The Friction screen differs from the Net Force and Motion screens in that it allows you to predict how forces change motion. In other words, you can move the arrows to predict what would happen in the scenarios shown in the pictures below and then check your predictions using the simulation. This will give you a better understanding of how forces change motion.
The programmable friction screen uses a special display panel that can generate different levels of friction by modulating the surface's electrical properties. To do so, a touch-screen sensor sends a dedicated output signal to piezoelectric actuators that are embedded in the display glass underneath the finger. They then vibrate the glass surface at specific points and frequencies to create different levels of friction. This is similar to existing haptic feedback technology, but unlike inertial-based solutions that shake the whole device, programmable friction only vibrates the area directly under the finger.
This technique is also known as "electrostatic friction." It does not require additional mechanical components such as motors or solenoids, and it can produce clearly perceptible stimuli without requiring that the fingertip contact the physical display panel . An electrostatic friction display has been incorporated into touchscreen devices by Senseg (with their short-lived Feelscreen product, a 7'' Android tablet overlaid with Tixel), as well as in academic studies of 3D shape rendering and texture gradients.
The current study evaluates the effect of friction stimulation on bottom-up sensation and cognitive processing using a real human-computer interaction task in which participants stroked virtual guitar strings in a touchscreen device while recording the electroencephalography (EEG). We report that friction stimulation induces stronger beta event-related desynchronization and rebound, particularly in the contralateral parietal area, during the late phase of the motor task.