Making an impression just got easier. Scientists in the United Kingdom have announced the development of biometric devices that detect finger pressure. The devices, known as piezo-electric (or pressure electricity) and piezo-resistive sensors, were developed by scientists Neil White and Neil Henderson at the University of Southampton in the United Kingdom with colleagues at the University of Twente in the Netherlands. The sensors detect the unique pressure stamp created by an individual as he taps out a rhythm or sequence, such as a PIN.White and his colleagues studied the waveforms generated by 34 subjects as they tapped on a piezo-electric sensor mounted on a smart card.The waveform properties of the pulses created by each individual tapping the sensor were captured and compared. Waveforms were studied for unique characteristics such as height and duration. Like sound waves, pressure points provide wavelengths that can be measured. The scientists found that the waveforms could be used to uniquely identify each member of the study group.The sensors can be screen-printed onto a thin layer of Mylar, then bonded onto a wide range of objects, from smart cards to PDAs.The notion of capturing an individual's unique tapping pattern is not new to the world of biometrics, according to James Wayman, director of the U.S. National Biometric Test Center at San Jose State University's College of Engineering. However, the addition of pressure waveform patterns to keystroke timing is a new twist. "If the pressure one uses on a keypad is stable enough to be used as an identifier, that's new," Wayman says.However, keypad pressure sensors may run up against many of the same obstacles as earlier keystroke pattern recognition technology. Users must supply the sensors with a substantial amount of initial input in order to train the sensor to recognize the individual's unique waveform signature. Physiological responses like fatigue can change the pattern of the user's input in the course of such a test. Factors such as posture or position relative to the sensor pad can also affect a user's pressure signature.Scientists suggest that more study of pressure sensors is needed to perfect the technology and reduce the error rate. Keep your fingers crossed.