When I was in college, many years ago, I worked for a company that made CNC systems (computerized numeric controls) for milling machines and lathes. And, at one point in time they were actively considering a capacitive touch interface to get around contamination problems. To evaluate the technology, the company even purchased a Qwerty keyboard made with capacitive touch buttons.
At the time, I was so impressed by the technology that I failed to see the inherent flaw in the design. Basically, by using capacitive touch for the buttons, they created a keyboard that no touch typist could ever use because touch typists rest their fingers on the home row keys. With a capacitive touch keyboard, that means that the keyboard will always report a press on the home keys. Now, you could get around the problem by having the typist lift and press for home row keys, but that requires the user to modify their normal behavior just to get around your design problem, so really, it is not a very clean solution. What you really need is something that has the same dust and moisture resistance of capacitive, while requiring an actual press by the user to actuate the key.
OK, so much for the lesson in ergonomics, cap touch and Qwerty are a bad combination. What does this have to do with the rest of the user interface world? Well, I’ll tell you; there is one other group that relies on touch to identify buttons locations, blind people. That’s right; the ADA (Americans with Disabilities Act) requires that critical systems, such as elevators and access controls, must have user interfaces that support Braille labeling on their controls. And because Braille uses a series of raised bumps, which are ‘read’ by the user passing their filters over the bumps, capacitive touch is basically useless because the buttons will trigger when the user is trying to find/identity the buttons.
So, how do we solve the problem? We want to seal the interface to prevent contamination by moisture and dust, but we need a system that only responds to an actual press by the users. The answer is simple, use the new inductive touch technology. The inductive touch system uses a solid Fascia of plastic or metal, so it can be sealed, and it detects a user’s touch by detecting the minute deflection of the Fascia caused by the user’s press. This gives us the best of both worlds, a solid front panel (Fascia) with no cracks or gaps for contamination, and the light brush of the Braille labeling will not cause a false press when someone is just reading the Braille legend because it requires a stronger actuation force by the user to cause a press. Simple and elegant, we have a simple sealed keyboard, and it won’t trigger when someone passes their fingers over the legends
One final note; it has been 30 years since I saw the capacitive touch Qwerty keyboard, and though I thought it was a cool keyboard, I have no idea who built the thing so please don’t email asking for the manufacturer. Just accept the fact that the manufacture probably discontinued the design once they figured out that their product had such a market limiting feature.