A touchscreen as a biomolecule detection platform.

In recent years, considerable effort has been dedicated to the development of a simple, instrument-free detection method that enables point-of-care testing (POCT) and decentralized clinical diagnosis of diseases. One of the most promising approaches to this goal involves the use of an electrical detection strategy. Owing to operational simplicity and ability to be miniaturized, this approach has been subjected to very extensive studies. Nevertheless, except for a glucose sensor or i-STAT blood analyzer, no practical portable POCT device has been developed to date because of the lack of success in readily integrating detection elements into electrical devices. A touchscreen is an input device, generally used in kiosk systems, PDAs (personal digital assistants), or smart phones, that can detect the presence and location of a touch within the device area. Among other touchscreen technologies, including those that employ resistive, infrared, and surface acoustic wave (SAW) signaling, the capacitive touchscreen has been widely used recently owing to the recent increasing popularity of smart phones. Basically, a capacitive touchscreen detects small capacitance changes of electrodes in the device that are induced by a human finger touching event in accord with the relationship shown in Equation (1):