Secret messages are similar to word puzzles, only instead of secret code, the writing is invisible. Players might need to use a blacklight, a candle, or steam to reveal phrases. Or, the message may be nonverbal. For instance, objects in photographs might spell out words, and paintings may...
You could also try filling up the color cartridge with fluorescent dyes of your choice, and print out you own blacklight posters. Or, put some invisible ink in the black cartridge, and print invisible messages to your friends. As our first real "bioprinting" experiment, we wanted to start ...