More and more of the interfaces we use are solid state: devices like touch screens and touch pads that sense our movement but have no moving parts of their own. While far more advanced than mechanical buttons, switches, and knobs, these solid state devices fail to provide (despite their name) the sense of touch. They have no shape, no texture, they provide no confirmatory “click” nor the feel of detents. They are dead to the finger and as such, must provide interactivity with graphics or sound. Wouldn’t it be wonderful to actually feel something, not just see it or hear it? This is what the TPaD enables. The TPaD is a novel technology for creating the sense of touch in a solid state interface. It does so through variations in surface friction. The TPaD surface friction can be adjusted from bare glass, which has rather high friction against human skin, to something more like an air hockey table. Friction levels in-between can be achieved, and the friction can be changed rapidly – in a matter of milliseconds. When combined with fingertip position tracking, the TPaD can be used to create compelling illusions of texture and useful haptic feedback for virtual controls. The current embodiment comprises a 25 mm diameter, 1 mm thick piezo-ceramic disk glued to a glass disk of equal diameter and 1.6 mm thickness; which forms a piezo bending element. When voltage is applied across the piezo disk it attempts to expand or contract, but due to its bond with the glass, cannot. The resulting stresses cause bending. The two disks are fixed atop a mounting ring to insure bending in the 01 mode. The TPaD experiences approximately 1-5 micron vibration when excited at resonance of 33kHz. This ultrasonic vibration causes a reduction of friction under the finger. Thus the TPaD is a form of solid state haptic feedback; ultrasonic vibration is not detected by the finger while the forces due to friction modulation are detected. Finger position tracking is performed using an optical sensing scheme. Linear sensor arrays (LSA) consisting of 768 photodiodes are mounted in two axes. Current is generated when light impinges on the photodiodes. Integration circuitry within the LSA outputs a voltage signal proportional to the light intensity on each photodiode at a refresh rate of approximately 500Hz. Infrared LEDs illuminate the LSAs, hence an exploring finger casts an “IR shadow” on the LSA. PIC microcontroller chips interpret finger position from the LSA output in two axes. A friction reduction experiment was constructed to quantify the continuous range of friction levels produced by the TPaD and develop a mapping from excitation voltage to the coefficient of friction on the display surface. The coefficient of friction between a human finger and the display surface was measured during different levels of excitation voltage, corresponding to different amplitudes of surface deflection. One-axis load cells measured normal and tangential forces at the TPaD. The experimental protocol required the experimenter to move her finger back and forth on the TPaD, while attempting to maintain constant normal force. During each trial, the excitation voltage at the piezo was stepped through a range of 0 to 40 volts peak to peak in pseudo-random order. At each voltage level the the experimenter performed approximately 7 back and forth motions. The coefficient of friction, µ, at the surface was calculated from the equation for coloumbic friction: µ = F_tangential/F_normal. A total of 18 trials data collection trials were performed. As the amplitude of oscilation is directly proportional to excitation voltage; the results of this experiment show an increase in oscillation amplitude leads to a decrease in friction. We see the coefficient of friction reduces with a continuous gradient from 0.9 to 0.1. Virtual textures on the TPaD are created with specified patterns of the coefficient of friction on the display surface. The coefficient of friction, µ, across the entire disk is uniform at any instant in time. Therefore, to create µ patterns on the TPaD, the value of µ is dependent on the position of the finger. A Virtual Library of textures and tactile sensations has been created for the TPaD. Several demonstrations have been developed using a visual screen to enhance the tactile sensation. Virtual task demonstrations including turning a page, tracing a box and pushing a ball have also been implemented.