Haptic feedback is simply feedback you can feel, usually via vibrations. The tiny technology that makes haptic footwear possible has been around for a while, and it's already present in so many electronic devices we use every day. Haptics can be simple to complex vibrations to convey information, like something particular going on in a game, a certain type of notification on a phone or a subtle vibratory cue to let you know you've successfully hit a virtual button on a tablet. The new Kindle Voyage e-reader provides haptic feedback on page-turns to simulate the feeling of pages sliding against each other. The new Apple Watch includes hardware they call the Taptic Engine that produces tapping and other sensations against the wrist of the wearer to give directions, notifications or even communicate with other Apple Watch users.
The necessary embedded computing components to create haptic feedback are widely available, and like all electronic components, they're getting smaller and smaller. They're also available in low-power varieties that allow for smaller batteries. This means they can be hidden more easily in small wearables, clothing and shoes.
To create haptic feedback, you usually need a microcontroller board, at least one vibrating actuator (which is just a little motor that vibrates on command) and a battery to provide power. Microcontroller boards are like tiny computer motherboards, complete with a processing chip, memory and input/output (I/O) connection points, for which you can write programs to send and receive signals to and from whatever electronic sensors, actuators or other components are connected to them. They usually don't have as much memory or processing capability as your computer's processor, or even your phone's. But they do have enough to hold some programming and to control various basic electronic parts, and they generally take up less space and consume less power.
Arduino is one brand of commercially available microcontroller board. It has a number of models that can be easily purchased (along with compatible electronic components) by hobbyists, researchers, or professionals and programmed with Arduino's open-source language using their integrated development environment (IDE) by connecting the board to a computer. Lots of people and companies have also made boards based on the Arduino, many of which can be programmed with its IDE. Commercial products with embedded electronics are more likely to involve mass-purchased boards, and haptic shoes will likely be no exception, but an Arduino board played a role in the first Lechal prototype.
Other small components, like modules that allow for WiFi, Bluetooth or other wireless communication, can be used to make any wearable haptic feedback items communicate with a smartphone or other device. Some microcontrollers have wireless communication built in.
These components can be used for grand things, like making a robot, or for smaller tasks, like setting off light-emitting diodes (LEDs) or vibrating actuators. Adding all the right components together can allow for communication methods like haptic feedback.