The introduction of the laptop computer presented a problem: namely, how to operate a computer's cursor without a mouse. The solution most widely adopted was created by American inventor Dr. George Gerpheide (b. 1952). His capacitive touchpad, invented in 1988, could detect a user's finger movement and transfer it to the on-screen cursor. Interestingly, Gerpheide developed this technology before point and click was the standard method of operating computer interfaces. This may explain why it was not until 1994 that Apple Computers bought the first license to use his technology (which first appeared on the Apple Powerbook 520).
His touchpad works by employing several layers of material. At the top is a protective layer, about 3 inches (8 cm) square, that the user touches. Underneath are successive layers of electrodes arranged in horizontal and vertical rows, each separated by a thin layer of insulation. The electrodes are all connected to a circuit board that provides them with a constant supply of alternating current. When the finger touches the pad, it interrupts the current, and the locality of this interruption is registered by the circuit board. Any further movements of the finger and new interruptions are then compared to the initial touch point and so the finger's movement can be recorded and reproduced on screen.
Nowadays touchpads are increasingly found on mobile devices, from personal digital assistants (PDAs) to cell phones. The reasoning behind the innovation is simple, as Gerpheide himself said: "When you're talking about mobile appliances, the mouse is not suitable. Nobody wants a mouse dangling from. Their net-connected cell phone."