, but because they are relatively thick and bulky, it would probably not be worth the effort. There might not be much point in incorporating printed electronics into a card if not all components can be made paper-thin. There are also limits to the capabilities of printed batteries for greeting cards with both lights and sound. One 0.5-W speaker, the size commonly used in greeting cards today, consumes a lot more power than several low-current LEDs at 4mW each. Xiachang Zhang, Ph.D., founder and CTO of printed battery manufacturer Enfucell, states that printed batteries would not be able to provide sufficient power for the design of Figure 1, even if the other components could be printed. Today’s commercially available printed batteries are best suited to low-power applications where the average power consumption is below 1.0 mW. Since printed electronics is relatively new, the infrastructure has not yet developed to the degree needed to produce the high volumes necessary to lower costs. Currently available solutions are probably about the same cost as conventional electronics, but White believes that as volumes ramp up there is potential for production cost to drop by 50 to 80 %. PragmatIC Printing recently announced plans for pilot production of printed logic for both greeting cards and other applications, which is a step in the direction of higher volume capability.
None of the greeting-card companies contacted for this article was interested in providing information. A company like Sound Expression may be a more likely collaborator. Their primary customers are businesses, and each design is made to order for the customer. Some businesses may find it attractive to be able to promote environmentally-friendly marketing materials produced locally, especially if the cost is comparable to conventional electronics. For European customers, sourcing for all components of an interactive card using printed electronics could be done within the EU. The silicon chips and other components used in tradition interactive cards come from Asia, which can mean supply chain delays for a greetingcard designer in Europe or the U.S. Conclusions Given the state of technology today, printed electronics appear to be a promising solution for light-up greeting cards but don’t yet have the capabilities to produce cards with sound. White describes interactive greeting cards as “a very attractive early application” for printed electronics with a “proven market opportunity and clear requirements regarding functionality, form factor and price.” It remains to be seen whether this market opportunity will result in volume production of light-up cards with designs and prices that will appeal to consumers.
Julia Goldstein, Ph.D. Julia Goldstein, Ph.D., is a freelance writer with a background in materials science. She provides commercial writing for companies in the semiconductor and printed-electronics industries. may/june 2012 | 13