Lightweight flexible keyboard with a conductive polymer-based touch sensor fabric

We developed a lightweight flexible keyboard with a touch sensor fabric that consists of conductive polymer-coated fibers. In our sensor fabric, the conductive polymer-coated fibers, which are sensing electrodes, are woven at a 2-cm pitch and the rest of the fabric is filled with pristine polyester fibers. The sensing principle for human touch detection is the measurement of the capacitance between the conductive polymer-coated sensing fibers and human fingers. The keyboard system consists of the touch sensor fabric, a capacitance measurement circuit, a signal processing circuit and software for entering characters into a personal computer (PC). The fabricated fabric has a large area, 20.5 cm × 12.5 cm, and weighs only 9 g, making it large enough for touch input and light enough to carry. In addition, the sensing electrode is bendable to a diameter of 1 mm because the sensor electrode is not inorganic material but rather polymer. When the sensor is touched, the capacitance between fiber and finger is increased by 2 pF, which is large enough to be detected with conventional capacitance measurement circuits. Finally, the keyboard input is demonstrated with our fabricated fabric sensors. This technology will lead to the development of keyboards that are especially well suited for wearable and portable electronic devices.