Miyashita’s device has five different gels, each containing an electrolyte solution that causes the tongue, upon contacting the surface, to sense one of those flavors at an intensity that is readily adjustable. Each gel is connected to a separate (exceedingly weak) electric current, and the taste associated with that gel diminishes when the current is turned up. A sixth, tasteless gel is also included as a buffer that keeps the overall current level—and the associated stimulation of the tongue—constant at all times.
The six different gels (including one that is tasteless) inside the part of the Taste Display that transmits flavor to the tongue.
By adjusting the current strengths for all six gels, which can be done automatically, the taste of a chocolate milkshake or a sirloin steak or any other desired treat can be experienced through the use of this device without any caloric intake."
Your perceptions of them rise and fall at different rates, and you're very sensitive to that. It's the reason a diet soda often tastes very good for the first sip, but tastes weirder once it's left your mouth, and subsequent sips don't taste right. Different molecules attach and detach from your taste cells differently, and that makes a big difference.
The article compares it to the first phonographs, and maybe that's apt: the first phonographs are barely recognizeable as the human voice. This will be barely recognizeable as flavors. I've got a sneaking suspicion that it will take longer than it took to get the phonograph right.