Taylor Made: Under pressure
Touchscreen technology has become ubiquitous in our daily routines, having been integrated into smart phones, car displays, kitchen appliances, laptops, and whatever else. Like any other invention, this technology has undergone a design evolution.
In the early days of touchscreens, a flexible outer screen protected layers of conductive material (the most commonly used material these days is indium tin oxide). Pressing on the screen contacted the layers, creating a circuit at the point of pressure. While documentation for early air traffic control touchscreen tech dates back to the late 1960s, an American-invented resistive touchscreen was patented in the mid 1970s and became available in the early ’80s. Meanwhile, a research group right here at Illinois patented an optical touchscreen to be used with one of the later generations of PLATO computers (another Illinois invention).
Although still used to this day in some applications (e.g. industrial machinery, restaurant service monitors, and some hospital equipment), resistive screens have been widely replaced by capacitive screens, which use electric field variations to read touch. This type of touchscreen does not rely on pressure; the charged screen’s electrical properties change under touch, regardless of the amount of applied force. The University of Toronto developed a tablet in the early ‘80s that could successfully read multiple touches, establishing the touchscreen’s ability to support activity from a hand, instead of just one finger or object.
There are two main types of capacitive technology: mutual capacitance, which works similarly to resistive screens by using layers of conductive material, and self-capacitance, which uses a single layer of circuits of electrodes. Apple’s first touchscreen device, the iPod touch, incorporated self-capacitive technology. Let me take a moment to note that, while Apple became a household name for touchscreen technology with the advent of the iPhone in 2007, other companies had achieved significant milestones decades earlier—Linus Tech released the first tablet, called the Write-Top, in 1987, and IBM released the first touchscreen phone in 1992, to name a couple.
In summary, the screens we use today are the product of roughly four decades of evolution. As they say, any overnight sensation was ten years in the making; indeed, a lot of work that has since fallen behind the curtain paved the way for smartphones. In engineering design, it may be years before you can witness the true impact of your concept—sometimes that’s just the nature of the beast. Stick with it.