Expansion of Human-Phone Interface By Sensing Structure-Borne Sound Propagation

ForcePhone is a novel system that enables commodity phones to recognize the force applied to their touch screen and body. Researchers have shown the usefulness and importance of this expressive input interface (especially for the one-hand operation), but this advanced function has not yet been realized and deployed in most state-of-the-art smartphones. Instead of employing or augmenting specialized/proprietary sensors, ForcePhone uses only the phone's built-in sensors to measure the applied force via a physical property called structure-borne sound propagation. ForcePhone has been implemented and evaluated on both iOS and Android phones. Multiple demo applications, such as getting the option menu by hard-pressing a button or surfing the previous webpage by squeezing the phone, have been implemented and tested successfully. The estimated force is shown highly correlated to the real applied force and the estimation error is less than 54g when the phone is stationary. Users can easily control the applied force at two different levels with a 97% accuracy. Moreover, ForcePhone can detect the squeeze of the phone body with a higher than 90% accuracy. Most participants in our usability study were able to master the ForcePhone-based apps and find them very useful.