In this blog post, we'll take a look at what Skinfoot is and how it works.

In recent years, various forms of computer user interfaces have been developed that can be naturally carried anywhere, anytime. An interface is a device that connects a human user to a computer. One form of this is "skinput," which literally uses the skin on your body as a touchscreen to enter information into a computer. A skinput device consists of a projector that allows a menu screen to appear on the palm or forearm, a vibration sensor that can detect the vibrations that occur when the user touches the skin with their fingers, and a connection that transmits the detected vibrations to the computer. When the screen is projected onto the forearm or palm of the user's hand by the projector, the area of skin is touched, causing the skin to vibrate. Skinfoot uses this vibration to detect the location of the skin you've touched, and receives that information.

This technology is possible because when a finger presses on the skin, the transmission characteristics of the vibration change depending on the location. When a vibration sensor is placed on the forearm at a certain location and a skinfoot is performed, the magnitude, shape, and frequency of the vibrations detected by the sensor will vary depending on the location of the skin. This is because the position and shape of body components such as muscles and bones are different at each point, and the distance between the sensor and the point pressed by the finger is different.

When you press your finger against the skin, it creates several different forms of vibrational energy, some of which becomes sound and travels through the air. The remaining vibrations are divided into transverse waves, which travel over the surface of the skin like waves, and longitudinal waves, which travel inside the body, vibrating the bones and returning to the skin. The frequencies of the vibrations produced by these longitudinal and transverse waves are important clues to location.

When a transverse wave generates a vibration, its amplitude depends on the force with which the finger is pressed, the strength of the skin area being pressed, and the ductility of the tissue. For the same pressing force, a faster pressing speed will generate more vibrations with a relatively higher frequency. Higher frequency vibrations are transmitted relatively faster and are more accurate. In addition, transverse waves travel farther because the thicker the flesh in the area of contact and the softer the skin, the greater the amplitude of the propagating vibration. Transverse waves tend to produce larger amplitude vibrations than longitudinal waves. Unlike transverse waves, which bounce around on the surface of the skin at high amplitudes, longitudinal waves travel through the skin and the soft tissues underneath to reach the bones. These longitudinal waves cause the bones to vibrate, and the vibrations are reflected back to the skin. Longitudinal waves have less strain than transverse waves and obey the laws of physics in solids. Longitudinal waves generate relatively higher frequencies than transverse waves. These frequencies are detected by the vibration sensor, and the connecting device converts them into a digital signal that is sent to the computer.

Skinfoot is still in early development and only has a simple user interface. While there is variation from person to person, and even within the same person, between the elbow and the fingers, it can identify the information you want to type with an average of 95% accuracy. That's not quite enough to replace your current keyboard. However, the reason this technology is so exciting is that user interfaces that utilize body parts could lead to computers that don't require a monitor or keyboard.